Abstract
The purpose of this study was to study whether horisontal transfer of the satA gene could take place between isogenic strains of Enterococcus faecium in the gastrointestinal tract. Two separate groups of germ-free Sprague-Dawley rats were dosed orally with a single high dose of approximately 5×108 colony forming units (CFU) of the streptomycin resistant recipient E. faecium BM4105-Str. One week later, after the establishment of the recipient, a rifampicin, fusidin and virginiamycin resistant donor, E. faecium AHA15(,satA), containing a transferable satA gene was given orally in a single high dose of approximately 1×108 CFU to the gnotobiotic rats. The different strains of E. faecium were identified in faecal samples using the specific antibiotic resistance pattern for isolation on selective agar plates. In both groups of rats transconjugants E. faecium BM4105-Str (satA) were identified in faecal samples using specific phenotypic antibiotic resistance pattern on selective agar plates. High numbers of transconjugants were observed throughout the remaining experimental period of approximately 18 days, indicating horizontal transfer of the satA gene followed by persistence and proliferation of the transconjugants in vivo. The donor persisted in low numbers throughout the experimental period. The present study demonstrated that transfer of the satA gene encoding resistance to streptogramin A between isogenic E. faecium strains takes place under experimental conditions in the mammalian gastrointestinal tract. This indicates that a similar transfer may take place under natural conditions.