In vitro activity of tigecycline against multidrug-resistant Enterobacteriaceae isolates from a Belgian hospital

Bacterial resistance among Gram-negative pathogens is a challenging clinical problem. Tigecycline has been developed specifically to overcome resistance. The aim of this study was to assess the in vitro activity of tigecycline against ESBL-producing Escherichia coli, ESBL-producing Klebsiella spp., and multidrug-resistant Enterobacter spp. Between May 2007 and March 2008, 26 strains of ESBL-producing Escherichia coli, 10 strains of ESBL-producing Klebsiella spp., and 27 strains of multidrug-resistant Enterobacter spp. were isolated consecutively from inpatients with a documented infection in which the collected isolate was identified as the probable causative organism. The in vitro susceptibility against tigecycline was measured by the E-test method. MIC₅₀ values were 1 µg/ml, 2 µg/ml, and 3 µg/ml respectively. MIC₉₀ values were respectively 1.5 µg/ml, 4 µg/ml, and 12 µg/ml. Nonsusceptibility rates of 35%, 100%, and 96% respectively were found using EUCAST breakpoints. Despite the limited number of strains tested, our in vitro data suggest that tigecycline is unsuitable for the treatment of infections with multidrug-resistant Enterobacteriaceae in our setting. Therefore, we suggest that larger multicenter studies should be conducted to reconsider the value of tigecycline for the treatment of infections with multidrug-resistant, Gram-negative bacteria.