Comparative assessment of Sensititre YeastOne and Micronaut-AM EUCAST for antifungal susceptibility testing in candidaemia isolates.

Antifungal susceptibility testing (AFST) is essential to ensure appropriate antifungal therapy in candidaemia. This study compared two commercial colorimetric broth microdilution tests: Sensititre YeastOne (SYO; Thermo Scientific) and Micronaut-AM EUCAST AFST (M-AM; Bruker) for the AFST of Candida spp. A total of 74 yeast strains, including C. albicans (n = 40) and non-albicans Candida species (NACS) (n = 34), were obtained from blood cultures of patients admitted to a tertiary care hospital in Belgium from 2017 to 2022. AFST by SYO and by M-AM were performed according to the manufacturers' protocols and interpreted using CLSI and EUCAST guidelines, respectively. Essential and categorical agreements (EA and CA), very major, major and minor discrepancies were calculated for amphotericin B, echinocandins and azoles considering SYO as the reference method. In total, 441 and 392 isolate-antifungal results were evaluable for EA and CA, respectively. SYO and M-AM, showed a high level of concordance for C. albicans strains, with an EA and CA ≥90 % for all tested antifungals. However, we noted significant discordances for NACS, the lowest EA were observed with micafungin (50 %) and voriconazole (58.8 %). These discrepancies were likely due to differences in the raw MIC values obtained by the two methods and the different interpretation breakpoints used by CLSI and EUCAST. Our study showed excellent agreement between SYO and M-AM for AFST of C. albicans, while the equivalency was lower for NACS. AFST method should be carefully selected, considering the results might impact the choice of antifungals for non-albicans candidaemia

Multicenter interlaboratory study of routine systems for the susceptibility testing of temocillin using a challenge panel of multidrug-resistant strains.

Accurate susceptibility result of temocillin (TMO) is important for treating infections caused by multidrug-resistant Enterobacterales. This multicenter study aimed to investigate the performance of routine temocillin testing assays against Enterobacterales challenging strains. Forty-seven selected clinical isolates were blindly analyzed by 12 Belgian laboratories using VITEK® 2 (n = 5) and BD Phoenix™ (n = 3) automated systems, ETEST® gradient strip (n = 3), and disk (3 brands) diffusion method (DD; n = 6) for temocillin susceptibility using standardized methodology. Results were interpreted using EUCAST 2023 criteria and compared to the broth microdilution (BMD; Sensititre™ panel) method used as gold standard. Methods' reproducibility was assessed by testing 3 reference strains in triplicate. A total of 702 organism-drug results were obtained against 33 TMO-susceptible and 14 TMO-resistant isolates. Excluding Proteae species (P. mirabilis and M. morganii), the essential agreement rates were excellent (91.5-100%) for all MIC-based methods. The highest category agreement was achieved by ETEST® (97.5%) followed by VITEK® 2 (93.2%), disk diffusion (91.6%), and BD Phoenix™ (88.5%). BD Phoenix™ and paper disk diffusion overcalled resistance (11.5% and 6.8% of major discrepancies, respectively), while ROSCO tablets diffusion and VITEK® 2 generated higher very major discrepancies (7.1% and 4.2% respectively). Inter-assay reproducibility was unsatisfactory using recommended E. coli ATCC 25922 strain but was excellent with E. coli ATCC 35218 and K. pneumoniae ATCC 700603 strains. This interlaboratory study suggests that routine testing methods provide accurate and reproducible TMO categorization results except for Proteae species