Antibiotic Resistance and Antibiotic Resistance Genes in Staphylococcus aureus Isolates from Hospital Patients in Islamabad, Pakistan

Two hundred and seventy-eight clinical samples from hospital patients including pus, blood, nasal swabs, ear swabs, urethral swabs, wounds and sputum were processed for isolation of S. aureus. From these samples 50 S. aureus isolates were recovered, which were subjected to sensitivity testing against 18 antibiotics. The isolates were also screened for antibiotic resistance genes through PCRs. In S. aureus isolates highest resistance rates were observed against co-trimoxazole (70%). The isolates also showed high resistance against erythromycin, sparofloxacin and ofloxacin to which 52%, 48% and 46% of the isolates were found to be resistant. Multiple drug resistance (MDR) was noted in 78% of the S. aureusisolates. Out of the 50 isolates, 28 (56%) were found to be methicillin resistant S. aureus (MRSA). In the MRSA isolates highest resistance rate was detected against co-trimoxazole (75.0%), followed by piperacillin-tazobactam (64.2%), ofloxacin (60.7%) and sparofloxacin (60.7%). All the 28 MRSA were found to possess the mecA gene and no mecC variant was detected. Thirty two percent of the S. aureus isolates possessed no antibiotic resistance gene. The resistance genes detected in the isolates were aacA-D (50%), tetK (38%), ermC (30%), tetM (8%) and ermA (6%), while ermB, dfrA and cfr were not found. Additional studies are needed to get a better picture of situation of antibiotic resistance and antibiotic resistance genes in the local S. aureus strains.