Fusarium

another example of molds

1. Fusarium Kenneth Bacalangco BSF III Capiz State University Dayao Satellite College

2. Most  Fusarium  species are soil fungi and have a worldwide distribution. Some are plant pathogens, causing root and stem rot, vascular wilt or fruit rot. Several species have emerged as important opportunistic pathogens in humans causing hyalohyphomycosis (especially in burn victims and bone marrow transplant patients), mycotic keratitis and onychomycosis ( Guarro 2013 ).

3. Other species cause storage rot and are important mycotoxin producers. Currently the genus  Fusarium  comprises at least 300 phylogenetically distinct species. 20 species complexes and nine monotypic lineages.

4. Morphological Description Colonies are usually fast growing, pale or bright-colored (depending on the species) with or without a cottony aerial mycelium . The color of the thallus varies from whitish to yellow, pink, red or purple shades.  Species of Fusarium typically produce both macro- and microconidia from slender phialides .

5. Macroconidia are hyaline, two to several-celled, fusiform to sickle-shaped, mostly with an elongated apical cell and pedicellate basal cell . Microconidia are one or two-celled, hyaline, smaller than macroconidia , pyriform , fusiform to ovoid, straight or curved. Chlamydospores may be present or absent.

6. Cultures of F. oxysporum  showing purple pigmentation and F. subglutinans  showing pink pigmentation.

7. Fusarium chlamydosporum   complex contains five phylogenetically distinct species and is common in soils and the rhizosphere of numerous vascular plants worldwide. It is occasionally isolated from human and animal infections. Fusarium chlamydosporum  complex, culture showing pink to ochraceous to brownish surface and a carmine red reverse.

8. Fusarium dimerum  complex contains 12 phylogenetically distinct species including F. delphinoides , F. penzigii  and F. dimerum . These are regarded as cosmopolitan saprotrophs in soil and on plant materials ( Domsch et al. 2007). They have also been isolated from human corneal ulcers after trauma and from disseminated or localised infections in immunocompromised patients Fusarium dimerum  complex culture showing orange to deep apricot colour due to confluent conidial slime, and macroconidia .

9. Fusarium fujikuroi  complex consists of 50 phylogenetically distinct species including 13 of which have been reported to cause human infection; F. acutatum , F. ananatum , F. andiyazi , F. fujikuroi , F. guttiforme , F. napiforme , F. nygamai , F. verticillioides , F. proliferatum , F. sacchari , F. subglutinans , F. temperatum  and F. thapsinum . Fusarium incarnatum-equiseti complex consists of 40 phylogenetically distinct species. They occasionally cause infections in humans and animals.

10. Fusarium oxysporum complex contains at least five phylogenetically distinct species and accounts for about 20% of human infections caused by fusaria . All are ubiquitous soil borne pathogens responsible for vascular wilts, rots, and damping-off diseases of a broad range of plants. A number of these fusaria are also clinically important, causing localised or deeply invasive life threatening infections in humans and other animals. Mortality in patients who are persistently and severely neutropenic is typically 100%.

11. Fusarium solani complex contains at least 60 species and accounts for about 50% of human infections caused by fusaria . All are ubiquitous soil borne pathogens responsible for vascular wilts, rots, and damping-off diseases of a broad range of plants. A number of these fusaria , notably F. keratoplasticum , F. petroliphilum , F. lichenicola and F. solani are clinically important, causing localised or deeply invasive life threatening infections in humans and other animals.

12. Identification of Fusarium species is often difficult due to the variability between isolates (e.g. in shape and size of conidia and colony colour ) and because not all features required are always well developed (e.g. the absence of macroconidia in some isolates after subculture). Colony growth diameters on potato dextrose agar and/or potato sucrose agar after incubation in the dark for four days at 25˚C. Culture pigmentation on potato dextrose agar and/or potato sucrose agar after incubation for 10-14 days with daily exposure to light . Microscopic morphology including shape of the macroconidia ; presence or absence of microconidia ; shape and mode of formation of microconidia ; nature of the conidiogenous cell bearing microconidia ; and presence or absence of chlamydospores .