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Salmonella in Low-Moisture Foods and Ingredients

Linda J. Harris Department of Food Science and Technology Western Institute for Food Safety and Security

Western Center for Food Safety University of California, Davis

June 8, 2010 Sacramento, CA

Outline

•  Salmonella –  Characteristics

•  Salmonellosis –  Example outbreaks –  Example recalls –  Example surveys

•  Myths and misconceptions •  Summary

Salmonella – factoids

•  Salmonella enterica –  Primary source: intestinal track of humans/animals –  Approximately 2,500 serovars

•  Enteritidis, Montevideo, Typhimurium are serovars

–  Serovars can by subtyped by many different methods •  Phage typing

–  Salmonella Enteritidis PT 8, 13a, 4, are common –  Salmonella Enteritidis PT 30, 9c are rare

•  Fingerprinting (PFGE) –  Used to further distinguish serovars of Salmonella

and other pathogens

Salmonelloisis factoids •  Associated with many foods

–  Animal origin (meat, poultry, eggs, dairy) –  Raw fruits and vegetables –  Low-moisture foods

•  Symptoms range: –  None to severe (septicemia infection of blood) –  Most common:

diarrhea, fever, vomiting, dehydration, cramps

•  Long-term impact: reactive arthritis •  Infective dose:

–  In some cases estimated less than 15 to 20 cells –  Low in dried foods?

•  Depends on age and health •  Probably serovar, physiological state, food matrix

•  Outbreaks with spices –  Spices: Pepper, paprika (1995, 2009, 2009-10) –  “Veggie Bootie” seasoning (2007)

•  Outbreaks with nuts, seeds, legumes: –  Almond (2000-01, 2003-04, 2006) –  Coconut (dried) (1999) –  Peanut (1994-95, 2001, 2005)

•  peanut butter (1996, 2006, 2009) –  Sesame seed

•  Halva (2001), Tahini (2002, 2003)

•  Outbreaks with other dry foods and ingredients: –  Chocolate (2001-02, 2006) –  Skim milk powder, dried eggs (1993, 2005, 2008) –  Cereal (1998, 2008) –  Dry pet food/pet treats (2004-05, 2006-07, 2008)

Salmonellosis and low-moisture foods 1990-

•  Outbreaks with spices –  Spices: Pepper, paprika (1995, 2009, 2009-10) –  “Veggie Bootie” seasoning (2007)

•  Outbreaks with nuts, seeds, legumes: –  Almond (2000-01, 2003-04, 2006) –  Coconut (dried) (1999) –  Peanut (1994-95, 2001, 2005)

•  peanut butter (1996, 2006, 2009) –  Sesame seed

•  Halva (2001), Tahini (2002, 2003)

•  Outbreaks with other dry foods and ingredients: –  Chocolate (2001-02, 2006) –  Skim milk powder, dried eggs (1993, 2005, 2008) –  Cereal (1998, 2008) –  Dry pet food/pet treats (2004-05, 2006-07, 2008)

Salmonellosis and low-moisture foods 1990-

Long shelf life

Consumed without further kill step

Often ingredients in foods

Apparently low infectious dose

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Why Apparent Increase?

•  Increased National focus on food safety •  Epidemiology

–  Increased investigation, cooperation, technology •  Microbiology

–  Improved methodologies •  Routine subtyping (serotyping/fingerprinting)

–  Digital sharing of fingerprints across the US –  International collaboration

•  To date, most low-moisture food/ingredient outbreaks have been associated with rare serovars or unique fingerprints

–  Facilitated investigation of widespread, sporadic illnesses

Almond Outbreaks 01,04,06

•  Raw almonds from California •  10/2000 - 7/2001

–  Salmonella Enteritidis Phage Type (PT) 30 –  168 cases Canada and U.S.

•  9/2003 – 6/2004 –  Salmonella Enteritidis PT 9c

•  47 cases in U.S. and Canada –  Handler (processor) unrelated to 2001 outbreak

•  12/2005 – 8/2006 (raw almond-link suspected) –  Salmonella Enteritidis Phage Type 30

•  15 cases Sweden

Isaacs et al. 2005. JFP 68:191-198

Outbreak of salmonellosis (S. Enteritidis PT 30) in raw almonds

Isaacs et al. 2005. JFP 68:191-198

2000 2001

Outbreak of salmonellosis (S. Enteritidis PT 30) in raw almonds

Isaacs et al. 2005. JFP 68:191-198

2000 2001

Rare strain (Phage Type) of Salmonella

Protracted outbreak (8 months)

International: Ontario, Canada routinely phage typing S. Enteritidis isolates

Peanut Butter 2008-2009 Salmonella Typhimurium, rare fingerprint

666* (691) cases in 45 (46) states and Canada (1)

>119 hospitalizations, 9 deaths

*Cases reported as of February 24, 2009. Cases reported in the previous 3 weeks might not yet be reported.

CDC, 2009

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666* (691) cases in 45 (46) states and Canada (1)

>119 hospitalizations, 9 deaths

*Cases reported as of February 24, 2009. Cases reported in the previous 3 weeks might not yet be reported.

Outbreak spanned 6 months

691 cases/ 6 months /46 states = 2 to 3 cases/month/state

Peanut Butter Outbreak 2008-2009

•  Peanut Corporation of America –  Passed AIB audit, state audit –  Failed Nestle audit

•  November 08 – March 09 –  691 cases, 9 deaths –  46 states and Canada

•  Recall of 3908 products over 2 years –  2007 to 2008

•  Product used as an ingredient –  Peanut paste –  Items as diverse as pet food, ice cream and energy bars

•  Raised issues related to ingredients in general

Salami 2009-2010 (9 months, 44+ states) (Black and Red Pepper - ingredient)

Salmonella Montevideo + Salmonella Seftenberg (?) 252 cases + 9? (4/1/10, CDC update)

Numerous Recalls

USDA/FSIS – meats long shelf life

FDA – spices CDC, 2010

Salmonella Montevideo

•  Common serovar (top 10), common fingerprint –  CDC used new statistical method to determine if

cases from PulseNet (reporting system) were above historical normal

–  Shopper card information used to narrow foods/brands

•  Ill persons gave permission, case control study

–  More identified outbreaks in future?

E. coli O157:H7

•  Nestle cookie dough outbreak –  June 2009 –  72 cases, 10 HUS

•  January 2010 Nestle announces switch to heat-treated flour after E. coli O157:H7 detected in 2 dough samples –  We do not know that flour is the source for E. coli O157.H7,” “It

is however a raw agricultural commodity and raw agricultural commodities can carry some risk. To improve our product safety and minimize risk we've made a prudent decision to switch to heat-treated flour.

http://www.foodqualitynews.com/Food-Alerts/Nestle-USA-heat-treated-flour-switch-planned-for-months

Recalls – Spices

•  1970-2003 – Vij et al., 2006. J. Food Prot. 69:233-237

•  21 recalls •  20 for Salmonella •  1 for Listeria monocytogenes

•  2004-present – ?

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Recalls – Nut Products

•  almonds (01,04), hazelnuts (09), macadamia (09), peanut butter (07, 09), pecans (09), pistachios (09), pine nuts (10) – Salmonella

•  walnuts (09) – Listeria monocytogenes

Recalls? What’s New?

•  Buyer testing programs –  have increased sampling and sample size

•  FDA directive –  Field assignment to inspect nut facilities and to do

environmental swabs of facilities –  Reportable Food Registry (2009)

•  Success of nut industry? –  Record crops, increased consumption, switch to out

of hand, raw

FDA Reportable Food Registry

•  New – Fall 2009 – Amendment to FDCA, 2007

•  All foods covered by FDA except infant formula and dietary supplements

•  Electronic portal for Industry http://rfr.fda.gov –  to report when there is reasonable probability

that an article of food will cause serious adverse health consequences

Surveys

•  Few have been done –  Typically: small sample size, multiple products

•  Retail Surveys – UK –  Little et al., 2010. Food Microbiol. 27:171-174.

•  Salmonella in 25-g samples –  2 of 469 Brazil nut samples (0.4%) –  Salmonella Senftenberg or Tennessee 9 or 23 per 100 g –  1 of 105 mixed kernels (5 nuts; 0.9%)

–  Little et al. 2009 J. Food Prot. 72:853-855 •  Salmonella in 1 of 727 (0.1%) roasted nuts (pistachio)

–  Willis et al., 2010. Food Microbiol. 26:847-852 •  Salmonella in 23 of 3735 “seeds” (0.6%): 13 sesame seed

Can Salmonella be isolated from Almonds? Survey of Almonds from Huller/Sheller (100 g)

Year Number Positive

% Positive MPN/100 g Number MPN >1.2 /100 g

2001 12 of 2003 0.60 Not done Not done

2002 24 of 2012 1.2 <1.2 - 2.9 1 of 24

2003 15 of 1764 0.80 <1.2 - 1.4 3 of 15

2004 12 of 1643 0.73 <1.2 - 1.4 1 of 12

2005 2006 2007

18 of 1852 30 of 1899 15 of 1799

0.97 1.6

0.83

<1.2 - 1.4 <1.2 – 15.5 Not done

1 of 18 10 of 30 Not done

Average 0.99% positive samples per year

Uesugi, Danyluk and Harris, 2007 JFP 70:820-827

Can Salmonella be isolated from Almonds? Survey of Almonds from Huller/Sheller (100 g)

Year Number Positive

% Positive MPN/100 g Number MPN >1.2 /100 g

2001 12 of 2003 0.60 Not done Not done

2002 24 of 2012 1.2 <1.2 - 2.9 1 of 24

2003 15 of 1764 0.80 <1.2 - 1.4 3 of 15

2004 12 of 1643 0.73 <1.2 - 1.4 1 of 12

2005 2006 2007

18 of 1852 30 of 1899 15 of 1799

0.97 1.6

0.83

<1.2 - 1.4 <1.2 – 15.5 Not done

1 of 18 10 of 30 Not done

Average 0.99% positive samples per year

Uesugi, Danyluk and Harris, 2007 JFP 70:820-827

Over 100 isolates – 50 unique serovars

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and Jenny Scott, FDA

FDA Test Data Surveys

•  Processors “surveys” – Routine testing is unpublished – Suppliers and buyers

•  Data is likely significant –  In volume

•  Lack of method standardization •  Not typically shared or published

Hazard Analysis - Nuts

•  Salmonella – Primary pathogen of concern – Given: Outbreaks, recalls, surveys

•  Prevalence and levels low – Few available studies –  (none for non-Salmonella)

Salmonella – myths and misconceptions

•  Salmonella is only of animal/fecal origin

•  Salmonella doesn’t survive at cold temperatures

•  Salmonella doesn’t survive in dry foods

•  Salmonella has a high infectious dose

•  Salmonella is easily killed by heat (in dry foods)

•  Traditional cleaning and sanitation can be applied to dry food processes.

M/M: Salmonella is only of animal/fecal origin

Routes of Contamination

Beuchat, 1996

ANIMALS, BIRDS

silage, feed plants

PRODUCE HUMANS water

feces insects

sewage

soil

meat, milk, eggs

(cross contamination)

harvesting, handling, processing environments

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Farm 1

Farm 2

Farm 3

15 of 32 - 61 hectare (150 acre) positive orchards - 10 square miles ���Origin of S. Enteritidis PT 30 never identified

Interstate 5

California aquiduct

100% of 53 isolates over 5 years (2002-2006) are ���Salmonella Enteritidis PT 30

Does Salmonella survive in soil?

•  Soil type –  Cerini clay loam (outbreak-associated orchard) –  Milham sandy loam (distant orchard)

•  Temperature –  35 ± 2 ºC –  20 ± 2 ºC

•  Moisture levels –  Field capacity –  Saturated

Cereni clay loam

Milham sandy loam

68 ± 2 ºF

68 ± 2 ºF

95 ± 2 ºF

95 ± 2 ºF

Temperature is the most important factor influencing Salmonella survival

Danyluk et al. 2008 J. Appl. Microbiol. 104:1391-1399

0

1

2

3

4

5

6

7

0 2 4 6 8 10 12 14

Time(days)

Lo

g C

FU

/g d

w

HE

water

no addition

Addition of Hull Extract to Soil

Addition

Danyluk et al. 2008 J. Appl. Microbiol. 104:1391-1399

Almonds are shaken from the trees to the ground where they dry for 7 to 10 days.

Dried almonds are gathered into windrows.

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Almonds are harvested from the field and may be

stockpiled before hulling and shelling.

Huller/Shellers Handlers

Hull

Shell

Hull

Shell

Approximately 250 Huller/Shellers

Kernel

Approximately 100 “Handlers” Treat and Package Final Product

M/M Salmonella doesn’t survive dry conditions or in the cold

How well does Salmonella survive on almonds?

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

0 25 50 75 100 125 150 175

Time (days)

Lo

g C

FU

/alm

on

d

Uesugi, Danyluk and Harris, 2006 JFP 69:1851-1857

Calculated reduction is:���23°C (73°F) 0.25 log CFU/month 4ºC (39°F) 0 log CFU/month -20ºC (-4°F) 0 log CFU/month

23ºC/73ºF

-20ºC/0ºF

4ºC/40ºF Long-term survival (months) noted in: Chocolate Halva Pecans (Beuchat, unpublished) Pistachios (Harris, unpublished) Black pepper Walnut kernels (Harris, unpublished)

1 log is a 10-fold or 90%

How well does Salmonella survive on almonds?

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

0 25 50 75 100 125 150 175

Time (days)

Lo

g C

FU

/alm

on

d

Uesugi, Danyluk and Harris, 2006 JFP 69:1851-1857

Calculated reduction is:���23°C (73°F) 0.25 log CFU/month 4ºC (39°F) 0 log CFU/month -20ºC (-4°F) 0 log CFU/month

23ºC/73ºF

-20ºC/0ºF

4ºC/40ºF

1 log is a 10-fold or 90%

M/M Salmonella has a high

infectious dose

1950s estimates near 100,000/serving

Assumption - growth: nutrients, moisture, temperature and time

critical factors for outbreaks

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Dose Response Model

   β-­‐Poisson  Dose-­‐Response  model  for  Salmonella  spp.  FAO,  2002.  

Food Salmonella Infectious Dose (cells per serving)

Cheddar cheese (1976) Heidelberg 100

Cheddar cheese (1984) Typhimurium 1 to 10

Chocolate (1973-74) Eastbourne 100

Chocolate (1982) Napoli 10 to 100

Chocolate (1987) Typhimurium ≤10

Paprika coated potato chips (1993)

Saint-paul, Javiana, Rubislaw

≤45

Ice cream (1994) Almonds (2001)

Enteritidis Enteritidis PT30

≤28 <10 to 200+

Examples of salmonellosis outbreaks with known low infectious doses

Salmonella in low-moisture foods: Survey of Almond Kernels (100 g)

Year Number Positive

% Positive MPN/100 g Number MPN >1.2 /100 g

2001 12 of 2003 0.60 Not done Not done

2002 24 of 2012 1.2 <1.2 - 2.9 1 of 24

2003 15 of 1764 0.80 <1.2 - 1.4 3 of 15

2004 12 of 1643 0.73 <1.2 - 1.4 1 of 12

2005 2006 2007

18 of 1852 30 of 1899 15 of 1799

0.97 1.6

0.83

<1.2 - 1.4 <1.2 – 15.5 Not done

1 of 18 10 of 30 Not done

Uesugi, Danyluk and Harris, 2007 JFP 70:820-827 Levels less than 3 to 15.5 MPN/100 g

M/M Salmonella is easily killed

by heat

165°F

Survival of S. Enteritidis PT30 on almonds exposed to hot oil 240, 250 and 260°F

Log

CFU

/g

Treatment time (min)

Du, Abd, McCarthy, and Harris, in press

Survival of S. Enteritidis PT30 on almonds exposed to hot oil 240, 250 and 260°F

Log

CFU

/g

Treatment time (min)

Du, Abd, McCarthy, and Harris, in press

Moist heat is more effective, Increased product moisture improves kill

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Temperature (°C/°F)

Time required for reduction (seconds)

4-log 10,000

fold 5-log

100,000 fold pasteurized

116/240 114 234 121/250 72 132 127/260 39 72

Time to 4- or 5-log reduction of Salmonella Enteritidis PT 30 on almonds exposed to hot oil,

according to the Weibull model 99% Confidence Interval

2 X

2 X

2 X

M/M Traditional cleaning and

sanitation can be applied to dry food processing facilities.

2 ml 3 ml 4 ml 0 ml

Dust A (1 g) Mixed With Water

1 ml 2 ml 3 ml 0 ml

Dust B (1 g) Mixed With Water

Du et al, .2010. J. Food Sci. 75:M7-M13

Salmonella Grows in Wet Almond Dust

Du et al. 2010. J. Food Sci. 75:M7-M13

0

1

2

3

4

5

6

7

8

Water Alcohol-based QUAT Aqueous-based QUAT

1 g H/S dust + 2 ml Salmonella (5 Log CFU/ml) + 1 ml treatment

0 hr

48 hr

Survival of S. Enteritidis NalR in Wet Dust Stored at 30°C for 48 h

Log

CFU

/g

Salmonella is Unaffected by Addition of 200 ppm Aqueous QUAT to H/S Dust

Trying to Make Sense of All the Data

Mean: 8 cases/year 78% chance of > 1 case/year 48% chance of > 10 cases/year 21% chance of > 100 cases/year

Risk Assessment of salmonellosis from Consumption���of Raw Almonds (Annual Illness) (@Risk Modeling Program)

Danyluk, Harris, and Schaffner, JFP 2006 69:1594-1599

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Mean: 8 cases/year 78% chance of > 1 case/year 48% chance of > 10 cases/year 21% chance of > 100 cases/year

Risk Assessment of salmonellosis from Consumption���of Raw Almonds (Annual Illness) (@Risk Modeling Program)

Danyluk, Harris, and Schaffner, JFP 2006 69:1594-1599

A 4 (10,000-fold) or 5 (100,000-fold) log reduction reduced chance of >1 case/year to a probability of less than 1 in 100 years. Almond Board based mandatory 4-log reduction on these data

Summary

•  Low-moisture foods including are increasingly recognized for association with Salmonella and salmonellosis

•  Challenges: low level prevalence, long-term survival, enhanced resistance, low dose?

•  Nuts –  Large category –  Risks may differ but generally categorized as one

•  Control –  Good Agricultural Practices, Validated Processes,

post-process Good Manufacturing Practices