VIM-2 metallo-b-lactamases genes found in Pseudomonas aeruginosa and Acinetobacter spp. from Russia and associated with unusual integrons
Abstract number: 1732_330
Toleman M.A., Collin I., Sidorenko S., Cherkashyn E., Ivanov D., Tishkov V., Walsh T.R.
Objectives: To determine the mechanism of resistance of eight multi-resistant clinical isolates collected by the National Research Centre of Antibiotics, Moscow, Russia in 2005.
Methods: Strains were identified using an API 20 NE kit. The MICs were determined using Etest ESBL or MBL strips (AB biodisk, Solna, Sweden) and a wide range of antimicrobial test discs. Isolates positive by Etest MBL strips were further investigated for resistance determinants by PCR using blaVIM, blaIMP, blaSPM-1, blaGIM, blaSIM-1 and class-1 integron specific primers, as well as primers designed to the transposition genes of Tn5090. Amplicons were sequenced by using custom designed primers using standard methods.
Results: Six strains were identified as P. aeruginosa and one as Acinetobacter spp. All strains were resistant to imipenem >256mg/L which reduced in the presence of EDTA from 1 to 8 mg/L (MBL Etest strip). All isolates were multi-resistant and only sensitive to colistin. Five P. aeruginosa isolates harboured the blaVIM-2 gene cassette in a class-1 integron containing the gene cassette array: aacA7, blaVIM-2, dhfrB5 and aacA5. The structure was very unusual as it did not contain a 3' conserved sequence (3'CS). However, it did contain Tn5090 transposition genes, absent from most commonly found integron structures. The integron array was identical to those found in P. aeruginosa strains harbouring the blaVIM-2 gene recently characterised from the USA and Norway, and very similar to one recently characterised from India. One strain of P. aeruginosa and an isolate of Acinetobacter spp. also contained the blaVIM-2 gene in a normal class-1 integrons as gene cassettes in the first position that also contained an OXA-2 gene cassette.
Conclusion: The absence of a 3'CS and the presence of the tniC transposition gene suggests that the integron containing the VIM-2 allele in most of the P. aeruginosa isolates predates the formation of both the 3'CS and a deletion event that immobilised the Tn5090 transposon that carries the class-1 integron. The geographic widespread location of this particular integron structure including blaVIM-2, suggests recent worldwide dissemination.
|Session name:||European Society of Clinical Microbiology and Infectious Diseases|
|Location:||ICC, Munich, Germany|
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