In vitro activity of rifaximin against clinical isolates of Escherichia coli and other enteropathogenic bacteria isolated from travellers returning to the UK

Katie L. Hopkins*, Shazad Mushtaq, Judith F. Richardson, Michel Doumith, Elizabeth De Pinna, Thomas Cheasty, John Wain, David Livermore, Neil Woodford

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)


Rifaximin is licensed in the EU and USA for treating travellers' diarrhoea caused by non-invasive bacteria. Selection for resistance mechanisms of public health significance might occur if these are linked to rifamycin resistance. Rifaximin MICs were determined by agar dilution for 90 isolates each of Escherichia coli, Shigella spp., nontyphoidal Salmonella enterica, typhoidal S. enterica and Campylobacter spp., an additional 60 E. coli with CTX-M ESBLs isolated from patients with travellers' diarrhoea, and 30 non-diarrhoeal carbapenemase-producing E. coli. Comparators were rifampicin, ciprofloxacin, azithromycin, trimethoprim/sulfamethoxazole and doxycycline. Isolates with rifaximin MICs>32 mg/L were screened for arr genes, and critical rpoB regions were sequenced. Rifaximin was active at ≤32 mg/L against 436/450 (96.9%) diverse Enterobacteriaceae, whereas 81/90 (90%) Campylobacter spp. were resistant to rifaximin at ≥128 mg/L. Rifaximin MICs were ≥128 mg/L for two Shigella and five MDR E. coli producing NDM (n = 3), OXA-48 (n = 1) or CTX-M-15 (n = 1). Two of the five MDR E. coli had plasmids harbouring arr-2 together with blaNDM, and two (one each with blaNDM and bla NDM) had His526Asn substitutions in RpoB. The rifamycin resistance mechanism remained undefined in one MDR E. coli isolate (with bla OXA-48) and the two Shigella isolates. Rifaximin showed good in vitro activity against diverse Enterobacteriaceae but was largely inactive against Campylobacter spp. Rifaximin has potential to co-select MDR E. coli in the gut flora, but much stronger associations were seen between ESBL and/or carbapenemase production and resistance to alternative treatments for travellers' diarrhoea, notably ciprofloxacin and azithromycin.

Original languageEnglish
Pages (from-to)431-437
Number of pages7
JournalInternational Journal of Antimicrobial Agents
Issue number5
Publication statusPublished - May 2014

Bibliographical note

Funding Information:
This work was supported by Norgine Pharmaceuticals Ltd .

Funding Information:
KLH and SM have received conference support from Norgine Pharmaceuticals Ltd.; KLH, DML and NW have received speakers’ or advisory board honoraria from Norgine Pharmaceuticals; DML consults for numerous pharmaceutical and diagnostic companies, including Meiji Seika, Achaogen, Astellas, AstraZeneca, Bayer, Basilea, bioMérieux, Cubist, Discuva, GSK, Kalidex, Merck, Pfizer, Roche and Tetraphase, holds grants from Basilea, Cubist, Meiji Seika and Merck, has received lecture honoraria or travel reimbursement from AstraZeneca, GSK, J&J, Merck, Novartis, Pfizer and Tetraphase, and holds shares in AstraZeneca, Dechra, Eco Animal Health, GSK, Merck and Pfizer, collectively amounting to <10% of portfolio value. All other authors declare no competing interests.


  • ADP-ribosyltransferases
  • CTX-M β-lactamases
  • Rifamycin resistance
  • Travellers' diarrhoea
  • rpoB


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