Phenotypic Investigation of Biofilm Formation and the Prevalence of icaA and icaD Genes in Staphylococcus epidermidis Isolates

Background and Aims: The most important factor for pathogenicity of Staphylococcus epidermidis is the ability to produce biofilm. Identification of biofilm-forming strains using an appropriate method and recognizing the mechanisms of biofilm formation can help understand the proper use of artificial medical equipment and prevent increased drugs resistance . The aim of this study was to 1) evaluate the biofilm formation of S. epidermidis isolates using phenotypic methods such as Tube Method (TM), Congo Red Agar Method (CRA) and Microtiter Plates Method (MTP) as well as PCR of the genes icaA and icaD 2) determine the drug resistance pattern of S. epidermidis isolates and its association with biofilm formation among clinical specimens and samples of healthy carriers. Materials and Methods: A total of 90 strains of S. epidermidis including 50 clinical isolates and 40 strains from healthy carriers were studied using the phenotypic methods TM, CRA and MTP, and the molecular PCR of the genes icaA and icaD. Antibiotic resistance profile of the strains was performed using disk diffusion method according to the CLSI standards. Results: A total of 90 strains ( 63.34% by TM, 37.78% by CRA method and 67.79% of MTP method) were able to form biofilm. No significant differences were found between the healthy and carriers groups in terms of antibiotic resistance. The icaA and icaD genes were detected among 100% and 85.24% of the biofilm forming strains, respectively.  Conclusions: Comparing the phenotypic and molecular methods for the detection of biofilm formation among S. epidermidis isolatesshowed that MTP is the best method with the highest sensitivity and specificity and its simultaneous use with molecular methods is recommended.