Foodborne Intoxications PDF

Dr. Elie Salem Sokhn, PhD 1  Introduction  Foodborne intoxication or food poisoning of microbial origin occurs by ingesting a food containing a preformed toxin.  Some general characteristics of food poisoning are:  The toxin is produced b...

Dr. Elie Salem Sokhn, PhD 1  Introduction  Foodborne intoxication or food poisoning of microbial origin occurs by ingesting a food containing a preformed toxin.  Some general characteristics of food poisoning are:  The toxin is produced by a pathogen while growing in a food.  A toxin can be heat labile or heat stable.  Ingestion of a food containing active toxin, not viable microbial cells, is necessary for poisoning (except for infant botulism, in which viable spores need to be ingested).  Symptoms generally occur quickly, as early as 30 min after ingestion.  Symptoms differ with type of toxin  Enterotoxins produce gastric symptoms and neurotoxins produce neurological symptoms.  Febrile symptom is not present 2 STAPHYLOCOCCAL INTOXICATION: Importance  Staphylococcal food poisoning (staphylococcal gastroenteritis; staphylococcal food poisoning; staph food poisoning), caused by toxins of Staphylococcus aureus, is considered one of the most frequently occurring foodborne diseases worldwide.  In the U.S., at least before the 1980s, it was implicated in many outbreaks.  In recent years, the number of staphylococcal food poisoning outbreaks has declined.  This decline is probably a reflection of the better use of refrigerated temperatures to store food and improved sanitary practices that can control contamination and growth of Sta. aureus.  Even then, the number of outbreaks and number of cases of staphylococcal gastroenteritis is much higher than several other microbial foodborne disease outbreaks. 3  Characteristics of Staphylococcus aureus  Sta. aureus are Gram-positive cocci, occur generally in bunches, and are nonmotile, noncapsular, and nonsporulating.  Most strains ferment mannitol and produce coagulase, and thermonuclease.  The cells are killed at 66⁰C in 12 min, and at 72⁰C in 15 s.  Sta. aureus are facultative anaerobes, but grow rapidly under aerobic conditions. 4  Cont’d  They can ferment carbohydrates and also cause proteolysis by extracellular proteolytic enzymes.  They are mesophiles with a growth temperature range of 7 to 48⁰C  With fairly rapid growth between 20 and 37⁰C.  They can grow at relatively low Aw (0.86), low pH (4.8), and high salt and sugar concentrations of 15% and in the presence of NO2. 5  Cont’d  Because of their ability to grow under several adverse conditions, Sta. aureus can grow in many foods.  Normally, they are poor competitors to many other microorganisms found in foods.  But their ability to grow under adverse environments gives them an edge in growth in many foods in which others do not grow favorably.  Enterotoxin-producing Sta. aureus strains have generally been associated with staphylococcal food intoxication. 6  Cont’d  Although strains of several other Staphylococcus species are known to be enterotoxin producers, their involvement in food poisoning is not fully known.  Sta. aureus, along with many other Staphylococci, are naturally present in the nose, throat, skin, and hair of healthy humans, animals, and birds.  Sta. aureus can be present in infections, such as cuts in skin and abscesses in humans, animals, and birds, and cuts in hands and facial-erupted acne in humans.  Food contamination generally occurs from these sources 7  Toxins and Toxin Production  Enterotoxigenic strains of Sta. aureus produce seven different enterotoxins:  A, B, C1, C2, C3, D, and E (also designated as SEA, SEB, etc.).  They are serologically distinct heat-stable proteins of molecular weight 26 to 30 kDa and differ in toxicity.  The toxins vary in heat stability  SEB being more stable than SEA. 8  Cont’d  Normal temperature and time used to process or cook foods do not destroy the potency of the toxins.  Outbreaks from SEA are more frequent, probably because of its high potency.  Rate of toxin production by a strain is directly related to its rate of growth and cell concentrations.  Optimum growth occurs between 37 to 40⁰C. 9  Disease and Symptoms  Staphylococcal toxins are enteric toxins and cause gastroenteritis.  A healthy adult has to consume 30 g or ml of a food containing 100 to 200 ng toxins produced by 106–7 cells/g or /ml  Infants and old and sick individuals need lesser amounts.  The symptoms occur within 2 to 4 h, with a range of 30 min to 8 h  Are directly related to the potency and amounts of toxin ingested and an individual’s resistance.  The disease lasts for 1 to 2 d and is rarely fatal. 10  Cont’d  The primary symptoms, from stimulation of the autonomic nervous system by the toxins, are:  Salivation  Nausea and vomiting  Abdominal cramps  Diarrhea  Some secondary symptoms are  Sweating  Chills  Headache  Dehydration  The symptoms and their severity vary among individuals in an outbreak. 11  Food Association  Many foods have been implicated in staphylococcal foodborne outbreaks.  The bacterium grows in the food and produces toxins without adversely affecting the acceptance quality.  Many protein-rich foods, foods that are handled extensively, foods in which associated bacteria grow poorly, and foods that have been temperature abused are associated with staphylococcal gastroenteritis.  Some of the foods that have been more frequently implicated are:  Ham, salami, bacon, barbecued meat, salads, baking products containing cream, sauces, and cheeses. 12  Cont’d  Pork, baking products, beef, turkey, chicken, and eggs are associated with the high percentages of outbreaks.  Different types of salads, because of extensive handling and high chance of temperature abuse, have been implicated in relatively high numbers in staphylococcal food poisoning.  Three major contributing factors  Improper holding temperature  Poor personal hygiene  Contaminated equipment  Major sources of outbreaks (where foods are prepared or served)  Food services  Homes  Picnics 13  Cont’d  In the case of imported foods, a raw or processed food exported from a country can have Sta. aureus toxins, but can cause food poisoning in a different country. 14  Prevention (Reduction) of the Disease  The normal occurrence of Sta. aureus in raw food materials, among food handlers, and many food environments makes it impossible to produce nonsterile foods that are free of this bacterium.  A zero tolerance is not economically possible to achieve.  Many foods can contain Sta. aureus, and consumption of a food containing 100 or 500 cells/g (or /ml) will, in all probability, not make a person sick  Unless the food has large amounts of preformed toxin  To reduce the incidence of staphylococcal food poisoning, the aim is to reduce initial load of Sta. aureus in a food by  Proper selection of the quality of the raw materials and ingredients  Sanitation of the food environments  Proper personal hygiene among food handlers 15  Cont’d  People with respiratory diseases, acute types of facial acne, skin rash, and cuts in hands should not handle the food.  Where possible, products should be heat-treated to ensure killing of live cells.  Following heating, recontamination of the products should be avoided.  The most important aim is to chill the processed products and ready-to-eat foods to ≤5⁰C quickly.  Suitable preservatives can also be used to kill or arrest growth. 16  Cont’d  The inside of the food, and not only the surface, should reach the chilled temperature, preferably within 1 h.  The food should not be subjected to temperature abuse and stored for a long period of time at growth temperature before eating.  Once heat-stable toxins are formed, heating before eating does not ensure safety. 17  BOTULISM: Importance  Botulism results following consumption of food containing the potent toxin botulin of Clostridium botulinum.  It is a neurotoxin and produces neurological symptoms along with some gastric symptoms.  Unless prompt treatment is administered, it is quite fatal.  Infant botulism occurs when an infant ingests Clo. botulinum spores  Which germinate, grow, and produce toxins in the GI tract and cause specific symptoms.  Most outbreaks occur with foods prepared at home. 18  Characteristics  Cells of Clo. botulinum strains  Are Gram-positive rods  Occur as single cells or in small chains  Many are motile  Obligate anaerobes  Form single terminal spores  Cells are sensitive to  Low pH (