Use of isothermal microcalorimetry to quantify the influence of glucose and antifungals on the growth of Candida albicans in urine

Abstract

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 (lW = lJ s À1 ).The influence of increasing concentrations of glucose and antifungal drugs on the growth of C. albicans was investigated. The growth rate increased linearly from 0Á024AE0Á010 to 0Á203AE0Á006 h À1 with increasing concentration of glucose from 20 to 1640 mg l À1 . The minimum inhibitory concentrations (MIC) against C. albicans were determined at a fixed glucose concentration of 560 mg l À1 . These MIC were 0Á5 lg ml À1 for amphotericin B, 5 lg ml À1 for flucytosine, 0Á8 lg ml À1 for fluconazole and 0Á5 lg ml À1 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.

Reduction of susceptibility to azoles and 5-fluorocytosine and growth acceleration in Candida albicans by glucose in urine

“…in urine induced by addition of glucose in a concentration-dependent manner. This was consistent with a previous study (10); however, that study was conducted by using artificial urine and only one C. albicans strain. Our present study strengthened the previous observations in that: 1) the fungal growth acceleration was observed in natural urine derived from healthy donors as a result of adding glucose, and 2) this acceleration was observed in multiple C. albicans clinical isolates, in addition to C. krusei and C. glabrata.…”

Efficacy of Experimental Mouth Rinses on Caries-Related Biofilms in vitro

“…The main advantage of this method in biofilm research is the opportunity to study them as entities as shown previously [ 18 ]. Over the last decade, the method has become more widely used in antimicrobial testing in various fields of medicine [ 19 – 22 ].…”

Comparison of Tunable Diode Laser Absorption Spectroscopy and Isothermal Micro-calorimetry for Non-invasive Detection of Microbial Growth in Media Fills

“…IMC therefore detects enthalpy changes associated with the cell metabolism (see ΔH of equations 1–3) and has been used already to monitor microbial growth1516171819.…”

“…In addition, metabolic reactions resulting from microbial proliferation emit heat which can be quantified continuously and non-invasively by isothermal micro-calorimetry (IMC). IMC therefore detects enthalpy changes associated with the cell metabolism (see ΔH of equations 1–3) and has been used already to monitor microbial growth 15 16 17 18 19 .…”