Dispersal of Carbapenemase bla VIM-1 Gene Associated with Different Tn 402 Variants, Mercury Transposons, and Conjugative Plasmids in Enterobacteriaceae and Pseudomonas aeruginosa

Abstract

ABSTRACT The emergence of bla VIM-1 within four different genetic platforms from distinct Enterobacteriaceae and Pseudomonas aeruginosa isolates in an area with a low prevalence of metallo-β-lactamase producers is reported. Forty-three VIM-1-producing isolates (including 19 Enterobacter cloacae , 2 Escherichia coli , and 2 P. aeruginosa isolates, 18 Klebsiella pneumoniae isolate, and 2 Klebsiella oxytoca isolate) recovered from 2005 to 2007 and corresponding to 15 pulsed-field gel electrophoresis types were studied. The Enterobacteriaceae isolates corresponded to a hospital outbreak, and the P. aeruginosa isolates were sporadically recovered. The genetic context of the integrons carrying bla VIM-1 (arbitrarily designated types A, B, C, and D) was characterized by PCR mapping based on known Tn 402 and mercury transposons and further sequencing. Among Enterobacteriaceae isolates, bla VIM-1 was part of integrons located either in an In2-Tn 402 element linked to Tn 21 (type A; In110- bla VIM-1 - aacA4-aadA1 ) or in a Tn 402 transposon lacking the whole tni module [type B; In113- bla VIM-1 - aacA4-dhfrII (also called dfrB1 )- aadA1-catB2 ] and the transposon was associated with an IncHI2 or IncI1 plasmid, respectively. Among P. aeruginosa isolates, bla VIM-1 was part of a new gene cassette array located in a defective Tn 402 transposon carrying either tniB Δ 3 and tniA (type C; bla VIM-1 - aadA1 ) or tniC and Δ tniQ (type D; bla VIM-1 - aadB ), and both Tn 402 variants were associated with conjugative plasmids of 30 kb. The dissemination of bla VIM-1 was associated with different genetic structures and bacterial hosts, depicting a complex emergence and evolutionary network scenario in our facility, Ramón y Cajal University Hospital, Madrid, Spain. Knowledge of the complex epidemiology of bla VIM-1 is necessary to control this emerging threat.