Frequency of Biofilm Producing Methicillin Resistant Staphylococcus epidermidis Strains Isolated from Patients in Isfahan

Staphylococcus epidermidis is an opportunistic pathogenic bacterium which is able to form biofilm and often associated with nosocomial infections. The aim of this study was to determine the frequency of biofilm formation and antibiotic resistance patterns among methicillin resistant S. epidermidis (MRSE) strains isolated from patients in a referral hospital in Isfahan.

In this study, during 2015 and 2016, a total of 139 suspected S. epidermidis strains were collected from clinical samples of patients in a referral hospital in Isfahan. All isolates were identified at the species level using standard biochemical tests and PCR. The resistance of strains to cefoxitin was detected using disk diffusion method by the guidelines of CLSI and antibiotic resistance patterns of methicillin resistant strains to 10 antibiotics was also determined. To measure the ability of MRSE strains to form biofilm, qualitative Congo-red agar and quantitative microtiter plate assays were employed.

Using standard biochemical tests and PCR, 107 S. epidermidis strains were identified and confirmed among clinical samples. According to the results of disk diffusion test, 52% of strains were methicillin resistant and the high level resistance to erythromycin was also observed. Moreover, all MRSE strains showed susceptibility to vancomycin, linezolid, quinupristin-dalfopristin and chloramphenicol. The results of Congo-red agar test showed that 41% of strains had black colonies and were slime positive. Also, in microtiter plate assay, 50% of strains produced strong biofilm.

The results of this study indicating the high prevalence of biofilm producing MRSE strains among desired hospital in Isfahan. Such strains which show high antibiotic resistance could be an important challenge for public health.