In vitro susceptibility of Staphylococci and Enterococci to vancomycin and teicoplanin

Abstract

Hospital-acquired infections (HAIs) pose a worldwide problem. They primarily concern intensive care, hematology-oncology, and surgical units. Coagulase-positive and coagulase-negative Staphylococci, especially their subgroups possessing the ability to develop resistance to methicillin, and Enterococci have a particular role in the etiology of HAIs. The aim of this study was to determine the therapeutic minimal inhibitory concentration (MIC) values for vancomycin and teicoplanin, two of the most commonly administered antibiotics in the treatment of infections caused by Staphylococci resistant to methicillin, and infections caused by Enterococci. The material analyzed included 200 bacterial strains collected from patients treated in the Intensive Care Unit, the Musculoskeletal Infections Unit, and Surgical Clinics of the Military Institute of Medicine in Warsaw, Poland. The study was conducted in accord with the European Committee for Antimicrobial Susceptibility Testing (EUCAST) criteria by means of the Etest® gradient strips. We demonstrate a full susceptibility of Staphylococci MSSA (methicillin susceptible Staphylococcus aureus), Staphylococci MRSA (methicillin resistant Staphylococcus aureus), and Enterococci to both antibiotics. Coagulase-negative Staphylococci had a higher sensitivity to vancomycin. Teicoplanin had a lower MIC than vancomycin against the analyzed strains of Enterococci. As regards the coagulase-negative Staphylococci, vancomycin had a lower MIC than teicoplanin. In conclusion, the study confirmed current recommendations on the use of vancomycin and teicoplanin in the treatment of infections caused by gram-positive bacteria, emphasizing the need for the determination of MIC values.