Lecture 15 Water and Foodborne disease PDF

Lecture 15 Water and Food as Vehicles of Bacterial Diseases © 2015 Pearson Education, Inc.  Water as a Disease Vehicle Agents and Sources of Waterborne Diseases Public Health and Water Quality © 2015 Pearson Education, Inc.  Tab...

Lecture 15 Water and Food as Vehicles of Bacterial Diseases © 2015 Pearson Education, Inc.  Water as a Disease Vehicle Agents and Sources of Waterborne Diseases Public Health and Water Quality © 2015 Pearson Education, Inc.  Table: Major Waterborne Pathogens Pathogen Disease Bacteria a Blank Vibrio cholerae Cholera Legionella pneumophila Legionellosis Salmonella enterica (typhi) Typhoid fever Escherichia coli Gastrointestinal illness Pseudomonas aeruginosa Nosocomial pneumonia, septicemia, and skin infections Campylobacter jejuni Gastrointestinal illness Viruses Blank Norovirus Gastrointestinal illness Hepatitis A virus Viral hepatitis Parasites b Blank Cryptosporidium parvum Cryptosporidiosis Giardia intestinalis Giardiasis Schistosoma Schistosomiasis a Except for S. enterica (typhi), these bacteria have been associated with major outbreaks of waterborne illness in the United States in recent years, as have the bacteria Shigella sonnei and Leptospira sp. b See Chapter 34. C. parvum and G. intestinalis are unicellular microbial parasites; Schistosoma is a microscopic worm 10–20 m m long (see MicrobiologyNow in the Chapter 28 opener). illi eters © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc.  Agents and Sources of Waterborne Diseases Common sources of waterborne disease transmission include: Potable water used for drinking and cooking Undergoes extensive treatment, including filtration and chlorination Recreational water from public ponds, lakes, swimming pools, etc. A waterborne outbreak is defined as two or more human illnesses specifically linked to the consumption of the same water at the same time. © 2015 Pearson Education, Inc.  Public Health and Water Quality It is impractical to screen water for every pathogenic organism Potable and recreational water are routinely tested for specific indicator organisms Presence of indicator organism signals potential for disease Coliforms (microorganisms that inhabit intestinal tract) constitute indicator organisms. They are facultatively aerobic, gram- negative rods, non-sporulating, and ferment lactose. Not all coliforms are fecal Fecal coliforms are used in water safety testing Escherichia coli is a key fecal coliform © 2015 Pearson Education, Inc.  Public Health and Water Quality Testing for coliforms and E. coli All tests examine the growth of organisms recovered from the water samples Common methods for enumerating the samples Membrane filter (MF) procedure E. coli can be distinguished from total coliforms with defined substrates. © 2015 Pearson Education, Inc.  Fecal coliforms and their detection in water samples by EMB and MF method © 2015 Pearson Education, Inc.  Fecal coliforms and their detection in water samples Detection of total coliforms and specific detection of E. coli using a set of substrates that fluorescent after being metabolized. © 2015 Pearson Education, Inc.  Public Health and Water Quality A commonly used method for performing coliform counts is the IDEXX Colilert test system Utilizes proprietary substrates Sample with no coliforms remains clear Coliforms turn media yellow E. coli turns media fluorescent blue © 2015 Pearson Education, Inc.  Waterborne Diseases Cholera Legionellosis Typhoid Fever © 2015 Pearson Education, Inc.  Vibrio cholerae and Cholera Cholera Severe diarrhea Caused by Vibrio cholerae (gram-negative, motile) Typically transmitted through ingestion of contaminated water Largely restricted to developing countries Endemic in Africa, Southeast Asia, the Indian subcontinent, and Central and South America Can be controlled by application of water treatment © 2015 Pearson Education, Inc.  Vibrio cholerae, the causative agent of cholera © 2015 Pearson Education, Inc.  Vibrio cholerae and Cholera Pathogenesis V. cholerae attaches to epithelial cells in the small intestine, where it grows and releases cholera toxin This enterotoxin (what type?) causes severe diarrhea Can result in dehydration and death unless treated © 2015 Pearson Education, Inc.  Vibrio cholerae and Cholera Diagnosis Presence of V. cholerae bacilli in the "rice water" stools of patients Prevention Immunization not recommended Public health measures are very important (water treatment) Treatment Placement on cholera cot Oral rehydration and electrolyte replacement therapy (glucose, salt, KCl, Na2CO3) Antibiotic treatment works, but together with rehydration measurements. © 2015 Pearson Education, Inc.  Cholera and its diagnosis © 2015 Pearson Education, Inc.  Legionellosis Legionella pneumophila Causes legionellosis Normally transmitted in aerosols, but highly linked to waterborne disease from residential water sources. Gram-negative bacterium, obligately aerobic, with complex nutritional requirements Common in terrestrial and aquatic habitats, persists in biofilms, and parasites Relatively resistant to heating and chlorination © 2015 Pearson Education, Inc.  Legionella pneumophila © 2015 Pearson Education, Inc.  Legionellosis Legionella pneumophila (cont'd) Common in cooling towers and evaporative condensers of large air conditioning systems The pathogen grows in the water and is disseminated in humidified aerosols Infection is not spread from person to person L. pneumophilia infect lungs and grow within macrophages and monocytes. More serious in elderly and immune compromised individuals. Diagnosis through culturing of bronchial washings, serological tests. © 2015 Pearson Education, Inc.  Legionellosis Treatment with antibiotics is effective: rifampin and erythromycin Can be prevented by improving maintenance and design of water-dependent cooling and heating systems and water delivery systems © 2015 Pearson Education, Inc.  Food as a Disease Vehicle Food Spoilage and Food Preservation Foodborne Diseases © 2015 Pearson Education, Inc.  Food Spoilage and Food Preservation Food spoilage Any change in appearance, smell, or taste of a food product that makes it unpalatable to the consumer Food may still be safe to eat but is regarded as unacceptable The physical and chemical composition of a food determines its susceptibility to microbial spoilage Perishable Semiperishable Nonperishable © 2015 Pearson Education, Inc.  Food Spoilage and Food Preservation Susceptibility to microbial spoilage is based in large part on moisture content Perishable foods have higher moisture content than nonperishable foods Fresh foods are spoiled by both bacteria and fungi Spoilage organisms are those that can gain access to the food and use the available nutrients For example, Escherichia coli frequently contaminates meat products because it is found in animals' digestive tracts © 2015 Pearson Education, Inc.  Food Spoilage and Food Preservation Food preservation Slows down the growth of microbes Refrigeration Slows microbial growth rate and delays spoilage Freezing allows for longer storage but isn't suitable for all foods © 2015 Pearson Education, Inc.  Food Spoilage and Food Preservation Heating Used to reduce the bacterial load (i.e., pasteurization) of a product or to actually sterilize it (i.e., canning) Canning isn't always 100% effective Failure results in swollen cans (DO NOT EAT!) © 2015 Pearson Education, Inc.  Changes in sealed tin cans as a result of microbial spoilage © 2015 Pearson Education, Inc.  Food Spoilage and Food Preservation Drying and dehydration Moisture content (water activity) is critical for microbial metabolic processes Sugar and salt reduce the availability of water for microbial growth (in effect, dehydrating it) Examples: jams, jellies, meats, fish Many foods are preserved by addition of antimicrobial chemicals. E.g. nitrites, sulfites, propionate, and benzoate. © 2015 Pearson Education, Inc.  Food Spoilage and Food Preservation Many common foods are preserved, produced, or enhanced by the actions of microbes (through their metabolic activities) Fermentation is the anaerobic catabolism of organic compounds (generally carbohydrates) Important bacteria in the fermented food industry are lactic acid bacteria (milk), propionic acid bacteria (cheese), and acetic acid bacteria (pickling) Products of fermentation include yeast bread, cheese, yogurt, buttermilk, sausage, sauerkraut, and soy sauce © 2015 Pearson Education, Inc.  Fermented foods © 2015 Pearson Education, Inc.  Foodborne Diseases Food poisoning (also called food intoxication) Disease that results from ingestion of foods containing preformed microbial toxins The microorganisms that produced the toxins do not have to grow in the host Food infection Microbial infection resulting from the ingestion of pathogen-contaminated food followed by growth of pathogen in the host © 2015 Pearson Education, Inc.  Foodborne Diseases Microbial sampling for foodborne disease In addition to nonpathogenic microorganisms, pathogenic microorganisms may be present in fresh foods Rapid detection methods have been developed to look for the presence of some of these pathogens (e.g., E. coli O157:H7) Tests are molecular and immunology based In the United States, foodborne outbreaks are reported to the CDC © 2015 Pearson Education, Inc.  Foodborne Diseases Microbial sampling for foodborne disease (cont'd) Standard method is isolation of pathogen Isolation from food Requires treatment of food to suspend microorganism Isolation from diseased patient to establish the cause- and –effect relationship between the pathogen and illness. © 2015 Pearson Education, Inc.  A stomacher (homogenizer) used to prepare a homogenized mixture of the food tested. © 2015 Pearson Education, Inc.  Food Poisoning Staphylococcal Food Poisoning Clostridial Food Poisoning © 2015 Pearson Education, Inc.  Staphylococcal Food Poisoning Food poisoning is often caused by toxins produced by Staphylococcus aureus S. aureus can grow on common foods, and some strains produce heat- and acid-stable enterotoxins Gastroenteritis occurs within a few hours (1-6 hr) of consumption It is estimated that 185,000 cases of staphylococcal food poisoning occur each year Enterotoxins of S. aureus classified as superantigens produce large T cell response and an inflammatory response © 2015 Pearson Education, Inc.  Clostridial Food Poisoning Clostridium perfringens and Clostridium botulinum cause serious food poisoning Produce endospores that may not be killed during cooking/canning process C. perfringens is the fourth most commonly reported form of food poisoning, with 248,000 annual cases Large numbers of cells (>108) must be ingested Enterotoxin is heat labile, produced in the intestinal tract 6– 15 hours after consumption. The disease is cleared within 24h (stomach flu). © 2015 Pearson Education, Inc.  Food poisoning clostridia © 2015 Pearson Education, Inc.  Clostridial Food Poisoning Botulism is a severe and often fatal food poisoning Caused by an exotoxin produced by Clostridium botulinum Botulinum toxin is a neurotoxin but is destroyed by heat Average of 150 cases annually 70% of cases are infant 15% of cases are wound 15% of cases are foodborne Home-prepared foods are a common source of illness © 2015 Pearson Education, Inc.  Food Infection Salmonellosis Pathogenic Escherichia coli Campylobacter Listeriosis Other Foodborne Infectious Diseases © 2015 Pearson Education, Inc.  Salmonellosis Salmonellosis is a gastrointestinal illness caused by foodborne Salmonella infection. The illness is referred to as enterocolitis Caused by eating food contaminated with Salmonella or handling Salmonella-infected animals Onset of the disease occurs 8–48 hours after ingestion Disease normally resolves in 2–5 days Salmonella ingested in food or water invades phagocytes and grows as an intracellular pathogen. Pathogenicity due to endotoxin, enterotoxins and cytotoxins. © 2015 Pearson Education, Inc.  Some sources of Salmonella © 2015 Pearson Education, Inc.  Pathogenic Escherichia coli Most E. coli are nonpathogenic A few strains are foodborne pathogens All pathogenic strains are intestinal parasites, and a few produce potent enterotoxins Shiga toxin–producing E. coli (STEC), formerly called enterohemorrhagic E. coli (EHEC, i.e., O157:H7), produces verotoxin Verotoxin (shiga-toxin) causes bloody diarrhea and kidney failure Other types of E. coli are enterotoxigenic (ETEC), enteroinvasive (EIEC), and enteropathogenic (EPEC) © 2015 Pearson Education, Inc.  Pathogenic Escherichia coli Detection: of E. coli requires culturing of feces from the patient and detection with antibodies of the antigens (LPS, flagella) and toxins. Treatment: hydration and monitoring renal function. Antibiotic treatment is limited in order to avoid release of endotoxins and verotoxin. © 2015 Pearson Education, Inc.  Campylobacter Campylobacter spp. Motile and spiral shaped, microaerophilic More than 2 million cases of bacterial diarrhea per year Transmitted to humans via contaminated food Poultry, pork, raw shellfish, or in surface waters Campylobacter replicates in the small intestine Causes high fever, headache, malaise, nausea, abdominal cramps, and bloody stools © 2015 Pearson Education, Inc.  Campylobacter © 2015 Pearson Education, Inc.  Campylobacter C. jejuni and C. fetus are mostly linked to human foodborne illnesses. C. jejuni is normal resident of the intestinal tract poultry. After Campylobacter are ingested the organism multiplies in the small intestine and invades epithelium and causes inflammation. Diagnosis requires isolation of the microbe from feces, identification of growth dependent tests, immunological tests or genomic analysis. Antibiotic treatment with azithromycin is commonly used. Prevention by hygiene, proper washing of uncooked poultry and thorough cooking. © 2015 Pearson Education, Inc.  Listeriosis Listeria monocytogenes is the cause of listeriosis May lead to bacteremia and meningitis No food product is safe from contamination Psychrotolerant, acid- and salt-tolerant L. monocytogenes is an intracellular (G+) pathogen Uptake of the pathogen by phagocytes results in the growth and proliferation of the bacterium Mortality rate of listeriosis is 20% © 2015 Pearson Education, Inc.  Listeria monocytogenes © 2015 Pearson Education, Inc.  Listeriosis The host becomes immune. Complications: Listeria can evade the immune system and taken up by phagocytic cells, which initiates their infection cycle. Pathogenicity of Listeria is due to listeriolysin O, which lyses the phagocytic cells and virulence factor ActA. ActA is an essential factor in motility of Listeria, which leads to moving of the microbial cell from tissue cell to tissues cell without exposure. They can infect central nervous system. Listeriosis is diagnosed by culturing bacteria from the blood or cerebrospinal fluid. Intravenous antibiotic treatment with penicillin, trimethoprim is common. © 2015 Pearson Education, Inc.  Other Foodborne Infectious Diseases Prions Proteins that adopt novel conformations that inhibit normal protein function and cause degeneration of neural tissue variant Creutzfeldt–Jakob disease Linked to consumption of meat from cattle suffering with bovine spongiform encephalopathy (BSE), a prion disease © 2015 Pearson Education, Inc.