ASLANGUL E, CHAU F, LEFORT A, COURVALIN P, FANTIN B; Interscience Conference on Antimicrobial Agents and Chemotherapy (43rd: 2003: Chicago, Ill.).
Abstr Intersci Conf Antimicrob Agents Chemother Intersci Conf Antimicrob Agents Chemother. 2003 Sep 14-17; 43: abstract no. E-1992.
Bichat Medical School, Paris, France.
BACKGROUND: High-level resistance to gentamicin (Gen) in enterococci abolishes synergism between amoxicillin (Amo) and gentamicin (Gen). We previously reported in vitro and in vivo emergence of E. faecalis mutants with low-level Gen resistance (AAC. 43:476-482 and 44:2077-2080). However, the therapeutic consequences of low-level Gen resistance are unknown. We investigated the synergism of the Amo-Gen combination against susceptible and Gen-resistant isogenic E. faecalis. METHODS: Mutants of strain JH2-2 were selected on BHI agar containing increasing Gen concentrations (conc). One mutant obtained at each of the 3 steps required to achieve high-level resistance was studied: E. faecalis 1477 (first generation mutant: G1), 1573 (G2), and 1688 (G3). The Amo MIC was 0.25 mg/L against all strains. Time-kill curves were performed in BHI broth with 0.25 mg/L of Amo and Gen conc. ranging from 1/2 to 1/16-fold the MIC for each strain. RESULTS: [table: see text]. CONCLUSIONS: Each step of Gen resistance required a relatively higher Gen conc. to achieve bactericidal synergism with Amo and to prevent emergence of mutants more resistant to Gen. According to the NCCLS guidelines and to the Gen conc. achievable in humans, Amo-Gen synergism is lost even against the first step mutants.
Publication Types:
Keywords:
- Amoxicillin
- Enterococcus
- Enterococcus faecalis
- Gentamicins
- Humans
- In Vitro
- Microbial Sensitivity Tests
Other ID:
UI: 102264932
From Meeting Abstracts