Non-susceptibility to tigecycline in enterococci from hospitalised patients, food products and community sources.

In this study, the in vitro activity of tigecycline against 1140 enterococci collected from humans, food products, animals and the environment in Portugal (1996-2008) was analysed. Ten isolates (seven Enterococcus faecalis and three Enterococcus spp.) non-susceptible to tigecycline (minimum inhibitory concentrations of 0.5-1.0 mg/L), which were also resistant to tetracycline and minocycline, were mostly observed in samples collected before the introduction of tigecycline in the therapeutic arsenal. The E. faecalis isolates were recovered from hospitalised patients (n=2; ST319/CC2 and ST34), healthy humans (n=2; ST21/CC21), chicken meat (n=1; ST260) as well as from two swine samples. The remaining isolates were also recovered from chicken meat (n=1; Enterococcus gallinarum) and swine (n=2; Enterococcus hirae and Enterococcus spp.). Recovery of enterococcal isolates with reduced susceptibility to tigecycline amongst different reservoirs, including animals for food consumption, suggests that selection of tigecycline-resistant isolates by antibiotics other than tigecycline might occur in non-clinical settings.