Database of Food Borne Human Pathogens
Bacteria, Virus, Fungi, Protozoa, Helminths
Fungal Food Pathogen
Fungi are living organisms that are distantly related to plants. They are uni- or multi- cellular eukaryotic microorganisms. As eukaryotes, fungal cell contain a membrane bound nucleus where the DNA is wrapped around the histone proteins. Unlike plant cells they do not possess chloroplast or chlorophyll. They show wide range of different colors through cellular pigments. These pigments are associated with cell wall and plays important role in protecting them from UV radiation and it can be toxic also.
Like animals they are heterotrophs: they use complex compounds as a source of carbon.
Fungi like mushrooms, molds and yeasts have been eaten for several thousand years. Although some types of fungi are poisonous to humans. Pathogenic fungi are mainly associated with food crops like maize, wheat or barley.
Fungal contamination of food is one of the most prevalent cause of disease. They produce toxins that cause diseases.
Mycotoxins can cause acute and chronic illnesses, induce cancer, and damage vital organs such as the liver kidney and brain. Fungi like Fusaria, Trichothecium, Cephalosporium etc may contaminate grains and produce illness with symptoms such as vomiting, diarrhea, headaches, chills, dizziness, and blurred vision.
Aflatoxins are produced by molds which favor nuts, corn, millet, and figs. These toxins may produce symptoms like loss of appetite and jaundice immediately and with repeated exposure, they are also carcinogenic.
The common fungi, which grow on food, even in the refrigerator, are Penicillium and Aspergillus. Over 15 tremorgenic mycotoxins have been isolated from these fungi.
The mycotoxin (ochratoxin A) is a common contaminant of foods and beverages such as beer, coffee and wine. It is produced as a secondary metabolite of moulds from Aspergillus and Penicillium genera. It inhibits protein synthesis by competition with phenylalanine, its structural analogue and also enhances the production of oxygen free-radicals. Its multiple toxic effects include cytotoxicity, teratogenicity, genotoxicity, mutagenicity and carcinogenicity.
Mucor is saprophytic fungus and grows on dead organic material. The body of Mucor is composed of a mass of white, delicate, cottony threads collectively known as mycelium. Fungus is heterotrophic in their mode of nutrition. Each thread of the mycelium is known as hypha which is aseptate.
Aspergillus flavus is a saprotrophic and pathogenic fungus. It is best known for its colonisation of cereal grains, legumes, and tree nuts. A. flavus is also an opportunistic human and animal pathogen, causing aspergillosis in immunocompromised individuals. They have also been isolated in air-conditioning systems.
Aspergillus ochraceus is a mold species in the genus Aspergillus known to produce the toxin ochratoxinA, one of the most abundant food-contaminating mycotoxins, and citrinin. It is a filamentous fungus in nature and has characteristic biseriate conidiophores. In humans and animals the consumption of this fungus produces chronic neurotoxic, immunosuppressive, genotoxic, carcinogenic and teratogenic effects.
Aspergillus versicolor is a slow-growing filamentous fungus.The most important species in the "Aspergillus versicolor group". commonly found in damp indoor environments and on food products. It is widely distributed in foods particularly stored cereals, cereal products, nuts, spices and dried meat products. The reported minimum temperature for growth is 9 C at aw 0.97 and the maximum temperature is 39 C at a w 0.87.
It is a thermophile with a temperature range for growth of between 10 and 55 C and an optimum between 40 and 42 C. It is one of the least xerophilic of the common aspergilla.It is best found in decaying vegetation, in which it causes spontaneous heating.It is best recognized as a human pathogen causing aspergillosis of the lung. It is isolated frequently from foods particularly stored commodities.
Aspergillus terreus occurs commonly in soil and foods particularly stored cereals and cereal products,beans, pulses and nuts. Produces rapidly growing pale brown colonies, with Aspergillus heads bearing densely packed metulae and phialides with minute conidia borne in long columns.
All Eurotium species are xerphilic. E. Repen are one of important spoilage moulds in all types of stored commodities like stored grains, spices, nuts and animal feeds.An ascomycete characterized by whitish to bright yellow spherical fruiting bodies (cleistothecia) containing spherical asci which in turn each enclose eight colourless ascospores.
Classification of the penicillia is based on microscopic morphology. The genus Penicillium is divided into subgenera based on the number and arrangement of phialides and metulae and rami on the main stalk cells.
P. citreonigrum is not a commonly isolated species, but it is widely distributed.P. citreonigrum grows in rice after harvest, when the moisture content reaches 14.6%. At 1% higher moisture, other fungi will overgrow it, so the moisture band for invasion is narrow. The fungus is reported to be favoured by the lower temperatures and shorter hours of daylight occurring in the more temperate rice growing areas. The Oriental disease known as "beriberi" has traditionally been regarded as a nutritional disease, an avitaminosis. However, beriberi is more than a single disease, and one form of it, known in Japan as acute cardiac beriberi, has been established to be a mycotoxicosis. Acute cardiac beriberi in Japan is now only of historical interest. However, P. citreonigrum and Citreoviridin may still occur in other parts of Asia. Citreoviridin is also produced by P. ochrosalmoneum
P. citrinum has been a well recognised species for most of this century. Its importance in the present context lies not so much in the production of a mycotoxin of particular human significance, but in its ubiquity, so that any toxins produced can be expected to be very widely distributed in food and feed supplies. P. citrinum is the major producer of citrinin,
Fusarium is one of the most important genera of plant pathogenic fungi on earth, with a record of devastating infections in many kinds of economically important plants. Fusarium species are responsible for wilts, blights, root rots and cankers in legumes, coffee, pine trees, wheat, corn, carnations and grasses. The importance of Fusarium species in the current context is that infection may sometimes occur in developing seeds, especially in cereals, and also in maturing fruits and vegetables. An immediate potential for toxin production in foods is apparent.