Rayhan Ahmed1; Md. Mehedi Hasan2; Kazi Selim Anwar3; P.K Rajesh4; Gokul Shankar Sabesan 5*
Staphylococcus aureus is one of the commonly isolated human pathogen important in causing several infections including childhood pneumonia. S. aureus often develops resistance to penicillin, cefoxitin, aminoglycosides, cephalosporins &/or β-lactams, but termed as ‘MRSA’ when it becomes resistant to oxacillin &/or methicillin. S. aureus according to different studies causes pneumonia ranging in 7-44% Malaysian children, but, MRSA in particular accounts for 3-5% community-acquired pneumonia (CAP) worldwide, including Malaysia. Since, reports on molecular epidemiology of MRSA remain scarce in Malaysian children, this research compared bacteriological, biochemical and molecular analysis between MRSA & MSSA (methicillin sensitive S.aureus) isolated from nasopharyngeal swabs (NPS) of pneumonic children. Total 220 randomly selected <5 years-old children admitted in two hospitals of Kedah, Malaysia were studied. With written consent from mother/guardian, NPS were cultured on to Mannitol salt and Blood agar plates. Following overnight aerobic-incubation (35-37oC) colony morphology were read, Gram-stained and bio-chemical (positive catalase and coagulase; and, CHO-fermentation) identifications recorded. Antimicrobial susceptibility-AST were tested with AMC20, CRO30, CIP5, E15, CN10, OX1, S10, TE30and VA30 and, MRSA strains were detected based on Oxacillin-resistance. Clinical diagnosis (by pediatricians) revealed 76% pneumonic cases among those hospitalized-children. Phenotypically, S. aureus was isolated from NPS of 32.6% pneumonic-children, 39.4% of which revealed as MRSA. For genotypic analysis, PCR was performed using two specific-primers: femA (S. aureus) and mecA (MRSA) and band-size were determined using agarose gel electrophoresis. Laboratory finding evidences less of MRSA prevalence using genotypic (32%) compared to that of phenotypic (39%) identification. No differences was obvious between MRSA and MSSA phenotypic methods, except in molecular method (p<0.00). Significant difference was observed between pneumonia and MRSA/MSSA (p<0.04) and with femA/mecA (p<0.00). These observations on nasopharyngeal S. aureus suggest that MSSA can also play an important role as potential cause of childhood-pneumonia other than MRSA, in small proportion.The present study strongly demands more detailed molecular-epidemiological research comparing the role of MSSA and MRSA to elucidate their genetic diversities associated with causing childhood pneumonia.
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