Prevalence and Genotyping of Methicillin-Resistant and - Susceptible Staphylococcus aureus Strains Isolated from Patients in a University Hospital, Isfahan, Iran

Staphylococcus aureus is one of the major causes of community- and hospital-acquired infections, with methicillin-resistant strains showing the highest rates of morbidity and mortality. In our previous experiment, isolates, which were also used in the present study, were assessed using multilocus sequence typing (MLST). The sequence types (STs) were determined and documented in the corresponding database.
In the current study, the isolates were subjected to genotyping with coagulase, SCCmec, and agr typing methods.
A total of 54 isolates were evaluated by polymerase chain reaction (PCR) assay for mecA gene, Sccmec typing, and finally PCR-restriction fragment length polymorphism (RFLP) for coagulase (coa) gene using Alul enzyme. MLST of the isolates showed that the majority of methicillin-resistant S. aureus (MRSA) isolates belonged to ST239.
Phenotypic and genotypic tests revealed that 21% of the isolates were MRSA. PCR-RFLP test for coa gene showed similar patterns of MRSA isolates. The majority of the isolates were community-acquired and belonged to the Sccmec type IV, whereas the remaining were hospital-acquired and classified as type I (22.2%) and type III (2.2%).
Most of the isolates belonged to agr type I, followed by type II and type III. Agar dilution method showed higher sensitivity and specificity, compared to the disk diffusion method. The majority of the isolates were community-acquired and belonged to Sccmec type IV and agr type I, whereas the remaining were hospital-acquired and classified as types I (22.2%), type III (2.2%), and agr type I.