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Antimicrobial Agents and Chemotherapy, Mar 1996, 646-651, Vol 40, No. 3
FJ Abadi, PE Carter, P Cash and TH Pennington
Rifampin-resistant (Rifr) Neisseria meningitidis strains are known to have
single point mutations in the central conserved regions of the rpoB gene.
We have demonstrated two distinct resistance phenotypes in strains with
identical mutations in this region, an intermediate level of resistance in
Rifr clinical isolates and a high level of resistance in mutants selected
in vitro. The possible role of membrane permeability in the latter was
investigated by measuring MICs in the presence of Tween 80; values for
high-level-resistance mutants were reduced to intermediate levels, whereas
those for intermediate-level- resistance strains were unaffected. The
highly resistant mutants were also found to have increased resistance to
Triton X-100 and gentian violet. Sequencing of the meningococcal mtrR gene
and its promoter region (which determine resistance to hydrophobic agents
in Neisseria gonorrhoeae) from susceptible or intermediate strains and
highly resistant mutants generated from them showed no mutation within this
region. Two-dimensional gel electrophoresis of two parent and Rif mutant
strains showed identical shifts in the pI of one protein, indicating that
differences between the parent and the highly Rifr mutant are not confined
to the rpoB gene. These results indicate that both permeability and rpoB
mutations play a role in determining the resistance of N. meningitidis to
rifampin.
Copyright © 1996 by the American Society for Microbiology. All rights reserved.
Rifampin resistance in Neisseria meningitidis due to alterations in membrane permeability
Department of Medical Microbiology, University of Aberdeen Medical School, Scotland.
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