Investigation of Antibiotic Susceptibility Pattern of Staphylococcus aureus Strains Isolated from Patients Referring to Some Treatment Centers of Qom City, Iran

Staphylococcus aureus is one of the important causes of nosocomial infections. Resistance to various antibiotics, such as beta-lactams, aminoglycosides, and macrolides is one of the major problems in treatment and prevention of infections caused by this bacterium. Therefore, accurate determination of antibiotic susceptibility pattern of organisms isolated from patients can be beneficial in treatment and prevention of dangerous infections. The objective of this study was to isolate S. aureus bacterium and to determine the antibiotic susceptibility pattern of the isolated strains in patients referred to some treatment centers of Qom city.
In this descriptive cross-sectional study, 340 clinical samples, were collected from September 2016 to July 2017. After isolation and primary identification of S. aureus isolates (using standard bacteriology methods), the isolated strains were confirmed by PCR technique and amplification of femA gene as a molecular diagnostic marker of S. aureus. Finally, antibiotic susceptibility pattern of the strains, was determined by disk diffusion method according to CLSI guideline.
Out of 340 clinical samples, 86 S. aureus strains were isolated and identified based on phenotypic characteristics. The femA gene was observed only in 45 strains (52.32%) based on molecular analysis. The results of the antibiotic susceptibility test showed that the highest resistance was to penicillin (86.04%) and the lowest resistance was to chloramphenicol (0%).
The results of this study indicated that femA gene cannot by itself identify all the S. aureus strains. Also, with regard to the results of antibiogram test, it seems that antibiotic susceptibility test is necessary for S. aureus strains isolated from patients.