PCR ribotype prevalence and molecular basis of macrolide-lincosamide-streptogramin B (MLSB) and fluoroquinolone resistance in Irish clinical Clostridium difficile isolates

Abstract

Resistance to MLS(B) and fluoroquinolone antimicrobial compounds is common among prevalent ribotypes of C. difficile. The genetic basis for antimicrobial resistance appears to be ribotype specific and conserved in the absence of recent antimicrobial selection pressure.

Identification of a novel mutation at the primary dimer interface of GyrA conferring fluoroquinolone resistance in Clostridium difficile

“…Five strains harboured wild-type DNA gyrase alleles, providing the first demonstration that fluoroquinolone resistance can occur in C. difficile independent of DNA gyrase mutations. Whilst the precise mechanism of resistance in these strains remains to be determined, these findings add credence to the role of alternative fluoroquinolone resistance mechanisms such as drug efflux or reduced permeability in C. difficile, as has been suggested in other studies [7,8].…”

“…DNA gyrase mutations occurring outside the QRDR are rarely investigated and their prevalence among fluoroquinoloneresistant strains is largely unknown [7,8,15]. Non-synonymous changes present outside the QRDR, including polymorphisms in GyrB (Ile139Arg and Val130Ile) and GyrA (Leu345Ile), were identified among our clinical strains exhibiting elevated ciprofloxacin MICs.…”

“…Strains were assayed for sensitivity to ciprofloxacin, moxifloxacin, levofloxacin and ofloxacin as previously described, adopting the previous definition of 'highly resistant' (MIC ! 32 mg/L) for ciprofloxacin and moxifloxacin in the absence of clinical breakpoints in C. difficile [8]. The relative levels of novobiocin sensitivity between strains were compared using antibiotic disks (5 mg/disc; Oxoid Ltd., Basingstoke, UK).…”

“…Several additional mutations that map to the QRDR of gyrA and gyrB have also been reported in C. difficile, whereas the type IV topoisomerase is absent in C. difficile as well as several other pathogenic species [6]. Molecular characterisation of fluoroquinolone resistance in C. difficile also suggests the existence of undetermined mechanisms among resistant strains lacking QRDR mutations [7,8]. Whilst the roles of alternative resistance mechanisms such as extra-QRDR The aim of this study was to determine whether alternative resistance mechanisms, other than mutation in the quinolone resistance-determining region (QRDR) of DNA gyrase, could confer fluoroquinolone resistance in Clostridium difficile.…”

Clostridium difficile Infection Diagnosis by Biological Molecular Methods

“…New patterns of C. difficile strains encourage the spread and persistence of these strains in healthcare facility settings; for this reason, the surveillance of resistance and the molecular characterization of these mechanisms are very important in CDI control and prevention [111]. Both conjunction [112] and translocation of the genetic mobile element CTn5 [113] were described. The genetic mechanisms were much better understood and easier to study after 630 strain genome sequences [114] and resequencing studies.…”