EVALUATION OF IN VITRO TIGECYCLINE ACTIVITY AGAINST MULTIDRUG-RESISTANT ACINETOBACTER BAUMANNII CLINICAL ISOLATES FROM POLAND.

Acinetobacter baumannii is a major cause of nosocomial infections worldwide. Therapeutic options in management of this bacteria are limited. Tigecycline is considered as an alternative treatment of infections caused by multidrug-resistant A. baumannii strains, however this resistance has emerged recently. Another growing problem is a lack of international consensus between U.S. FDA and EUCAST recommendations, regarding tigecycline breakpoints for Acinetobacter spp., and frequently off-label use. The aim of the present study was to assess the in vitm susceptibility to tigecycline and other antimicrobials, routinely used in the treatment of infections, among 155 A. baumannii isolates, collected between 2008-2013 from a hospital in Poland. The most active agent against the tested MDR strains was colistin (99.3% susceptible isolates). Our study has shown a low efficiency of tigecycline, with 74.2% of non-susceptible strains (according to the U.S. FDA guidelines). Tigecycline MIC values ranged from 0.125 to 48 mg/L. The MIC50 and MIC90 were 3 and 8 mg/L, respectively, and 25.8% (40) of the isolates displayed MIC = 2 mg/L. The highest percentage of tigecycline-resistant strains were noted in 2010 (56.3%). Our study revealed remarkably high tigecycline non-susceptibili- ty rates among MDR A. baumannii isolates, therefore this antimicrobial should be administered with caution.