This study aimed at investigating the in vitro effectiveness of aztreonam/avibactam, colistin/avibactam, colistin/apramycin, and meropenem/apramycin combinations against carbapenemase-producing, extensively drugresistant (XDR) Klebsiella pneumoniae strains. This study evaluated 38 carbapenem-resistant, carbapenemaseproducing, and XDR K. pneumoniae strains. The checkerboard method was used to examine the efficacy of aztreonam/avibactam, and meropenem/apramycin combinations in all strains and the colistin/apramycin combination in colistin-resistant strains (n = 26). It was found that when used alone, aztreonam and avibactam had high minimum inhibitory concentration values in all strains and that all strains were resistant to aztreonam. Nevertheless, the aztreonam/avibactam combination was found to have a synergistic effect against all strains. Apramycin alone was effective against 30 K. pneumoniae strains (79%); however, 8 strains (21%) were found to be resistant. In the synergy testing of 26 colistin-resistant strains with the checkerboard method, the colistin/ apramycin combination was found to have a synergistic effect against 4 strains (15.3%), an antagonistic effect against 8 strains (30.7%), and an additive effect against 14 strains (54%). By comparison, the meropenem/ apramycin combination had a synergistic effect against 20 strains (52%) and an additive effect against 12 strains (31%). The aztreonam/avibactam combination showed a high in vitro synergistic effect on carbapenemaseproducing and XDR K. pneumoniae strains, such as Metallo-b-lactamase, and provided good prospects for the successful treatment. The meropenem/apramycin combination was also highly synergistic. The synergistic effects were low for the colistin/apramycin combination that was tested on colistin-resistant strains. However, it is promising that apramycin has low minimal inhibitory concentration values.

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Introduction: It is important to identify infection-causing yeasts rapidly and perform antifungal susceptibility tests in order to determine the treatment to be applied. The aim of this study was to use direct germ tube test (GTT) from blood culture bottle for rapid differentiation of albicans/ non-albicans Candida species to evaluate the possble contribution of this test to the implementation of earlier and narrower-spectrum antifungal therapy compared to conventional methods. Materials and Methods: This 4-years retrospective study included 129 positive automated blood culture samples with yeast detected in Gram staining among 11,080 blood cultures obtained from inpatients in various wards. GTT was performed directly from these bottles. All isolates were identified by VITEK (bioMérieux, Marcy-l'Étoile, France) and antifungal susceptibility tests were performed with the VITEK 2® automated system (bioMérieux, Marcy-l'Étoile, France). Results: Candida albicans was identified as the causative agent in 57 (44.2%) of the 129 blood cultures with direct Gram staining from the bottle. Conventional GTT was positive for all C. albicans isolates (100%), while direct GTT from blood culture bottle was positive in 54 (94.73%). Direct GTT from blood culture yielded false-negative results in the remaining three samples (5.27%). There was 97.6% (126/129) agreement between conventional GTT method and direct GTT from blood culture bottle. Non-albicans Candida species were isolated from the 72 samples with negative direct GTT from blood culture bottle (43 C. parapsilosis, 17 C. tropicalis, 7 C. famata, 4 C. glabrata, and 1 C. lipolytica). Conventional GTT results were also negative for all of these isolates. Conclusion: Direct GTT from positive blood cultures that are shown to contain yeast by Gram staining enabled differentiation of albicans/nonalbicans Candida species one day earlier than conventional culture. This method shows a high agreement rate with conventional diagnostic tests. It should be kept in mind that false negative results may be obtained at very low rates. This test may be helpful for initiation of a more appropriate empirical antifungal treatment. Furthermore, it is easy and can be applied in all clinical microbiology laboratories.

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