Rapid flow cytometric bacterial detection and determination of susceptibility to amikacin in body fluids and exudates

Abstract

A flow cytometry-based method for rapid and quantitative detection of bacteria in various clinical specimens and for rapid determination of antibiotic effect is described. Achieving such a measurement with high sensitivity required discrimination between bacteria and other particles which were often present in clinical samples in high concentrations. This discrimination was facilitated by detecting the bacterial characteristic light scatter and fluorescence signals following staining, e.g., with the fluorescent nucleic acid-binding dye ethidium bromide, as well as by measuring bacterial proliferation during short time intervals. Antibiotic susceptibility was measured by observing the inhibition of such proliferation. The method was applied to 43 clinical specimens from various sources, such as wound exudates, bile, serous cavity fluids, and bronchial lavage. Bacterial detection, achieved in less than 2 h, agreed with results of conventional methods with a sensitivity of 74% and a specificity of 88%. Susceptibility to amikacin was detected in 1 h in 92% of 13 positive specimens.