Biofilm production among methicillin resistant Staphylococcus aureus strains isolated from catheterized patients with urinary tract infection.

Between June 2011 and May 2014, we isolated a total of 419 Staphylococcus aureus strains from catheterized patients with UTI in a referral hospital in Tehran. Of these, 108 were identified as methicillin resistant (MRSA) based on their phenotypic resistance to oxacillin and the presence of mecA gene. The MRSA isolates were tested for their clonality using a combination of PFGE, prophage typing, SCCmec and ccr typing and examined for their biofilm formation as well as their resistance against 17 antibiotics. In all, 15 common pulsotypes consisted of 105 isolates and 3 single types were identified among the MRSA strains of which, 97% carried SCCmec type III and type 3 ccr. Eighty three (77%) strains were positive for biofilm formation and also carried icaA and icaD genes. Moreover, agr group III and its related tst gene were detected in 81% and 77% of biofilm producing strains, respectively 105 of the 108 MRSA were multidrug resistant with 82.4% being resistant to more than 10 antibiotics. Strains with SCCmec type IV and type 2 ccr, contained SGA and SGL prophage types, were positive for pvl gene and belonged to single PFGE types. This study highlights the important role of biofilm formation and virulence factors of MRSA strains in catheterized patients.