spa typing of staphylococcus aureus strains isolated from clinical specimens of patients with nosocomial infections in tehran, iran

Background: the incidence of nosocomial staphylococcus aureus infection is increasing annually and becoming a true global chal- lenge. the pattern of staphylococcus aureus protein a (spa) types in different geographic regions is diverse. objectives: this study determined the prevalence of methicillin-resistant s. aureus and different spa types in s. aureus clinical iso- lates. materials and methods: during a six-month period, 90 s. aureus isolates were recovered from 320 clinical specimens. the in vitro susceptibility of various s. aureus isolates to 16 antibiotic discs was assessed using the kirby-bauer disk diffusion method. molecular typing was carried out with s. aureus protein a typing via polymerase chain reaction. results: the frequency of methicillin-resistant s. aureus in our study was 88.9%. twenty-three (25.5%) isolates were positive for panton-valentine leukocidin encoding genes. s. aureus presented a high resistance rate to ampicillin (100%) and penicillin (100%). no resistance was observed to vancomycin, teicoplanin, or linezolid. the rates of resistance to the majority of antibiotics tested var- ied between 23.3% and 82.2%. the rate of multidrug resistance among these clinical isolates was 93.3%. the 90 s. aureus isolates were classified into five s. aureus protein a types: t037 (33.3%), t030 (22.2%), t790 (16.7%), t969 (11.1%), and t044 (7.7%). eight (8.9%) isolates were not typable using the s. aureus protein a typing method. conclusions: we report a high methicillin-resistant s. aureus rate in our hospital. additionally, t030 and t037 were the predomi- nant spa-types among hospital-associated s. aureus. our findings emphasize the need for continuous surveillance to prevent the dissemination of multidrug resistance among different s. aureus protein a types in iran.