Investigating antibiotic susceptibility and biofilm formation among Staphylococcus aureus isolated from urinary tract infection outpatients

Background: Staphylococcus aureus (S. aureus) has become increasingly reported as a community-acquired uropathogen. S. aureus biofilm plays an important role in recurrent and persistent urinary tract infections (UTI) with increased resistance to antimicrobial agents. Aim: To investigate the antibiotic susceptibility and assess phenotypically and genotypically biofilm formation in S. aureus isolated from outpatient UTI cases. Methods: A cross-sectional study was conducted among outpatients with UTIs who showed inadequate responses to treatment. Following isolation and identification from midstream urine specimens, S. aureus isolates were tested for antibiotic susceptibility using the disc diffusion method. Biofilm production was assessed using the microtiter plate method, and the biofilm-related genes fnbA, icaA, and icaD were tested using PCR. Results: S. aureus had an isolation rate of 10.1% from UTI outpatients. A ratio of 45.5% of the isolates were methicillin-resistant (MRSA). Susceptibility rates to nitrofurantoin, sulfamethoxazole-trimethoprim, and ciprofloxacin were 47.7%, 34.1%, and 59.1%, respectively. A ratio of 72.7% of the isolates were found to produce biofilm, with 31.8%, 25.0%, and 27.3% being strong, moderate, and weak biofilm producers, respectively. The fnbA gene had the highest frequency among S. aureus isolates (86.4%), followed by icaA (72.7%), then icaD (47.7%). Both fnbA and icaA were significantly associated with phenotypic biofilm formation (p=0.001 and 0.000, respectively). Conclusion: The present findings highlight S. aureus as an emerging community-acquired uropathogen and demonstrate its improved capacity for biofilm formation. Combined with their reduced sensitivity to commonly prescribed antibiotics, this may underscore the significance of tailored treatment strategies.