Changes in serotype and resistance pattern of the intestinal Escherichia coli flora during travel. Results from a trial of mecillinam as a prophylactic against travellers' diarrhoea.

The changes in the intestinal Escherichia coli flora during travel has been studied by serological methods. A group of 74 tourists visiting Egypt and the Far East were given mecillinam or placebo in a randomized double-blind study. In all but 3 participants, 2 in the placebo group and 1 in the mecillinam group, a complete change in the E. coli flora occurred after a few days, and changes continued to occur during the 25 days of travel. The percentage of multiresistant strains rose from 8% in the pretravel samples to 50-60% in the posttravel samples. Less than 5% of the pretravel E. coli strains were resistant to mecillinam, whereas in the posttravel samples 42.9% of the E. coli strains in the mecillinam group and 19.1% in the placebo group were resistant to mecillinam. Of the 30 mecillinam resistant E. coli strains from the diarrhoeal samples only 6 showed transferable mecillinam resistance.