Heterogeneity of macrolide-lincosamide-streptogramin B resistance phenotypes in enterococci.
We determined the macrolide resistance phenotypes of 241 clinical isolates of erythromycin-resistant enterococci (MICs, > or = 1 microg/ml), including 147 Enterococcus faecalis strains and 94 Enterococcus faecium strains, collected from a hospital in Seoul, Korea, between 1999 and 2000. By the erythromycin (40 micro g)-josamycin (100 microg) double-disk test, 93 strains were assigned to the constitutive macrolide, lincosamide, and streptogramin B (MLS(B)) resistance (cMLS(B)) phenotype, and the remaining 148 strains were assigned to the inducible MLS(B) resistance (iMLS(B)) phenotype. Of the strains with the iMLS(B) phenotype, 36 exhibited a reversibly inducible MLS(B) (riMLS(B)) phenotype, i.e., blunting of the erythromycin zone of inhibition, which indicates that the 16-membered-ring macrolide josamycin is a more effective inducer than the 14-membered-ring macrolide erythromycin. Sequence analysis of the regulatory regions of the erm(B) genes from all of the strains exhibiting the riMLS(B) phenotype revealed not only erm(Bv) [where v represents variant; previously erm(AMR)] (n = 13), as reported previously, but also three kinds of erm(B) variants, which were designated erm(Bv1) (n = 17), erm(Bv2) (n = 3), and erm(Bv3) (n = 3), respectively. In lacZ reporter gene assays of these variants, the 16-membered-ring macrolide tylosin had stronger inducibility than erythromycin at > or = 0.1 microg/ml. These findings highlight the versatility of erm(B) in induction specificity.
College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Korea.
Yu-Hong
YH
Min
Jae-Hee
JH
Jeong
Yun-Jeong
YJ
Choi
Hee-Jeong
HJ
Yun
Kyungwon
K
Lee
Mi-Ja
MJ
Shim
Jin-Hwan
JH
Kwak
Eung-Chil
EC
Choi
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001483:Base Sequence; D024881:Drug Resistance, Bacterial; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000254:growth & development; D016984:Enterococcus faecium / Q000187:drug effects* / Q000254:growth & development; D007763:Lac Operon / Q000235:genetics; D055231:Lincosamides; D018942:Macrolides / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D025381:Streptogramin B / Q000494:pharmacology*; D001616:beta-Galactosidase / Q000096:biosynthesis
D000900:Anti-Bacterial Agents; D055231:Lincosamides; D018942:Macrolides; D025381:Streptogramin B; D001616:beta-Galactosidase