Detection of VanA type vancomycin resistance among MRSA isolates from an emergency hospital in Egypt

Abstract

Resistance of methicillin-resistant Staphylococcus aureus (MRSA) strains to vancomycin is increasing and represents a major threat in the therapeutic fields. To assess susceptibility of S. aureus to vancomycin and determine the occurrence of VanA gene among MRSA isolates. Agar diffusion method using cefoxitin disc (30 μg) was used to identify MRSA among 100 isolates of S. aureus. Among MRSA, vancomycin resistance was determined by broth macrodilution and VanA gene was detected by PCR. Frequency of MRSA was 92%. Phenotypically, MRSA isolates were vancomycin-susceptible S. aureus (VSSA) (67.4%), vancomycin-intermediate S. aureus (VISA) (10.9%), and vancomycin-resistant S. aureus (VRSA) (21.7%). 17.4% of MRSA were VanA positive (75% were VRSA and 25% were VSSA). 82.6% of MRSA were VanA negative (76.3% were VSSA, 13.2% were VISA, and 10.3% were VRSA). Sixty percent of VRSA and 6.5% of VSSA were VanA gene positive but none of the detected VISA isolates was carrier of VanA gene. Percentage of MRSA, VISA, and VRSA detected in this study is alarming and highlights the need for implementation of strict infection control measures to prevent further dissemination of such resistant strains in our region.