Frequency of biofilm production among methicillin resistant Staphylococcus aureus strains isolated from patients with urinary tract infection in Tehran during 2020-2022

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging cause of community- and hospital- associated urinary tract infections (UTIs), and known as one of the main pathogens causing chronic infections, mainly due to its capacity to form biofilms. The aim of this study was to determine the frequency of biofilm formation among MRSA strains isolated from patients with UTI in Tehran.

During 2020-2022, a total of 519 suspected S. aureus isolated from patients with UTI were collected from a hospital laboratory in Tehran, and confirmed using PCR by specific primers for nucA gene. A combination of agar screening (supplemented with oxacillin), disk diffusion method using cefoxitin disk (30 μg/ml) and specific primers for mecA and mecC genes were employed for determination of resistance to methicillin. The ability of MRSA strains to produce biofilm was tested using qualitative Congo red agar (CRA) and quantitative microtiter plate (MTP) assays. Prophage typing and SCCmec typing methods were employed using separate multiplex-PCR assays to type the MRSA strains.

Totally 92% of strains were confirmed as S. aureus in which 134 strains (28%) which showed resistance to cefoxitin and harbored mecA gene were selected as MRSA. Using combination of qualitative CRA test, 55 strains (41%) were slime positive in which 78% of strains were able to form biofilm. Thirteen percent of strains harbored SCCmec types IVa and V and confirmed as community acquired MRSA (CA-MRSA). Also, 4 prophage patterns and 5 prophage types were identified among strains, in which prophage type SGF and its two subtypes (SGFa and SGFb) were the most prevalent types. Moreover, prophage pattern 3 (consisting of SGB, SGF, SGFa and SGFb prophage types) were the dominant ones. All CA-MRSA strains were positive for SGA and SGL prophage types.

The results of the present study revealed the high frequency of biofilm formation among MRSA strains with different prophage types among patients with UTI in Tehran. The potential ability to produce a wide range of virulence factors, biofilm formation and high rate of antibiotic resistance results in emergence of highly pathogenic bacteria; which indicating the importance of more expansion healthcare monitoring and infection control in the hospitals.