Hidden VIM-1 metallo-beta-lactamase phenotypes among Acinetobacter baumannii clinical isolates.

Journal of clinical microbiology

PubMedID: 18032624

Ikonomidis A, Ntokou E, Maniatis AN, Tsakris A, Pournaras S. Hidden VIM-1 metallo-beta-lactamase phenotypes among Acinetobacter baumannii clinical isolates. J Clin Microbiol. 2008;46(1):346-9.
A total of 87 Acinetobacter baumannii nonrepetitive consecutive clinical isolates were tested for the presence of metallo-beta-lactamases (MBLs). Results of phenotypic assays (MBL Etest, imipenem/imipenem-EDTA combined-disk test, and imipenem/EDTA double-disk synergy test) were negative in all cases, but molecular testing revealed the presence of two bla(VIM-1)-carrying isolates. One isolate had bla(VIM-1) preceded by a weak P1 promoter, and both had inactivated P2 promoters and reduced bla(VIM-1) expression, partially justifying the results revealing hidden MBL phenotypes.