Examination of detection methods for metallo-β-lactamase produced by Aeromonas genus

Abstract

Some species of the genus Aeromonas carry genes that encode carbapenemase in their chromosomes; these species are classified under Ambler classification class B2. We experienced treating a patient from whom a carbapenem-resistant Aeromonas isolate showed a discrepancy between the results of VITEK2, an automatic analyzer for drug susceptibility testing, and the disc diffusion method (E test). Therefore, using carbapenem-resistant strains of the genus Aeromonas, we examined the difference in drug susceptibility results among different models of an automatic analyzer and examined the carbapenemase confirmation test results. Carbapenem-resistant Aeromonas hydrophila and Aeromonas veronii detected at our hospital were tested for drug susceptibility using three models of the automatic analyzer, namely, VITEK2, MicroScan WalkAway, and RAISUS ANY, and the results showed discrepancies. Among the automatic analyzers used, VITEK2 could detect carbapenem resistance best. By conducting a carbapenemase confirmation test, we found that carbapenem drugs may show false results in Aeromonas susceptibility tests. We speculate that it will lead to treatment and nosocomial infection control.