Molecular Characterization of Staphylococcal Cassette Chromosome mecA and Concomitant Panton-valentine Leukocidine in Clinical Isolates of Community-acquired Methicillin-resistant Staphylococcus aureus

Background: Staphylococcus aureus (S. aureus) remains, to date, one of the major causes of both Healthcare Associated (HA) and Community Associated (CA) infections. S. aureus causes a variety of infections, ranging from Skin and Soft Tissue Infections (SSTI) to life threatening endocarditis. Healthcare Associated Methicillin-resistant Staphylococcus aureus (HA-MRSA) and Community-associated Methicillin-resistant Staphylococcus aureus (CA-MRSA) have been increasingly reported from India. Efficacious dissemination of the complex and heterologous Staphylococcal Cassette Chromosome (SCC) mec elements necessitate to detect its SCC mec typing. Panton-Valentine Leucocidin (PVL) is a cytotoxin produced by S. aureus associated CA infections of S. aureus. Aim and Objectives: To investigate the prevalence of HA-MRSA and CA-MRSA in tertiary care hospital and to analyse the demographic and clinical characteristics of patients with Methicillin-resistant Staphylococcus aureus (MRSA) infections with mec A gene and PVL gene-positive strains and to compare with those for PVL gene-negative strains. Material and Methods: Isolation and identification has been done by standard conventional methods. Results: A total of 400 MRSA; 107 (26.75%) MRSA were from blood sample of Body Substance Isolation (BSI) and endocarditis 81(20.25%) were from osteomyelitis and septic arthritis, 97(24.25%) were from skin and soft tissue infections, 62(15.5%) were from pneumonia, 45(11.25%) were from Urinary Tract Infection (UTI). Of the total 400 MRSA strains; 183(45.75%) strains were isolated from paediatric and neonatal age group. All MRSA strians were susceptible to tigecycline and vancomycin. 95.5% strains were susceptible to linezolid. Of the total MRSA;40.5% strains were susceptible for clindamycin and all strains isolated from SSTIs were susceptible clindamycin. MRSA strains 248(62%) were resistant to tetracycline. 75.25% and 42.75% MRSA strains were defined as CA-MRSA and HA-MRSA respectively by clinical criteria: CDC epidemiologic definitions .76% (41/54) of patient isolates had presence of both the genes in the genome whereas 16% had only mecA gene. Small percent of isolates (5.5%) did not have both the genes on the genome. Conclusion: Our laboratory analysis of MRSA isolates indicated a high number of PVL-positive CA-MRSA isolates, carrying a novel mecA gene. The co-occurrence of multidrug-resistant MRSA and PVL-positive CA-MRSA highlights the risk for the emergence of a multidrug-resistant PVL-positive MRSA clone.