antibiotic susceptibility pattern of gram-positive cocci cultured from patients in three university hospitals in tehran, iran during 2001-2005

bacterial resistance to antibiotics is a serious problem and is increasing in prevalence world-wide at an alarming rate. the antimicrobial susceptibility patterns of 1897 gram-positive bacterial isolates were evaluated. the minimum inhibitory concentration (mic) of isolates which comprised staphylococcus aureus (927 isolates), coagulase-negative staphylococci (cns; 425 isolates), enterococcus faecalis (320 isolates), enterococcus faecium (157 isolates), and pneumococci (50 isolates) collected from 3 teaching hospitals in tehran were determined by agar dilution method according to clinical and laboratory standards institute (clsi) guidelines. the presence of meca gene was investigated in methicillin-resistant staphylococci by pcr method and vana and vanb genes were targeted in enterococcal isolates by multiplex pcr method. the resistance rate to methicillin among s. aureus and cns isolates were 33% and 49%, respectively. all s. aureus isolates were susceptible to vancomycin .the lowest rate of resistance in all s. aureus isolates was found for rifampicin (