Molecular identification and antifungal susceptibility testing of Aspergillus species among patients with chronic pulmonary aspergillosis in Nigeria.

BACKGROUND

Triazole resistance in Aspergillus spp. has therapeutic implications for managing chronic pulmonary aspergillosis (CPA) worldwide. However, antifungal susceptibility testing (AFST) is not routinely performed in Nigeria, a country with a high CPA burden.

OBJECTIVE

This study aimed to confirm the identity of Aspergillus spp. isolated from patients with CPA using molecular methods, determine their antifungal susceptibility profile, and ascertain phylogenetic relatedness.

METHODS

This study examined 47 Aspergillus isolates from sputum samples obtained in a prospective longitudinal study of CPA prevalence among 141 consenting symptomatic tuberculosis patients in Lagos, Nigeria, between June 2021 and May 2022. The preliminary phenotypically identified Aspergillus spp. were further identified by amplifying the calmodulin gene and performing AFST against seven antifungal agents using the Clinical Laboratory Standard Institute (CLSI) micro-dilution method, as well as determining their phylogenetic relatedness.

RESULTS

The 51 patients who met the diagnostic criteria for CPA included 30 (59.0%) male and 21 (41.0%) female patients (age range: 17-68 years). Thirty-six (71.0%) had positive Aspergillus cultures. An isolate, initially identified phenotypically as A. fumigatus, was reidentified as A. pseudonomiae. Phylogenetic analysis on A. fumigatus and A. flavus isolates suggested the absence of clonal transmission. All isolates were susceptible to the tested antifungals.

CONCLUSION

Clinical Aspergillus isolates from azole-naïve patients with CPA did not demonstrate triazole resistance. Nonetheless, AFST is required for patients on long-term azole therapy and systematic surveillance of clinical and environmental isolates is recommended to detect the emergence of azole-resistant phenotypes.

WHAT THIS STUDY ADDS: This study underscores the importance of routine surveillance for antifungal resistance to detect the occurrence of resistance strains early in clinical settings, as this has therapeutic implications for patients harbouring resistant phenotypes.