Microbial Risk Assessment of Salmonella in Ready-To-Eat fruit and vegetables

1

Microbial Risk Assessment Project

‘What is the risk of infection from Salmonella spp. in the Republic of Ireland from eating ready-to-eat

fruit and vegetables?’

Francis Higgins, Cliodhna McMahon and Karen Duffy

Department of Microbiology

National University of Ireland, Galway

March 2015

2

Contents

1. Executive Summary: Pg. 3

2. Statement of Purpose: Pg. 4

3. Hazard identification: Pg. 4

4. Hazard characterisation: Pg. 5

5. Exposure Assessment: Pg. 16

6. Risk characterisation: Pg. 27

7. Discussion: Pg.

8. Conclusions: Pg.

9. Bibliography: Pg.

3

1. Executive Summary

4

2. Statement of Purpose

The aim of this project is to identify the risk of Salmonella infections from consumption of

ready-to-eat fruit and vegetables in the Republic of Ireland through qualitative analysis of

each step undertaken by the products during their journey from ‘farm to table’. Extensive

research was carried out using journals, scientific papers, national health and food

publications and online resources in order to determine the probable level of risk associated

with each step.

3. Hazard identification

Salmonella spp. are a group of rod shaped, oxidase negative, gram-negative facultative

anaerobes belonging to the family Enterobacteriaceae (Christenson, 2013).

Salmonella precedes Campylobacter spp. as the cause of most zoonotic infections in Europe

(Jordan et al, 2006). It is located in the intestinal tract of animals and humans, and is spread

through faeces. There is an average of 350-450 cases of salmonellosis annually in the

Republic of Ireland (HPSC, 2009). Contaminated food is regarded as the number one mode

of transmission of Salmonella spp. into humans, leading to salmonellosis, costing the health

care system significant sums of money annually (FSAI, 2011). Salmonella spp. have also

been known to be transmitted from animals to humans, and humans to humans (D’aoust,

2000).

There are only 2 species of Salmonella - S. enterica and S. bongori. However, more than

2400 Salmonella serotypes have been identified (Adak et al, 2005). They are facultative

anaerobes and are oxidase negative. They can grow at anywhere between 5 - 46ºC, but grow

optimally at 35ºC - 45ºC. They can survive for extended periods of time in refrigeration

(shown to survive for 28 days on surface of vegetables stored in fridges). Antimicrobial

strains are becoming more prevalent around the world which is an increasing cause of

concern.

An infective dose of Salmonella spp. (i.e., the amount of bacteria needed to be ingested to

cause illness) can be as low as 5-20 cells (FDA, 2012). Salmonellosis typically manifests as a

self-limiting case of enterocolitis. This is characterized by abdominal pain, diarrhoea, fever,

nausea, vomiting and chills. The incubation time is 5 – 72 hours with recovery time ranging

5

from 2 – 5 days depending on the strain and host characteristics (D’aoust, 2000). 93% of

individuals showing symptoms of salmonellosis recover without seeking medical attention.

Typically no treatment is needed other than taking oral fluids. In severe cases of dehydration

fluids may need to be replenished through an intravenous drip (CDC, 2013). Complications

may arise leading to systematic infections, and can also be a cause of various chronic

conditions, e.g., reactive arthritis (FSAI, 2011). All groups are susceptible to salmonellosis,

with the highest number of incidences being seeing in children 0 – 4 years old. In adults, it is

estimated that 1-3 working days are lost due to an occurrence of the illness (D’aoust, 2000).

Salmonella spp. are prevalent in many animals, both domestic and wild. They can pass

through the food chain all the way to homes/ food catering services. Humans generally

contract salmonellosis through consuming contaminated foods, including those of animal

origin (meat, eggs, poultry and milk) and vegetables and fruit that become contaminated, e.g.,

from manure or irrigation water (WHO, 2013). Imported fruit and vegetables that are

irrigated with untreated wastewater are of particular concern (Ait Melloul et al, 2001).

Non-typhoid salmonellosis is a notifiable disease in the Republic of Ireland. Data obtained

from the Food Safety Authority of Ireland (FSAI) showed that 333 cases of salmonellosis

were reported in 2009 (a crude incidence rate of 7.9 cases per 100,000) (FSAI, 2011). This

was a part of a large outbreak in the EU, which totalled 108,614 human cases of

salmonellosis. A crude incidence rate of 10.6 per 100,000 was seen in Ireland the previous

year. Due to the ability of Salmonella spp. to cause illness at considerable low doses, it is of

the upmost importance to protect consumer health through vigilant controls at all stages of

preparation and supply of foods.

4. Hazard characterisation

There are numerous host factors that have an effect on the pathogenicity of Salmonella spp.

following ingestion, including (but not limited to): age, gender, nutritional status, immune

status and previous exposure (WHO/FAO, 2002). These factors cause a variation in the

infective dose of the bacteria, which may be very high (>10 5 cells) or in the 10s of cells

(Hara-Kudo & Takatori, 2011).

6

It is a common trend that the highest numbers of incidences of reported Salmonella infections

are found in young children and elderly people (WHO/FAO, 2002). Although the majority of

these cases are usually mild, children and the elderly also possess a higher occurrence of the

infection progressing to a more severe state than with other age groups, including death in

some instances. However, the associations of these two age groups with the illness may have

an effect on data pertaining to their increased incidence rates. For example, medical care is

more likely to be sought after for infants and elderly showing symptoms relating to

salmonellosis infections than in adults (and subsequent testing for Salmonella infections).

Furthermore, young children are far more susceptible to infection if it is their first incidence

of exposure to the bacteria (WHO/FAO, 2002).

The immune status of the host is also a considerable factor in the occurrence of infection

from Salmonella spp, as it is with any other disease causing bacteria. People who are

immunocompromised or suffer from debilitating illnesses are particularly susceptible to

developing salmonellosis from eating contaminated food, such as fruit and vegetables, and

are also at greater risk at repeat infections or progression of the infection to more severe

ailments (WHO/FAO, 2002). In healthy people, the development of immunity has been seen,

whereby patients who were voluntarily infected with S. enterica twice had less severe

symptoms from the second trial, even though they were administered a higher dose of the

bacteria the second time round (McCullough and Eisele, 1951). Further evidence suggests

that immunity to Salmonella is serotype specific due to the higher incidences of salmonellosis

in people who are travelling and thus exposed to new serotypes, often from the consumption

of fruit and vegetables in foreign countries (WHO/FAO, 2002).

Virulence plasmids have been associated with the pathogenicity of different Salmonella

strains and their ability to spread after colonizing the stomach, invade the intestine,

proliferate in the spleen and suppress the immune responses of their hosts (Slauch, Taylor &

Maloy, 1997). A study investigating the presence of virulence plasmids in different strains of

Salmonella found that all isolates of the highly invasive serotypes S. Enteritidis, S. Dublin

and S. Choleraesuis.

The clinical manifestations of salmonellosis range from general gastroenteritis symptoms to

enteric fevers (e.g. typhoid fever) (Giannella, 1996). The incubation time for Salmonella

gastroenteritis is dependent on the dose that is ingested. Initial sympoms include vomiting,

nausea, diarrhoea and abdominal cramps (with myalgia, headache, fever and chills also

7

arising in many cases). Enteric fevers are life threatening systematic sicknesses which require

swift antibiotic treatment. The most comprehensively studied of these is typhoid fever

(caused by S. Typhi). The incubation period for enteric fevers caused by salmonellae is

typically 10 – 14 days, with gastroenteritis often preceding it. Other syndromes arising from

salmonellosis include an asymptomatic carrier state, focal infections and septicaemia.

Although any of the serotypes can be responsible for any of these syndromes arising, some

serovars have been strongly linked to particular syndromes, for example:

Enteric fever – S. Typhi, S. Paratyphi, S. Schottmuelleri

Septicemia/ focal infections – S. Choleraesuis

Gastroenteritis – S. Typhimurium, S Enteritidis

The majority of non-typhoidal salmonellae are ingested in contaminated food. Salmonellae

must have a number of virulence factors in order to be pathogenic, including:

Ability to invade cells

Lipopolysaccharide coat

Ability to replicate in cells

Production of toxins (in some cases)

Once ingested, the ilium and colon are colonized by the bacteria (Giannella, 1996). They then

invade the epithelial cells of the intestines (and the lymphoid follicles) where they proliferate.

When invading the epithelial cells the bacteria first bind to specific receptors found on the

cell surface. They then induce ruffling of the enterocyte membrane, followed by pinocytosis

of the bacterial cells. Multiple genes (located on chromosomes and plasmids) are involved the

attachment and invasion mechanisms of the pathogens into host cells.

In order to diagnose salmonellosis, bacterial isolates are required. (Giannella, 1996)

Biochemical tests are used to identify the genus Salmonella while serological testing is used

to confirm the serological type. Samples (typically faeces or blood) are then plated on

selective and non-selective agars, as well as enrichment broths.

There are vaccines for treating typhoid fever that are moderately effective (particularly in

children) (Giannella, 1996). However no vaccines currently exist for treating non-0thyphoidal

salmonellosis, although research is on-going for their development. To treat general

salmonellosis oral and intravenous replacement of lost fluid is implemented, along with

8

medication to control and nausea, vomiting or pain. Antibiotics are administered for typhoid

fever and enteric fever, while with non-typhoidal salmonellosis they are only used for cases

of septicaemia, focal infections syndromes and enteric fever. They are typically not used for

normal gastroenteritis symptoms as they do not reduce the duration of the illness, but do

extend the period of faecal excretion of the pathogens and run the risk of producing more

antibiotic-resistant strains of the bacteria.

Epidemiology of Salmonella spp. infections in the Republic of Ireland and Europe

Figure 1: Reported no. of confirmed S. Agona cases, sorted by age and gender, S. Agona

Outbreak, Europe, Summer 2008 (N=163). (NSRL, 2008)

163 confirmed cases of Salmonella were reported between February and September 2008

across Europe. These cases affected a range of people differing in ages (NSRL, 2008). The

youngest affected was 3 months old, to the oldest affected who was 87 years old. The median

age affected was 27 years. 57% of the people affected were males. During this outbreak 25

people were hospitalised, and two elderly patients died. The first reported dead was a 77 year

old female who contracted Salmonella whilst in hospital, the second dead was a 78 year old

male. Both cases occurred in the UK.

9

Figure 2: Distribution of confirmed S. Agona cases, S Agona Outbreak, Ireland and the

UK, Summer 2008 (NSRL, 2011)

Eleven cases were reported in Ireland. England reported the majority of cases - 96. Thirty

four cases were identified in Scotland and 11 in Wales. Two cases were reported in Northern

Ireland.

Figure 3: Epidemic Curve - Reported number of confirmed cases by date of onset and

country of infection, S. Agona Outbreak, Europe, Summer 2008 (N=163). (NSRL, 2011)

10

During the S. Agona outbreak in 2008, 56 cases were interviewed to identify the source of the

infection. 40 cases stated that they ate takeout food and 38 people said that they had

consumed made-to-order sandwiches before becoming ill. The fillings in the made-to-order

sandwiches were unknown at the time of the study.

Figure 4: Seasonal variation of Salmonella isolates (NSSLRL, 2010)

Figure 5: Number of cases and CIR of human salmonellosis in Ireland, 2008 (HPSC,

2010)

11

Figure 6: Number of cases of salmonellosis in Ireland for years 1990-2008 (HPSC, 2010)

Salmonellosis cases in Ireland have remained reasonably constant in the last eight years.

There are approximately 350-450 cases confirmed each year (HPSC, 2010). The cases of

salmonellosis have decreased from the late 1990’s, where the incidences of cases confirmed

rose to 1257 cases in 1998. 26% of the confirmed cases in 2008 were found to be children

under the age of 5. The age specific incident rate was 46 per 100’000 in this age group. This

was similar across all HSE-areas apart from the North West which showed the highest

incidence was in the 20-24 year old group. Salmonella was isolated from 447 people. These

isolates were referred to the National Salmonella Reference Laboratory for further typing; it

was found that 12 of the isolates were S. typhi or S paratyphi. The remaining isolates were

non-typhoidal Salmonella. S. Enteritidis (28%) and S. Typhimurium (32%) were the most

common serotypes detected. The number of cases of S. Typhimurium exceeded the number

of cases of S. Enteritidis. S. Agona with found in 13 isolates, most of these were found in the

international outbreak in 2008.

12

Figure 7 : Non-typhoidal Salmonella isolates referred to NSRL by serotype and HSE

area, Ireland 2008 (HPSC, 2010)

Figure 8: Salmonella serotypes reported on CIDR by age groups 2008. (HPSC, 2008)

13

Figure 9: Clinical isolates of S.enterica (n=444) sorted by age and gender from NSRL 2007 (HPSC, 2007)

456 cases of salmonellosis were confirmed in Ireland in 2007 (HPSC, 2007). 440 of these

cases were confirmed in a laboratory. All possible cases were linked to Salmonella outbreaks

on CIDR. 457 cases of Salmonella isolates were referred to the National Salmonella

Reference Laboratory. In 2007 there was a slight predominance in males. The female: male

ratio in 2007 was 1:1.1. The highest number of cases occurred in children under five years of

age. 24% of cases occurred in this age category

Figure 10: Incidence rate of salmonellosis in Ireland 2007 by age group (HPSC, 2007)

14

The national crude incidence rate of salmonellosis cases for 2006 was 10.0/100’000. In 2007

there was an increase observed to 10.7/100’000. Most significantly the incident rate of

salmonellosis in the HSE‐S region increased from 8.3 in 2006 to 21.1 in 2007. This may be

due to an outbreak of S Enteritidis. 52 cases occurred in HSE-S

Figure 11 & 12: Number of cases [2006 and 2007] and CIR of human salmonellosis

[’00-‘07] in Ireland (HPSC, 2007)

It was stated that the CIR of salmonellosis cases were similar in 2006 and 2007 (HSPC,

2007). There was further investigations into regional rates and found that the cases were not

similar. The CIR in the regions of HSE‐M, HSE‐NW and HSE‐S experienced a change in

rate of greater than one case per 100,000. In the midland and the North West a decline in

cases occurred, from 14.3 to 19.1 per 100,000 in the midlands and 16.0 to 8.9 per 100,000 in

the north‐west. The CIR of the southern region increased from 8.3 per 100,000 to 21.1 per

100,000 this increase is probably due to an outbreak of S. Enteritidis. The CIR in Northern

Ireland was slightly lower with an estimated rate of 9.0 per 100,000 likely for the year. Cases

of Salmonellosis were observed in all age groups. There was a higher incidence in the 0‐4 age

bracket. This is probable due to clinicians seeking clinical samples in children under five.

15

The Number of male and female cases has been similar in past years, female: male ratio of

1:1 in 2007, 1.3:1.0 in 2006 and 1:0.9 in 2005 (HSPC, 2007). Serotyping data showed that S

Typhimurium and S Enteritidis remain the most prominent strains. 64 serotypes were

identified by the NRSL in 2007. The number of S. Typhi and S. Paratyphi A cases in 2007

increased from previous years. There were 9 cases of S. Typhi in 2003, five cases in both

2004 and 2005, and, seven in 2006. There was only one case of S. Paratyphi A in 2006.

A Review of European data shows the rate of Salmonella is decreasing in continuing in

2007. Salmonellosis is still the second most commonly reported zoonotic disease in Europe.

The major sources of human Salmonella infections are due to the consumption of eggs, pork

and chicken. There were 151,995 confirmed cases notified on the European Surveillance

System in 2007. This is 31.1 cases per 100,000. CIR’s varied by country by as much as 2.9

confirmed cases per 100,000 to 171.6 confirmed cases per 100,000. S. Enteritidis and S.

Typhimurium were the most common serovars reported they accounted for 81% of all known

serovars in human cases.

The most dominant serotypes of Salmonella in Ireland are S. Enteritidis and S. Typhimurium

(McKeown et al. 2012). These two serotypes accounted for 20% and 38% respectively, of

human clinical isolates identified in Ireland in 2010, while other serotypes made up the

remaining 42% of isolates. DT104 and DT104b have been the most common phage types

detected. In Ireland overseas travel plays an important role in Salmonella epidemiology. It is

now estimated that up to half of all notified cases may be travel associated.

16

Farm

Distribution & Storage

Retail and home

Figure 13:

17

5. Exposure assessment

Table 1: Variables and data inputs for the exposure pathway for Salmonella spp. in

ready-to-eat fruit and vegetables (P=Probability) (C=Concentration of m/o)

Main Stage Sub Stage Outputs Inputs

Farm Seed/ Plant

imports

P1: The probability that the

imported seeds/plants are

carrying Salmonella.

C1: The concentration of

Salmonella in the imported

seeds/plants

In the production of seeds, the

practice of animal grazing to

initiate flowering can result in

the introduction of enteric

bacteria in faeces.

Allowing wild or domestic

animals to graze in seed fields

can also cause contamination

of seeds.

Regional difference

Season of infection

Management factors

Seed/ Plant

transport

vendors


seeds/plants will be exposed to

Salmonella during transportation


Salmonella contacted by the

seeds/plants during

transportation

P1,C1

Conditions of the containers

used for the transport the

seeds?

Storage conditions in vehicles

used for transport?

What is the duration of the

transport journey?

Avian P3: The probability that birds

defecating causes the soil to be

contaminated with Salmonella


Salmonella in bird faeces

P2,C2

Birds defecating onto soil,

plants, fertiliser, irrigation

water or manure can cause

contamination of the produce

18

with Salmonella

Growth/survival dynamics

Manure/

irrigation water/

fertilizer


manure/irrigation/fertiliser

spread onto soil is contaminated

with Salmonella


Salmonella present in the

manure/fertiliser/irrigation water

P3,C3

Improperly treated manure

can contain Salmonella.

Irrigation water or fertiliser

can become contaminated

with Salmonella due to wild

or domestic animals

defecating into these sources.


Management factors

Insects P5: The probability that insects

are carrying Salmonella and can

contaminate the produce plants


Salmonella present in the insects

P4,C4

Insects can be carriers of

Salmonella onto the

plant/produce.

Insect defecate onto plants

during feeding and

contaminate plants with

Salmonella.

Soil P6: The probability that the soil

is contaminated with Salmonella


Salmonella in the soil

P5,C5

Soil can carry pathogenic

bacteria. Spraying of soil with

improperly treated manure can

cause contamination

Wild or domestic animals

defecating onto soil can lead

to the transmission of

Salmonella from the host to

the soil.

Survival/growth dynamics

Harvesting of

fruit and veg


fruits and vegetables will be

P6,C6

Harvesting equipment may be

19

contaminated during harvesting


Salmonella contracted by the

vegetables during harvesting

contaminated with pathogens

and can cause the fruit and

veg to become contaminated

Management factors

Survival dynamics

Washing of

produce

P8: The probability of the fruit

and vegetables being exposed to

Salmonella during washing.


Salmonella present in the wash

water

P7,C7

Improperly washed fruit and

vegetables may still contain

Salmonella

Temperature of the water used

for washing

How clean the water is for

washing?

Management factors

Storage on Farm P9: The probability of the fruit

and vegetables contracting

Salmonella during storage on the

farm

C9: The concentration of the

pathogen being contracted

during storage on the farm

P8,C8

The storage containers on the

farm may not be cleaned

properly and can cause

contamination

Temperature and duration of

storage and how these may

vary

Packaging on

farm


fruit and vegetables with be

exposed to Salmonella during

packaging on the farm


Salmonella being contracted

during packaging

P9,C9

Human handling can cause

contamination

Faecal matter spread from

humans to produce

Other sources of

contamination

20

Distribution &

Storage

Transport of

fruit and veg



Salmonella during transport



transporting environment

P10,C10



produce?

Storage conditions in vehicles

used for transport?


transport journey?

Wholesale

market


and vegetables becoming

exposed to Salmonella in the

wholesale market



wholesale market environment

P11,C11

Improper handling from

sellers/customers examining

produce.

Contaminated containers

Storage conditions in market

Duration of produce at

wholesale market

Management factors

Processing

station


fruit and vegetables will contract

Salmonella during processing,

such as cutting, slicing and

dicing


Salmonella that could be

contracted by the produce in the

processing station

P12,C12

Contaminated surfaces

Contaminated equipment

Improper handling of produce

Other sources of

contamination

Preliminary

washing

P14: The probability of the

produce becoming contaminated

with Salmonella during washing

with chlorinated water


pathogen present in chlorinated

water

P13,C13

Washing produce with

unclean water

Human handling can

contaminate produce after

washing

Temperature of the water used

21

for washing

Slicing or

shredding


produce coming into contact

with the pathogen during slicing

and shredding


pathogen present on the slicing

and shredding equipment

P14,C14

Unclean equipment

Cross contamination between

equipment and produce

Unclean surfaces

Washing/

disinfection



with Salmonella during

disinfection

P15,C15

Improperly washing the

produce

Improperly disinfection of

produce

Temperature of water used?

How clean is the water that is

used for disinfection?


Packaging P17: The probability that the

fruit and vegetables with be

exposed to Salmonella during

packaging


Salmonella being contracted

during packaging.

P16,C16

Is the package contaminated?

Damage to the packaging can

cause contamination of

produce

Improperly sealed packaging

Human handling

Retail & Home Retail storage P18: The probability of the fruit


Salmonella during storage in

retail facilities


Salmonella present in storage

containers in retail facilities

P17,C17

Storage time and temperature

in retail facilities

Produces stored in clean

containers

Human handling of produce

Management factors

Survival dynamics

Other sources of

22

contamination

Consumer

transport home



Salmonella during transportation

to consumers home.



transporting environment

P18,C18



produce?

Storage conditions in vehicle

used for transport?


transport journey?

Temperature during transport?

Storage in home P20: The probability of the


with Salmonella in the

consumer’s home.


Salmonella contracted by the

produce whilst present in the

consumers home

P19,C19

Storage time and temperature

in the home and how these

vary?

Poor hygiene in home

Potential cross-contamination

Survival/growth dynamics

Human handling

Prep before use P21: The probability of the fruit

and vegetables becoming

contaminated with Salmonella

during preparation


Salmonella present on the fruit

and vegetables during

preparation

P20,C20

Unclean surfaces

Unclean equipment

Improperly washing of

produce

Cross contamination from

other sources

23

Serving size S: Serving size Amount of produce consumed

in any serving and variation of

this within and between

different population

groups( ages, sex, regions,

health)

Estimate of

exposure

P: Probability of exposure of

Salmonella per serving

C: Number of organisms

consumed per serving

P21,C21,S

Date relating to stages of exposure pathway of Salmonella spp. in ready-to-eat fruit and

veg:

Pathogens can contaminate fruit and vegetables during different points throughout pre-

harvesting and post-harvesting systems. (Beuchat, 2002) Potential pre-harvest sources of

microorganisms include soil, faeces, irrigation water, dust, insects, manure, wild and

domestic animals, and human handling. Post-harvest sources include faeces, human handling,

harvesting equipment, transport containers, wild and domestic animals, insects, dust, rinse

water, ice, transport vehicles, and processing equipment. Containers that are used for harvest,

24

transport, and display raw fruits and vegetables may not be cleaned and sanitized, which can

lead to the development of biofilms.

Before harvest:

Most microorganisms are naturally present in the environment. These microorganisms can be

non-pathogenic or pathogenic. Pathogenic organisms can contaminate fruit and vegetables

throughout many stages from farm to fork. Pre-harvest contamination can occur by animal

faeces by wild or domestic animals, dust, irrigation waters, runoff water, and insects. They

may also be contaminated from septic tanks leaching through soil.

Microbiological analyses have found that alfalfa seeds can contain high levels of

microorganisms, which include faecal coliforms (NACMCF, 1999).

The environmental conditions under which seeds are sprouted (such as growing time,

temperature, moisture and nutrients) are ideal for bacterial proliferation. It is found that an

increase of 100 to 1000 fold of microorganisms can occur on the sprouted seeds without

affecting the appearance of the product (Taormina et al, 1999).

Several pathogens have been implicated in sprouted seed-associated outbreaks these include

Salmonella, enterohaemorrhagic E. coli, Bacillus cereus, and Listeria monocytogenes. (López

Camelo, 2002)

Salmonella in soil:

Salmonella is a microorganism that commonly inhabits the large intestines of warm blooded

animals. The host species provides Salmonella with a warm environment and supplies the

bacteria with nutrients such as amino acids and sugars (Davies and Wray, 1996). Salmonella

can get into the soil when manure and fertiliser is spread onto the soil. Salmonella is an

enteric or faecal organism that is found in the intestines of animals such as birds and

mammals. When these animals defecate the Salmonella is passed out of the body of the

animal and onto the soil. This may also cause the soil to become contaminated with

Salmonella. When the Salmonella is secreted from the host it battles with various

environmental conditions to survive. Salmonella in the soil can then be taken up into the

roots, or stems of fruits such as berries or vegetables such as carrots, potatoes and lettuce. To

survive in the soil Salmonella needs water, food source and the right conditions such as pH

25

and temperature. If manure is treated effectively then the Salmonella contamination can be

reduced so it is less applied to the soils. Manure is commonly treated by changing the pH and

temperature (Davies and Wray, 1996).

On the soil, Salmonella counts start to decrease and will eventually become low or non-

detectable. Salmonella has been found to survive in the soil for up to 900 days. Some

research has found that Salmonella will reach low levels over 30 days. It is recommended to

not use produce, roots or tubes between 30 days of the manure being spread on the soil. Birds

and insects such as flies are also very important vectors for the widespread transmission of

Salmonella in the environments (Davies and Wray, 1996).

The infection of wild bird populations with Salmonella has been linked with proximity to

farms and the incidence of human salmonellosis in the same area (Monaghan et al, 1985).

The common house fly can also be a carrier of Salmonella. This is a problem on dairy farms

and poultry farms. Salmonella survives in flies for up to 4 weeks. Flies inoculated with

Salmonella show a total defecation output of as much as 107 cfu. This is a problem as flies

that come into contact with manure food and water can transmit Salmonella.

Rapid transmission of Salmonella between the host species can also occur by the passage of

the bacteria from infected animals to fruit and vegetables due to the field being fertilised with

raw untreated manure. The detection of Salmonella on vegetables is linked with warm, moist

weather conditions during summer seasons. When Salmonella come into contact with

flowers, stems or fruits it colonizes the plant tissues.

Salmonella can be disseminated in soil even when fertiliser or manure is absent. This is a

result of water currents, rain runoff and underground springs which carry the contaminated

material onto the soil (Chao et al, 1987).

Salmonella spp. can survive in soils for 968 days. Survival times for up to 300 days in soils

spread with cattle slurry have been observed, with survival of 259 days reported for soils

amended with animal faeces (Jones, 1986). From a study conducted by Marsh et al (1998), S.

Typhimurium LT2 was detected from soil at a minimum concentration on 103 cells/ g.

Water sources:

Salmonella is frequently isolated from water sources. This source can aid the transmission

between hosts (Cherry et al, 1972). It is found that Salmonella can survive up to 15 days in a

26

septic tank system. Seepage can occur for the septic tanks onto the fields. Sewage and storm

runoff can also facilitate the bacterial passages into surface waters. Salmonella has a high

survival rate in aquatic environments. Wastewater and municipal wastes should only be used

if effective disinfecting systems are available. Surface water from streams and lakes can

contain pathogenic bacteria, protozoa and viruses which may lead to the contamination of

fruit and vegetable plants.

Manure:

The main causes of contamination includes animal manure or sewage waste. Manure should

be composted aerobically to reach 60-80 °C for a minimum of 15 days. Manure is often

applied to fields as fertiliser for fruit and vegetable production. Manure from pigs (or cattle)

is most commonly used. The application of untreated manure onto fields has a high risk of

contaminating the soil in the fields with harmful microorganisms such as E.coli and

Salmonella. According to a study conducted by Tauxe (1997) there is an increased

association between food-borne disease and fresh vegetable consumption in recent years.

Investigations have been conducted in some foodborne outbreaks linked to the consumption

of raw fruits and vegetables, and have identified manure as the primary source of

contamination.

Harvesting:

In an investigation of several foodborne illnesses associated with fresh produce (NACMCF,

1999) agricultural workers were in many cases the likely source of the pathogen.

Washing:

Washing of fruits vegetables during harvesting can remove soil and dirt. However, washing

can also be a source of microbial contamination. Chlorine can be used to disinfect and

prevent microorganisms growing during the sprouting of seeds (Sivapalasingam et al, 2000).

There are a wide range of agents available to disinfecting or sanitising fresh produce but their

efficiency can be variable and none of the disinfecting agents are able to ensure the

elimination of pathogens.

Retail:

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2672.2004.02208.x/full#b39

27

A survey of fresh fruit and vegetables was conducted by Abadias et al (2008) in retail

establishments in Catalonia in Spain in 2006 to determine if the produce was contaminated

with pathogenic microorganisms. A survey of fresh and minimally-processed fruit and

vegetables, and sprouts was conducted in several retail establishments in the Lleida area

(Catalonia, Spain) during 2005–2006 to determine whether microbial contamination for the

fresh-cut vegetables that we analysed showed that, in general, the highest microorganism

counts were associated with grated carrot, arugula and spinach 7.8, 7.5 and 7.4 log cfu g−1 of

aerobic mesophilic microorganisms; 6.1, 5.8 and 5.2 log cfu g−1 of yeast and moulds; 5.9,

4.0 and 5.1 log cfu g−1 lactic acid bacteria and 6.2, 5.3 and 6.0 log cfu g−1 of

Enterobacteriaceae. The processing stages of fresh-cut products, such as handling, cutting,

shredding, slicing and grating, are all potential sources of contamination, which could further

increase the microbial load.

Handling and personal hygiene in retail environment can also cause contamination of fruits

and vegetables. Workers should use hairnets and clean outfits when handling the product.

The main source of contamination in terms of product preparation for the market is probably

water. Water is essential for packinghouse operations either for washing the product and

containers.

Packaging and transport:

Foreign materials may be found on products or inside the packaging of products (López

Camelo, 2002). These materials include dust, animal faeces, grease, oils, human hairs,

insects, and plant debris. This is usually due to insufficient care in handling. Packaging

environment can create favourable conditions for pathogens to live in. Other considerations

to prevent cross contamination include not storing or transporting fruits and vegetables with

other fresh food items. The atmosphere at which a product is stored also influences microbial

development.

Processing of ready to eat fruit and vegetables:

28

Cutting, slicing, skinning and shredding removes or damages the protective surfaces of the

plant or fruit (Garg et al, 1990). Cutters and slicers can be sources of contamination. They

can since provide inaccessible sites, which harbour bacteria. It may be very difficult to clean

these sites on the slicers and cutters so cross contamination of bacteria from the equipment

onto the fruit and vegetables can occur. The presence of cut surfaces on fruit and vegetables

can allow bacteria to enter into the produce. This is very hard to eliminate during washing.

Bruises and cuts allow the microbial infiltration of the tissues. Exposing vegetables to various

types of cutting has been shown to result in a six to seven-fold increase in microbial numbers.

29

6. Risk characterisation

Table 2: Summarised qualitative risk assessment for Salmonella spp. in ready-to-eat fruit and vegetables

FARM

Output required Summarised information Assessed probability of concentration and

key uncertainties

P6: The probability that the soil is contaminated

with Salmonella

C6: The concentration of Salmonella in the soil

P10: The probability that the fruit and vegetables

with be exposed to Salmonella during packaging

on the farm

C10: The concentration of Salmonella being

contracted during packaging

Pathogens can contaminate fruit and

vegetables during different points

throughout pre harvesting and post

harvesting systems

Potential pre-harvest sources of

microorganisms include soil, faeces,

irrigation water, dust, insects, manure,

wild and domestic animals, and human

handling

Infected animals are likely to excrete

Salmonella into the soil, into manure, or

onto the plant

The probability of Salmonella in soil is

High probability of seeds and soil being

contaminated.

If seeds and soil are contaminated

probability of fruit and vegetable plants

to be contaminated is high

If contamination occurs during washing

of packaging of produce the

concentration of Salmonella is likely to

be low

Key Uncertainties:

Frequency of faecal contamination

Frequency of human contamination to

fresh produce

Numbers of organisms on the fresh

30

high. If contamination does occur the

concentration of Salmonella found in the

soil is likely to be high. Salmonella is

found to survive for 900 days in the soil.

Washing, storage and packaging of

produce on the farm can cause

contamination

If contamination is to occur during

washing, this risk may be low

If contamination is to occur during

packaging the risk of contamination may

be low.

produce if contamination occurs

DISTRIBUTION & STORAGE

31

P12: The probability of the fruit and

vegetables becoming exposed to Salmonella

in the wholesale market

C12: The concentration of Salmonella present

in the wholesale market environment

P13: The probability that the fruit and

vegetables will contract Salmonella during

processing, such as cutting, slicing and dicing

C13: The concentration of Salmonella that

could be contracted by the produce in the

processing station

It is unlikely that Salmonella will

contaminate the fresh produce during

transportation and storage of the

produce to wholesale markets.

If the transport containers are cleaned

properly and good hygienic practices

are in place with handlers of the fruit

and veg then the risk of contamination

will be low.

If contamination does occur the

concentration of organisms is likely to

be low

Fresh produce can become

contaminated during the processing of

the produce. Processing involves

preparing the fruit and veg for sale as

ready-to-eat products

Contamination can occur during

processing due to contaminated

equipment or surfaces used for slicing,

dicing and washing of the produce.

Contamination during processing

There are 2 scenarios which could result in

contamination:

Scenario 1:

Fresh produce may be contaminated during

harvesting in the farm. If not washed

adequately the produce may contain high

numbers of organisms. These organisms are

the transported to wholesale markets and pose

a high risk of salmonellosis.

Scenario 2:

The produce may be properly disinfected

during farming and may become

contaminated during the processing stages,

due to unsanitary processing equipment.

If the produce is contaminated, the

concentration may be high. There is a high

risk of causing salmonellosis if produce is

contaminated during processing as the ready-

to-eat products are consumed usually without

32

stages is likely to be due to cross-

contamination due to poor hygienic

practices in place in the processing

plant. Cutters and slicers can be

sources of contamination. They can

provide inaccessible sites, which

harbour bacteria. It may be very

difficult to clean these sites on the

slicers and cutters so cross

contamination of bacteria from the

equipment onto the fruit and

vegetables can occur

If processing equipment is improperly

sanitised then there is a high risk of

contamination of produce during

processing. It is uncertain what the

concentration of organisms on the

fresh produce will be if contaminated

during processing.

any preparation.

Key uncertainties:

Frequency of post-harvesting

contamination

Frequency of contamination in

wholesale markets

Frequency of contamination during

processing due to contaminated

equipment.

RETAIL & HOME

33

P18: The probability of the fruit and

vegetables being exposed to Salmonella

during storage in retail facilities

C18: The concentration of Salmonella present

in storage containers in retail facilities

P20: The probability of the produce

becoming contaminated with Salmonella in

the consumer’s home.

C20: The concentration of Salmonella

contracted by the produce whilst present in

the consumers home

P: Probability of exposure of Salmonella per

serving

C: Number of organisms consumed per

serving

Fresh fruit and vegetables are unlikely

to be contaminated with Salmonella in

retail environments. If they are

contaminated with Salmonella then the

number of organisms present is likely

to be low.

The contamination of the fresh

produce is likely to occur from the

processing stages.

Possible sources of contamination in

the retail facilities can be due to

unclean storage containers of cross-

contamination by human handling of

produce

Fresh produce is unlikely to become

contaminated in the consumer’s home

if stored under correct conditions.

Uncertainty associated with

temperature and storage abuse in the

home

Uncertainty associated with hygiene

Probably a Low probability of

exposure per serving, this risk could

be higher if post harvesting and

processing contamination occurs.

Key uncertainties:

Storage conditions in retail or home

environment

Sources of contamination in

consumers home

Preparation of produce before

consumption

34

practices in home.

The organism is unlikely to grow if

produce is stored in clean containers

and under the correct conditions in

retail and home environments.

Probability of contamination in these

environments is likely to be low, but

could be high if hygiene practices are

not in place.

If they are contaminated in both

environments the concentration of

organisms could be low, but may be

high if contamination occurred pre and

post processing stages.

35

7. Discussion

Recommendations

Seed/ plant imports: To ensure that there is no risk of contamination at this stage , it would

be wise for importers/farmers who will be growing them to know where the products are

coming from and the hygiene/ disinfection procedures in place. It would also be ideal to have

a quarantine area for imported goods to avoid cross contamination with equipment and other

plants in the facility.

Seed/ plant transport: To avoid possible contamination, any imported seeds/plants should

be transported in sealable, easily sterilised containers. These could then be easily re-sterilised

if contamination was later found in the seeds/plants and the containers can be disinfected to

remove the possibility of affecting any produce thereafter.

Soil: To reduce the level of contamination in soils prior to growing of fruit and vegetables, it

is advised to treat soils, by influencing the temperature or pH.

s

Manure/irrigation water/ fertilisers: The Food Safety Authority has produced draft

guidelines for growers to minimise the risks of microbial contamination of RTE crops (FSA

2009). The guidelines point at a range of measures that can help kill pathogens that are

present in manures and slurries including:

exposure to sunlight and ultra violet rays

high temperatures (above 55°C)

low acid or high alkaline conditions (use of quick lime or slaked lime to raise pH

levels)

drying

the passage of time (though some bacteria such as E. coli can survive for several

months)

The draft guidance recommends a package of measures before, during and after the growing

season including:

careful selection of sites of fields

lay off periods between application of manures and slurries before harvesting

36

not allowing livestock to roam on lands where crops will soon be grown or harvested

recommendations for storing manures and slurries

the use of potable water for washing procedures

Water for irrigation: To avoid contamination from the water used to irrigate crops, it is

recommended that the water source be isolated off and covered to protect against becoming

contaminated from nearby livestock, run off from the land, heavy rainfall causing seeping of

contaminated water into the water source. Elevating the source above ground level will aid

with this immensely. Water should also be tested for contamination at regular, pre-specified

intervals.

Animals (including insects and avian species): It is recommended to keep livestock away

from areas where crops are to be grown and harvested by putting up physical barriers around

fields and crops as well as careful selection of sites for crops (also taking into consideration

the factor of runoff of faecal matter into the soil from heavy rainfall).

Harvesting of fruit/vegetables: There are many recommended steps that need be taken at

this stage in order to avoid contamination of the crops.

Direct contamination from field workers hands (if being manually harvested from fields) or

handling when being prepared for processing is a significant aspect of this process. So a

effective hygiene regime for workers is key to reduce this risk.

To prevent cross contamination during harvesting, thorough cleaning and decontamination of

equipment, containers and transport vehicles must be undertaken.

Washing of produce on farm (Food Safety Authority of Ireland, 2000) : Washing produce

reduces the chances of micro-organisms and chemicals remaining on the surface. This is an

essential step since most contaminants are on the surface of fruit and vegetables and can also

contaminate surrounding produce, thus spreading the hazard. Most post-harvest processes

involve a considerable degree of water to surface contact.

The following points should be considered:

The washing process must be sufficient to remove soil, chemicals, micro-organisms

and foreign bodies.

37

If the produce is not subject to bruising, then vigorous washing increases the chances

of removing the microbiological or chemical hazard. Surface scrubbing using brushes

is even more effective but only if the brushes are regularly cleaned and sanitised.

A series of washes is more effective than a single wash if the produce is washed with

fresh clean water each time. This prevents the build-up of micro-organisms and

washed-off chemicals in the wash water.

Wash water should be maintained below 10°C to reduce the growth rate of

microorganisms that are washed off the fresh produce. This is important if water is

not replaced frequently with clean water.

Wash water must be renewed frequently to prevent a build-up of micro-organisms and

preferably be treated with an effective antibacterial water treatment, such as chlorine,

with frequent monitoring to ensure effective concentrations are maintained.

The inclusion of a decontamination step to destroy micro-organisms should be

considered where appropriate. It is especially important where the quality of water

cannot be guaranteed or when produce items are intended to be eaten without further

cooking. However, a decontamination step may only be effective if produce is pre-

washed in potable water to remove as much soil as possible before decontamination.

This ensures that the decontamination step, using water treated with an antibacterial

treatment like chlorine, remains effective. Organic matter inactivates chlorine.

Storage of produce on farm: To avoid contamination on the farm when storing produce, it

is essential that good hygiene practices are upheld so that there are no pathogenic bacteria

(for example, Salmonella) left on the surfaces of the fruit and vegetables and the containers

that they are being stored in so that they can grow and proliferate during storage at ambient or

refrigeration temperatures, both at which Salmonella can grow, abet sub-optimally.

Packaging on farm: (Safefoods, 2007) Modified Atmospheric packaging (MAP) is defined

as an atmosphere created by altering the normal composition of air to provide an atmosphere

capable of extending shelf-life. In MAP, gases such as oxygen, carbon dioxide and nitrogen

are used to alter the composition of the atmosphere around the product so that the storage life

can be extended. The product is then sealed in a wrap like polyethylene, polypropylene,

polyvinyl chlorine or edible film. This is the optimal packaging type for storing fresh

produce in as it reduces risk of pathogenic bacteria proliferating on the crops.

38

Tissue disruption caused by processing results in elevated respiration and transpiration, which

can lead to rapid deterioration. In addition, cut tissues release nutrients that support the

growth of micro flora present on raw produce. The O2 level in packs of fruit or vegetables is

usually kept between one and five per cent, which will reduce the respiration rate and,

therefore, oxidative breakdown of fruits and vegetables (Lee, Arul et al. 1995). Respiration

uses O2 and typically produces CO2 therefore making packages anaerobic. O2 levels below

eight per cent also reduce the level of ethylene, which delays ripening and maturation.

However, low levels of O2 can increase anaerobic respiration and sensory degradation.

Given that MAP alone is not sufficient to prevent pathogen growth, chilling is extremely

important and Hazard Analysis Critical Control Point (HACCP), Good Manufacturing

Practice (GMP) and Good Agricultural Practice (GAP) should be in place to prevent

pathogen contamination.

Transport of fruit and vegetables: As recommended before with seeds/plants, packaged

goods should be transported in sealable, easily sterilised containers. This helps prevent

possible contamination from the environment and from the transport vehicle itself. It also

protects the products when being moved around and transferred to warehouses and retail

locations. These could then be easily re-sterilised and can be disinfected to remove the

possibility of affecting any produce thereafter. Fresh fruit and vegetables also need to be

transported in chilled vehicles so as to preserve them and reduce risk of contaminates

growing.

Wholesale market: Even though the produce is usually packaged and sealed at this point, it

is still crucial for wholesalers to be as vigilant as if the produce was uncovered. If handled

improperly, fruits and vegetables can be crushed or damaged, allowing for easy proliferation

of pathogenic bacteria. The transport vehicles that are used to distribute the produce must be

cleaned down and decontaminated as standard and be refrigerated to reduce bacterial growth.

Processing station:

Preliminary washing: To avoid contamination, produce that comes into a processing plant

needs to be washed to remove any remaining debris, soil and possible contaminants on the

surface of the fruit or vegetables. Also, potable or disinfected water must be used so as not to

add any more bacteria onto the surfaces of the produce.

39

Slicing or shredding: Once any stalks and outer leaves are trimmed and removed from

vegetables, they are sliced or shredded, usually using machinery for both steps. Given this, all

machinery must be disinfected and cleaned regularly and very thoroughly in order to avoid

microbial build up, growth and subsequent cross contamination into the internal tissues of the

fruits and vegetables, which are optimal for bacteria growth and proliferation.

Washing/Disinfection: Again, as mentioned previously, washing is a key step to remove

possible contaminants on the surface of the produce. Bacteria can also be internalised via

waterborne contamination. This can occur when fruits are put into a wash tank and water is

taken up into fruits, particularly when the fruits are warm and the wash water is cold.

Therefore, clean, potable water must be used.

Internalisation of contaminants into the internal tissues is a significant problem as washing

will not remove these contaminants. Great care needs to be taken at this step, along with all

previous and subsequent steps to avoid this.

An effective decontamination stage is essential prior to packaging to help reduce the level of

pathogenic and spoilage organisms in RTE produce. The most common substance used for

decontamination is chlorine, however, care must be taken so that appropriate concentrations

are used and that organic matter is completely removed from the produce as it would deem

the chlorine ineffective.

Packaging: As with packaging on the farm, the same procedures can be used for processing

for retail. A comprehensive strategy should be employed at this stage so as to keep

uncontaminated produce free from contamination or produce that has contaminated can be

preserved so as to avoid growth and proliferation. Use of packaging such as MAP along with

storage at refrigerated temperatures is therefore essential here.

Retail storage: Fresh produce needs to be stored at refrigerated temperatures of 2-5°C.

Ideally, they must be kept separately, or stored at the top of the fridges if being stored along

with other raw foods, as they can cause cross contamination if being stored improperly. This

is key especially since a large portion of fruits and salad vegetables are not subjected to

another heating step, so pathogenic contaminants cannot be killed at this stage in the

pathway.

Consumer: In the case of ready-to-eat (RTE) fruits and vegetables, they are often sold in

individual portions so make them perfect for eating straight away, marketed as a on the go

40

snack or lunch accompaniment. This being said, many people do not wash or treat them in

any way, so it is a notable source of disease from pathogen bacteria present in RTE products,

such as Salmonella.

To avoid this, consumers should be advised to wash fruits and vegetables, even if pre-

packaged.

Storage at home: In a domestic setting, this is a crucial step to not only prevent

contamination of RTE fruit and vegetables but can be where contamination can happen

frequently if they are stored improperly. To avoid contamination, these products need to be

stored, refrigerated, separately from raw produce such as raw meats, either in a chilled drawer

or in sealed containers so that any liquids cannot drop into them or that they do not touch and

become cross contaminated. Good hygiene of the fridge is also essential, since there are

pathogenic bacteria that can persist and survive at refrigeration temperatures and begin to

grow once they come in contact with foods.

Preparation before use: To avoid contamination, fresh fruit and vegetables that will not

undergo any further cooking must be prepared separately to raw meats, especially chicken in

regard to Salmonella contamination. Hygiene of the person preparing the foods as well as all

the utensils used is of the greatest importance, as it is through those that contamination occurs

and leads to food-borne gastroenteritis. Knowledge of effective procedures for hand washing

as well as decontamination of tools, utensils and containers must be in place, even at a

domestic level.

8. Conclusions

41

Bibliography

Abadias, M., Usall, J., Anguera, M., Solson, C., Vinas, I. (2008). Microbiological quality

of fresh, minimally-processed fruit and vegetables, and sprouts from retail establishments. Int

J Food Microbiol 123:121–9

Adak, G.K., Meakins, S.M., Yip, H., Lapman, B.A. and O’ Brien, S.J. (2005). Disease

risks from foods, England and Wales, 1996- 2000, Emerg Infect Dis, 11 (3)

Beuchat, L.R. (2002). Ecological factors influencing survival and growth of human

pathogens on raw fruits and vegetables. Microbes and Infection 4 413–423

CDC (2013). Salmonella: Diagnosis and Treatment. Available at:

http://www.cdc.gov/salmonella/general/diagnosis.html [Accessed 4 March 2015]

Chao, W., Ding, R. and Chen, R. (1987). Survival of pathogenic bacteria in environmental

microcosms. Chinese J. Microbial Immunol. 20:339-348.

Cherry, W. B., J. B. Hanks, B. M. Thomason, A. M. Murlin, J. W. Biddle, and J. M.

Croom. (1972). Salmonellae as an index of pollution of surface waters. Appl.

Microbiol. 24:334-340

Christenson J.C. (2013). Salmonella infections. Pediatr Rev. 34(9):375-83.

D’Aoust, J.Y. (2000). Salmonella. In The Microbiological Safety and Quality of Food,

Volume II (eds. Lund, B.M., Baird-Parker, T.C., and G. W. Gould) 1233-1299

Davies, R.H. and Wray, C. (1996). Seasonal variations in the isolation of Salmonella

typhimurium, Salmonella enteritidis, Bacillus cereus and Clostridium perfringens from

environmental samples. J. Vet. Med. Ser. 43:119-127.

FDA (2012). Salmonella spp. Bad Bug Book: Foodborne Pathogenic Microorganisms and

Natural Toxins Handbook Available at:

http://www.fda.gov/food/foodborneillnesscontaminants/causesofillnessbadbugbook/

ucm069966.htm [Accessed 5 March 2015]

Food Safety Authority of Ireland (2000). Code of Practice For Food Safety in the Fresh

Produce Supply Chain in Ireland - Code of Practice No.4. Available at:

http://www.fda.gov/food/foodborneillnesscontaminants/causesofillnessbadbugbook/ucm069966.htm

http://www.fda.gov/food/foodborneillnesscontaminants/causesofillnessbadbugbook/ucm069966.htm

http://www.ncbi.nlm.nih.gov/pubmed/24000341

http://www.ncbi.nlm.nih.gov/pubmed/?term=Christenson%20JC%5BAuthor%5D&cauthor=true&cauthor_uid=24000341

http://www.cdc.gov/salmonella/general/diagnosis.html

42

http://www.teagasc.ie/faol/NR/rdonlyres/2CA6F678-AE67-4B88-BAEB-

B5D4BC9D0B80/62/Fresh_Produce_Code1.pdf [Accessed 3 March 2015]

Food Safety Authority of Ireland (2011). Salmonella species. Available at:

https://www. fsai .ie/ salmonellaspecies .html [Accessed 3 March 2015]

Food Standards Agency (2009). ”Managing Farm Manures for Food Safety Guidelines for

growers to reduce the risks of microbiological contamination of ready-to-eat crops” Available

at:http://www.food.gov.uk/sites/default/files/multimedia/pdfs/manuresguidance.pdf

[Accessed 3 March 2015]

Garg, N., Churey, J.J. and Splittstoesser, D.F. (1990). Effect of processing conditions on

the microflora of fresh-cut vegetables. Journal of Food Protection 53: 701-703.

Giannella RA. (1996). Salmonella. In: Baron S, editor. Medical Microbiology 4th edition.

Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter

21. Available at: http://www.ncbi.nlm.nih.gov/books/NBK8435/ [Accessed 7 March 2015]

Hara-Kudo, Y. and Takatori, K. (2010). Contamination level and ingestion dose of

foodborne pathogens associated with infections. Epidemiol. Infect. 23, 1–6.

HPSC (2007). Epidemiology of Salmonellosis in Ireland, 2007. Available at:

http://www.hpsc.ie/A-Z/Gastroenteric/Salmonellosis/Publications/AnnualReportsonSalmonel

losisinIreland/File,3853,en.pdf [Accessed 6 March 2015]

HPSC (2008). HPSC Annual Report 2008, Infectious Intestinal Diseases. Available at:

http://www.hpsc.ie/A-Z/Gastroenteric/Salmonellosis/Publications/AnnualReportsonSalmonel

losisinIreland/File,4246,en.pdf [Accessed 6 March 2015]

HPSC (2010). Indigenous salmonellosis low in Ireland. Available at:

http://ndsc.newsweaver.ie/epiinsight/hkybj5cdjbb1l6t6mifk6p [Accessed 1 March 2015]

Jones, P.W. (1986). Sewage sludge as a vector of salmonellosis. In: Epidemiological Studies

of Risks Associated with the Agricultural Use of Sewage Sludge. J.C. Block, A.H. Haielaar,

and P. L’Hermite (eds), pp. 21–33.

http://ndsc.newsweaver.ie/epiinsight/hkybj5cdjbb1l6t6mifk6p

http://www.hpsc.ie/A-Z/Gastroenteric/Salmonellosis/Publications/AnnualReportsonSalmonellosisinIreland/File,4246,en.pdf




http://www.ncbi.nlm.nih.gov/books/NBK8435/

http://www.food.gov.uk/sites/default/files/multimedia/pdfs/manuresguidance.pdf

https://www.fsai.ie/salmonellaspecies.html

http://www.teagasc.ie/faol/NR/rdonlyres/2CA6F678-AE67-4B88-BAEB-B5D4BC9D0B80/62/Fresh_Produce_Code1.pdf

http://www.teagasc.ie/faol/NR/rdonlyres/2CA6F678-AE67-4B88-BAEB-B5D4BC9D0B80/62/Fresh_Produce_Code1.pdf

43

López Camelo, A.F. (2002). Manual for the preparation and sale of fruits and vegetables:

from field to market. FAO agricultural services bulletin. Available at:

http://www.fao.org/docrep/008/y4893e/y4893e00.HTM [Accessed 3 March 2015]

Marsh, P., Morris, N. Z. and Wellington, E.M.H. (1998). Quantitative molecular detection

of Salmonella typhimurium in soil and demonstration of persistence of an active but non-

culturable population. FEMS Microbiology Ecology, 27: 351–363

McCullough, N. B. and C. W. Eisele (1951). "Experimental Human Salmonellosis: III.

Pathogenicity of Strains of Salmonella newport, Salmonella derby, and Salmonella bareilly

Obtained from Spray-Dried Whole Egg." The Journal of Infectious Diseases 89(3): 209-21

McKeown, P., Garvey, P. and Cormican, M. (2012). Eludicating the Epidemiology of

Human Salmonellosis: The Value of Systematic Laboratory Characterisation of Isolates.

Available at: http://cdn.intechopen.com/pdfs-wm/37791.pdf [Accessed 7 March 2015]

Melloul, A.A., Hassani, L. and Rafouk, L. (2001). Salmonella contamination of vegetables

irrigated with untreated wastewater. World J Microbiol Biotechnol 17, 207–209.

Monaghan, P., Shedden, C. B., Ensor, K., Fricker, C. R. and R. W. A. Girdwood, R. W.

A. (1985). Salmonella carriage by herring gulls in the Clyde area of Scotland in relation to

their feeding ecology. J. Appl. Ecol. 22:669-680.

NACMCF. (1999). National Advisory Committee on Microbiological Criteria for Foods:

Microbiological safety evaluations and recommendations on fresh produce. Food Control 10:

117-143.

NACMCF (1999). National Advisory Committee on Microbiological Criteria for Foods:

Microbiological safety evaluations and recommendations on sprouted seeds. International

Journal of Food Microbiology 52: 123-153.

NSRL. (2008). Report of an International Outbreak Investigation into a Multi-country

Outbreak of Salmonella Agona, Europe, 2008. Available at:

http://www.hpsc.ie/A-Z/Gastroenteric/Salmonellosis/Outbreaks/File,12549,en.pdf [Accessed

7 March 2015]

http://www.hpsc.ie/A-Z/Gastroenteric/Salmonellosis/Outbreaks/File,12549,en.pdf

http://cdn.intechopen.com/pdfs-wm/37791.pdf

http://www.fao.org/docrep/008/y4893e/y4893e00.HTM

44

NSSLRL (2010). Annual Report for 2011. Available at:

http://www.nuigalway.ie/research/salmonella_lab/downloads/nsslrl_annual_report_2011.pdf


Safefoods. (2007). Consumer focused review of the fruit and vegetable food chain. Available

at: http://www.safefood.eu/safefood/files/89/8964f665-9bea-4c05-bacf-79e1eda9cd98.pdf


Sivapalasingam, S. Kimura, A., Ying, M., Frisch, A., Barrett, E., Phan, Q., Sillam, P.,

Reddy, S., Breslowsky, T., Gould, E., Van Duyne, M.S. and Slutsker, L. (2000). A

multistate outbreak of Salmonella Newport infections linked to mango consumption,

November-December 1999. Infectious Diseases Society of America, Abstract 52.

Slauch, J., Taylor, R. and Maloy, S. (1997). Survival in a cruel world: how Vibrio cholerae

and Salmonella respond to an unwilling host. Genes Dev. 1997 11(14) 1761-74.

Taormina, P.J., Beuchat, L.R. and Slusker, R. (1999). Infections associated with eating

seed sprouts: An international concern. Emerg. Infect. Dis. 5: 629-634.

Tauxe, R., Kruse, H., Hedberg, C., Potter, M., Madden, J. and Wachsmuth, K. (1997).

Microbiological hazards and emerging issues associated with produce: A preliminary report

to the National Advisory Committee on Microbiologic Criteria for Foods. J. Food Prot. 60:

1400-1408.

WHO/FAO (2002). Risk Assessments of Salmonella in Eggs and Broiler Chickens.

Available at: http://www.fao.org/docrep/005/y4392e/y4392e09.htm [Accessed 5 March

2015]

http://www.fao.org/docrep/005/y4392e/y4392e09.htm

http://www.ncbi.nlm.nih.gov/pubmed/9242485

http://www.ncbi.nlm.nih.gov/pubmed/?term=Maloy%20S%5BAuthor%5D&cauthor=true&cauthor_uid=9242485

http://www.ncbi.nlm.nih.gov/pubmed/?term=Taylor%20R%5BAuthor%5D&cauthor=true&cauthor_uid=9242485

http://www.ncbi.nlm.nih.gov/pubmed/?term=Slauch%20J%5BAuthor%5D&cauthor=true&cauthor_uid=9242485

http://www.safefood.eu/safefood/files/89/8964f665-9bea-4c05-bacf-79e1eda9cd98.pdf

http://www.nuigalway.ie/research/salmonella_lab/downloads/nsslrl_annual_report_2011.pdf

Documents

Microbial Risk Assessment of Salmonella in Ready-To-Eat fruit and vegetables