Comparative antibiotic resistance of S. aureus strains isolated in surgical and therapeutic departments of hospitals

Objectives – to identify the characteristics of resistance of clinical isolates of S. aureus, obtained in hospitals of various specialization, to beta-lactam antibiotics, and to improve recommendations for empirical etiotropic therapy prescribed to patients with staphylococcal infections.

Materials and methods. The subject of the study is the clinical isolates of S. aureus received from patients hospitalized to Vitebsk Regional Clinical Infectious Diseases Hospital "therapeutic" isolates, n=117) and purulent surgery departments and intensive care units of Vitebsk Regional Clinical Hospital ("surgical" isolates, n=111) in 2016–2017 years. Methods for the study of antibiotic resistance of clinical isolates of S. aureus: disk diffusion method, method for determining the beta-lactamase activity of bacterial suspension using the "BioLactam" test system.

Results. It was found, that 80.6% of the therapeutic isolates and 73.2% of the surgical isolates were resistant to the 1st generation penicillins. 5.4% of therapeutic isolates and 34% of surgical isolates were resistant to inhibitor-protected beta-lactams. 36.8% of surgical isolates and no therapeutic isolates were resistant to cephalosporins of the 3rd generation. No MRSA were detected among the therapeutic isolates, and among the surgical isolates the prevalence of MRSA was 30.5%. 93.3% of therapeutic isolates of S. aureus did not show any beta-lactamase activity. Among surgical isolates there were only 34.4% of such isolates. Direct Spearman’s correlations of moderate strength were revealed between the levels of beta-lactamase activity of S. aureus isolates, the duration of hospitalization and febrile period, as well as between the isolation of MRSA and the duration of hospitalization, fever and diarrheal syndrome.

Conclusion. The use of inhibitor-protected penicillins and 3rd generation cephalosporins is recommended for empirical antibiotic therapy of "therapeutic" infections caused by S. aureus. Reserve antibiotics with selective antistaphylococcal activity (such as glycopeptides or oxazolidinones) are required for empirical antibacterial therapy of staphylococcal infections in surgical departments and resuscitation units.