Evaluation of Genotypic and Phenotypic Biofilm Formation by Staphylococcus aureus Isolated from Clinical Samples and Their Association with Antimicrobial Resistance

 Staphylococcus aureus is one of the most important bacteria causes nosocomial infections, which by the biofilm formation can be effective in the creation of chronic diseases, and the creation and strengthening of drug resistance. The present study aimed to evaluate the genotypic and phenotypic biofilm formation by S. aureus isolated from clinical samples and their association with antimicrobial resistance.

   In this descriptive cross-sectional study from Dec 2019 to Sep 2019, 200 clinical samples were obtained from AJA hospitals in Tehran. All samples were analyzed using blood agar, Baird-Parker Agar, mannitol salt agar and catalase, OF and coagulase assays. Antimicrobial resistance pattern of isolates was determined by the disc diffusion method. Multiplex PCR method was used to identify biofilm formation genes, includes icaA, icaB, icaC, and icaD genes. Data analyzed using SPSS 20 and the X2 test.

Out of 200 cultivated samples, 83 (41.5%) cases were confirmed as S. aureus. The highest resistance was observed to Penicillin (94%), Tetracycline (72%), Ampicillin (54%), and Cefoxitin (51%), respectively. Phenotypic biofilm formation ability reported in 65% of isolates. The frequency of presence of icaA, icaB, icaC, and icaD genes was estimated at 67.4%, 60.2%, 61.4%, and 62.6%, respectively. Eighty-seven percent of biofilm producing strains were multidrug-resistant, while all the biofilm negative strains were non- multiple drug resistance (P< 0/05).

  According to the results, Biofilm-positive strains have a very high propensity to demonstrate antimicrobial resistance, multidrug resistance and resistance to methicillin.