Prevalence of methicillin resistant Staphylococcus species isolated from burn patients in a burn center, Ahvaz, Iran

Introduction and objective: Today methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase negative Staphylococci (MRCNS) are frequent causes of nosocomial infection. Extensive burn injuries, extended hospitalization and inappropriate antibiotic therapy have been identified as risk factors for MRSA and MRCNS carriage and infection. The aim of this study was to assess the prevalence of methicillin resistance among clinical isolates of Staphylococci taken from burn patients using four separated methods and also determination of susceptibility pattern to amikacin, ciprofloxacin, vancomycin, carbenicillin and gentamicin.

Materials and methods: A total of 185 clinical staphylococcal isolates from wound and blood specimens were evaluated for susceptibility to oxacillin using oxacillin and cefoxitin disk diffusion method, agar screening containing 6 microgram oxacillin /ml, oxacillin E test and polymerase chain reaction for predicting mecA gene.

Results: The results showed that 27.8% of wound and blood specimens were infected by Staphylococci and among these 60% were identified as methicillin resistant. We found no significant differences between the results of PCR assay and conventional disk diffusion method by oxacillin and cefoxitin disk, however the results of cefoxitin disk was more significant than oxacillin and gave better results. Both of the sensitivity and specificity value were similar (99%, 100%) for E test and agar screen test. Furthermore in E test for detection of minimum inhibitory concentration (MIC), more than 93% of MRSA and 15% of MRCNS isolates had MIC value more than 256µg/ml. We also determined a significant difference pattern between methicillin resistant and methicillin susceptible Staphylococci to five antimicrobial agents.

Conclusion: In conclusion, our results showed that the prevalence of methicillin resistant Staphylococci in our center was very high and cefoxitin disk test is reliable alternation for detection of methicillin resistant Staphylococci.