Phenotypic and Molecular Characterization of an Enterobacter ludwigii Clinical Isolate Carrying a Plasmid-Mediated blaIMI-6 Gene.

We report a plasmid-encoded IMI-6 carbapenemase in a clinical isolate of Enterobacter ludwigii from Spain. The isolate belongs to ST641 and was susceptible to expanded-spectrum cephalosporins and resistant to carbapenems. The modified carbapenem inactivation method (mCIM) test was positive, but ß-Carba was negative. Whole-genome sequencing identified the blaIMI-6 gene located in a conjugative IncFIIY plasmid and associated with the LysR-like regulator imiR. Both genes were bracketed by an ISEclI-like insertion sequence and a putatively defective ISEc36 insertion sequence. IMPORTANCE IMI carbapenemases confer an unusual resistance pattern of susceptibility to broad-spectrum cephalosporins and piperacillin-tazobactam but decreased susceptibility to carbapenems, which may make them difficult to detect in routine practice. Commercially available molecular methods for the detection of carbapenemases in clinical laboratories do not usually include blaIMI genes, which could contribute to the hidden dissemination of bacteria producing these enzymes. Techniques should be implemented to detect minor carbapenemases that are not very frequent in our environment and control their dissemination.

Rapid detection and identification of strains carrying carbapenemases directly from positive blood cultures using MALDI-TOF MS.

MALDI-TOF MS has been evaluated to detect carbapenemases activity and pathogen identification directly from positive blood cultures. 21 non-carbapenemase producers and 19 carbapenemase producers Enterobacteriaceae and Pseudomonas aeruginosa strains were included in the study. This technique is simple and detects carbapenemases in 4.5h with high sensitivity and specificity.