Genetic characterisation of the new blaVIM-18 and comparative antimicrobial susceptibility profile of VIM-18 with highest homologous VIM-variant, VIM-2: report from the SENTRY Antimicrobial Surveillance Program
Abstract number: P899
Castanheira M., Mendes R., Bell J., Sader H., Jones R.
Objective: To characterise the genetic context of a new blaVIM-variant from India; and to compare the antimicrobial susceptibility (S) profiles of E. coli carrying recombinant plasmids harbouring blaVIM-18 and blaVIM-2. We recently found that VIM-producing P. aeruginosa were highly prevalent in Indian medical centres (55% of the carbapenem [CARB]-resistant [R] isolates) and VIM-2 was the most common VIM-variant (38.6%).
Methods: As part of the SENTRY Program, CARB-R isolates were screened for metallo-b-lactamases (MBL). Positive isolates were then amplified and sequenced with MBL internal primers and primers targeting conserved structures of class 1 integrons. blaVIM-2 and the new blaVIM were amplified, cloned into PCRScript plasmid and transformed in E. coli XL1 Blue. Colonies were selected with chloramphenicol (30 mg/L) and ceftazidime (4 mg/L). The presence and orientation of blaVIM was confirmed by PCR and sequencing. S testing was performed by E-test (ABBIODISK, Solna, Sweden). The region flanking the MBL integron was amplified using a degenerate primer approach. Plasmid contents analysis was also carried out.
Results:P. aeruginosa isolate 24331C was recovered from a sputum specimen in Kolkatta, India (2006). PCR and sequencing showed the presence of new blaVIM variant, named blaVIM-18 (Lahey Clinic). The deduced VIM-18 protein comprised 262 amino acids showing 74.3 to 99.2% identity to other VIM enzymes. VIM-18 was identical to VIM-2, except for the deletion of four amino acids. The MBL active sites were all present. The E. coli carrying blaVIM-18 showed lower MIC values for ampicillin, cefoxitin, cephalothin and ertapenem (3-, 6-, 4- and 4-fold, respectively) when compared to those obtained from the E. coli carrying blaVIM-2, while similar MIC values were noted for imipenem, meropenem, piperacillin, cefotaxime, ceftazidime and cefepime. blaVIM-18 was the only R gene cassette in a class 1 integron that was flanked upstream by a resolvase gene (tnpR) from Tn5051-like. Further analysis showed that this isolate carried no plasmid.
Conclusions: VIM-18 displayed reduced activity to some b-lactams, while retaining similar activity against anti-pseudomonal agents when compared to VIM-2. Thus, the 12-bp deletion in VIM-18 seems to have little effect in the activity against target CARB and anti-pseudomonal cephems. VIM-18 was found in one P. aeruginosa isolate among numerous VIM-2-producing strains, and it appears to be an evolutionary derivative.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
|Back to top|