Paper No.: 03 Paper Title: FOOD MICROBIOLOGY Module 30: Fungal agents for food borne diseases
INTRODUCTION Food, a vital necessity for all organisms present on this earth, is huge repertoire of microorganisms. Among the plethora of microorganisms present in food, some are beneficial while others are pathogenic. Food-borne illnesses impact the entire world. Food-borne diseases result in 325,000 hospitalizations and at least 5,000 deaths per year.
A great many numbers of microbes are associated with food poisoning like Bacteria, Viruses, Fungi, Protozoa and so many other Parasites. The quality of food is subsequently checked by Food and Drug Administration (FDA) and local public health authorities to prevent food borne diseases.
The International Food Safety Authorities Network (INFOSAN) is a joint program of the WHO and FAO which has been connecting national authorities from around the globe since 2004, with the goal of preventing the international spread of contaminated food and foodborne disease and strengthening food safety systems globally.
FOOD BORNE ILLNESS A food borne illness event can be caused by contamination of food with biological agents or pathogens, chemical agents or physical agents. Food borne Illness occurs when either a pathogen itself or one of its toxin (excreted product like dead cell) is ingested with food.
Based on the infection s main causative agent, food borne illness is generally classified into two main categories; 1) Food borne infection, 2) Food borne intoxication. Food borne Infections: It occurs as a consequence of growth of the pathogen in the human body. The two basic categories of food borne infections are:
Invasive Infections: These infections are those which are caused by pathogens that invade body tissues and organs. Examples: Viruses, Salmonella, Aeromonas, Campylobacter, Shigella, Escherichia coli come under this type of infection group.
Toxico infections: These types of infection are caused by infective bacteria that are not considered invasive in nature, but are capable of multiply or colonize in human intestinal tract and produce toxins. Examples: Vibrio cholerae, Bacillus cereus, C. Botulinum, C. Perfringens and verotoxigenic E. Coli.
Food borne Intoxications: This infection is caused by toxins produced by organisms which have grown to sufficient numbers in the food product. Some of the primary bacteria causing food borne intoxications are C. Botulinum, B. Cereus and Staphylococcus aureus. Other non-bacterial toxins that cause illness include:
Paralytic shellfish toxin Ciguatera toxins Scombroid toxins Fungal toxins or mycotoxins Aflatoxins Patulin
FACTORS AFFECTING MICROBIAL GROWTH IN FOOD Various intrinsic and extrinsic factors of food are responsible for the microbial growth in the food product which are given as follows: Food Source: According to the Food and Drug Administration, the food having high protein, low acid, high moist protein content are defined to be potentially hazardous food.
Temperature: Majority of bacteria are mesophilic and grow best in the temperature range of 60-110 F which includes human body temperature (98.6 F). Psychrophilic bacteria grow in cold temperatures 32-60 F and Thermophilic bacteria grow best in hot temperatures -110-171 F. Temperature Danger Zone is -40 F-140 F.
Acidity (ph) : Foods with a ph around 7 are ideal for bacterial growth. Most animal food products including meat, fish, poultry, eggs, and milk have a ph around 7. Vegetables and pasta products which have a high ph in their raw state become ideal for bacterial growth when heated as heating decreases the ph.
Time : Food should not be in the Temperature Danger Zone for more than two hours. The two-hour time frame is culminative and includes all steps in processing, preparation and serving of potentially hazardous foods.
Air/Oxygen : Bacteria reproduce with or without the presence of oxygen. Aerobic bacteria require oxygen, while anaerobic bacteria require no oxygen. Facultative bacteria can survive in environments that may or may not have oxygen present. Most bacteria that are responsible for food borne illnesses are facultative.
Moisture: All bacteria need moisture in a useable form to grow and reproduce. The amount of water that is not part of the food and is available to bacteria for their growth is called water activity. The water activity of pure water is 1.0 as the salt and other chemicals get added in water, its water activity decreases.
MODE OF ACTION OF PATHOGENS Pathogen present in food, enter the body through the digestive tract. In digestive gland they multiply or colonize themselves either to invade the host body or to produce the endotoxins. These invaded microorganisms then generate infection and toxins acts as ligand and interfere in normal functioning of many signaling pathways.
PATHOGENS RESPONSIBLE FOR ILLNESS Fungi: Spore forming fungal agent : Conidiospores Ascospores Basidiospores
Toxin producing fungal agents : Fusarium Trichothecium Cephalosporium Penicillium Aspergillus Claviceps
DISEASES CAUSED DUE TO FUNGI Cirrhosis: It occurs due to Aflotoxin, produced by Aspergillus spp. It may be found in products made from these foods including breads and peanut butter. Symptoms of it are usually low grade fever in humans, weakness.
Balkan Endemic Nephropathy: It is a kind of urinary tract tumors caused by Ochratoxin A (OTA). OTA is a potent nephrotoxin and was first isolated from Aspergillus ochraceus in South Africa. As ochratoxin A may be passed through the food chain in meat products to humans so it can be transmitted easily.
Kodua poisoning: This disease occurs commonly in India due to consumption of kodo millet (Paspalum scrobiculatum) which is both a staple food and an animal feed. Disease is associated with growth of Aspergillus flavus and A. tamarii in millet.
Poisoning in cattle and humans is associated with symptoms of nervousness, lack of muscle coordination, staggering gait, depression and spasms. In human sleepiness, tremors and giddiness may last for one to three days.
Cattle poisoning: Poisoning of cattle is caused by mycotoxin patulin. It is produced by several species of Penicillium, Aspergillus and Byssochlamys but is especially associated with P. expansum.
Yellow Rice Disease: It is a complex of disorders first recognized in Japan. The species of Penicillia associated with yellow rice disease is P. islandicum which produces two groups of toxins, hepatic toxic chlorinated cyclopeptides such as island toxin and less acutely toxic having carcinogenic nature dianthraquinones such as luteoskyrin.
Alimentary Toxic Aleukia: An outbreak due to this disease had been noted down from 1942 1947 in Russia. This disease was found to be associated with the consumption of cereals moulded by Fusarium sporotrichioides and F. poae.
The first symptoms related to this disease are damage of the mucosal membranes of mouth, throat and stomach followed by inflammation of the intestinal mucosa, bleeding, vomiting and diarrhea. Continuous exposure of the toxin leads to damage of the bone marrow and the hematopoietic system followed by anemia and a decrease in erythrocyte and platelet counts.
Red-mould disease: This mould disease involves nausea, vomiting and diarrhea. It is associated with the consumption of wheat, barley, oats, rye and rice contaminated by species of Fusarium.
CONSEQUENCES OF FOOD BORNE DISERASES Although symptoms of food borne illness cease after a relatively short time, complications like Chronic sequalae still occur in certain infected individuals. Examples of chronic sequalae include: reactive arthritis, Reiters syndrome, Guillain-Barre syndrome, ankylosing spondylitis, meningitis, rheumatoid arthritis, septic arthritis, septicemia, and cardiac manifestations.
A person infected with a food borne pathogen can be a carrier and a source of infection to others. Even infected individuals that do not show signs of illness can be chronic carriers. While this is especially true for persons infected with viruses (e.g. hepatitis A).
PREVENTIVE MEASURES Proper handling Proper storage Proper cooking Prevent cross contamination Temperature control Personal hygiene during cooking and eating
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