Frequency of Reduced Vancomycin Susceptibility among Clinical Staphylococcus aureus Isolated in Ahvaz Iran

One of the most important agents in hospital-acquired infections is Staphylococcus aureus. Treatment of methicillin-resistant S. aureus (MRSA) infections with decreased susceptibility to vancomycin has recently been more difficult. The aim of this study was to evaluate the possible presence of vancomycin intermediate S. aureus (VISA) and vancomycin- resistant S. aureus (VRSA) and also to determine the frequency of MRSA in clinical specimens. In this study, 195 S. aureus isolates were collected from the patients were examined. All of the isolates were identified using standard biochemical tests. Susceptibility of S. aureus isolates against 10 antibiotics was detected by disk diffusion method and was followed by E-test and vancomycin screen agar methods. Minimum inhibitory concentration (MIC) of vancomycin was determined according to the CLSI guidelines. Also, detection of mecA gene was performed by PCR and finally, the results were compared. All of the isolates were susceptible to vancomycin (i.e. MIC range of vancomycin was between 0.25-2 µg/ml). Out of 195 S. aureus isolates, 99 isolates (50.8%) were resistant tomethicillin, and mecA gene was detected in 96 isolates. These results also showed that thehighest and lowest resistance rate of isolates was to penicillin (96.9%) and chloramphenicol(0%), respectively. Our findings showed that vancomycin can still be used as a valuable drug fortreatment of S. aureus infections in our region. However, periodic evaluation of vancomycinMIC of S. aureus isolates is critical for monitoring MRSA and preventing the spread of VISA orVRSA among patients.