Genetic characterization of methicillin resistant staphylococcus aureus isolated from patients in hospital Tengku Ampuan Afzan, in terms of mecA, mecC and PVL genes

Abstract

Methicillinresistant Staphylococcus aureus (MRSA) is globally a major public health threat. This strain has challenged therapeutic options and increased the mortality rate. Increased economic burden on patients and society is the other problem imposed by MRSA. Resistance to methicillin originates from a modified protein called PBP2a encoded by mecA gene. Recently, a new divergent of mecA gene has been reported which is called mecC and encodes PBP2c. Detection of this new divergent has challenged the status of mecA gene as a golden standard to confirm resistance to methicillin. MecC cannot be detected with the same strategies of mecA detection. The presence and expression of PVL gene in MRSA increases the health risk of these pathogens. To justify infection control policy, updates on the epidemiology and characterization of MRSA is the first demand. Meanwhile, epidemiology and characterization of MRSA differ in different geographical regions. To fill the gap this study was conducted to characterize MRSA isolated from patients in HTAA, Kuantan, Malaysia in terms of the mecA, mecC, PVL genes and their antibiotic susceptibility profile. In this study a total of 36 isolates of MRSAs have been collected from patients in different wards at HTAA during a period of three months (1stFebruary –30thApril, 2018). The isolates were taken from blood, tissue, sputum, pus, skin swabs, throat swabs, nasal swabs, bronchial lavage, and tracheal aspirate. The isolates were reconfirmed as MRSA with known phenotypic tests. Based on the published criteria for identifying community acquired and hospital acquired infections 44.4% of the isolates were CA-MRSA, while the rate of HA-MRSA was 55.5%. Susceptibility tests to ten different commonly used antibiotics were performed. It was found that resistance to oxacillin, cefoxitin and penicillin was 100%, to gentamycin 88.8%, erythromycin 33.3%, tetracycline 77.7%, trimethoprim-sulfamethoxazole 61.1%, clindamycin 13.8%, chloramphenicol 11.1%, and none of the isolates was resistant to vancomycin. Real-time PCR revealed that all isolates were mecA positive but only 4of the isolates were PVL positive. All PVL positive strains were CA-MRSA and all were susceptible to clindamycin. The study confirms the presence of multidrug resistant MRSA in the study area, and shows that resistance to methicillin is mecA rather than mecC mediated. PVL carrier strains were all among the CA-MRSA and constituted 11.1% of the total MRSAisolates.