title: The 'hidden' carbapenemase of Aeromonas hydrophila.
abstract: It has been presumed that there are just two beta-lactamases in the motile Aeromonas species, a carbapenemase and a cephalosporinase, based on the premise that all beta-lactamases can be detected by hydrolysis of the chromogenic cephalosporin, nitrocefin. However, when it was recently found that a non-motile species of Aeromonas that causes furunculosis in salmon, contained three beta-lactamases, one of which was a carbapenemase which could not be detected with nitrocefin, it was hypothesised that genetic exchange could occur between fish pathogens and human pathogens resulting in the transfer of the carbapenemase-encoding gene. This could have a potentially serious impact on intensive therapy units where carbapenems are employed. The purpose of this study was to determine whether the human pathogen Aeromonas hydrophila demonstrated the same beta-lactamase profile. After anion and cation exchange chromatography had been employed to separate the beta-lactamases of a clinical strain of A. hydrophila, three different beta-lactamases were found, one of which is a carbapenemase which does not hydrolyse nitrocefin. It is, therefore, probable that many strains of Aeromonas spp. contain a similar array of beta-lactamases which include a carbapenemase that cannot be detected with nitrocefin. Similar carbapenemases may well remain hidden in other species of bacteria unless appropriate techniques to detect the enzymes are employed.
authors.affiliation: Department of Medical Microbiology, Medical School, University of Edinburgh, UK.
authors.forename: M V
authors.initials: MV
authors.lastname: Hayes
authors.forename: C J
authors.initials: CJ
authors.lastname: Thomson
authors.forename: S G
authors.initials: SG
authors.lastname: Amyes
mesh_terms: D016980:Aeromonas hydrophila / Q000187:drug effects / Q000201:enzymology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins; D006801:Humans; D007525:Isoelectric Focusing; D008826:Microbial Sensitivity Tests; D008970:Molecular Weight; D001618:beta-Lactamases / Q000032:analysis*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001618:beta-Lactamases; C063912:carbapenemase