Isolation of Enteric Pathogens from Asymptomatic Students from the United States and Latin America

Abstract

Specimens of stools from 223 students attending a Mexican university were evaluated every three days for 60 days for the presence of enteric bacterial and protozoal pathogens during an ongoing study evaluating the incidence and etiology of diarrhea. One or more enteric pathogens were isolated from stools of 83 (37%) of 223 asymptomatic students. A pathogen was isolated from a significantly (P < 0.005) greater number of newly arrived summer students from the United States compared with that in other student groups, including students from the United States who had been in Mexico for more than one year. A shigella strain was isolated from 27 (12%) of 223 students enrolled, and there was no significant difference with regard to isolation of Shigella among various student groups. Toxigenic Escherichia coli and Salmonella were isolated from a significantly (P < 0.005) greater number of summer students from the United States compared with that in other student groups. The finding of enteric pathogens in stools of a large number of asymptomatic students indicates that the presence of enteric pathogens need not be associated with disease. Healthy transient carriers may be an important reservoir for and mode of spread of bacteria implicated as the cause of travelers' diarrhea. The newly arrived traveler from the United States appears to be more susceptible than Latin Americans to colonization by E. coli that produce heat-labile enterotoxin.