Role of Efflux Pumps and Mutations in Genes for Topoisomerases II and IV in Fluoroquinolone-ResistantPseudomonas aeruginosaStrains

Abstract

We have investigated the occurrence of mutations in topoisomerase II (DNA gyrase) subunit B(gyrB) and topoisomerase IV subunit E(parE) and the hyperexpression of genes for four efflux pump proteins in 20 previously described, fluoroquinolone-resistant clinical strains of Pseudomonas aeruginosa. Amino acid alterations were found in GyrB in five strains and in ParE in three strains with MIC of norfloxacin > or = 8 mg/L, and it is likely that some of the alterations contribute to the quinolone resistance exhibited by these strains. Seventeen of the 20 strains overproduced mRNA for one or more pump proteins (MexB, MexD, MexF, or MexY), which caused multidrug resistance phenotype in more than half of strains. Two strains were hypermutable and one of them was highly resistant, but the other strain was only moderately resistant.

Critical biophysical properties in the Pseudomonas aeruginosa efflux gene regulator MexR are targeted by mutations conferring multidrug resistance

“…Mutation sites studied in this work are highlighted in chain A by displaying native sidechains in orange (L13M), red (R21W), green (G58E), blue (R70W), and magenta (T69I, R83H, R91H, L95F). Identified mutation sites in MexR leading to deficient DNA binding and/or multidrug resistance [23][24][25]27,30,35 are indicated with Ca spheres in chain B. The figure was drawn in PyMOL.…”

“…The emergence of ß-lactam resistance associated with MexAB-OprM in vivo has been shown to be directly linked to mutations affecting its regulator gene mexR. 22,23 A range of MexR mutations with highly elevated MIC values to common antibiotics have been identified both from clinical isolates, [23][24][25][26] by selection for resistant strains 24,27 and by combining random mutagenesis and resistance selection. 28 These mutations appear scattered over the entire MexR structural scaffold [ Fig.…”

“…1(A)], as was also observed for the homologous MarR protein. 29 MDR mutations in MexR lead to constitutive overexpression of efflux pump proteins, 24,25,30 presumably due to deficient DNA binding. 20,28 However, because MDR mutants of MexR and related proteins have been so far poorly characterized on a molecular level, the biophysical reason for their disfunction is largely unknown.…”

Pseudomonas aeruginosa Resistance Mechanisms: Efflux Pump Systems

“…Atım pompa sistemlerinin incelendiği bir başka çalışmada ise karbapenem dirençli izolatlarda MexXY-OprM (% 37.5)'den sonra ikinci sıklıkta MexCD-OprJ (% 31) aşırı ekspresyonu görülmüştür (13) . Benzer bir çalışmada ise MexD aşırı ekspresyonu tespit edilen florokinolon dirençli P.aeruginosa izolatlarının tümünde topoizomerazdaki mutasyonlarla açıklanamayan yüksek florokinolon MİK değeri bulunmuş ve dolayısıyla MexCD aşırı üretiminin antibiyotik direnci üzerine etkisini anlamlı bulmuşlardır (30) . Diğer bir çalışmada ise izole kinolon dirençli gruptaki izolatların tümünde MexD aşırı ekspresyonu tespit edilmiştir.…”

Viability and survival capability of quinolone-resistant uropathogenic Escherichia coli

“…The widespread use of quinolones as therapy for urinary tract infections has lead to an increased number of E. coli strains that are resistant to these agents [1][2][3]. Recently, mechanisms of quinolone action and resistance have been thoroughly studied and discussed by many authors [4][5][6]. Acquisition of quinolone resistance has been commonly associated with reduced fitness and decreased virulence of E. coli strains [7,8].…”