Molecular Typing of Methicillin-Resistant Staphylococcus Aureus Strains Isolated from Patients Admitted to Intensive Care Units of Hospitals in Tehran City, Iran, Based on agr Pattern

Staphylococcus aureus is one of the most commonly diagnosed infections in hospitals. Increased infections caused by this bacterium and its resistance to many antibiotics is leading to increasing morbidity and mortality in the hospital setting. The aim of this study was to investigate the molecular status of methicillin-resistant Staphylococcus aureus (MRSA) isolated from patients admitted to intensive care units (ICUs) of hospitals in Tehran City, Iran.
This cross-sectional study was performed by analyzing 125 MRSA strains isolated from hospitalized patients in ICUs. In vitro antibiotic susceptibility testing of isolates was assessed using Kirby-Bauer disk diffusion method. MRSA strains were genetically typed by agr typing and virulence and adhesion genes profile via conventional polymerase chain reaction (PCR) method.
Findings: Of 443 clinical studied samples, 125 MRSA strains were observed. The highest resistance rates were observed for penicillin antibodies (122, 97.6%), kanamycin (105, 84.0%), and gentamicin (95, 76.0%). Frequency of pvl and tst genes was 67.2% and 20%, respectively. Type I was the most prevalent agr type (52.0%), followed by type III (34.4%), type II (9.6%), type I 5(5.3%), and type IV (4%). All the isolates carrying Panton-Valentine leukocidin (PVL)-encoding genes and high-level mupirocin-resistance (HLMUPR)-MRSA strains corresponded exclusively to agr type I.
This study demonstrates the increased resistance of Staphylococcus aureus to different antibiotics, which is a serious warning for the treatment of Staphylococcus aureus infection in the region. Therefore, in order to avoid resistance to other antibiotics, uncontrolled and unnecessary administration of antibiotics should be avoided.