Conjugal transfer of aminoglycoside and macrolide resistance between Enterococcus faecium isolates in the intestine of streptomycin-treated mice.

The purpose was to study conjugal transfer of resistance genes between a multi-resistant Enterococcus faecium isolate and a sensitive E. faecium isolate. Co-transfer of erm(B)-Tn5405-like element and aac(6')-Ie-aph(2'')-Ia was obtained in both in vivo and in vitro. Plasmid profiles and Southern blots showed that both the erm(B)-Tn5405-like element and aac(6')-Ie-aph(2'')-Ia were placed on the same large plasmid (>147 kb). These data show to our knowledge the first co-transfer of the erm(B)-Tn5405-like element and aac(6')-Ie-aph(2'')-Ia. The in vivo study also indicates that transfer of resistance genes between enterococci might occur under natural conditions in the gut of animals.