Epidemiology of Extended-Spectrum β-Lactamase Producing Escherichia coli in the Stools of Returning Japanese Travelers, and the Risk Factors for Colonization

Objective: Travel overseas has recently been considered a risk factor for colonization with drug-resistant bacteria. The purpose of this study was to establish the epidemiology and risk factors associated with the acquisition of drug-resistant bacteria by Japanese travelers. Methods: Between October 2011 and September 2012, we screened the stools of 68 Japanese returning travelers for extended-spectrum beta-lactamase (ESBL) producing Escherichia coli. All specimens were sampled for clinical reasons. Based on the results, the participants were divided into an ESBL-producing E. coli positive group (18 cases; 26%) and an ESBL-producing E. coli negative group (50 cases; 74%), and a case-control study was performed. Microbiological analyses of ESBL-producing strains, including susceptibility tests, screening tests for metallo-beta-lactamase, polymerase chain reaction amplification and sequencing of bla(CTX-M) genes, multilocus sequence typing, and whole genome sequencing, were also conducted. Results: In a univariate comparison, travel to India was a risk factor (Odds Ratio 13.6, 95% Confidence Interval 3.0-75.0, p<0.0001). There were no statistical differences in the characteristics of the travel, such as backpacking, purpose of travel, interval between travel return and sampling stool, and duration of travel. Although 10 of 13 analyzed strains (77%) produced CTX-M-15, no ST131 clone was detected. Conclusion: We must be aware of the possibilities of acquiring ESBL-producing E. coli during travel in order to prevent the spread of these bacteria not only in Japan but globally.