Food-Borne Diseases Lecture 2 PDF

Lecture: Food-borne diseases 2  Cholera Cholera is caused by Vibrio cholera bacterium. Cholera vibrios are ingested in drink or food. In natural infection, the dosage is usually very small. The organism multiply in the small intestine to produce a very potent enterotoxi...

Lecture: Food-borne diseases 2  Cholera Cholera is caused by Vibrio cholera bacterium. Cholera vibrios are ingested in drink or food. In natural infection, the dosage is usually very small. The organism multiply in the small intestine to produce a very potent enterotoxin, which stimulates a persistent out pouring of isotonic fluid by the gut mucosal cells.  Transmission Man is the only natural host of the cholera vibrios Spread of infection is from person-to-person, through contaminated water or foods. Shrimps and vegetables are the most frequent carriers. Cholera is an infection of crowded poor class communities and it tends to persist in such areas. Cholera outbreaks occur either as explosive epidemics usually in non-endemic areas or as protracted epidemic waves in endemic areas  Clinical symptoms Cholera is typically characterized by the sudden onset of effortless vomiting and profuse watery diarrhea. Vomiting is seen frequently, but very rapid dehydration and hypovolemic shock. The frequent watery stools may be accompanied with small parts of the mucosa being liberated from the intestines. Death may occur in 12 to 24 hrs due to rapid dehydration  Clinical symptoms cont… Patients may produce up to 20-30 stools per day, losing many litres of water and electrolytes. Patients therefore exhibits extreme dehydration, urine is suppressed, the skin becomes wrinkled, the eyeballs are sunken and the voice becomes weak and husky. Blood pressure falls, the heart sounds become barely audible and the pulse become rapid and weak just before death.  Diagnosis A vibrio immobilization test with dark field microscopy. In the acute stage, vibrios are abundantly present in watery stool upto 107to 109 organisms per ml. Bacteriological examination can be done in stool, suspect water and food. Precise identification of biotype and serotype done using serological (e.g. CFT) and phage sensitivity tests.  Control measures 1. Provision of potable water 2. Proper sewage disposal 3. Proper cooking and hygienic handling of food 4. Observation of personal hygiene 5. Vaccination -The heat killed, phenol preserved vaccine has protection that lasts for 3 to 6 months.  Vibrio parahemolyticus food-borne infections Vibrio parahemolyticus is a pathogenic bacterium, whose natural habitat is the sea. Human infections occur solely from sea foods such as oysters, shrimps, crabs, lobsters, clams and related shellfish.. Cross-contamination may lead to other foods becoming vehicles.  Symptoms of the disease V. parahemolyticus causes gastroenteritis and extra intestinal infections in man. Symptoms include: diarrhea, cramps , weakness, nausea, chills, headache and vomiting. Symptoms last from 1 to 8 days with a mean of 4.6 days. Listeria monocytogenes infection Listeria monocytogenes is a gram positive bacterium that is pathogenic to both animals and human beings. The organism is widespread in nature and is a transient constituent of the intestinal flora excreted by 1-10% of healthy humans. It is extremely hardy and can survive for many years in the cold in naturally infected sources.  Vehicle foods Listeria monocytogenese occurs after consumption of raw vegetables, salads, raw milk, soft cheese, meat and meat products. milk, ice cream, cheese, poultry, sauerkraut, salads, sea foods, meat and meat products contaminated by Listeria. Delicatessens and other ready-to-eat foods are important in causing Listeria food poisoning.  Clinical symptoms In man, Listeria monocytogenes causes abortion in pregnant women and meningitis in newborn infants and immuno-compromised adults. Pregnant women, infants and elderly people are particularly at risk of infection with Listeria monocytogenes. The infection is fatal in susceptible individuals with a mortality of 25-30%. Deaths have been reported in fetuses, neonates and other individuals with compromised health status.  Yersinia enterocolitica infection This organism has been isolated from beef, lamb, pork, sea foods, vegetables milk and cakes, vacuum-packed meat. Of all the sources, swine appears to be major source of strains pathogenic to man. Virulence appears to be as a result of tissue invasiveness of this organism.  Yersinia gastroenteritis symptoms Symptoms of syndrome develop several days following ingestion of contaminated foods. Symptoms include abdominal pain, diarrhea, fever, vomiting, headache and pharngitis.. Children appear to be more susceptible than adults The organism may be shed in stools for up to 40 days following illness.  Disease symptoms A variety of systemic involvement may occur as a consequence of the gastroenteritis syndrome. They include pseudo appendicitis, mesenteric lymphadenitis, peritonitis, terminal ileitis, reactive arthritis, colon and neck abscess, cholecystitis, and erythema nodosum. The organism can be recovered from urine, stool, blood, cerebrospinal fluid and eye discharges of infected individuals.  Viral food-borne infections Viruses are common pathogens transmitted through food. Hepatitis A and Norwalk-like virus )Novovirus) are the most important viral food borne pathogens. These viruses are highly infectious and may lead to widespread outbreaks. Characteristics of viral food-borne infections Only a few viral particles are necessary for the disease to develop High numbers of viral particles are further transmitted via feces of infected persons (up to 1011 particles per gram of feces. Specific lining cells are necessary for virus replication. Accordingly they cannot multiply in foods or water. Food borne virus are relatively stable and acid resistant outside host cells  Infectious hepatitis A The incubation period is long, being an average of 30 days, range 15-50 days. It is a systemic infection characterized by gastrointestinal manifestations and liver injury, fever, malaise anorexia, nausea, abdominal discomfort, bile in urine and jaundice. The duration of the disease could be from a few weeks to several months.  Norwalk -like virus (Norovirus) food borne infection Norovirus infection is relatively mild with an incubation period of 3 days. Clinical manifestations/symptoms include vomiting and diarrhea, and rarely convulsions. Asymptomatic infection are common and may contribute to the spread of the infection. Infections have resulted from consumption of raw oyesters.  Food- borne intoxication Food poisoning or food intoxication can be result of either chemical poisoning or the ingestion of toxicant ( which is produced by microorganism , plant and animals). Types of intoxication a. Bacterial intoxications b. Fungal intoxications c. Chemical intoxication d. Plant toxicants e. Poisonous animals  Bacterial intoxication There are four chief bacteria which caused the food intoxication. Staphylococcus aureus Bacillus cereus Clostridium perfringens Clostridium botulinum  Staphylococcal food intoxication This is a type of food borne intoxication is caused by consumption of food contaminated with staphylococcal enterotoxins produced by certain strains of Staphylococcus aureus while growing in food.  The organism produces the following five serologically different enterotoxins that are involved in food borne intoxication. 1. Staphylococcal enterotoxin A(SEA) 2. Staphylococcal enterotoxin B (SEB) 3. Staphylococcal enterotoxin C (SEC) 4. Staphylococcal enterotoxin D (SED) 5. Staphylococcal enterotoxin E (SEE) Individual strains of S. aureus may produce one or more of enterotoxin types while growing in food.  Food involved Growth of staphylococcus and their toxin production required a food sources. E.g Milk and milk products (including pasteurized milk, yoghurt, chocolate milk, fermented milk, cream filled pastries), poultry, fish, shellfish, meat and meat products, non meat salads, egg and egg products, vegetables and cereal products have been involved.  Toxin production Toxin production occurs at growth temperature 12- 44°C, pH 4.2 and salt concentration of≤10%. No toxin production occurs attemperatures below 12°C, pH < 4.2 and > 10 % salt 75% of all staphylococcal food poisoning outbreaks occurs because of inadequate cooling of foods.  Prevention The means of prevention of out breaks of staphylococcus food poisoning include: 1. Prevention of contamination of food with staphylococci. 2. Prevention of growth of the staphylococcus. 3. Killing staphylococci in foods.  Control Contamination of food can be reduced by general method such as 1. By pasteurization of raw milk 2. By adequate refrigeration of food 3. By addition of bacteriostatic substance such as serine , antibiotic.  Clostridium botulinum foodborne Intoxication Botulism : botulism is caused by the ingestion of food containing the neurotoxin produced by clostridium botulinum. The intoxication is caused by botulinal toxins A, B, E, F and G, produced by C. botulinum type A, B, E, F and G, while the organism grows in food. C. botulinum types C and D produce toxins C and D that cause disease in animals. Type E strains are non-proteolytic while the rest are proteolytic. Spores of C. botulinum type A can survive temperatures of 120°C.  The strains are divided into proteolytic and non- proteolytic types according to whether they hydrolyze proteins or not. Growth characteristics Proteolytic strains grow at temperature range between 10-50°C, while non-proteolytic grow at 3.3- 45°C (optimum 35-37°C). Toxin production occurs at temperature range between 25-30°C. Botulinus toxin is one of the most lethal poisons known. The calculated lethal dose for an adult person is 10 μg.  Food involved Canned food-string beans , corn , beets, peas , figs etc. Preserved meat and fish Preventive measures Proper manufacturing practices e.g. ensure proper sterilization and preservation of canned meat. Preserved foods possessing rancid or other odors should be rejected.  Clostridium perfringens intoxication Clostridium perfringens intoxication caused by Clostridium perfringens enterotoxin (CPE) produced in the gastrointestinal tract. The organism is found in the soil, dust, water, sewage marine sediments, decaying materials, intestinal tracts of humans and other animals If the spores are present as contaminants on raw meat they may resist boiling or steaming for 4 or more hours, and on slow cooling the spores will germinate into rapidly multiplying bacterial cells,which produce large amounts of toxin..  Vehicle foods Foods that have been involved include red meats, chickens, fish, pork, fruits, vegetables, etc. Foods poisoning occurs when the level reaches 107-108 cells/g of food. Growth is enhanced by anaerobic conditions achieved after removal of oxygen.  Prevention Proper cooking of food and eating freshly prepared foods. Fast cooling of cooked food. Storing food in small quantities will enhance cooling. Storage of leftovers or unused foods in freezers.  Fungal intoxications These are caused by consumption of metabolites produced by fungi, when growing in food. These metabolites are calledmycotoxins. Grains, oilseeds, fruits and vegetables are mostly involved if they are stored at high humidity or if they are not properly dried before storage. Types of fungal toxin Aflatoxin Patulin Ochratoxin ……..and many more.  Prevention of mycotoxin Proper drying and storage of grains and other affected foods. Quality control of potentially hazardous foods by use of appropriate analytical tests. Use of fungicides as seed dressings to protect stored cereals and other foods like pulses and potatoes against fungal invasion.  Chemical intoxication Poisoning by consumption of chemicals is rather uncommon and usually is characteristic by appearance of the symptoms with in short time after the poisonous food is eaten. E.g antimony, arsenic, cadmium ,chlorinated hydrocarbons, copper ,cyanide, fluoride, nicotinic acid, lead and zinc.