Novel class 1 Integrons and sequence types in VIM-2 and VIM-11-producing clinical strains of Enterobacter cloacae

All VIM-producing Enterobacteriaceae (six Enterobacter cloacae) submitted to the Argentinian Reference Laboratory in Antimicrobial Resistance in the period 2008-13 were characterized. The isolates were referred from 6 nosocomial institutions located in 5 different cities across the country. All isolates showed carbapenem disk diffusion inhibition zones ≤22mm and synergism between a carbapenem disk and EDTA/SMA. The six isolates were PCR positive for bla_VIM. Imipenem MICs were ≤1 to 8μg/ml. Typing by PFGE and MLST distinguished six pulsotypes and sequence types with bla_VIM located on novel class 1 integron arrays: ECL-1: ST182, In883; ECL-2, ST90, In885; ECL-3, ST88, In346 with bla_VIM-11; ECL-4, ST184, In900; ECL-5, ST749-new, In900; ECL-6, ST91 and uncharacterized In. Only ECL-2 was able to transfer bla_VIM-2 to E. coli J53 by biparental conjugation. bla_VIM was located in plasmids of 53-82Kb and in the chromosome (ECL-1 and ECL-5). The diversity of clones, class 1 integrons, plasmids and location of bla_VIM, reveals the plasticity of the genetic elements described and highlights the importance of surveillance programs as tools to identify the transmission of these highly resistant metallo-β-lactamase-producing Enterobacteriaceae.