Quantification and long-term carriage study of human extended-spectrum/AmpC β-lactamase-producing Escherichia coli after international travel to Vietnam.

OBJECTIVES

Extended-spectrum β-lactamase/AmpC β-lactamase-producing Escherichia coli (ESBL/AmpC-E. coli) are common in developing countries and travellers represent potential reservoirs for their dissemination. The aim of this study was to quantify cefotaxime (CTX)-resistant E. coli harboured by travellers to Vietnam and to conduct a follow-up study.

METHODS

In total, 19 travellers and 34 travel events were investigated. After confirming that travellers were not colonised with CTX-resistant E. coli before travel, 15 travellers and 20 travel events were studied to quantify travellers harbouring CTX-resistant E. coli after travel. A stool sample (0.1 g) in 10 mL of PBS was diluted and plated. Selected colonies were identified, genotyped and further verified by pulsed-field gel electrophoresis (PFGE).

RESULTS

After travel, travellers harboured an average of 3.6 × 107 CFU/g faeces of CTX-resistant E. coli, which continued to be detected for an average of 14 weeks. In the follow-up study, travellers from two travel events had ESBL-E. coli for 12 months. Multiplex PCR showed blaCTX-M-55 and blaCTX-M-27, with replicon types FIA and F, and FIB and F, respectively. PFGE showed that two travellers harboured a single clonal ESBL-E. coli strain for 12 months. By PFGE, the follow-up study showed that a single type of ESBL/AmpC-E. coli was only detected in individuals living in Japan. Moreover, the same clonal ESBL-E. coli isolate was detected in a group that travelled to Ho Chi Minh City.

CONCLUSION

ESBL/AmpC-E. coli colonised the gut of travellers to Vietnam with CTX-resistant E. coli (>107 CFU/g faeces) lasting for 14 weeks.