[Occurrence of methicillin-resistant Staphylococcus aureus strains at the University Hospital Olomouc].

Objective: This study aimed to evaluate the occurrence of methicillin-resistant Staphylococcus aureus (MRSA) at the University Hospital Olomouc (UHO) over a 10-year period (2013-2022).

Material And Methods: Data was obtained from the ENVIS LIMS laboratory information system (DS Soft, Czech Republic, Olomouc) of the Department of Microbiology, UHO, for the period 1/1/2013-31/12/2022. Standard microbiological procedures using the MALDI-TOF MS system (Biotyper Microflex, Bruker Daltonics) were applied for the identification. Antimicrobial susceptibility was determined by the standard broth microdilution method according to EUCAST criteria. All Staphylococcus aureus strains were tested for methicillin resistance using selective diagnostic chromogenic media (ColorexTMMRSA, TRIOS) and an immunochromatographic test for PBP2a detection (PBP2a SA Culture Colony Test, AlereTM). Positive results were confirmed by mecA gene detection. Molecular typing to determine clonality/relatedness was performed on isolates from 2022 using pulsed-field gel electrophoresis (PFGE).

Results: The prevalence of MRSA at the UHO does not show an increasing trend and ranges between 3-6 %. The highest MRSA prevalence was detected in blood culture specimens (6 %), followed by lower respiratory tract specimens (5 %) and wound/abscess/aspirate specimens (5 %). The departments with the highest MRSA prevalence were the Geriatrics Department and the Second Internal Medicine Department. The antibiotic resistance patterns of MRSA were as follows: erythromycin 89 %, clindamycin 86 %, ciprofloxacin 80%, tetracycline 18 %, gentamicin 13 %, cotrimoxazole 7 %, and tigecycline 1 %. Resistance to antibiotics of choice for serious MRSA infections (vancomycin, ceftaroline, linezolid) was 0-1 %. Genetic analysis of selected MRSA isolates by PFGE revealed one cluster of five, two clusters of three, and two clusters of two isolates with indistinguishable restriction profiles.

Conclusion: The prevalence of MRSA at the UHO remains low, therefore oxacillin or possibly combined aminopenicillins (amoxicillin/clavulanic acid and ampicillin/sulbactam) or cefazolin can be relied upon for initial therapy of infections likely caused by Staphylococcus aureus.