The potential for isothermal microcalorimetry to detect venous catheter infection isolates and establish antibiograms

Abstract

Objectives: Because bloodstream infection and venous catheter (or cannula) bloodstream infection are associated with high morbidity and cost, early identification and treatment are important. Isothermal microcalorimetry can detect microbial growth using thermal power (heat flow), essentially in real time. The aim of this study was to examine the potential of this technique in clinical practice.

Methods: Thermal power of wild-type bacteria (Escherichia coli, Staphylococcus epidermidis, Klebsiella pneumoniae, and Enterococcus faecium) isolated from blood cultures of adult inpatients receiving parenteral nutrition in routine clinical practice was measured at 37°C every 10s using a Thermometric 2277 instrument. Temporal patterns of heat flow were used to detect the presence of bacteria, differentiate between them, and test their antibiotic sensitivity. Within and between batch reproducibility (% coefficient of variation [%CV]) was also established.

Results: Isothermal microcalorimetry always correctly detected the absence or presence of wild-type bacteria. Thermograms differed distinctly between species. Key thermographic features, such as peak heights, timing of peak heights, and interval between peak heights, were highly reproducible within each species (within-batch %CV usually about ≤1%, although between-batch %CV was usually higher). The antibiotic sensitivities (tested only for S. epidermidis and K. pneumoniae) confirmed the results obtained from the hospital laboratory.

Conclusions: Isothermal microcalorimetry is a promising and highly reproducible real-time measurement technique with potential application to the investigation, species identification, and targeted antibiotic treatment of bloodstream infection and venous catheter (or cannula) bloodstream infection.

Keywords: Antibiogram; Blood culture; Bloodstream infection; Catheter; Isothermal microcalorimetry.