High frequency of pathogenic Aspergillus species among nonsporulating moulds from respiratory tract samples

Area of Science:

• Medical Mycology
• Clinical Microbiology
• Diagnostic Laboratory Science

Background:

• Nonsporulating moulds (NSM) present significant identification challenges in clinical microbiology laboratories.
• Limited data exists on the prevalence of pathogenic fungal species within NSM clinical isolates.
• Accurate identification of NSM is crucial for appropriate patient management and infection control.

Purpose of the Study:

• To prospectively investigate the prevalence of pathogenic fungal species among thermotolerant NSM isolates from respiratory tract samples.
• To evaluate the utility of phenotypic characterization for identifying Aspergillus species within NSM.
• To address the knowledge gap regarding the clinical significance of NSM in respiratory infections.

Main Methods:

• Prospective collection of consecutive thermotolerant (36°C) clinical NSM isolates from respiratory samples.
• Identification of 123 NSM isolates using DNA sequencing.
• Phenotypic characterization of identified isolates to assess presumptive identification methods.

Main Results:

• Out of 123 NSM isolates, 13 (11%) were identified as pathogenic species.
• Aspergillus fumigatus was the most common pathogenic species (n = 10), followed by Aspergillus flavus (n = 1), Aspergillus hiratsukae (n = 1), and Schizophyllum commune (n = 1).
• Simple phenotypic testing demonstrated potential for presumptive identification of Aspergillus species among NSM.

Conclusions:

• Pathogenic fungal species, particularly Aspergillus fumigatus, are present in a notable proportion of thermotolerant NSM clinical isolates from respiratory sources.
• Phenotypic methods may offer a practical approach for the initial identification of Aspergillus species within NSM.
• Further research into NSM identification and their clinical impact is warranted for improved diagnostics.