Genetic diversity of Staphylococcus aureus strains from a teaching hospital in Isfahan, Iran: The emergence of MRSA ST639- SCCmec III and ST343- SCCmec III

Background and Objectives: Staphylococcus aureus is an important pathogen that can be colonized in the nose and increase the risk of spreading infections in hospitals. The present study aimed at determining the phenotypic and genotypic characterization of S. aureus strains isolated from patients and healthcare workers (HCWs) from a teaching hospital in Isfahan, Iran. Materials and Methods: This cross-sectional study was performed on 262 nasal swabs and 23 clinical isolates that were collected from a teaching hospital during February and April 2016. Staphylococcal cassette chromosome mec (SCCmec) and multilocus sequence typing (MLST) were performed for selected isolates. Results: Overall, 23% and 18% of healthcare workers and patients were carriers, respectively. Methicillin-resistant S. aureus (MRSA) rate was 13%, 33% and 52% in nasal HCWs, nasal patients, and clinical samples, respectively. The molecular typing of MRSA isolates revealed that the most common SCCmec type is SCCmec type III (88%). The highest rate of resistance was observed against tetracycline and erythromycin, with 48.7%. The most frequently detected toxin genes among S. aureus isolates were hla (99%) and sea (44%), moreover, pvl genes were detected in (40%) of MRSA isolates. The results of MLST showed 7 different sequence types (STs): ST859 (2/9), ST6 (2/9), ST639 (1/9), ST343 (1/9), ST239 (1/9), ST291 (1/9) and ST25 (1/9). Conclusion: Our results revealed that ST clones associated with healthcare-associated MRSA (HA-MRSA) are actively circulating among nasal carriage in our healthcare setting, and thus, effective infection control policies are needed to reduce nasal carriage in healthcare settings.