Tehran University Medical Journal

Background: Coagulase-negative staphylococci (CoNS) were considered as contaminats previously, but, during the past decade considered as one of the most common photogenic bacteria in hospital. Resistance to beta-lactams especially methicillin in staphylococcus species is being worrying in hospitals. Rapid identification of mechanisms of resistance and confirmation of their resistance to methicillin is a basic principle for antibiotic treatment. The aim of this study was to determine antibiotic resistance, frequency of mecA gene, and determination of SCCmec types in CoNS isolates from teaching hospitals in Iran.

Methods: The descriptive cross-sectional study was carried out one hundred clinical samples isolated from patients with an average age of 7-69 years at teaching hospitals in Hamadan City, Iran, from September 2014 to February 2015. After confirmation of isolates by microbiological standard biochemical tests, antimicrobial susceptibility testing was performed by disk agar diffusion (DAD) method. After extraction of isolated genomicm, mecA gene was detected. Then, the types of SCCmec were performed by PCR.

Results: In this study, 387 clinical samples were collected which among 100 CoNS isolated, Staphylococcus epidermidis was the most prevalent species with frequency 55 (55%), followed by S. haemolyticus 40(40%) and S. saprophyticus 5(5%). The highest antibiotic susceptibility was to rifampin 96(96%) and the lowest resistance was detected for trimethoprim/sulfamethoxazole (TMP/SMX) 47(47%). None of the strains were resistant to vancomycin. Resistance to methicillin was detected in 50% of CoNS isolates. Typing of SCCmec was performed by The polymerase chain reaction (PCR). Frequency types of SCCmec was type III with frequency 13(13%), type V 11(11%), type II 6(6%), type IV 4 (4%), type I 3(3%) respectively. Thirteen isolated was not typable in this study.

Conclusion: The result of this study showed that a large percentage of coagulase-negative staphylococci are resistance to methicillin, and the prevalence of SCCmec type was type III, which encodes the largest number of resistance genes. This information could be use in epidemiological study for preventing of infectious control in hospital and health centers.