Co-occurrence of antibiotic resistance and virulence Genes in Methicillin Resistant Staphylococcus aureus (MRSA) Isolates from Pakistan

INTRODUCTION: Methicillin resistant Staphylococcus aureus (MRSA) is one of the major human pathogen that is associated with hospital as well as community acquired infections and is responsible for huge amount of life-threatening diseases. OBJECTIVE: Objective of the study was to determine MRSA prevalence, their antibiotic sensitivity patterns, frequency of virulence genes (sea, seb, sed, tst, hla, hld) and their co-occurrence with resistance marker mecA among Rawalpindi and its nearby regions of Pakistani clinical isolates. METHODOLOGY: The present study was carried out to identify the virulence and antibiotic resistance genes that co-occur in MRSA through polymerase chain reaction. Antibiotic sensitivity, presence of virulence genes and their co-occurrence with resistance marker mecA were analyzed. RESULTS: These isolates were found resistant to number of antibiotics i.e. Amoxicillin (16.1%), Cefixime (48.38%), Doxycycline (27.415), Trimethoprim/sulfamethoxazole (37.09%), Clindamycin (30.64%), Erythromycin (83.87%), Penicillin (100%), Vancomycin (4.83%), Ciprofloxacin (70.96%), Tetracycline (20%), Linezolid (3.22%) and Fusidic acid (11.295). The frequency of antibiotic resistant gene (mecA) was 69.35% and that of virulence genes hla, hld, sea, seb, sed and tst was 100, 100, 53.2, 30.6, 3.2 and 24.2% respectively. Amongst all examined genes, hla and hld genes had the highest and sed gene had the lowest frequency. The maximum coexistence of genes was observed for hla+hld+mecA gene combination (42 out of 62 isolates). CONCLUSION: This study reports the presence of multidrug resistant, vancomycin-resistant and mecA negative MRSA isolates in infected patients of Rawalpindi and nearby regions of Pakistan that may have attributed to treatment failures, adaptability of new virulence characteristics and spread of antibiotic resistance.