Lect #26 .pptx

Lecture #26- Other Water- and Foodborne diseases, food spoilage and food preservation Waterborne diseases Microbiologically safe drinking water can no longer be assumed, even in Canada and other developed countries, and the situation will worsen unless measures are taken in the immediate future-the...

Lecture #26- Other Water- and Foodborne diseases, food spoilage and food preservation Waterborne diseases Microbiologically safe drinking water can no longer be assumed, even in Canada and other developed countries, and the situation will worsen unless measures are taken in the immediate future-the crisis is global." The first epidemic of a waterborne disease probably was caused by an infected caveman relieving himself in waters upstream of his neighbors Lecture Overview This lecture discusses the microorganisms associated with foods. Some of these microorganisms are associated with food spoilage, some are disease-causing organisms that are transmitted via foods. The lecture also includes a section on the control of food spoilage. Lecture Objectives After this lecture the student should be able to: • discuss the interaction of intrinsic (food-related) and extrinsic (environmental) factors related to food spoilage •describe the various physical, chemical, and biological processes used to preserve foods •discuss the various diseases that can be transmitted to humans by foods • differentiate between food infection and food poisoning Microorganisms and Concepts Legionella pneumophilia, Cryptospordium, Giardia, Cyclospora, Campylobacter • beaver fever • trimethylamine oxide • choleglobin • food preservatives • botulism • enterotoxin In the United States, an increase in waterborne disease is expected because of a number of factors, including: • newly recognized agents (Cryptospordium, Giardia, Cyclospora) that have a high resistance to chemicals used in water treatment and development of antibiotic resistant strains of pathogens. • less immunity to pathogens (because of better sanitary conditions, increased exposure to ultraviolet rays, and a higher population of immuno-compromised individuals) and resulting higher susceptibility and risk of disease during systems failures. • anthropogenic alternations of water systems that have stimulated eutrophication, changes in food chain structure, and unrestricted growth of "nuisance species," creating breeding sites for vectorborne diseases. • changes in agricultural production methods, including high-density animal operations carried out in proximity to urban development, leading to an increase in transmission of animal pathogens to humans. • aging and deteriorating environmental infrastructure, particularly in inner cities. Bacteria Coliforms E. coli Shigellosis Shigella spp. Salmonellosis Salmonella typhimurium Gastroenteritis Campylobacter spp.* Cholera Vibrio cholera Legionellosis Legionella pneumophilia* Protozoa Giardiasis Giardia lamblia* Cryptosporidiosis Cryptosporidium parvum* Amebiasis Entamoeba histolytica* Cyclosporosis Cyclospora cayetanensis Legionella • Legionnaires disease is caused by a bacterium known as Legionella pneumophila, as well as, other species of legionella. • The legionella bacteria can live in water and has thus been spread through air conditioning systems in hotels and hospitals. • outbreak of respiratory illness that caused twenty nine deaths among American Legion members who were attending a convention in a Philadelphia hotel in 1976. • lives in warm, moist conditions. The source of most outbreaks have come from water or air conditioning systems in large public buildings. • droplets of heavily contaminated water inhaled. 8 http://www.you tube.com/watc h?v=dD4d_ap Ltl0 Legionella pneumophila-gram- bacteria. It requires complex nutritional requirements such as high cysteine levels and low sodium levels to grow. Campylobacter • Campylobacter jejuni is slender, curved & rod-shaped. • microaerophilic organism • sensitive to environmental stresses (e.g., 21% oxygen, drying, heating, disinfectants, acidic conditions). • C. jejuni is the leading cause of bacterial diarrheal illness in the United States. It causes more disease than Shigella and Salmonella combined. •Common symptoms The most common symptoms of Campylobacter infection are: Diarrhoea, stomach cramps, fever, nausea and vomiting •How you can become infected Campylobacter bacteria are found in the faeces of many animals, including farm animals and household pets. Eating undercooked meat, especially chicken. Drinking unpasteurised milk or drinking water contaminated with Campylobacter. Handling infected animals and not washing hands afterwards. Scanning electron microscope image of Campylobacter jejuni, illustrating its corkscrew appearance and bipolar flagella. Cryptosporidium • Cryptosporidium is a protozoan, a single-celled parasite, that lives in the intestines of animals and people. •The dormant (inactive) form of Cryptosporidium, called an oocyst, is excreted in the feces (stool) of infected humans and animals. The tough-walled oocysts survive under a wide range of environmental conditions. Differential interference contrast (DIC) image of several Cryptosporidium parvum oocysts. Oocysts are spheroidal objects, 4 to 6 microns in diameter. Oocysts may contain as many as 4 banana shaped sporozoites. Giardia “Beaver fever” It is an example of what is known as a zoonosis, a parasite found in wild animals which can be transmitted to humans. It gained notoriety some years ago when an outbreak occurred in Banff National Park and was termed by the Media as BEAVER FEVER because the local beavers were thought to be the source of contamination of the water supply. •Giardia have a simple direct life cycle. •Cysts are taken in orally, usually via contaminated drinking water. •The trophozoites excyst in the small intestine and may divide by binary fission. •Trophozoites which are free in the lumen of the intestine can encyst and pass out with the faeces. A single Giardia can create one million new cysts in just ten days! The best way to avoid Giardia is by treating any water source in the outdoors before you drink it and practice proper hygiene. Today there are three solutions to treating your water. • boil your water • treat it chemically • filter it with or without additional chemical treatment http://www.youtube.com/watch?v=bGMor71WkFc Amebiasis or Amebic dysentry •Amebiasis is an intestinal illness caused by the parasite, Entamoeba histolytica. • Approximately 10% of the world's population are infected. • symptoms include chills, fever, cramps, bloody diarrhea or constipation. •infections happen after eating food or drinking water that has been contaminated by feces that contain the amebic cysts. The parasite is transmitted from person to person by the fecal-oral route. •. Sexual transmission can also occur by anal-oral contact. Food spoilage, Preservation and Foodborne Diseases • food spoilage is any change in the visual appearance, smell, or taste of a food product. • not necessarily unsafe • stable foods have low water activity • bacteria and fungi Stinky Fish Smell Trimethylamine oxide (TMAO) is an osmolyte in marine fish. In decaying fish TMAO is an alternate electron acceptor for many bacteria, which reduces TMAO to trimethylamine (TMA) Slimy spoilage, souring and greening of sliced meats includes Lactobacillus, Enterococcus and Bacillus thermosphacta. Greening caused by presence of hydrogen peroxide (HP) which forms on the surface of vacuum packaged meats. HP then reacts with nitrosohemochrome to produce choleglobin which is green in colour. Food Preservation • moisture and temperature are crucial factors • pH-- most food spoilage bacteria do not grow below pH 5. • addition of sugar or salt to lower water activity • canning-food is heated and sealed--dependent on acidity • chemical food preservation-- sodium propionate (bread) , sorbic acid (cheese, pickles), sulfur dioxide (dried fruits, ethylene oxides (dried fruit and nuts), sodium nitrate (smoked ham and bacon). • some generally recognized as safe others, like nitrates are carcinogen precurors. • ionizing radiation? Foodborne Diseases: Food Poisoning &Food Infection •food poisoning (FP) is illness due to ingestion of preformed toxins •food infection (FI) is illness due to ingestion of pathogencontaminated foods Staphyloccocal Food Poisoning • enterotoxins released into food- S. aureus •7 enterotoxins known (A, B, C1, C2, C3, D, & E) • enterotoxin A associated with food poisoningsuperantigen • inflammation, vomiting, diarrhea • custard- and cream-filled goods, poultry, meat, gravies, egg and meat salads, pudding, salad dressings •picnics and other non-chilled environments Clostridium perfringens food poisoning • obligate anaerobe • major cause of food poisoning • symptoms last only 24 hr • enterotoxin • tainted meat products • spores germinate under anoxic conditions and grow quickly in meat Botulism • most severe type of food poisoning • exotoxin • toxins destroyed at 80oC for 10 min • eating foods not cooked after processing- canned veggies and soups •vacuum packed meats and fish Foodborne Diseases: Food Infection • growth of microbes after ingestion of contamined foods • Salmonellosis- food handlers, milk, meat products, cakes, etc. • pathogen grows in the intestine • E. coli - enterotoxins- uncooked meats • Campylobacter - raw clams, shellfish, almost all poultry carcasses have Campylobacter,- beef rarely infected. • Listeriosis -Listeria monocytogenes- acid tolerant and psychrotolerant, intracellular pathogen • hepatitis- virus-mediated infection- picornovirus- ssRNA virus