The use of the antibiotic colistin, a last-resort treatment option in the infection by multidrug-resistant bacteria, is increasingly impeded by colistin-resistant bacteria. Researchers used biochemical and genetic assays to track resistant strains of bacteria in Japanese travelers returning from Vietnam. The researchers found short trips to a developing country can lead to the appearance of the colistin-resistance gene mcr-1. The study highlights that even brief international trips can contribute to the spread of colistin resistance.