Authors : Shane C. Burgess , Timmothy S. Cummings , Anneke M.T. Steegh , Larry A. Hanson , Donna C. Sullivan and Rathel L. Nolan
Abstract: Human infections caused by Enterococcus species are increasing; they are the third most common cause of nosocomial infections. E. faecium, though a relatively rare Enterococcal nosocomial infection, is very commonly resistant to multiple antibiotics. Quinupristin/Dalfopristin, a Streptogramin, is an antibiotic of "last resort" for treating multi-antibiotic-resistant E. faecium. However, E. faecium isolates are now becoming resistant to Quinupristin/Dalfopristin. The source of Streptogramin-resistant E. Faecium is controversial. Although medical environments are a potential source, Streptogramin-resistant Enterocci are present in livestock fed Streptogramin growth-promoters. However, E. faecium subspecies are suggested to be predominantly host-species specific and thus livestock may not be a reservoir for Streptogramin-resistant E. faecium that infect humans. To resolve this issue, sensitive methods to quantify Streptogramin-resistant E. faecium relatedness are essential. We designed a rapid sensitive, specific, molecular diagnostic technique, targeting one E. faecium 16S/23S intergenic spacer region to distinguish between E. faecium at the nucleotide level. This region has no obvious evolutionary-conservation pressure and has been used to quantify relatedness in other bacteria. We analyzed streptogramin-resistant E. faecium from chickens from one grower house, on one farm, to quantify nucleotide polymorphism between isolates that would be expected to be closely related. We detected single nucleotide polymorphisms in four out of ten Streptogramin-resistant E. faecium isolated from this single source. The chicken-derived E. faecium sequences were more similar to each other than they were to the reference human E. faecium strain. Our method will be useful for studies of E. faecium ecology, pathogenicity and antibiotic resistance.
Shane C. Burgess , Timmothy S. Cummings , Anneke M.T. Steegh , Larry A. Hanson , Donna C. Sullivan and Rathel L. Nolan , 2006. Distinguishing Closely-Related Streptogramin-Resistant Enterococcus faecium: SNPs in One Specific 16-23S rRNA Intergenic Region. Journal of Animal and Veterinary Advances, 5: 855-862.