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Hidden VIM-1 metallo-beta-lactamase phenotypes among Acinetobacter baumannii clinical isolates
Alexandros Ikonomidis1, Eleni Ntokou, Antonios N Maniatis
1Department of Microbiology, Medical School, University of Thessaly, Larissa, Greece.
Abstract:
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.
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