Journal of Antimicrobial Chemotherapy, Vol 42, 821-824, Copyright © 1998 by The British Society for Antimicrobial Chemotherapy
Z Pragai and E Nagy
We have evaluated the ability of imipenem and meropenem to select, in
vitro, resistant mutants of two clinical isolates of Klebsiella pneumoniae
producing both SHV and TEM beta-lactamases. Only meropenem selected mutants
of both isolates for which the MICs of meropenem, but not imipenem, were
markedly higher than those for the parent strains; the MICs of several
other beta-lactam antibiotics, including beta- lactam/beta-lactamase
inhibitor combinations, for these mutants were also higher than those for
the parent strains. In contrast, the MICs for the imipenem-selected mutants
were the same as, or similar to, those for the parent strains. Sodium
dodecyl sulphate-polyacrylamide gel electrophoresis analysis revealed that
an outer membrane protein in both parent strains was absent in the
meropenem-selected mutants, but not in the imipenem-selected mutants. This
protein is likely to be a porin, the absence of which is presumably
associated with impaired beta- lactam permeability and, therefore, the
reduced susceptibilities to these antibiotics exhibited by the mutant
strains. We believe that this is the first report of the in-vitro selection
of porin-deficient mutants of K. pneumoniae following exposure to
meropenem.
In-vitro selection of porin-deficient mutants of two strains of Klebsiella pneumoniae with reduced susceptibilities to meropenem, but not to imipenem [In Process Citation]
Department of Clinical Microbiology, Albert Szent-Gyorgyi Medical University, Hungary.
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