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Standardization of isothermal microcalorimetry in urinary tract infection detection by using artificial urine

Bonkat, Gernot ; Braissant, Olivier ; Rieken, Malte ; Solokhina, Anna ; Widmer, Andreas ; Frei, Reno ; van der Merwe, Andre ; Wyler, Stephen ; Gasser, Thomas ; Bachmann, Alexander

In: World Journal of Urology, 2013, vol. 31, no. 3, p. 553-557

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    Title
    • Standardization of isothermal microcalorimetry in urinary tract infection detection by using artificial urine
    Author
    • Bonkat, Gernot. Department of Urology, University Hospital Basel, Spitalstrasse 21, 4031, Basel, Switzerland
    • Braissant, Olivier. Department of Urology, University Hospital Basel, Spitalstrasse 21, 4031, Basel, Switzerland
    • Rieken, Malte. Department of Urology, University Hospital Basel, Spitalstrasse 21, 4031, Basel, Switzerland
    • Solokhina, Anna. Laboratory of Biomechanics and Biocalorimetry (LOB2), Faculty of Medicine, University of Basel, c/o Biozentrum-Pharmazentrum, Klingelbergstrasse 50-70, 4056, Basel, Switzerland
    • Widmer, Andreas. Division of Infectious Diseases and Hospital Epidemiology, University Hospital Basel, Petersgraben 4, 4031, Basel, Switzerland
    • Frei, Reno. Clinical Microbiology Laboratory, University Hospital Basel, Spitalstrasse 21, 4031, Basel, Switzerland
    • van der Merwe, Andre. Department of Urology, Faculty of Health Sciences, University of Stellenbosch, PO Box 19063, 7505, Tygerberg, South Africa
    • Wyler, Stephen. Department of Urology, University Hospital Basel, Spitalstrasse 21, 4031, Basel, Switzerland
    • Gasser, Thomas. Department of Urology, University Hospital Basel, Spitalstrasse 21, 4031, Basel, Switzerland
    • Bachmann, Alexander. Department of Urology, University Hospital Basel, Spitalstrasse 21, 4031, Basel, Switzerland
    Document Type
    • Postprint
    OAI-PMH Identifier
    • oai:doc.rero.ch:316224
    Summary
    Purpose: Isothermal microcalorimetry (IMC) has recently been reported as a new method to rapidly detect urinary tract pathogens (UTP). However, further application of microcalorimetry in the clinical setting requires a standardized procedure. An important step toward such standardization is to use a reproducible growth medium. In this study, we investigated the potential of artificial urine in combination with microcalorimetry for detection of common UTP. Methods: A microcalorimeter equipped with 48 channels was used. Detection was accomplished, and growth was monitored for four bacterial strains in artificial urine at 37°C by measuring metabolic heat flow (μW=μJ/s) as a function of time. The strains were Escherichia coli, Proteus mirabilis, Enterococcus faecalis, and Staphylococcus aureus. Result: Bacterial growth was detected after 3-32h with decreasing inoculums down to 1CFU. The gram-negative strains grew and were detected faster than their gram-positive counterparts. The growth rates the different strains were 0.75±0.11 for E. coli, 0.74±0.10 for E. faecalis, 1.31±0.04 for P. mirabilis, and 0.56±0.20 for S. aureus. The shape of individual heat flow curves was characteristic for each species independent of its initial concentration. Conclusions: IMC allows rapid detection of UTP in artificial urine. Clearly, different heat flow patterns enable accurate pathogen differentiation. UTP detection after only 4h is realistic. The rapid detection of UTP tested in standardized artificial urine proves the diagnostic potential of IMC and warrants further microcalorimetric studies in the clinical setting of urinary tract infections