EH 352 Food Poisoning

7/29/2019 EH 352 Food Poisoning

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Food poisoning

Allan R Mbewe

EH 352 Food Microbiology


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WHAT IS FOOD POISONING Definition: Food poisoning could include any

pathological condition conveyed by food or water e.g.Typhoid, dysentery, brucellosis etc. but in public healthterminology illnesses notified in their own right areexcluded from the term and the following definition isusually applied

An acute attack of diarrhoea and/or vomiting,nausea, abdominal pain and involvement of thenervous system coming on within a few hours (1-36hrs) of eating food which is contaminated orotherwise affected so as to cause these symptoms.


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TYPES OF FOOD POISONING

Bacterial food poisoning Non-bacterial food poisoning:

Chemical poisoningMetallic food poisoning

Intrinsic poisoning foods

Putrefied foods when it causes illness


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Bacterial food poisoning This is an illness due to ingestion of food which either contains

pathogenic organisms capable of setting up an acute inflammationof alimentary canal (food infection) or irritative substances knownas toxin which have been produced by the growth andmultiplication of organisms in the food before eating (foodintoxication). It should be noted that toxins may return theirportances after being exposed to temperatures sufficiently high todestroy the bacteria producing them.

The Salmonella group of infectionStaphylocal enterotoxinsClostridium welchii infectionsClostridium botulinum enterotoxinOther less common infections from other organisms such ashaemolytic steptococil, B. cereus, vibro parahaemolyticus,viruses such as echo and coxsackie and moulds such asAspergillus flavus


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Cont. Salmonella: These organisms inhabit the intestinal

tract of man, animals, birds, reptiles and insects(including cockroaches) and therefore anycontamination by faecal matter is likely to spread theinfection. The contamination may be direct by animals

or insects or unwashed hands or from crossedcontamination from raw meat, poultry carcases, duckeggs, dirty hen eggs or polluted water or indirectly viaflies, dust, fruit, or vegetables. The contamination islikely to spread illness if the type of food involvedspreading illness if the type of food involved is a goodmedia for bacteria growth and is held for several hoursat a dangerous temperature i.e. 5 60 0C.


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Cont. Staphylococci: Staphylococcus is common in

mucous membrane of nose, throat of evenhealthy people, also on human skin, ears andhair. They are present in very large numbers inboils, pimple, abscesses and suppurating wounds.It is also found in raw milk (mainly from mastitiscows) and dust. Consequently coughing,sneezing, hand to nose or hand to mouth contact,

suppurating wounds, etc. are all liable for foodcontamination and incubation at wrongtemperature are liable to cause products of toxin.


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Cont. Cl. welchii: It is found on dust, soil, clothing,

raw meat and faeces. And direct or indirectcontamination of a suitable food following byincubation is liable to result into an illness.

Cl. botalinum: This anaerobic organisms hasbeen isolated from dust, faeces, soil, mudfrom the sea bottom, mud from fish pondsand such contamination in law acid food and

packed in such a manner as to exclude oxygenis liable to permit the production of highlypoisonous poisons.


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Other organisms

Several other organisms may product food poisoninge.g. vibrio parahaemolyticus resulting from shell fish.Certain streptococcus from raw milk, protons from dust(in rice) all come from similar sources to the majorfood poisoning agents and similar principals therefore

apply i.e.Avoid faecal exposureWash hands before handling food.Avoid insect and rodent infestations

Protect from animal contaminationReduce dust to a minimumThoroughly cock all meat


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Cont.Do not hold any food at dangerous

temperatures.Give special attention to special foods.Use drinking water quality only.Pasteurise milk supplies.Provide hygienic abattoirs.Avoid cross contamination with raw meat.Medical examination of food handlers.

Avoid cross contamination with washed andcooked vegetablesWear clean overalls


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Chemical poisoning

Chemical food poisoning is rare but when it occursthe consequences can very serious

Symptoms:

Acute on set of less than one hour;

Vomiting, diarrhoea and

Burning sensations in the chest, neck andabdomen

Chronic poisoning; chemical builds up in the bodyover a period of time causing problems e.g. cancerand damage to nervous system


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Causes of chemical food poisoning Contamination by fungicides, rodentalcides and

insecticides Excessive quantities of pesticide sprayed onto fruit

and vegetables as they grow Misuse of antibiotics during the rearing of animals

Environmental contamination of soil or water Misuse of cleaning chemicals at food premises Incorrect storage of cleaning materials, weed killer or

pesticides Fraud e.g. olive oil sold in Spain was contaminated by

a toxic and Austrian wine was contaminated by anti-freeze type chemical


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Metallic food poisoning

Metals can enter food chain from the soil if they areabsorbed by animals as they graze or by vegetables,fruit and cereals as they grow

Acid foods are most dangerous when consideredwith metallic food poisoning especially when storedin close contact with copper, zinc, lead, cardinium.

Fish caught in polluted waters may be contaminated

by metals Acidic foods coming into contact with metals such as:


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Cont.

Antimony; typically from the enamel coating of cooking pots

Cadmium; typically cookers, refrigerator shelvesand some types of earthenware pots and dishes

Copper; usually from cooking utensils and someinstances where copper pipes have contaminatedcold drinks or milk dispensed by machines

Lead; from some types of earthenware, leadcrystal or ceramics


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Cont.

Tin and iron; usually from cans

Zinc; typically from galvanised equipment

Accidental use of poisons as food e.g.cockroach poisons used as baking powder


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Cont. Misuse of poisonous substance e.g. spraying

food stuffs with poison during storing,spraying crops immediately before harvesting,spillage of poison near food, accidental misuseof poison and the use of unsuitable containersfor the storage or distillation of food are allcommon courses of chemical poisoning

Berries, roots and green on potatoes due tosun (solanine)


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Intrinsic poisoning foods (plants andfish) Certain plants or creatures may continuously

or from time to time be poisonous e.g. Poisonous plants and fungi eaten accidentally

e.g. poisonous mushrooms, rhubarb leavesand plants including deadly nightshade andmore common members of the nightshadefamily e.g. bittersweet


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Poisonous fish

Scombrotoxic fish poisoning Paralytic shellfish poisoning and

Diarrhetic poisoning


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1. Scombrotoxic fish poisoning

This is caused by toxins produced from some dark-flesh fish during storage e.g. mackerel, tuna andsardine.

The toxin cannot be destroyed by refrigeration,smoking, sousing or canning once spoilage hasoccurred.

Onset period is 10 minutes to 3 hrs

Symptoms which last up to 8 hrs; headache,nausea, vomiting, abdominal pain, diarrhoea,rashes and mouth burning sensation


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2. Paralytic shellfish poisoning

The sources are mussels and other bivalvemolluscs fed on plankton that produceneurotoxins.

Toxins can survive cooking Symptoms are within 4 12 hrs.; numbness of

the mouth, then neck, arms and legs, paralysisand death


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3. Diarrhetic poisoning

This may occur in a similar manner. Symptoms include diarrhea and vomiting

which last only a few days


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Cont. Certain natural poison such as belladonna is well

known. But with other foods it is often difficultto separate traditional beliefs and scientific facts.One can only accept advice on local bases of what is safe to be eaten until science confirms thesafety of those in doubt. Mushrooms cover

family members and every year many cases arereported causing cases of eatable variety. Certainnormal foods may become infected withpoisonous infection such as ergot rye, busariumon maize and similar infections on groundnuts.The aflatoxins produced are believed to bepathogenic and extreme cases have been knownto cause deaths in dogs and ducks


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Putrefied foods when it causes illness

This must not be confused with the incorrecthypophases of ptomaine food poisoning.

It is known that certain people like scavengers onrefuse pits appear to eat without ill effect where aspeople used to good food will become ill evenwithout bacterial contaminations (do not confusewith the outdated and incorrect theory of ptomainepoisoning where it was believed that putrefaction

gave rise to poisonous substances called ptomainewhich caused all food poisoning as it was due tomultiplication of pathogenic organisms)


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Allergic reaction

Individuals may develop allergic reaction tocertain foods particularly in shellfish but alsoeggs, milk, gluten (flour made from grain), foodcolorants and nuts.

Only a few individuals are affected by foodallergies and shellfish are the food mostcommonly involvedSymptoms; vomiting, diarrhoea, migraine,difficulty in breathing, collapse andunconsciousness


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Bacteria and physical environment The development of bacterial colonies is dependant on thefollowing factors: Food : Generally those foods which are nutritious for

human beings are those on which bacteria will thrive best.For this reason, certain rich foods are known as dangerousfoods e.g. milk, milk products, and puddings, cooked andprocessed meat and meat products, soups, gravies andstews and egg products.

Moisture : As with all living creatures moisture is requiredfor development but note that organisms may strive in dryconditions e.g. B. cerous in rice or E. cold in dried milk,salmonella in dried egg S. typhi in desiccated coconut; andthese will multiply when moisture is added. Foods eatendry e.g. bread and biscuits etc. are fairly safe foods.


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Cont. Temperature : Generally bacteria will thrive at

the same temperature as that for the humanbody and at 37 0C in a suitable medium willdouble in number every 15-20 minutes. Mostorganisms can survive much lower temperaturesbut only a few can develop below 5 0C(psycrophilic organisms). Some species cansurvive and develop at higher temperatures than60 0C (thermophilic). Thus, most dangeroustemperature is 37 0c. Dangerous temperatures

ranges is 50

C to 600

C and remember (outsidedangerous temperatures range (DTR) does notsterilize) it is only inactivated and survivingorganisms will multiply when within D.T.R.


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Cont. Time : The importance of time is interrelated with

degree of initial contamination and temperature.Bacteria will double in number every 15 minutes atoptimum temperature i.e. 37 0C on either side of thistemperature bacteria growth will decrease to aperimeter of 5 0C at a lower end and 60 0C at a higherend. Below 5 0C food poisoning organisms are not aproblem although putrefactive organisms may stilldevelop slowly.

The time when foods stands in dangerous areas musttherefore be reduced to an absolute minimum and

where foods are to be stored for a long period, thetemperature must be outside the dangerous range i.e.below 5 0C and above 60 0C.


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Cont. pH : The safety of food is related to their pH

value in that foods on the acid side of pH 4.5are relatively safe in that most food poisoningorganisms will not multiply and they can beeffectively heat processed by boiling where asfoods on an alkaline side (less acid) requiretemperatures in the region of 115 0C. Acidfoods are generally fruits including berries e.g.

tomatoes, appeals, roseberries, strawberriesetc. The above is most important with cannedfoods.


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Thermol death point Salmonella

550

C for 1 hour60 0C for 20 minutes65 0C for 2 minutes

Staphylococcus 60 0C for 30 minutes

Note: Toxin is gradually destroyed by boiling for 30 minutes Clostriduim botulinum

100 0C for 330 minutes104 0C for 150 minutes115 0C for 10 minutes120 0C for 6 minutes127 0C for 0.7 minutes

Note: Toxin destroyed by 5 minutes at boiling point


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Cont. Clostridum welchii: as per botulism

Salmonella typhi: 600C for 30 minutes

Shegella: 60 0C for 30 minutes Entamoeba histolytic cysts: killed by 68 0C Taenia saginata: killed by 71 0C for 5 minutes Necator amerianus: killed by 45 0C for 50 minutes Trachinella spirolis: killed by 62 0C Brucella abortus: killed by 61 0C 3 minutes at

Tuberculosis: killed by 62.50C for 30 minutes orfor a few seconds at 67 0C

Diphtheria: as for TB


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GENERAL SAMPLE COLLECTION

Authority: Under sec. 24 of Food and Drugscap. 303, an authorized officer is empoweredto take samples


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Classes of samples1. Official sample:

Those samples suitable for initiating aprosecution in the court. These generallyrepresent lots which have been manufactured,sold or exposed for sale. It is important thatthe authenticity of the official samples ismaintained scrupulously so that this is not

challenged in court of law


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2. General sample for the purpose of information

Some categories of informal samples are: Factory sample: samples of batches being processed,

raw material and photographs of plant condition. General sample asked in order to collect information

of interest to regulatory agencies. Sample taken during general survey. Injury or poisoning investigation sample, where the

sample offers no basis for subsequent legal action. Sample from reconditioned lots


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3. Food standard sample

Sample drawn for the purpose of establishingstandards usually for laboratoryexamination. The authenticity of thesesamples must be maintained in the same wayas official sample


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4. Post seizure sample These are collected on court order from goods under

seizure. The court order may provide comparablesamples to be obtained by a claimant at the same time.If a court order was obtained by a claimant, allow hisrepresentative (larger) to decide on how the selectionshould be made. It is observed that the selection isimproper due to inexperience, make constructivesuggestions, but do not argue. Report exactly how thesample was collected. Unless the claimant objects,

mark subdivision of the sample drew by him for lateridentification with P.S (post seizure), the date andyour initials. Maintain authenticity as for officialsample since they may become court evidence


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5. Documentary sample

These are collected by copying thedocuments covering the sale of an itemwithout collecting an actual physical sample of the item. This situation arises whenexamination of photographs or a copy of thelabel of the item on the literature or claims

made for it, is sufficient to show a violation of the Act or Registration

Documents

EH 352 Food Poisoning