title: Relevant role of efflux pumps in high levels of rifaximin resistance in Escherichia coli clinical isolates.
abstract: BACKGROUND
  Enteropathogens have shown a high level of resistance against commonly used antibacterial drugs in Peru and it is necessary to explore alternative treatments. The aim of this study was to analyse the in vitro activity of rifaximin against diarrhoeagenic and commensal Escherichia coli in children less than 2 years of age.
  
  
  METHODS
  The minimal inhibitory concentration (MIC) to rifampicin and rifaximin was determined for 210 strains in the presence and absence of phenyl-arginine-β-naphthylamide (PAβN) and the mechanisms of resistance were investigated.
  
  
  RESULTS
  The MIC levels ranged between 8 and >256 mg/litre and the predominant mechanism of resistance to rifaximin was the efflux pumps inhibited by PAβN in 95.2% of the isolates.
  
  
  CONCLUSIONS
  The present MIC values are higher than those observed in other studies. Efflux pumps inhibited by PAβN were the cause of the rifaximin resistance in the majority of cases and suggest the presence of an environmental selective pressure. Consequently, rifaximin should be used with caution in the treatment of diarrhoea in Peru.
authors.affiliation: Barcelona Centre for International Health Research CRESIB, Hospital Clinic - Universitat de Barcelona, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Gomes
authors.forename: L
authors.initials: L
authors.lastname: Ruiz
authors.forename: M J
authors.initials: MJ
authors.lastname: Pons
authors.forename: T J
authors.initials: TJ
authors.lastname: Ochoa
authors.forename: J
authors.initials: J
authors.lastname: Ruiz
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003967:Diarrhea / Q000188:drug therapy* / Q000382:microbiology; D004151:Dipeptides; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000302:isolation & purification; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012294:Rifamycins / Q000494:pharmacology*; D000078262:Rifaximin
chemical_list: D000900:Anti-Bacterial Agents; D004151:Dipeptides; D012294:Rifamycins; C419365:phenylalanine arginine beta-naphthylamide; D000078262:Rifaximin
keywords: Antibiotic resistance; Diarrhoea; Efflux pumps; Escherichia coli; Rifaximin