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Antimicrobial Agents and Chemotherapy, 05 1997, 931-935, Vol 41, No. 5
B Fantin, R Leclercq, L Garry and C Carbon
The influence of inducible cross-resistance to macrolides, lincosamides,
and streptogramin B (MLS(B)) type antibiotics (inducible MLS(B) phenotype)
on the activity of quinupristin-dalfopristin was investigated against
Enterococcus faecium in vitro and in rabbits with experimental
endocarditis. In vitro, quinupristin-dalfopristin displayed bacteriostatic
and bactericidal activities against a MLS(B)- susceptible strain similar to
those against two strains with the inducible MLS(B) phenotype. In addition,
induction of the two MLS(B)- resistant strains with quinupristin (0.016 to
1 microg/ml) or quinupristin-dalfopristin (0.08 to 0.25 microg/ml)
increased the MICs of quinupristin from 8 microg/ml to 32 to > 128
microg/ml, but did not modify the MIC of dalfopristin (2 microg/ml) or
quinupristin- dalfopristin (0.5 microg/ml). In a rabbit endocarditis model,
quinupristin-dalfopristin was as active as amoxicillin against the
MLS(B)-susceptible E. faecium strain. In contrast, the activity of
quinupristin-dalfopristin was significantly decreased in animals infected
with either of the two inducible MLS(B)-resistant strains (P < 0.05),
although no mutants resistant to quinupristin-dalfopristin were detected.
Against the clinical strain with the inducible MLS(B) phenotype,
quinupristin-dalfopristin was not effective and was less active than
amoxicillin (P < 0.001); however, the activity of the combination of
amoxicillin and dalfopristin-quinupristin was superior to that of
amoxicillin (P < 0.01). The different impact of the inducible MLS(B)
phenotype in E. faecium on the activity of quinupristin-dalfopristin in
vitro and in experimental endocarditis may be related to the reduced
diffusion of dalfopristin compared with that of quinupristin into cardiac
vegetations that we previously reported. This result emphasizes the
importance of the constant presence of dalfopristin at the site of
infection to ensure synergism with quinupristin.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Influence of inducible cross-resistance to macrolides, lincosamides, and streptogramin B-type antibiotics in Enterococcus faecium on activity of quinupristin-dalfopristin in vitro and in rabbits with experimental endocarditis
Institut National de la Sante et de la Recherche Medicale, Unite 13,and Universite Paris VII, Paris, France.
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