Food Borne Illness Food Borne Illness n Food
Food Borne Illness
Food Borne Illness n Food Borne Illness Can be caused by: • Food Borne Infections ( Living organisms ) • Food Borne Toxins ( non living chemicals ) n Food Poisoning • Food Borne Toxins ( non living chemicals ) • Generated by Microbes n n n Bacteria Fungi Algea • Man made toxins n n n Agricultural residues Antibiotics Preservatives • Naturally occuring toxins
Bacterial Food Poisoning n n Toxins that are destroyed by heating Clostridium botulinum Heat stable toxins Produced by bacteria Staphylococcus aureus Clostridium perfringens Bacillus cereus
Food Borne Infections n Causes by Bacteria that must grow in food before eaten • Require large infective dosage n n Only Bacteria Caused by Organism that do not have to grow in the food before it is eaten • Require small infective dosage Bacteria n Viruses n Parasites n
Staphylococcus aureus Staphylococcal Infections • Gram-positive cocci in irregular clusters • Coagulase negative strains make up to 90% of skin microbiota (S. epidermidis). Only pathogenic when skin is broken or through invasive entry. • Coagulase positive strains tend to be pathogenic. Almost all pathogenic S. aureus strains make coagulase. High correlation between ability to produce coagulase and production of damaging toxins: n n n Leukocidin: Destroys phagocytic white blood cells. Exfoliative toxin: Responsible for scalded skin syndrome. Enterotoxins: Affect gastrointestinal tract. • S. aureus is commonly found in nasal passages.
Staphylococcal Food Poisoning Characteristics: n Acute onset of cramps, vomiting, nausea, occasional diarrhea, low body temperature and blood pressure. n Recovery is usually complete within 24 hours. n Mortality is low in healthy individuals, higher among immunosuppressed individuals. n Pathogens: S. aureus strain that produces an enterotoxin. n Reservoir: Human skin, nasal secretions, and cow milk.
• On Manitol salt agar Heamolysis on HBA
Staph Poisoning in USA 2000 n Principal symptoms • Nausea, vomiting, retching, abdominal cramps, prostration n Potential food contamination • Meat and meat products, poultry, egg • salads (chicken, potato, macaroni), • cream-filled bakery products, milk and dairy products n No. of illnesses • 185, 060 n No. of deaths • 2
Micro & Macroscopic C. perfringens NOTE: Large rectangular gram-positive bacilli NOTE: Double zone of hemolysis Inner beta-hemolysis = θ toxin Outer alpha-hemolysis = α toxin
Clostridial Cellulitis
Exotoxins Associated with C. perfringens Types A-E Major
Perfringens Poisoning in USA 2000 n Principal symptoms Intense abdominal cramps, diarrhea n n n Potential food contamination n Meat, meat products, gravies No. of illnesses n 248, 520 No. of deaths n 7
Clostridium perfringens Two syndromes – diarrhoea and ‘pig-bel’ (necrotizing enteritis) n n The organism – large, non-motile G+ve, anaerobic rod - bacillus 2 forms – vegetative and sporeforming Strains – Type A (diarrhoea) - Type C (‘pig-bel’)
Clostridium botulinum n Principal symptoms • Weariness, weakness, vertigo, double vision, difficulty swallowing and speaking n n n Potential food contamination n Improperly canned or fermented goods No. of illnesses n 58 No. of deaths n 4
Clostridium botulinum Botulism & infant botulism (& wound botulism) n The organism – anaerobic, G+ve, spore -forming rod
Clostridium botulinum n Group I – spoilage n type A, B & F – food Group II – type B, E & F Types A, B, E & F – human botulism Types C & D – botulism in animals
Clostridium botulinum n Characteristics - grows anaerobically - spores & toxin resist freezing - spores resist desiccation
Clostridium botulinum n Pathogenesis - neurotoxin inhibits acetylcholine release - ultimately affects peripheral NS
Clostridium botulinum Botulinum toxin inhibits acetylcholine release at neuromuscular junction
Clostridium botulinum n The illness, continued - infective dose – few nanograms - all individuals susceptible; infants <1 yr - Rx – toxin removal, supportive Rx
Clostridium botulinum n Sources - human – no - animal – can be affected - food – Type E in seafood, Type A in vegetables, honey - environment – Types A, B & F in soils/sediments Type E – marine Dust (vacuum cleaner)
Clostridium botulinum n Outbreaks/sporadic cases Very rare in NZ – one case in 1984 – puha & mussels (incomplete lactic acid fermentation) Overseas: - roasted egg plant in oil, chopped garlic in oil, salted fish, tinned salmon, yoghurt, cheese & cheese sauce
Bacillus cereus n Principal symptoms • Diarrheal—watery diarrhea, abdominal cramps and pain • Emetic—nausea and vomiting n Potential food contamination • Meats, milk, vegetables, fish 0 n No. of illnesses • 27, 360 No. of deaths • 0
Bacillus cereus Two syndromes – diarrhoeal & emetic n n The organism – G+ve sporeforming rod Toxins – diarrhoeal & emetic
Bacillus cereus n Characteristics - rapid growth in food at 30 -400 C - vegetative cells killed by heat - spores resistant, emetic toxins resistant to heat
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