Rifampin resistance in Neisseria meningitidis due to alterations in membrane permeability

Abstract

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.

A proteomic analysis of erythromycin resistance inStreptococcus pneumoniae

“…2B). The majority of the proteins resolved under these conditions had isoelectric points < 6.2, based on the carbamylated marker proteins, which contrasted with the broader distribution of isoelectric points determined for the soluble proteins prepared from Gram-negative bacteria analysed under the same electrophoretic conditions [8,10,11,19]. …”

“…We have previously used nonionic detergent to lyse Gram-negative bacteria to prepare soluble proteins for analysis by 2-DE [8,11,19]. Fig.…”

“…Proteomics has been widely used to characterise the proteins expressed by a diverse range of bacterial groups (reviewed in [8] [18] reported on the action of the antibiotics sulfamethoxazole and trimethoprim on tetrahydrofolate synthesis in H. influenzae. In addition, protein mobility differences have been observed between rifampicin-susceptible and -resistant Neisseria meningitidis isolates [19]. The following report describes the application of two-dimensional electrophoresis (2-DE) to analyse the proteins expressed by erythromycin-susceptible and -resistant S. pneumoniae isolates.…”

Neisseria meningitidis rifampicin resistant strains: analysis of protein differentially expressed

“…Moreover, other mechanisms have been described in both Neisseria meningitidis and in Neisseria gonorrhoeae [7,8], i.e. resistance to diverse hydrophobic agents, including Triton X, is associated with mutations in the mtrR gene and in its promoter [7,9,10]. Overall, in other species, such as Mycobacterium tuberculosis , resistance was not related to any changes in the rpoB gene in around 5% of clinical rifampicin resistant isolates [11].…”

Virulence determinants involved in differential host niche adaptation of Neisseria meningitidis and Neisseria gonorrhoeae

“…In addition, gonococci are specialized on survival of the abundant hydrophobic compounds in the urogenital tract [151] and therefore rely on the MtrRCDE and FarRAB systems for controlled eZux of these antimicrobials [63,64,[152][153][154]. Although meningococci have a functional MtrCDE system, they have no functional repressor MtrR and only natural downregulation of mtrC expression by IHF-dependent insertions of Correia Elements prevents a constitutively active MtrCDE eZux pump [155][156][157][158], suggesting that there is no need of this eZux pump system in the nasopharynx. The genes for the remaining eZux pump system FarRAB are also present in meningococci, yet their role in virulence remains to be determined.…”