Methicillin resistant Staphylococcus aureus: a review of the present Indian scenario and drug treatment

Abstract

Methicillin-resistant strains of S. aureus cause infections that are associated with higher mortality rates and increased length of hospital stays, than infections caused by methicillin-susceptible strains. The mechanism by which MRSA strains develop resistance is by the production of an altered penicillin-binding protein (PBP), which has a decreased affinity for most semisynthetic penicillins. MRSA has increased in prevalence and has become endemic in the Indian subcontinent, with incidence varying from 25% in Western regions to 50% in Southern India. A multi-centric study conducted across 15 tertiary care centers in India from 2008 to 2009 showed overall prevalence of MRSA infection to be 41% among S. aureus isolates, and recent Indian studies from 2014 and 2018 have also suggested an increasing prevalence of MRSA. Transmission is mainly horizontal and concerns high risk populations (patients with prolonged hospital stay, on haemodialysis, receiving cancer treatment or specific medications that affect immune function, intravenous drug users and individuals who have had surgery in the recent past. Community Acquired MRSA has emerged as significant pathogen responsible for potentially fatal infections including life-threatening pneumonia, necrotizing fasciitis, endocarditis, osteomyelitis, severe sepsis, and toxic shock syndrome. Diagnosis is mainly by gram stain, culture and quantitative PCR. Newer techniques include Multi-locus sequence typing (MLST), Pulsed-field gel electrophoresis (PFGE), Bacteriophage typing, spa locus typing and SCCmec typing. Although Vancomycin was previously considered the definitive treatment for serious MRSA infections, the emergence of less-susceptible strains, poor clinical outcomes, and increased nephrotoxicity with high-dose therapy have deterred its use as first-line therapy in many cases. Although a number of new and effective antimicrobial agents are now available for the treatment of MRSA, their exact role and choice of agent needs to be well-defined.