Isolation and characterization of vancomycin and erythromycin resistant Staphylococcus aureus from Cairo, Egypt

Abstract

Aims: Staphylococcus aureus is an important opportunistic human pathogen. The emergence of macrolide and vancomycin resistant S. aureus is of great concern for treatment of S. aureus infections. The current study aimed to investigate the pattern of antibiotic resistance in S. aureus clinical isolates recovered from El Boos Students’ hospital in Cairo, Egypt. Methodology and results: Sixty unduplicated S. aureus isolates were recovered from El Boos Students’ hospital in Cairo, Egypt for 11 months period. The antibiotic susceptibility test revealed that all isolates were resistant to eleven antibiotics, but only 49 S. aureus isolates were resistant to cefoxitin. The minimum inhibitory concentrations (MIC) of both erythromycin and vancomycin were determined by broth microdilution method. Two methicillin resistant S. aureus (MRSA) isolates showing tolerance to both erythromycin and vancomycin at high concentration were selected for further characterization. One isolate was recovered from eye infection and had MIC at 256 µg/mL of both erythromycin and vancomycin. While another isolate was recovered from throat infection and had MIC of erythromycin and vancomycin up till 512 µg/mL. The presence of resistance genes (ermA, ermB, ermC, mef, msrA, vanA and vanB) were confirmed by polymerase chain reaction (PCR). Both MRSA isolates carried all tested resistance genes. Conclusion, significance and impact of study: This study highlights the concern of presence of multidrug-resistant S. aureus which showed resistance to high concentrations of erythromycin, vancomycin and carried ermA, ermB, ermC, mef, msrA, vanA and vanB genes, therefore imposes risk of failure to treat such infections.