Comparative Study on Characterization of Three Staphylococcal Isolatesfrom Varied Origin

Two strains of Staphylococcus isolated from urine and sputum samples were compared with a laboratory strain of Staphylococcus. Since all three grew on the same media specific for S. aureus, they were studied for their relatedness by morphological, biochemical and molecular characterization. Variation in properties among the isolates pointed towards their different identity which was confirmed through 16S rRNA gene sequence based phylogenetic analysis. The isolate A from urine was found to be closely related to S. haemolyticus, while isolate P from sputum was S. aureus and isolate S from NICED culture collection was closest to S. epidermidis. Thus the Hicrome aureus agar (Himedia M1468) was not specific for the species S. aureus and could only screen at genus level. The antibiotic profile of the strains was evaluated using a spectrum of 18 antibiotics. The lecithinase activity was retained only in freshly isolated strains and totally ceased in subsequent subculturing.