Two cases of fungal keratitis caused by Metarhizium anisopliae

Abstract

We present two cases of keratitis due to Metarhizium anisopliae in geographically separated areas of the United States. The isolates were microscopically similar but morphologically different and were identified by ribosomal DNA sequencing. Both isolates had low minimum inhibitory concentration (MIC) values to caspofungin and micafungin, but high MIC values to amphotericin B. The morphologic and antifungal susceptibility differences between the two isolates indicate possible polyphylogeny of the group.

Keywords: Antifungal susceptibility; Fungal keratitis; Keratomycosis; Metarhizium.

Fig. 1

Morphologically different colony types of the B10964 (A, B), Georgia isolate, and B11022 (C, D), Missouri isolate, Metarhizium anisopliae isolates after 7 days of growth on Sabouraud dextrose agar at 25 °C (BBL, Becton, Dickinson and Company, Franklin Lakes, NJ). Colonies are floccose with a dense heaped center that was either light with a dark green ring (B10964) or yellow-green (B11022), both with a white fringe. The reverse of both isolates was a brownish orange color.

Fig. 2

Lactophenol cotton blue stain of slide culture of the Georgia Metarhizium anisopliae (B10964) isolate, showing slender conidiophores with verticilliate branching ending with clavate, parallel phialides and cylindrical microconidia in chains (original magnification, 400 ×).

Fig. 3

Neighbor-joining tree of combined ITS and D1/D2 regions of the ribosomal cistron. Alpha-numeric numbers are NCBI accession numbers.