Nosocomial dissemination of VIM-2-producing ST235 Pseudomonas aeruginosa in Lithuania

Pseudomonas aeruginosa multidrug resistance, and particularly the production of carbapenemases linked to international high-risk clones, is of growing concern. While high levels of carbapenem resistance (>60 %) have been reported in Lithuania, so far, there is no information on the underlying mechanisms. Thus, the aim of this work was to determine the molecular epidemiology and prevalence of acquired carbapenemases among 73 carbapenem-resistant P. aeruginosa isolates recovered in a hospital from Kaunas, Lithuania in 2011-2012. The presence of acquired carbapenemases was evaluated through phenotypic (modified Hodge test, cloxacillin inhibition test, double-disc synergy test) and genetic methods [polymerase chain reaction (PCR) and sequencing]. Clonal relatedness was assessed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Acquired β-lactamases were detected in 19 (26 %) of the isolates, whereas resistance was exclusively chromosomal (OprD inactivation ± AmpC hyperproduction) in the remaining 54 (74 %) isolates. The acquired β-lactamases detected included 16 VIM-2, one PER-1 and two GES enzymes. PFGE revealed that 15 of the 16 VIM-2 isolates belonged to a single clone, identified as the international high-risk clone ST235 by MLST. bla VIM-2 was preceded by aacA7 in a class I integron, similar to epidemic ST235 isolates described in nearby countries. Additionally, sequencing of bla GES revealed the presence of the carbapenem-hydrolysing enzyme GES-5 in one of the isolates and a novel GES variant, designated GES-27, in the other. GES-27 differed from GES-5 by a single amino acid substitution, proline 167, that was replaced by glutamine. Increasing emergence and dissemination of concerning resistance mechanisms and international clones warrants global surveillance and control strategies.