Microbiology

The PROMEC Unit is considered a centre of excellence with regard to the identification of Fusarium and other fungi of food-borne, agricultural and medical origin. The Subprogramme Microbiology forms an integral part of the PROMEC Unit and performs identifications of fungi, purifications of cultures and toxin profiling of mycotoxigenic fungi for projects undertaken within the PROMEC Unit, and with national and international collaborators. The necessary expertise in general and medical mycology as well as plant pathology exists, and a great scope for research capacity development is realised through personnel training and the training of pre- and postgraduate students and scientists from South Africa, Africa and overseas. The Subprogramme strives for research excellence on goals and research projects, which are in line with the MRC’s Strategic Plan.

The Projects and Activities of the Subprogramme Microbiology include:

Isolation, Enumeration, Identification and Preservation of Food-borne, Pathogenic and Medically Important Fungi

 Food-borne fungi, as well as those of pathogenic origin, are cultured on routine, selective and specialised media and identified. Fungi present in a wide range of food samples are enumerated by means of direct and plate dilution techniques in order to quantify fungi from a specific food source. National and international liaisons are well established for confirmation of identifications whenever necessary. Pure cultures, free from any bacterial or other fungal contamination, are prepared from single-spored cultures before deposition in the MRC PROMEC Unit culture collection. The culture collection housed in Microbiology is of paramount importance and forms the basis of many of the studies in the PROMEC Unit. Several methods for the preservation of fungi are currently being used, namely lyophilization (freeze-drying), preservation at -80°C in glycerol, distilled water and agar slants. The collection consists of more than 9000 cultures, is unique from both a food-borne and pathogenic fungal point of view and is of one of the largest Fusarium collections in the world. A complete database on information regarding the culture collection has been set up and is being maintained.

Determination of the Occurrence and Toxigenicity of Food-borne Fungi and Their Toxicology

Fungi that occur regularly in high concentrations in staple foodstuffs and their health implications are investigated. The occurrence and incidence of food-borne fungi in samples of staple foods obtained from commercial and home-grown sources are determined. Fungi are taxonomically investigated, grown in bulk, tested for toxicity and carcinogenicity in animals and chemically analysed for mycotoxins. Staple foods are analysed for the natural occurrence of mycotoxins in collaboration with the Subprogramme Biochemistry. The aim is to identify the food-borne fungi that present a threat to human health and to devise methods to protect populations throughout South Africa from dietary exposure to mycotoxins. Several mycotoxins, including fumonisins, patulin and aflatoxin, are involved.

Fusarium infested homegrown maize, Transkei region of South Africa

Post-harvest fungal infection due to Penicillium expansum in Granny Smith apples

Investigations into the in vitro Production of Mycotoxins and Carcinogens

Research is directed to the mechanisms in the production of fumonisins by Fusarium verticillioides due to the national and international demand for fumonisin analytical standards. The biosynthesis of mycotoxins and the conditions that influence mycotoxin production by food-borne fungi, under natural and experimental conditions, both in solid and liquid media under varying physiological conditions, are investigated. The research ensures high-grade fungal metabolites for experimental research to determine carcinogenic, mutagenic and toxicological effects and for commercial sales. Molecular studies into the gene regulation of fumonisin production by F. verticillioides are essential to understand and stabilise the mechanism of toxin production. Toxin levels and food-borne fungi, occurring in consumables and staple foods are correlated to experimental findings. This will also assist in establishing legal tolerance levels of mycotoxins in foods in South Africa. 

Reduction of Fusarium Species and Their Mycotoxins as Risk Factors of Oesophageal Cancer and Other Health Problems in Rural Communities

 Oesophageal cancer (OC) has reached near "epidemic" proportions in certain districts of the Transkei region in the Eastern Cape Province. Incidences of neural tube defects are also very high in the region. Both these health problems are associated with mycotoxins in the staple diet, i.e. maize, of these rural communities. Several factors have been implicated that may influence the presence of F. verticillioides and the consequent production the fumonisin mycotoxins in maize, and include agricultural practices, pre- and post harvest insect infestations and fungal contamination. To investigate and identify the interaction of these important risk factors, the effect of the introduction of Bt maize, fungal and insect resistant maize hybrids on fungal incidence and mycotoxin production are being done. Research results would assist in devising methods by which these risk factors can be reduced within the rural population by means of the implementation of intervention strategies.

Studies in Pathogenic and Medically Important Fungi

Continued research into pathogenic fungi, particularly superficial and subcutaneous infections such as dermatophytoses and sporotrichosis, has indicated that new drugs including itraconazole and terbinafine, as alternative treatment regimens, are efficacious in their treatment. Molecular studies are currently being conducted on human and environmental isolates of Sporothrix schenkii. The incidence of tinea capitis and tinea corporis in school children in the Transkei region was conducted with excellent outcome of treatment, which was obtained from local pharmaceutical companies. Medical mycology workshops have been presented throughout South Africa in an attempt to standardise laboratory methods in the handling and identification of human pathogenic and opportunistic fungi. Laboratories serving underprivileged communities, where fungal infections are of great public health concern, have been included. The Pan African Medical Mycology Society was launched in 2005 in an attempt to stimulate medical mycology in South Africa and the rest of Africa and to ensure collaboration between scientists of the African continent particularly due to emergence and sharp increase of fungal infections amongst HIV/AIDS subjects. Continued clinical, epidemiologic and therapeutic studies as well as morphological, ecological and molecular studies on the fungi causing mycoses, are in progress.