Food Poisoning
Food poisoning Advisory commitee on Microbiological safety of food (ACMSF, UK) has defined food poisoning as : An acute illness with gastrointestinal or neurological manifestation affecting two or more persons, who have shared a meal during the previous 72 hours. These can either be fungal, bacterial, viral or parasitic Most people get better without the need for treatment.
FOOD BORNE INFECTIONS Food borne infections by bacteria can be classified as : Food infections bacteria are ingested which later initiate the infection. Onset can take 6 hours or longer to appear. Toxicosis toxins are released by bacteria such as Clostridia, Bacillus and Staphylococcus. Onset of illness is as quickly as 30 minutes
Food Borne Infections
Food borne intoxications 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: 1. Staphylococcus aureus intoxication 2.Bacillus cereus food borne intoxication 3.Clostridium perfringens food borne intoxication 4.Clostridium botulinum food borne intoxication b.fungal intoxications : Aflatoxin, Ergot alkaloid 6
FOOD CONTAMINATION STAGES Food production and processing : during washing or irrigation slaughter meat & poultry Food preparation and handling : infected individuals & cross contamination Improper storage : warm temperature (10 50 0 C) allows multiplication of pathogens 7
Mode of infection Ingestion 5F s Fingers, Food, Flies, Faeces, Fomites.
Mechanism of Pathogenesis
Mechanism Location Illness Examples of Pathogens Involved Ingestion of preformed bacterial toxins Proximal small bowel Watery diarrhea Bacillus cereus, Staph. aureus,clostridium botulinum, Clostridium perfringens Noninflamma tory (enterotoxin) Proximal small bowel ETEC :enterotoxigenic Escherichia coli EAEC :enteroaggregative E. Coli Watery diarrhea Vibrio cholerae, ETEC (LT and/or ST), EAEC Rotavirus, Norovirus, Enteric adenoviruses Giardia lamblia, Cryptosporidium spp., Cyclospora spp., microsporidia
Mechanism Location Illness Examples of Pathogens Involved Inflammatory (invasion or cytotoxin) Colon or distal small bowel, Dysentery or inflammatory diarrhea Shigella spp., non enteric Salmonella spp., Campylobacter jejuni, EHEC, EIEC, Yersinia enterocolitica, Vibrio parahaemolyticus, Clostridium difficile Penetrating/I nvasive Distal small bowel Enteric fever Entamoeba histolytica Salmonella typhi, Y. enterocolitica, Campylobacter EHEC :entero hemorrhagic Escherichia coli EIEC :enteroinvasive E. Coli
Associated Foods & Incubation periods Time Symptoms < 6 hrs Nausea and vomiting Asso Micro organisms 1.Staphylococcus aureus Asso. Food Ham, poultry, potato, egg, salad, cream, pastries. 2.Bacillus cereus Fried rice 8 16 hrs Abdominal cramps and diarrhoea 1.Clostridium perfringens 2. Bacillus cereus Beef, poultry, meats, legumes, vegetables, cereals, dried beans, gravies
Time Symptoms Asso Micro organisms Asso. Food 18 36 hrs Nausea, vomiting, Constipation and paralysis Clostridium botulinum Canned or bottled meat, vegetables, Milk and fish. 16 48 hrs Fever, abdominal cramps and diarrhoea 1.Salmonella 2.Shigella 3.Vibrio & V. Parahemolyticus Beef, poultry, eggs, diary products Potato, egg, salad, lettuce Shell fish, Molluscs, Crustaceans 4.Enteroinvasive E.coli 5.Campylobacter jejuni Beef, raw milk, vegetables Poultry, raw milk
Time Symptoms Asso Micro organisms 16 48 hrs Fever and abdominal cramps Yersinia enterocolitica Asso Food Pork 16 72 hrs Abdominal cramps and watery diarrhoea 1.ETEC 2.Vibrio cholerae O1, O139, Vibrio parahemolyticus 3.Norwalk virus Salad, cheese, meats Shell fish, Molluscs, Crustaceans Raw oyesters 72 120 hrs Bloody diarrhoea without fever Entero hemorrhagic E.coli O157:H7 Beef, raw milk, vegetables
LAB DIAGNOSIS 1. Culture, Isolation, Identification: Isolation of the organism from both stool and food 2. Serological tests : ELISA 3. Toxin detection : ELISA, Enzyme linked fluorescence assays (Automated), Reversed passive latex agglutination 4. Invasive property detection : Sereny test for EIEC: inoculating suspension of bacteria into guinea pig's eye. Severe mucopurulent conjunctivitis and severe keratitis indicates a positive test. 5. Molecular techniques : PCR
CULTURE MEDIA Pathogen Culture media used Staphylococcus aureus Bacillus cereus Clostridium perfringens Clostridium botulinum ETEC Mannitol salt agar, Ludlam s medium,baird Parker medium PLET medium (polymyxin, lysozyme, ethylene diamine tetra acetic acid, thallous acetate) Egg yolk agar, RCM Egg yolk agar, RCM, Blood Agar MacConkey agar
FOOD BORNE PATHOGENS CULTURE MEDIA Pathogen EHEC Vibrio parahemolyticus Salmonella enteritidis Yersinia enterocolitica Campylobacter jejuni Culture media used Sorbital MacConkey agar, MacConkey agar TCBS agar, Wagatsuma agar DCA Selenite F broth (4 0 C), DCA Campy BAP, Skirrows medium
VIRAL FOOD BORNE INFECTIONS Common pathogens transmitted through food & water. Hepatitis A, Rota virus and Norwalk like virus (Norovirus) are most important. Others : enteric Adeno viruses These viruses are highly infectious and may lead to widespread outbreaks Norovirus
Characteristics of viral food borne infections Few viral particles are enough High numbers of viral particles are transmitted via feces of infected persons (up to 10 11 particles per gram of feces). Specific lining cells are necessary for virus replication. Cannot multiply in foods or water. Food borne virus are relatively stable and acid resistant outside host cells 19
Parasitic Food Poisoning Protozoa: Cryptosporidium spp, Entamoeba histolytica Toxoplasma gondii, Cyclospora cayetanensis,giardia lamblia Helminths : Trematodes : Clonorchis sinensis, Fasciolopsis buski,opisthorchis viverrin, Fasciola hepatica, Opisthorchis felineus, Paragonimus westermani Cestodes : Diphyllobothrium spp, Echinococcus spp, Hymenolepis nana, Taenia solium / saginata Nematodes : Ascaris lumbricoides,trichinella spiralis, Trichuris trichiura 20
Lab Diagnosis Amebic colitis Cyclospora cayetanensis Giardia