ABSTRACT
Background: C. krusei is an opportunistic fungal pathogen that known of its intrinsic fluconazole resistance and its frequency is increasing especially among hematology patients. The increase in the frequency of high mortality fungal infections have accelerated the efforts of new drug development with broad spectrum, low toxicity and the studies including their combination. However, there is no standardized method to evaluate the activity of drug combinations. Aims: To evaluate the activity of caspofungin (CAS) with voriconazole (VOR) and amphotericin B (AMB) alone and in combination and the utility of Etest and disk diffusion methods for antifungal combinations. Methodology: The minimum inhibitory concentrations of VOR, CAS and AMB against 30 clinical C. krusei isolates were determined by using Etest, disk diffusion and reference broth microdilution methods. Combinations of CAS with VOR and CAS with AMB were evaluated using disk diffusion (three different ways) and Etest (two different ways) methods. Results: All isolates tested were susceptible to VOR and CAS in vitro by all three methods. Categorical agreements of Etest and disk diffusion methods with reference microdilutiontest were 100% for CAS and VOR (for each method), 86.7% and 50% for AMB, respectively. In the all ways of both combination methods, we did not observe distinctly antagonistic or synergic interaction. Conclusion: Etest and disk diffusion could be easy, convenient, and nontime-consuming alternative methods to evaluate the antifungal combinations. The combinations of CAS with VOR and AMB exhibited promising results because of an apparent antagonistic interaction was not detected in this study.
ABSTRACT
Aims: Candida species cause a wide spectrum of diseases, including hospital-acquired and device-associated infections. The biofilm formation is a major virulence factor in Candida pathogenesis and the cells in biofilm show enhanced resistance to disinfectants. Our aim was to evaluate the efficiency of the commonly used hospital disinfectants (glutaraldehyde (GLU), hydrogen peroxide (HP), peracetic acid (PA), ortho-phtalaldehyde (OPA) and sodium hypochlorite (SH) on biofilms of clinical Candida (C. albicans, C. glabrata, C. parapsilosis, C. krusei and C. tropicalis) isolates. Study Design: An experimental study. Place and Duration of Study: Department of Microbiology, Faculty of Medicine and Electron Microscope Laboratory, Eskisehir Osmangazi University, between January 2011 and May 2011. Methodology: These disinfectants were selected due to their common application in hospital environment. Their concentrations were adjusted to manufacturer’s recommendations for instrument disinfection: 5% HP, 0.2% PA, 5.25% SH (5000 ppm of chlorine), 2% GLU and 0.55% OPA. They were also prepared at the 1:2 and 1:4 times of recommended concentration to evaluate the activity of lower concentrations. The biofilms were grown in microplates and treated with disinfectants at contact times 1, 5 and 10 minutes (20 min for GLU), then stained with the biomass indicator (2, 3-Bis [2-methoxy-4- nitro-5-(sulfenylamino) carbonyl-2H-tetrazolium-hydroxide]). Results: The disinfectants reduced the biofilm for all concentrations studied, however none of them completely removed the biofilm. When they were used at low concentration, longer contact times were more effective. However, when the disinfectants were used in recommended concentration, results showed many variations depending on the disinfectant type, contact times and species. Conclusion: Our results also emphasize the importance of regular disinfection, before the starting of biofilm formation.