Reduction of the aerobic Gram negative bacterial flora of the gastro-intestinal tract and prevention of traveller's diarrhea using oral erythromycin

Abstract

Traveller's diarrhea is mostly due to aerobic Gram-negative bacterial species, especially enterotoxigenic Escherichia coli. Until today no fully satisfactory prophylactic regimen has been designed. We have previously reported that erythromycin can eliminate Enterbacteriaceae from the human faecal flora during several weeks without recolonization by highly resistant Gram-negative aerobic organisms. This effect has been reproduced in 17 out of 18 volunteers taking 1, 2 or 3 g per day of oral erythromycin base during 5 days. This effect is due to the very high faecal concentrations of the antibiotic (2,000-4,000 micrograms/g) compared to the MIC of erythromycin on aerobic Gram-negative species (10-500 micrograms/ml). MIC of erythromycin on bacterial species which cause traveller's diarrhea are within the same range. These considerations led us to perform a double-blind, randomized, placebo-controlled clinical trial of the efficacy of 1 g daily intake of erythromycin base in preventing traveller's diarrhea. Fourty-eight US citizens travelling to Acapulco (Mexico) were enrolled in the study. Mean duration stay was 5.87 days. Seven out of 24 subjects of the placbo group experienced diarrhea and non (p=0.0047) in the treated group. Study should be undertaken to evaluate the efficacy of oral erythromycin in preventing traveller's diarrhea in other parts of the world.