TRANSFERABILITY AND GENETIC RELATEDNESS OF HIGH-LEVEL GENTAMICIN RESISTANCE AMONG ENTEROCOCCI

Gentamicin resistance in six enterococcal species was investigated. Tr ansfer of resistance was observed for the donors E. faecium UC 79, E. avium CC 54, and E. gallinarum B 51, but not for E. raffinosus UC 78 o r E. casseliflavus UC 73. Except for E. casseliflavus UC 73, homology was observed between the E. faecalis aac6'-aph2'' gene and DNA from ot her species. Whereas 2.6-kb HindIII fragments encoded resistance in E. faecalis UC 244, its transconjugant, and E. raffinosus UC 78, 3.4-kb fragments encoded resistance in E. faecium UC 79, E. gallinarum B 51, and their transconjugants. A 3.4-kb fragment encoded resistance in E. avium CC 54, but 2.6-kb fragments encoded resistance in the transconju gants. Although many similarities were found among the strains, the he terogeneity in gentamicin resistance exhibited by some isolates indica tes diversity among these determinants.