A KOH mount from a lung abscess sample shows hyphae that are septate and branch at acute angles of approximately 45 degrees. A second sample from another patient shows broad, ribbon-like aseptate hyphae branching at right angles. The second patient's specimen most likely represents infection by fungi belonging to which taxonomic group?

• A Basidiomycetes, genus Filobasidiella
• B Hyphomycetes, order Moniliales
• C Ascomycetes, genus Aspergillus
• D Mucorales, class Zygomycetes ✓

Explanation

Broad, ribbon-like, pauciseptate hyphae with right-angle branching define the Mucorales (formerly Zygomycetes), including Rhizopus, Mucor, and Lichtheimia, agents of mucormycosis in diabetics and neutropenic patients. Septate hyphae with acute 45-degree branching describe Aspergillus, which belongs to the Hyphomycetes among the ascomycetous anamorphs, not to the Mucorales. Filobasidiella is the teleomorphic state of Cryptococcus, a yeast, and would not produce hyphae in tissue.

Reference: Sherris Medical Microbiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.