Phenotypic and Genotypic Characterization of Biofilm Formation among Staphylococcus aureus Strains Isolated from Patients with Urinary Tract Infection in a Hospital in Isfahan during 2016

Staphylococcus aureus is one of the most common causes of a variety of infections in humans, such as urinary tract infection; which is due to its ability to form biofilm in different parts of the urinary tract. In this study we characterized the phenotypic and genotypic analysis of biofilm formation among S. aureus strains isolated from urinary tract infections in Isfahan.

During 2016, a total of 96 S. aureus strains were collected from a referral hospital in Isfahan and were identified at the species level using specific primers. The ability of strains to form biofilm was measured using phenotypic qualitative Congo-red agar and quantitative microtiter plate assays. The different genes involved in biofilm formation were detected by the specific primers.

All isolates were confirmed as S. aureus using the PCR test. The results of Congo-red agar test revealed that 5% and 72% of the strains were able to produce black and dark red colonies, respectively. Moreover, in microtiter plate assay, 72% of the strains were biofilm positive. The frequency of icaA, icaD, clfA, fnbA and cna genes among biofilm producing strains were 84, 86, 75, 61 and 43%, respectively.

The results of this study indicating the high prevalence of biofilms producing S. aureus strains in the desired hospital. Moreover, our findings revealed the importance of genotypic method for identification of biofilm positive strains compared to phenotypic methods.