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Antimicrob Agents Chemother. 2018 Nov 26. pii: AAC.01745-18. doi: 10.1128/AAC.01745-18. [Epub ahead of print]

Emergence of resistance to quinolones and β-lactam antibiotics in enteroaggregative and enterotoxigenic Escherichia coli causing traveler's diarrhea.

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Institute of Global Health of Barcelona, Barcelona, Spain.
Department of Clinical Microbiology, Hospital Clinic, School of Medicine, University of Barcelona, Barcelona, Spain.
Institute of Global Health of Barcelona, Barcelona, Spain


The objective of this study was to assess the antimicrobial resistance of enteroaggregative Escherichia coli (EAEC) and enterotoxigenic E. coli (ETEC) causing traveler's diarrhea (TD) and investigate the molecular characterization of antimicrobial resistance genes to third generation cephalosporins, chepamycins and quinolones. Overall, 39 EAEC and 43 ETEC clinical isolates were studied. The susceptibility of EAEC and ETEC against ampicillin, amoxicillin-clavulanic acid, cefotaxime, imipenem, chloramphenicol, tetracycline, cotrimoxazole, nalidixic acid, ciprofloxacin, azithromycin and rifaximin was determined. All genes encoding resistant determinants were detected by PCR or PCR and DNA sequencing. The epidemiology of selected EAEC and ETEC strains was studied using MLST. The resistance to quinolones of EAEC and ETEC strains causing TD has significantly increased over the last decades, and high percentages has been found especially in patients traveling to India and sub-Saharan Africa. The ST38 and ST131 carrying the bla CTX-M-15 and bla CTX-M-27 genes, respectively, are highly prevalent among ESBL-producing EAEC and ETEC. The cephamycinase ACT-20 is described in the present study for the first time in EAEC and ETEC strains causing TD in patients who had traveled to Central America. The percentages of resistance to azithromycin in EAEC and ETEC isolates from patients to South-East Asia/India and Africa are above 25%. Meanwhile, rifaximin is still active against EAEC and ETEC with the prevalence of resistant strains not being high. In conclusion, fluoroquinolones should no longer be considered the drugs of choice for the prevention or treatment in TD for travelers traveling to India and Africa. Azithromycin and rifaximin are still a good alternative to treat TD caused by EAEC or ETEC.


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