RESUMO
Objective:To compare the in vitro susceptibility of fluconazole-resistant Candida albicans strains from superficial and deep infections to 8 antifungal drugs, and to compare drug resistance mutations in these strains. Methods:According to the Clinical and Laboratory Standards Institute (CLSI) protocol M27-A4, 26 deep infection-derived and 33 superficial infection-derived drug-resistant Candida albicans strains were tested for in vitro susceptibility to 8 antifungal drugs (fluconazole, voriconazole, itraconazole, posaconazole, amphotericin B, fluorocytosine, terbinafine, and micafungin) alone or in combination. DNA was extracted from all drug-resistant strains, and mutations in 3 drug resistance genes, including ERG3, ERG11 and FUR1, were detected by PCR. Normally distributed measurement data with homogeneous variance were compared between two groups by using two-independent-sample t test, non-normally distributed measurement data with non-homogeneous variance were compared using Mann-Whitney U test, and enumeration data were compared using chi-square test. Results:The minimum inhibitory concentrations (MICs) of fluconazole, itraconazole, voriconazole, posaconazole and fluorocytosine all significantly differed between the superficial infection group and deep infection group (all P < 0.05) , while there was no significant difference in the MIC of amphotericin B or micafungin between the two groups (both P > 0.05) . The MIC of terbinafine was >64 μg/ml in 96.6% of the above strains, so could not be compared between groups. As combination drug susceptibility testing revealed, the combination of terbinafine with azoles (fluconazole, voriconazole, itraconazole or posaconazole) showed synergistic inhibitory effects against 15 Candida albicans strains (7 strains from deep infections, 8 strains from superficial infections) , with fractional inhibitory concentration (FIC) indices being 0.033 to 0.187; no marked synergistic effect was observed in the combinations between fluorocytosine and azoles, between fluorocytosine and amphotericin B, or between amphotericin B and fluconazole, with the FIC indices being 0.56 to 1.125. The missense mutation V351A in the ERG3 gene was identified in all the 33 (100%) superficial infection-derived strains, as well as in 13 (50%) deep infection-derived strains, and the mutation A353T in the ERG3 gene was identified in 4 (15%) deep infection-derived strains; as for the ERG11 gene, missense mutations identified in the superficial infection-derived strains included I437V (32 strains, 97%) , Y132H (23 strains, 70%) , T123I (16 strains, 48%) , K128T (6 strains, 18%) , D116E (5 strains, 15%) , A114S (4 strains, 12%) , E266D (2 strains, 6%) , G448E (2 strains, 6%) , and G465S (2 strains, 6%) , while missense mutations identified in the deep infection-derived strains included I437V (23 strains, 88%) , E266D (13 strains, 50%) , E260G (5 strains, 19%) , and V488I (4 strains, 15%) ; the missense mutation R101C in the FUR1 gene was identified in 11 (33%) superficial infection-derived strains, but not identified in deep infection-derived strains. Conclusion:The drug susceptibility and drug resistance mutations differed to some extent between superficial infection- and deep infection-derived fluconazole-resistant Candida albicans strains.
RESUMO
Objective:To summarize clinical characteristics of patients with Aspergillus fumigatus infection in a hospital in Nanjing, to preliminarily assess azole resistance in clinical isolates of Aspergillus fumigatus, and to investigate risk factors for the emergence of azole-resistant Aspergillus fumigatus. Methods:Clinical isolates of Aspergillus fumigatus were collected from inpatients in Department of Laboratory, Nanjing Drum Tower Hospital from March 2017 to February 2021. Clinical data on these infected patients were analyzed, azole sensitivity testing and mutation analysis of the cyp51A gene and its promoter region were performed for these Aspergillus fumigatus isolates. Results:A total of 201 strains of Aspergillus fumigatus were collected, and mainly isolated from sputum specimens. Among the infected patients, there were 131 males and 70 females, and their age were 64.2 ± 15.8 years. The patients were mainly collected from department of respiratory medicine (79 cases), department of intensive medicine (34 cases), department of rheumatology (19 cases), etc. Among these patients, common underlying diseases included interstitial pneumonia (32 cases), malignant tumors (18 cases), pneumonia (13 cases), trauma (12 cases), systemic lupus erythematosus (8 cases), etc. Drug susceptibility testing showed that 6 (2.99%) strains of Aspergillus fumigatus were resistant to itraconazole and posaconazole, and 3 patients infected with azole-resistant Aspergillus fumigatus had used antifungal drugs before testing. Sequencing was performed on the cyp51A gene and its promoter region in the 6 strains of azole-resistant Aspergillus fumigatus, and showed TR34/L98H/S297T/F495I mutation in 5 strains and TR34/L98H mutation in 1 strain. Conclusion:Compared with previously published data about azole resistance in China during 2010 -2015, the resistance of Aspergillus fumigatus to azoles in Nanjing Drum Tower Hospital did not increase from 2017 to 2021, and the mechanism of azole resistance was mostly associated with TR34/L98H/S297T/F495I mutation in the cyp51A gene and its promoter region.