Molecular analysis of resistance and detection of non-wild type strains using ECV values of Etest for amphotericin B and echinocandins for bloodstream Candida infections from a tertiary hospital in Qatar. [PublishAheadOfPrint]

A total number of 301 Candida bloodstream isolates were evaluated from 289 patients collected over five years at a tertiary hospital in Qatar. Out of all Candida infections, 53% were diagnosed in patients admitted to the ICUs. Steady increases in non-albicans Candida species were reported from 2009 to 2014 (30.2% C. albicans vs. 69.8% for other Candida species). Etest antifungal susceptibility testing was performed on all recovered clinical isolates to determine echinocandin (micafungin and anidulafungin) and amphotericin B susceptibilities and assess non-wild type (WT) strains (MICs above the epidemiological cutoff values). DNA sequence analysis was performed on all isolates to assess the presence of FKS mutations, which confer echinocandin resistance in Candida species. A total of 3.9% of isolates (12/301) contained FKS hot spot mutations including heterozygous mutations in FKS1 among strains of C. albicans and C. orthopsilosis. For C. tropicalis, the Etest appeared to overestimate non-WT for micafungin, anidulafungin, and amphotericin B, as 14%, 11%, and 35% of strains were above the ECV. However, no FKS mutations were identified in this species. For all other species, micafungin best reported echinocandin non-WT strains relative to FKS genotype, as anidulafungin tended to overestimate non-wild type. Besides C. tropicalis, few strains were classified as non-WT towards amphotericin B.

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