Nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) among hospitalized patients: a cross-sectional study

Methicillin resistant Staphylococcus aureus (MRSA) infection is an important cause of increased morbidity and mortality among hospitalized patients. Major issues with multidrug resistant hospital associated (HA) strains are the treatment failures. The community associated MRSA (CA-MRSA) are discerned for the production of Panton valentine leucocidine (PVL) which makes them more virulent and capable of causing necrotizing pneumonia and necrotizing fasciitis. Nasal carriers of MRSA are thought to be the prime sources of infection in health care settings. This study was designed to estimate the burden of MRSA nasal colonization among hospital inpatients and also to type them based on antibiogram, PVL production and SCC mec type. After obtaining the clearance from institutional ethics committee, nasal swabs were collected and processed from 71 inpatients of a teaching hospital at Udupi taluk of Karnataka state, India. Suspected colonies of Staphylococcus aureus grown in blood agar were confirmed by coagulase test and latex agglutination test. MRSA were identified by cefoxitin disc diffusion test as per CLSI guidelines. All MRSA were subjected to multiplex PCR for SCC mec typing and single locus PCR for PVL assay. MRSA colonization was found in 15.5% of study subjects and none of the strains were producing PVL. Five isolates were identified as HA-MRSA which included four SCC mec type I and one type II. One SCC mec IV CA-MRSA was also identified. All the rest were non-typeable by the oligoprimers used in the study. Since majority of the MRSA were likely to be of HA-MRSA type, it is assumed that the patients would have been colonized with them after hospitalization. This demands the necessity of screening the health care workers for identifying the carriers of MRSA which aids in planning strategies to control their outbreaks in health care settings.