Biofilm Producing Staphylococcus epidermidis Strains Isolated From Clinical Samples in Tehran, Iran

Background: Staphylococcus epidermidis is well documented as an opportunistic pathogen causing biofilm in patients and healthy individuals. Objectives: The aim of this experimental study was to describe the antibiotic resistance patterns of biofilm producing S. epidermidis strains isolated from clinical samples in Tehran, Iran. Moreover, the role of different genes in biofilm formation was also described. Patients and Methods: A total of 250 S. epidermidis strains were isolated from patients in a private hospital of Tehran, Iran from February to December 2014. The biofilm formation of each strain was determined using combination of qualitative Congo-Red agar and quantitative microtiter plate assay, and presence of different genes involved in control and formation of biofilm was detected by the polymerase chain reaction (PCR). Susceptibility of S. epidermidis strains to 19 antibiotics was examined. Results: The results of the biofilm assay revealed that 82% of strains produced black colonies on Congo red agar plates and 68% were able to attach strongly to polystyrene microplates. One hundred percent, 88%, 84%, 64% and 60% of biofilm-producing strains were resistant to penicillin, cefoxitin, erythromycin, trimethoprim-sulfamethoxazole and kanamycin, respectively. On the other hand, none of the strains showed resistance to vancomycin, linezolid, quinupristin/dalfopristin. The icaA, icaD, aap and atlE genes were detected in all biofilm-producing strains and presence of IS256 transposon was limited to 84% of biofilm positive strains. Conclusions: The results of this study illustrated the high prevalence of antibiotic resistant biofilm-producing S. epidermidis strains in this hospital, which could be a reservoir for antibiotic resistance genes.