Isolation of Biofilm Producing Methicillin Resistant and Methicillin Sensitive Staphylococcus aureus Strains from Patients with Urinary Tract Infection in Isfahan

Staphylococcus aureus is one of the most common causes of a variety of infections ranging from simple wound infections to complicated urinary tract infections (UTI) in hospital and community. During past decades, resistance of S. aureus to different classes of antibiotics such as methicillin has increased which making infections by these bacteria difficult to treat. The aim of this study was the isolation and determination of antibiotic resistance pattern of biofilm producing methicillin resistant and methicillin sensitive S. aureus strains from patients with urinary infection in Isfahan during 2015-2017. During 2 years a total of 729 urine samples were collected from patients in a referral hospital in Isfahan. All isolates were identified using Polymerase Chain Reaction (PCR) with specific primers and the ability of strains to produce biofilm was tested using qualitative Congo red agar and quantitative microtiter plate assays. The resistance of biofilm producing methicillin resistant and sensitive strains to 15 antibiotics was examined. Totally, 294 S. aureus strains were identified using PCR test, in which 50.7% of strains were slime producers and 102 strains were classified as biofilm producing strains. Among biofilm producing strains, 56.9% were resistant to cefoxition and showed high rate of resistance to penicillin, erythromycin and ciprofloxacin. Except for chloramphenicol, significant difference was observed among methicillin resistant and methicillin sensitive strains for resistance to different classes of antibiotics. Moreover, all of the strains showed susceptibility to linezolid and quinupristin-dalfopristin. Presence and persistence of highly resistant biofilm producing strains among patients in this hospital, indicating the widespread and transmission of such strains in the hospital.