Determination of methicillin-resistant and methicillin-susceptible Staphylococcus aureus bacteria in blood by capillary zone electrophoresis.

Serious bloodstream infections are a significant complication in critically ill patients. The treatment of these infections has become more difficult because of the increasing prevalence of multiresistant strains, especially methicillin-resistant Staphylococcus aureus (MRSA). Rapid differentiation of low number of MRSA from methicillin-susceptible S. aureus (MSSA) cells (10(1)-10(2) cells mL(-1)) in blood is necessary for fast effective antibiotic therapy. Currently, three groups of techniques, phenotyping, genotyping, and mass spectrometry, are used for MRSA and MSSA strains differentiation. Most of these techniques are time-consuming. PCR and other molecular techniques allow the detection and differentiation between MSSA and MRSA directly from blood cultures. These methods alone are rapid and they have good reproducibility and repeatability. Potential disadvantages of the genotyping methods include their discrimination ability, technical complexity, financial costs, and difficult interpretation of the results. Recently, capillary electrophoresis (CZE) was successfully used to differentiate between the agar-cultivated MRSA and MSSA strains in fused silica capillaries etched with supercritical water and modified with (3-glycidyloxypropyl)trimethoxysilane. The possible use of CZE as a fast and low-cost method for distinguishing between the blood-incubated MRSA or MSSA cells has been tested in this manuscript. Our goal was to test low amounts of bacteria (∼10(2) cell mL(-1)) similar to those in clinical samples. The migration times of the purified blood-incubated cells and the agar-cultivated cells were different from each other. However, their isoelectric point was the same for all strains.