In vitro activities of tigecycline against recently isolated Gram-negative anaerobic bacteria in Greece, including metronidazole-resistant strains

The in vitro activity of tigecycline was compared with those of benzylpenicillin, piperacillin + tazobactam, cefoxitin, imipenem, metronidazole, clindamycin, and tetracycline against 249 Gram-negative anaerobic bacteria (158 Bacteroides fragilis group, 27 non-fragilis Bacteroides spp., 44 Prevotella spp., and 20 miscellaneous), recently isolated from 8 general hospitals in Athens, Greece. Overall tigecycline MIC50 and MIC90 were 0.25 and 2 mg/L, respectively, whereas B. fragilis group MIC50 and MIC90 were 0.5 and 4 mg/L, respectively. In total, 93% of the isolates were susceptible to tigecycline (MIC ≤ 4 mg/L) and no high-level resistance (MIC ≥ 32 mg/L) was detected. In addition, tigecycline exhibited good activity against metronidazole- and tetracycline-resistant isolates (MIC90, 0.5 and 8 mg/L, respectively). In summary, tigecycline exhibits good in vitro activity against Gram-negative anaerobic bacteria isolated in Greece, as well as stability to the most common occurring resistance mechanisms, attributes that make this parenteral agent an attractive alternative for use against infections involving these microorganisms.