Phenotypic and Genotypic Analysis of biofilm Formation in Staphylococcus epidermidis Strains Isolated from Patients and Healthy Individuals

Background and Objectives: Staphylococcus epidermidis is an opportunistic pathogenic bacterium and is often associated with bacteremia and hospital infections due to its ability to form biofilm. In this study, we determined the clonality and antibiotic resistance patterns of biofilm producing S. epidermidis strains, isolated from clinical samples and healthy individuals in Isfahan, Iran during 2016 and 2017. Materials and Methods: A total of 107 and 123 S. epidermidis strains were isolated from clinical specimens in a referral hospital and healthy individuals, respectively. All strains were identified by the specific primer for gseA gene, and their ability to form biofilm was determined using a combination of Congo-red agar (CRA) and microtiter plate (MTP) assays and presence of ica operon, aap and IS256 genes were tested. The resistance of strains to 12 antibiotics was evaluated according to the recommendations of clinical and laboratory standard institute (CLSI), and all biofilm producing strains were typed using PhenePlate (PhP-CS) system and the presence of staphylococcal cassette chromosome mec (SCCmec) gene was detected by multiplex polymerase chain reaction (multiplex-PCR). Results: Phenotypic biofilm methods could detect the presence of 43 biofilm producer S. epidermidis strains among clinical and healthy individuals, in which all of them were positive for aap gene, while the presence of ica operon was limited to 86% and 27% of strains isolated from clinical samples and healthy individuals, respectively. Moreover, icaA and icaD genes were also more prevalent among clinical isolates, compared to healthy strains (68% vs. 27%). All biofilm producing strains showed susceptibility to vancomycin, quinupristin-dalfopristin, linezolid, and the highest rate of resistance was to erythromycin, ciprofloxacin, cefoxitin, and clindamycin. Among all 34 (79%) methicillin resistant S. epidermidis (MRSE), SCCmec types III, IV and V were detected, in which SCCmec type III was the dominant one (79%). Three common types (CTs) and seven single types (STs) were determined, in which CT1 and CT2 were common among clinical and healthy strains and presence of STs was only limited to the strains with SCCmec types IV and V.Conclusion: Results of this study indicate the presence and persistence of diverse clone types of biofilm producing S. epidermidis strains with common PhP and SCCmec types in hospital and community in Isfahan. Dissemination and circulation of antibiotic resistant and biofilm producer clone types of these opportunistic normal biota from hospitals to healthy individuals could be an urgent issue for public health.