In Vitro Activity of Eravacycline and Comparator Antimicrobials Against 143 Strains of Bacteroides Species.

BACKGROUND: Eravacycline (ERV is the first fully synthetic fluorocycline with activity against tetracycline (TET)-resistant organisms. In addition, it is 2–8 times more potent than tigecycline (TGC). Like other tetracyclines, it inhibits protein synthesis by binding to the 30S ribosomal subunit exhibiting a broad spectrum of activity. To further explore its activity, we tested 143 clinical isolates of Bacteroides and included TET, TGC and other drugs frequently used to treat serious infections. METHODS: Clinical isolates recovered during the past 3 years from patients in southern California were saved as pure cultures in 20% skim milk at −70°C. Prior to testing, they were transferred at least twice to ensure purity and good growth. Antimicrobials included ERV, TET, TGC, piperacillin-tazobactam (P-T), meropenem (MER), clindamycin (CLI), and metronidazole (MET). The method was agar dilution as described in the CLSI M11-A8 document for testing anaerobes using Brucella agar and incubation in the anaerobic chamber at 36°C for 44h. The MIC was defined as the lowest dilution that completely inhibited growth or resulted in a marked reduction compared with a drug-free growth control. RESULTS: The MIC(90) values (µg/ml) for Bacteroides and Parabacteroides are presented in the table: CONCLUSION: This study confirmed the improved activity of ERV over TGC against Bacteroides and suggests that ERV may be an appropriate choice for infections involving these organisms. DISCLOSURES: E. Goldstein, Tetraphase Pharmaceuticals: Research Contractor, Research grant