Food borne diseases Food Poisoning Food borne infection
Food borne diseases (Food Poisoning) Food borne infection Salmonella , Campylobacter and E. coli
Salmonellosis • The salmonellae constitute a group of organisms with over 2500 different serotypes • Many salmonella species have a wide host range.
Salmonellosis • some salmonella serotypes are associated with human disease e. g. S. typhi and Salmonella paratyphi. • Salmonella are ubiquitous in the gut of human and animals and act as sources of food contamination.
Salmonellosis cont. . • People who are carriers of the salmonellae contaminate the food. • A heavy dose up to 10, 000 -1, 000 organisms per gram of food is required to cause infection
Common food poisoning serotypes • Some of the salmonella species involved in food poisoning include; Salmonella typhimurium, Salmonella enteritidis, Salmonella dublin, Salmonella softenburg, • These species are also involved in causing diarrhoea in animals
Heat resistance • The salmonellae are killed by temperatures attained in commercial pasteurization, • They can remain alive in moist earth for one year and in dry earth for 16 months, • They are not destroyed in carcasses or offal maintained at chilling or freezing
Factors associated with Salmonella food poisoning outbreaks • Consumption of inadequately cooked or thawed meat or poultry. • Cross-contamination of food from infected food handlers. • Presence of flies, cockroaches, rats, in the food environment that act as vectors of the disease.
Transmission • Salmonellae reach food in many different ways; a) Directly from slaughter animals to food b) From human excreta, and transferred to food through hands, utensils, equipments, flies etc.
Foods involved • Any food contaminated with Salmonella may be involved, specially: a. meat and meat products. b. milk and milk products. c. egg and egg products.
Clinical symptoms • The ordinary symptoms include abdominal pain, headache, diarrhea, fever, vomiting, prostration and malaise. • In severe cases there is septicaemia with leucopenia, endocarditis, pericarditis. • Severe cases in young children , the sick and in elderly persons.
Control measures • Efficient refrigeration and hygienic handling of food. • Consumption of properly cooked meat. • Complete thawing of frozen meats and adequate cooking. • Heat processing of meat, milk , fish and poultry to destroy Salmonella organisms in food
Campylobacteriosis Ø main symptoms u u mild to severe diarrhoea fever nausea abdominal cramps Ø persons at risk u u babies and young people debilitated people Ø incubation usually 2 -5 days
Electron microscope picture of Campylobacter
Survival of Campylobacter A very fragile organism, it does not survive well in food processing environments u heat-sensitive u sensitive to drying u survives freezing (several months in frozen meat and poultry)
Pathogenic E. coli Ø Enteropathogenic E. coli ( EPEC ) Ø Enteroinvasive E. coli ( EIEC ) Ø Enterotoxigenic E. coli ( ETEC ) Ø Enterohaemorrhagic E. coli ( EHEC )
Pathogenic E. coli EPEC Acute watery diarrhoea - young children particularly susceptible EIEC Dysentery-like syndrome ETEC Acute watery diarrhoea - often in travellers EHEC Bloody diarrhoea syndrome Incubation 8 -44 hours depending on type
Raw food materials likely to be contaminated with pathogenic E. coli Ø meat Ø fish Ø vegetables Ø milk Ø polluted water
Minimum infective dose Ø EPEC 106 Ø ETEC 106 Ø Shigella, EIEC 10 -100 Ø EHEC 100 Ø L. monocytogenes Unknown probably low in risk groups Ø Salmonella ( excluding typhi ) 106 Ø Campylobacter ca. 500 Ø Salmonella typhi 10 -100 Ø V. cholerae 106 ( lower nos (i. e. 10 -1000) ma cause infection in fatty foods such as chocolate & cheese )
Food borne intoxications have short incubation periods (minutes to hours) and are characterized by lack of fever. Food borne intoxications can be classified into: a. Bacterial intoxications b. Fungal intoxications c. Chemical intoxication d. Plant toxicants, and e. Poisonous animals.
Bacterial food borne intoxications 1. 2. 3. 4. Staphylococcus aureus Bacillus cereus Clostridium perfringens Clostridium botulinum
Microscope picture of S. aureus
Staphylococcus aureus food borne intoxication This is a type of food borne intoxication is caused by consumption of food contaminated with staphylococcal enterotoxins produced by certain strains of Staphylococcus aureus while growing in food.
The five enterotoxins are: 1. Staphylococcal enterotoxin A(SEA), 2. Staphylococcal enterotoxin B (SEB), 3. Staphylococcal enterotoxin C (SEC), 4. Staphylococcal enterotoxin D (SED), 5. Staphylococcal enterotoxin E (SEE) Individual strains of S. aureus may produce one or more of enterotoxin types while growing in food
Characteristics of FBD due to S. aureus Ø Ø incubation period 1 - 6 h main symptoms at 6 - 24 h u u u nausea vomiting diarrhoea abdominal pain NO fever collapse and dehydration in severe cases
Thermal resistance of S. aureus • D - value at 77°C ~ 0. 001 - 0. 0105 minutes • Enterotoxin highly heat - resistant • ( not inactivated by boiling at 100°C)
Characteristics of FBD due to C. botulinum Characteristic Proteolytic type • onset 12 -36 hours • duration days to several months • symptoms nausea vomiting visual disturbances, vertigo • toxic dose 0. 005 -0. 1 mcg Non-proteolytic SAME 0. 1 -0. 5 mcg
Minimal conditions for growth and heat - resistance of C. botulinum Proteolytic Non-proteolytic toxin types A, B, F B, E, F minimum p. H 4. 6 5 maximum Na. Cl 10 % 3% minimum aw 0. 93 0. 97 temp. range for growth 12. 5 - 48°C 3. 5 - 48°C decimal reduction time of spores at 100°C 25 min. <0. 1 min.
Thermal resistance of C. botulinum toxins Ø toxin is sensitive to heat Ø treatment at 80°C rapidly denatures toxin Ø approx. 1000 x reduction of types A and B in 1 minute Ø all toxins inactivated by heating at 80°C 30 minutes Ø in pure form the toxin may be destroyed by boiling but may be protected when mixed with protein or other food material for
Characteristics of FBD due to Bacillus cereus Characteristic onset of symptoms duration of symptoms number of bacteria in incriminated food Diarrhoeal Syndrome Emetic Syndrome 4 - 16 hours 1 - 14 hours 12 - 24 hours 6 - 36 hours abdominal pain, watery diarrhoea nausea and vomiting 108 / g
Thermal resistance of B. cereus • D - value of 0. 02 - 0. 06 minutes at 121°C • = 0. 3 - 27 minutes at 100°C
Food materials likely to be contaminated by B. cereus raw foods u u u u cereals dried vegetables potatoes milk cream rice Spices cooked / processed foods u u u roast / fried meat products soups cooked / fried rice meals
Minimum toxic doses of bacterial toxins Minimum toxic dose (cells /g) S. aureus 106 C. botulinum 104 - 105 B. cereus 107 - 108
Fungal intoxications • Grains, oilseeds, fruits and vegetables are mostly involved if they are stored at high humidity (≥ 0. 75) or if they are not properly dried before storage. • Poor dry storage practices of grains and other foods leads to mould growth and production of mycotoxins.
Aflatoxicosis • Aflatoxicosis is caused by aflatoxins produced by the fungi, e. g. Aspergillus flavus. • Four types of aflatoxins have been described i. e. aflatoxin B 1, B 2, G 1 and G 2. • Animals consuming feeds contaminated with aflatoxin B 1 leads to secretion in the milk of aflatoxin M 1 and M 2
Effects of aflatoxins • When consumed in large doses, they are lethal in causing acute hemorrhagic syndromes • Sub-lethal doses cause histotoxic changes • Long term consumption of small doses cause liver tumors as these are potent carcinogens.
Electron microscope picture of A. flavus
Foods where toxigenic moulds and their toxins may be found Fungal species Toxin Foods which may be contaminated Aspergillus flavus aflatoxins corn, peanuts, copra Aspergillus parasiticus aflatoxins some nuts Fusarium moniliforme fumonisins corn Fusarium graminearum trichothecenes zearalenone wheat, corn Claviceps purpurea ergot alkaloide rye Penicillium verrucosum ochratoxins barley
Prevention of aflatoxicosis • Proper drying and storage of grains and other affected foods • Quality control of potentially hazardous foods to ensure that they do not contain above the allowable limits of 20 ppb before consumption by use of appropriate analytical tests. • Use of fungicides as seed dressings to protect stored cereals and other foods like pulses and potatoes against fungal invasion.
CHEMICAL FOODBORNE INTOXICATION • These may be intentionally or unintentionally added to foods as a result of producing, processing, transporting or storage. • A number of substances can enter the food chain from the environment and through their use as growth promoters or veterinary therapeutics giving rise to chemical residues.
Chemical substances involved Chemical food borne intoxication involve the following substances: • Heavy metals e. g. antimony, mercury, arsenic, flouride, lead, cadmium, cyanide etc. • Pesticides and insecticides e. g. DDT, BHC Organochlorines and organophosphates. • Herbicides • Fungicides e. g. organomercurials
Chemical substances involved. . • Preservatives e. g. nitrites, nicotinate, etc • Antibiotics e. g. pencillin, tetracyclines, chloramphenicol etc. • Radionuclides e. g. cesium, strontium, radium, molybdenum, barium, ruthenium, lanthanum, iodine isotopes etc.
Clinical signs and symptoms • Chemical food borne intoxication exhibit a very short incubation period, usually a few minutes to a few hours, with an average of one hour. • Symptoms are nausea, headache, convulsions, gastrointestinal irritation, abdominal cramps, vomiting and diarrhea, pallor, cyanosis, blurred vision, sweating, and collapse. • Other signs may be due to effects on circulatory system. • Symptoms of radionuclide toxicity depend on dose, time and organ affected.
Preventive measures • Do not use utensils or containers that are able to leach chemicals such as antimony, cadmium, zinc, copper, etc. • Use of coloured pesticides and proper storage of the same. • Prevent contamination of foods when using insecticides. • Prevent acid foods or carbonated liquids from contact with exposed copper.
Preventive measures • Prevent misuse or avoid use of dangerous additive e. g. sodium nicotinate. • Education of persons preparing food (e. g. possibility of Zn poisoning). • Ensure that withdrawal periods are observed after use of pesticides and antibiotics in animal and crop husbandry.
Biotoxications • These are disorders resulting from ingestion of a poisonous substance (a biotoxin) present in the body of a plant or animal. • Only a small proportion of the species of fish and shellfish taken for human consumption throughout the world contain biotoxins.
Animals biotoxications • This type of intoxication occurs as a result of consumption of poisonous animals. • Primary toxicity occurs due to inherent toxicants that arise due to normal metabolic processes,
Animals biotoxications cont. . • Inherent animal toxins are water soluble and heat labile. • High concentrations of these toxins are usually found in viscera and dark meats.
1. Toxic fishes • They include puffers, triggerfish and parrot • Types of biotoxications associated with fish include ciguatera poisoning, tetraodon.
2. Mollusca • protozoa toxins by the mollusca. • Mollusca involved are oysters, mussels and clams, which feed on dinoflagellates and planktons containing alkaloids making them toxic.
3. Poisonous mammals • Mammals are not commonly inherently poisonous, but secondary toxicity may affect many of them. • Most human poisoning involves secondarily transvectered toxins.
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