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

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-␤-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 Tn402 and mercury transposons and further sequencing. Among Enterobacteriaceae isolates, bla VIM-1 was part of integrons located either in an In2-Tn402 element linked to Tn21 (type A; In110-bla VIM-1 -aacA4-aadA1) or in a Tn402 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 Tn402 transposon carrying either tniB⌬3 and tniA (type C; bla VIM-1 -aadA1) or tniC and ⌬tniQ (type D; bla VIM-1 -aadB), and both Tn402 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.

Carbapenem Heteroresistance in VIM-1-Producing Klebsiella pneumoniae Isolates Belonging to the Same Clone: Consequences for Routine Susceptibility Testing

“…The level of expression of a resistance gene can be influenced by the position of the cassette in the insert region and by differences in promoter strength (5,8). In this study, all the strains belonged to the same clone, and in all of them, the bla VIM cassette was located in the first position of the integron and was expressed from a P1/Pant promoter variant that has been considered a hybrid of the weak and the strong versions of Pant, showing an intermediate strength (14,26; also M. Tato, M. T. Coque and R. Cantón, unpublished data). Another source of MIC variability could be related to the potential unstable plasmids containing the bla VIM gene.…”

Fecal Carriage of Carbapenemase-Producing Enterobacteriaceae: a Hidden Reservoir in Hospitalized and Nonhospitalized Patients

“…Characterization of class 1 integrons containing bla MBL was performed by PCR, sequencing, comparison of the restriction fragment length polymorphism (RFLP) patterns obtained by PCR, and further digestion with AluI enzyme. DNA of each integron showing a distinct RFLP type was sequenced using specific primers as previously described (33).…”

Molecular Basis of Sulfonamide and Trimethoprim Resistance in Fish-Pathogenic Aeromonas Isolates

“…The combination dfrA12-orfF-aadA2 has been seen in Salmonella Typhimurium from imported seafood (7), Salmonella enterica serovar Schwarzengrund from chicken (22), and A. hydrophila (15) or E. coli (6) from swine. The combination dfrB1-aadA1-catB2 was seen as part of larger bla VIM-1 -carrying integron structures in Klebsiella pneumoniae (19) and E. coli (20).…”