title: Exploring the contribution of efflux on the resistance to fluoroquinolones in clinical isolates of Escherichia coli.
abstract: Resistance to ciprofloxacin in Escherichia coli is increasing parallel to increased use of fluoroquinolones both in The Netherlands and in other European countries. The objective was to investigate the contribution of active efflux and expression of outer membrane proteins (OMPs) in a collection of clinical E. coli isolates collected at a clinical microbiology department in a Dutch hospital. Forty-seven E. coli isolates a wide range of ciprofloxacin minimum inhibitory concentrations and known mutations in the quinolone resistance determining region were included. A fluorometric determination of bisbenzimide efflux was used two different efflux pump inhibitors and compared to quantitative reverse transcription-polymerase chain reaction (qRT-PCR) for the expression levels of acrA, acrB, tolC, yhiV, and mdfA efflux pump genes and the OMPs ompF and ompX. Six isolates (12.7%) showed increased efflux. Although in 35 isolates (76%), overexpression of ≥1 efflux pump genes using qRT-PCR was present. Only the combined overexpression of acrAB-TolC and mdfA correlated with the phenotypic efflux assay using glucose/carbonyl cyanide m-chlorophenylhydrazone with glucose. Thus, efflux was involved in ciprofloxacin resistance in a limited number of E. coli isolates collected at a clinical microbiology department in a Dutch hospital complementing other resistance mechanisms.
authors.affiliation: Department of Medical Microbiology, Leiden University Medical Center , Leiden, The Netherlands .
authors.forename: Sunita
authors.initials: S
authors.lastname: Paltansing
authors.forename: Anouk C
authors.initials: AC
authors.lastname: Tengeler
authors.forename: Margriet E M
authors.initials: ME
authors.lastname: Kraakman
authors.forename: Eric C J
authors.initials: EC
authors.lastname: Claas
authors.forename: Alexandra T
authors.initials: AT
authors.lastname: Bernards
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D006690:Bisbenzimidazole / Q000378:metabolism; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000382:microbiology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D024841:Fluoroquinolones / Q000494:pharmacology*; D015964:Gene Expression Regulation, Bacterial; D019450:Genes, MDR; D005947:Glucose / Q000378:metabolism; D006801:Humans; D006867:Hydrolases / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D018272:Porins / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D005456:Fluorescent Dyes; D024841:Fluoroquinolones; C118438:Mdfa protein, E coli; D026901:Membrane Transport Proteins; C109237:OmpF protein; D018272:Porins; C482905:OmpX protein, E coli; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D006867:Hydrolases; D005947:Glucose; D006690:Bisbenzimidazole