Studies on coexistence of mec gene, IS256 and novel sasX gene among human clinical coagulase-negative staphylococci.

Methicillin-resistant coagulase-negative staphylococci (MRCoNS) are major nosocomial pathogens which cause device-related infections. Presence of various virulence factors along with methicillin resistance favor improved CoNS pathogenicity and their dissemination among population. In the present study, mec gene prevalence was analyzed along with SCC mec diversity among 55 human clinical CoNS isolates. PCR screening of insertion sequence (IS256) was also conducted to elucidate their association with methicillin resistance among selected CoNS species. In addition to this, PCR screening and sequence analysis of novel colonization-associated gene sasX was also carried out. High incidences of mec gene, IS256 and their association have been noted among all of the CoNS species tested. Interestingly, eight CoNS isolates were found to harbor sasX gene including S. epidermidis, S. hemolyticus and S. saprophtyicus species. Remarkably they were also found to have the coexistence of mec gene and IS256 in their genome. Increased SCC mec diversity with non-typeable elements was also observed among CoNS isolates. Presence of sasX gene in CoNS with mec gene and insertion sequence 256 and also the identification of non-typeable SCC mec element make the study novel and interesting.