Fusarium: The versatile pathogen

Fusarium is an emerging human opportunistic pathogen of growing importance, especially among immunosuppressed haematology patients due to an increased incidence of disseminated infections over the past two decades. This trend is expected only to continue due to the advances in medical and surgical technologies that will prolong the lives of the severely ill, making these patients susceptible to rare opportunistic infections. Production of mycotoxins, enzymes such as proteases, angio-invasive property and an intrinsically resistant nature, makes this genus very difficult to treat. Fusarium is frequently isolated from the cornea and less commonly from nail, skin, blood, tissue, Continuous Ambulatory Peritoneal Dialysis (CAPD) fluid, urine and pleural fluid. Conventional microscopy establishes the genus, but accurate speciation requires multilocus sequence typing with housekeeping genes such as internal transcribed spacer, translation elongation factor-1? and RPB1 and 2 (largest and second largest subunits of RNA polymerase), for which expansive internet databases exist. Identifying pathogenic species is of epidemiological significance, and the treatment includes immune reconstitution by granulocyte–colony-stimulating factor, granulocyte macrophage–colony-stimulating factor and a combination of the most active species – specific antifungals, typically liposomal amphotericin-B and voriconazole. However, patient outcome is difficult to predict even with in vitro susceptibility with these drugs. Therefore, prevention methods and antifungal prophylaxis have to be taken seriously for these vulnerable patients by vigilant healthcare workers. The current available literature on PubMed and Google Scholar using search terms 'Fusarium', 'opportunistic invasive fungi' and 'invasive fusariosis' was summarised for this review.

Banana peel culture as an indigenous medium for easy identification of late‑sporulation human fungal pathogens.

Aim: Fungi are increasing in incidence as human pathogens and newer and rarer species are continuously being encountered. Identifying these species from growth on regular culture media may be challenging due to the absence of typical features. An indigenous and cheap medium, similar to the natural substrate of these fungi, was standardised in our laboratory as an aid to species identification in a conventional laboratory setting. Materials and Methods: Ripe banana peel pieces, sterilised in an autoclave at 121°C temperature and 15 lbs pressure for 15 min promoted good growth of hyphae and pycnidia or acervuli in coelomycetes, flabelliform and medusoid fruiting bodies of basidiomycetes and fruit bodies such as cleistothecium in ascomycetes. The growth from the primary isolation medium was taken and inoculated onto the pieces of double‑autoclaved ripe banana peel pieces in a sterile glass Petri dish with some moisture (sprinkles of sterile distilled water). A few sterile coverslips were placed randomly inside the Petri dish for the growing fungus to stick on to it. The plates were kept at room temperature and left undisturbed for 15–20 days. At a time, one coverslip was taken out and placed on a slide with lactophenol cotton blue and focused under the microscope to look for fruit bodies. Results: Lasiodiplodia theobromae, Macrophomina phaseolina, Nigrospora sphaerica, Chaetomium murorum, Nattrassia mangiferae and Schizophyllum commune were identified by characteristic features from growth on banana peel culture. Conclusions: Banana peel culture is a cheap and effective medium resembling the natural substrate of fungi and is useful for promoting characteristic reproductive structures that aid identification.