Good Literature Review On Foodborne Illnesses

Food itself does not readily cause diseases except when it contains intrinsic toxins or allergenic components, or when consumed in toxic or physically incapacitating quantities. Many of the infectious agents capable of causing foodborne diseases readily occur in enormous numbers. A variety of pathogens present in different types of food can cause illnesses, which may be life threatening. Examples of such pathogens are Clostridium perfringens, Staphylococcus aureus and Salmonella . The exposure of human beings to a variety of foodborne pathogens readily occur over secure geographical barriers at a higher rate, which the human evolution cannot keep pace. Susceptibility to foodborne diseases increases as a result of impairment of the immune system caused by infection.
Clostridium perfringens is one of the most widely occurring bacterial pathogens and the most prolific toxin-producing species within the clostridium group. The bacterium possesses several attributes that contribute significantly to its ability to cause foodborne illnesses. The attributes are a ubiquitous distribution throughout the natural environment, giving it ample opportunity to contaminate foods, the ability to form heat-resistant spores allowing it to survive in incomplete cooking or improper sterilization of foods, the ability to grow quickly in foods allowing it to reach the highest levels necessary to cause food poisoning, the ability to produce an intestinally-active enterotoxin responsible to cause gastrointestinal disorders . C. perfringens is a virulence factor responsible for the diarrheal and cramping symptoms associated with the foodborne diseases.
C. perfringens is an anaerobic, rod-shaped, gram positive, encapsulated, spore-forming bacterium found in soil, food, water and air. The various types of C. perfringens bacterium are type A, B, C, D and E. the apparent cause of foodborne illness is type A bacterium. Type C and D produce enterotoxin, but there is no data implicating the strains of the bacteria in foodborne illnesses. Types B, C and D primarily occur in the intestines of animals rather human beings. The pathogenicity of type E is not clear. The foodborne diseases caused by type A C. perfringens are gas gangrene, food poisoning, necrotic enteritis of infants, necrotic enteritis of poultry and colitis . C. perfringens is fermentative and grows rapidly in food containing carbohydrates. The bacterium produces copious amounts of H2 and CO2 to maintain an anaerobic environment.
Meat and poultry are the most common carriers of C. perfringens with being contributing 30 percent followed by turkey and chicken, which account for 15 percent. The number of individuals affected per outbreak of foodborne disease caused by C. perfringens is typically between 40 and 70. Temperature abuse of cooked foods invariably involves in the outbreak of the disease with a high optimum growth temperature between 43 and 46oC. Pasteurization temperatures of 72oC for five to ten minutes and routine cooking procedures readily inactivate the vegetative cells of the pathogen . The most significant contributing factor for the outbreak of C. perfringens bacterium is the failure to properly cool previously-cooked foods, especially when prepared in larger portions.
Staphylococcus is another infectious agent associated with the foodborne illnesses and is the major cause of sporadic food poisoning episodes around the world. Many of the 32 species and subspecies in the genus Staphylococcus are potentially present in food due to environmental, human and animal contamination. The growth and proliferation of S. aureus present a potential hazard to human health since many strains of S. aureus produce enterotoxins. Foods commonly associated with S. aureus food poisoning fall into general categories, such as meat and meat products, cream-filled bakery products, salads and dairy products . The contamination of food takes place while preparation at homes or food-service establishments, mishandled prior consumption. Processed foods destroy the presence of S. aureus; however, the presence of the pathogen indicates contamination from the skin, mouth or nose of 50 percent or more of healthy individuals.
S. aureus is a spherical bacterium, which on microscopic examination appears in pairs, short chains or grape-like clusters. Some strains of the bacterium produce a highly heat-stable protein toxin capable of causing illness in humans. The bacterium is non-motile and asporogenous in nature. S. aureus may be aerobe or facultative anaerobe having both respiratory and fermentative metabolism. Although S. aureus are mesophilic, some strains grow at temperatures as low as 6.7oC. The general temperature for the growth of the bacterium ranges from 7 to 47.8oC with an optimum temperature of 35oC . The pH range for the growth of the bacterium ranges between 4.5 and 9.3. Most of the strains of S. aureus are highly tolerant to the presence of salts and sugars.
S. aureus is capable of producing a large number of extracellular enzymes, toxins and chemical components. The pathogen is multi-resistant gram-positive bacterium, which is the root cause for the most common symptoms of foodborne illnesses, such as nausea, vomiting, abdominal cramping, headache, muscular cramping and diarrhea . The symptoms are rapid and occur within 2 to 6 hours from the consumption of contaminated food. The severity of the symptoms depend on the individual susceptibility to the toxin, the amount of contaminated food consumed, the amount of toxin in the ingested food and the immune system of the victim. Death from staphylococcal food poisoning is rare, although such cases are common in the elderly, infants and deliberate persons.
S. aureus grows and produces acid from glucose and mannitol anaerobically. The cells of the bacterium contain teichoic acids in the cell wall. The presence of clumping factor is another characteristic of the bacterium. A coagulase test helps to best determine the presence of S. aureus in the food substances. The complete destruction of the S. aureus bacterium is possible by treating the food with lethal or sublethal stresses, such as heat, cold, drying, irradiation and chemicals . In order to prevent the food-poisoning outbreaks, it is necessary to keep the foods at temperatures below 10oC or above 45oC to prevent the proliferation of the bacterium in large numbers. It is also important to place the foods in small layers and portions in order to facilitate quicker cooling. While the bacterial inoculum size is important, time-temperature abuse and nutritional composition of the contaminated food are critical.
Salmonella is another type of bacteria, which are widespread and an important cause of foodborne illnesses in human beings. They are the most frequent etiologic bacterial agents of foodborne disease outbreaks, such as typhoid and paratyphoid fever, which is an important cause of morbidity. The genus of the bacteria is motile, gram-negative, facultative anaerobic, non-spore-forming rods, which grows at temperatures between 35 and 37oC . A variety of disease syndromes caused by Salmonella include enterocolitis, bacteremia or enteric fever, and focal infections including absorption. During the course of infection, Salmonella colonizes the intestine. Human beings commonly acquire salmonella as a foodborne infection with raw or undercooked eggs, poultry, meat and pasteurized milk as the transmitters.
The incidence of Salmonella is usually the highest in infants and young children. There is also a slight increase among elderly persons. Salmonella infections have a marked seasonality. In the northern hemisphere, the infections are common in the month of August, while in the southern hemisphere, the infection peaks in the month of March. Salmonella enters the human body through the fecal-oral route, although swallowing of contaminated aerosols causes infections in rare situations . The number of organisms ingested, transmission of infection and several host factors are important in determining the outcome of exposure. Direct or indirect contact with animals colonized with Salmonella is another source of infection. Chronic illness, including immunosuppressive disease, malignant disease and diabetes decrease the number of bacteria required to cause the illness .
Salmonella-induced enterocolitis is the second most common cause of bacterial foodborne diseases. The classical symptoms of Salmonella as an acute gastrointestinal illness are indistinguishable from those caused by other pathogens. Within 6 to 48 hours after ingestion of the contaminated food, diarrhea with fever and abdominal cramps occurs . Most patients develop symptoms 24-48 hours after exposure to contaminated food containing larger numbers of bacteria. In some patients, symptoms develop as late as 10 days after exposure. The mean duration of carriage of Salmonella is 4-5 weeks after the resolution of the infection. The use of antibiotics to control the latent infection with Salmonella increases the risk of antimicrobial resistance development. The complete elimination of the infection from the human body is virtually impossible.
It is important to prevent the foodborne diseases as they are the major cause of death in the world. Control measures to reduce the prevalence of foodborne diseases include vaccination and blocking the routes of transmission by improving sanitation. The prevention of the foodborne-causing pathogens must focus not only on the destruction of the bacteria, but also multiplication of vegetative cells in cooked foods . Government agencies and public health officials must issue effective guidelines specifying the cooling parameters for food. People should be aware of the recommended food handling procedures to prevent the contamination of food and water. Following proper hygienic techniques prevents the spread of contamination of food. Food processors in addition to insuring good hygienic practices among food handlers should screen workers for signs of potential infections.

References

Cliver, Dean O., Morris Potter and Hans P. Riemann. Foodborne Infections and Intoxications. Academic Press, 2011.
Labbé, Ronald G. and Santos García. Guide to Foodborne Pathogens. John Wiley & Sons, 2013.
Landau, Elaine. Food Poisoning and Foodborne Diseases. Twenty-First Century Books, 2010.
Simjee, Shabbir. Foodborne Diseases. Humana Press, 2011.