Evaluation of Clonality and Carbapenem Resistance Mechanisms among Acinetobacter baumannii-Acinetobacter calcoaceticus Complex and Enterobacteriaceae Isolates Collected in European and Mediterranean Countries and Detection of Two Novel β-Lactamases, GES-22 and VIM-35

Abstract

ABSTRACTWe evaluated doripenem-resistantAcinetobacter baumannii-Acinetobacter calcoaceticuscomplex (ACB;n= 411) andEnterobacteriaceae(n= 92) isolates collected from patients from 14 European and Mediterranean countries during 2009 to 2011 for the presence of carbapenemase-encoding genes and clonality. Following susceptibility testing, carbapenem-resistant (doripenem MIC, >2 μg/ml) isolates were screened for carbapenemases. New β-lactamase genes were expressed in a common background and susceptibility was tested. Class 1 integrons were sequenced. Clonality was evaluated by pulsed-field gel electrophoresis and multilocus sequence typing (Pasteur scheme). Relative expression of β-lactam intrinsic resistance mechanisms was determined for carbapenemase-negativeEnterobacteriaceae. ACB andEnterobacteriaceaedisplayed 58.9 and 0.9% doripenem resistance, respectively.blaOXA-23,blaOXA-58, andblaOXA-24/OXA-40were detected among 277, 77, and 29 ACB, respectively (in 8, 6, and 5 countries). Ten Turkish isolates carriedblaGES-11orblaGES-22. GES-22 (G243A and M169L mutations in GES-1) had an extended-spectrum β-lactamase profile. A total of 33 clusters of ≥2 ACB isolates were observed, and 227 isolates belonged to sequence type 2/international clone II. Other international clones were limited to Turkey and Israel. Doripenem-resistantEnterobacteriaceaeincreased significantly (0.7 to 1.6%), and 15blaKPC-2- and 22blaKPC-3-carrying isolates, mostly belonging to clonal complexes 11 and 258, were observed.Enterobacteriaceaeisolates producing OXA-48 (n= 16; in Turkey and Italy), VIM-1 (n= 10; in Greece, Poland, and Spain), VIM-26 (n= 1; in Greece), and IMP-19, VIM-4, and the novel VIM-35 (n= 1 each from Poland) were detected. VIM-35 had one substitution compared to VIM-1 (A235T) and a similar susceptibility profile. One or more resistance mechanisms were identified in 4/6 carbapenemase-negativeEnterobacteriaceae. This broad evaluation confirms results from country-specific surveys and shows a highly diverse population of carbapenemase-producing ACB andEnterobacteriaceaein Europe and Mediterranean countries.