Aims: Urinary tract infection (UTI) caused by Candida spp. is an increasing problem in clinical practice. Risk factors include diabetes mellitus, extremes of age, urinary tract abnormalities and indwelling catheters. Here, we determined the applicability of isothermal microcalorimetry (IMC) for the detection and antifungal drug susceptibility testing of Candida albicans in artificial urine.
Methods and results: Isothermal microcalorimetry was used to monitor the metabolic heat production rates of C. albicans at 37 °C (μW = μJ s(-1) ). The influence of increasing concentrations of glucose and antifungal drugs on the growth of C. albicans was investigated. The growth rate increased linearly from 0.024 ± 0.010 to 0.203 ± 0.006 h(-1) with increasing concentration of glucose from 20 to 1640 mg l(-1) . The minimum inhibitory concentrations (MIC) against C. albicans were determined at a fixed glucose concentration of 560 mg l(-1) . These MIC were 0.5 μg ml(-1) for amphotericin B, 5 μg ml(-1) for flucytosine, 0.8 μg ml(-1) for fluconazole and 0.5 μg ml(-1) for tioconazole, respectively.
Conclusions: IMC is able to detect and quantify growth of C. albicans in artificial urine and to determine the MIC of antifungal drugs against C. albicans. This study demonstrated that IMC can be used for basic research on Candida-UTI and opens promising avenue for the use of IMC as rapid drug resistance screening tool and diagnostic tool.
Significance and impact of study: Little is known on the growth of C. albicans in urine. Our study provides measurements of the growth rate of this yeast in urine with various glucose concentrations. Thus, important insights are gathered for risk group such as patients with diabetes or patients with prolonged parenteral nutrition resulting in higher urinary glucose concentration.
Keywords: disease processes; infection; metabolism; mycology; yeast.
© 2013 The Society for Applied Microbiology.