Identification of chromosomal antibiotic resistance genes in Streptococcus anginosus ("S. milleri")

Abstract

Determinants encoding resistance to antibiotics, except penicillin, of 5 of 21 Streptococcus anginosus clinical isolates that we examined transferred by conjugation into Enterococcus faecalis and into 1 to 5 streptococcal recipients at frequencies of 10-6 to 10-8 transconjugants per donor. No R plasmids were detected in any wild-type strain. DNA homology was detected between fragments and the following genes: aadE in 7 strains that were highly resistant to streptomycin, aph-3 in 8 strains that wre highly resistant to Kanamycin, ermB in 11 of 15 that were resistant to erythromycin, and tetM in 14 and tetO in 3 of the 18 strains that were resistant to tetracycline-minocycline. A Tn916-like structure was found in 10 of the 14 strains that carried the tetM gene.