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Adherence to HEp-2 tissue culture cells has been proposed as a virulence characteristic of enteropathogenic Escherichia coli (EPEC). A preliminary study revealed that E. coli that adhered to HEp-2 cells, but did not produce conventional enterotoxins and did not belong to recognized EPEC serogroups, could be isolated from adults from the United States who acquired diarrhea in Mexico. The purpose of this study was to determine the prevalence of these enteroadherent E. coli (EAEC) in 188 travelers with diarrhea and in 92 well travelers. EAEC were found in 14.9% of patients with diarrhea and in 7.6% of well individuals. Compared with well travelers, patients with diarrhea in whom no recognized enteropathogen could be identified had a 30.4% prevalence of EAEC (P less than .0003). These results further support our finding that EAEC are associated with diarrhea in travelers to Mexico and may help to explain the effect of antibiotics in the prevention and therapy for travelers' diarrhea in patients with no recognized bacterial enteropathogens.

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Bicozamycin was compared with a placebo in a prospective, randomized, double-blind study of the prevention of acute diarrhea among 30 American travelers newly arrived in Guadalajara, Mexico. None of the 11 subjects given bicozamycin orally for 3 wk at a dosage of 500 mg four times a day developed diarrhea as compared with an incidence of 53% diarrhea (10 of 19 subjects) in the placebo group (p = 0.003). Bicozamycin was well tolerated. Studies of changes in predominant aerobic fecal flora among the 11 subjects treated with bicozamycin showed the appearance of only one highly resistant Citrobacter freundii at the end of 1 wk of therapy and only a total of six resistant isolates at the end of 3 wk. All resistant isolates failed to transfer this resistance to a recipient Escherichia coli. Bicozamycin seems to be well suited and safe as a prophylactic agent against traveler's diarrhea.

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Ninety-four U.S. students who acquired diarrhea in Mexico were treated with furazolidone (47 subjects) or ampicillin (47 subjects) on a double-blind random basis. Of 47 students, 26 (55%) who received furazolidone (100 mg four times daily for 5 days) recovered from illness within 48 h after initiation of therapy, in contrast to 15 of 47 (32%) who received ampicillin (500 mg four times daily for 5 days) (P less than 0.05). Altogether, 74% of students treated with furazolidone and 49% of those receiving ampicillin were well within 72 h (P less than 0.05). When furazolidone was compared with ampicillin, clinical illness was shortened on the average from 65 to 61 h for enterotoxigenic Escherichia coli diarrhea, from 83 to 58 h for shigellosis, from 82 to 51 h for diarrhea unassociated with a detectable agent, and from 72 to 57 h for all cases irrespective of etiology. Although not dramatically effective in the current trial, the broad spectrum of activity of furazolidone is of interest. Because of in vitro activity against Campylobacter strains and known effectiveness in treating giardiasis, furazolidone should be considered in therapy for diarrhea of unknown etiology in certain settings when laboratory processing of stools for etiological agent is not feasible.

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When trimethoprim-sulfamethoxazole was given to US travelers in Mexico to prevent diarrheal illness, high-level resistance to the drug emerged [2], although in previous studies such resistance had not been observed among enteric flora following administration of trimethoprim-sulfamethoxazole as prophylaxis against urinary tract infection [3]. Since food has been shown to be an important vehicle of transmission of travelers' diarrhea, food samples were examined for the presence of drug-resistant bacteria to explain the acquisition of high-level resistance among enteric flora of individuals taking antibiotics as prophylaxis against traveler's diarrhea. Of 34 strains of ETEC isolated from US students in Guadalajara, Mexico, who had acute gastroenteritis, one was resistant to trimethoprim and one was resistant to trimethoprim-sulfamethoxazole. Eight of the ETEC strains tested demonstrated multiple drug resistance. Twenty-two of 149 isolates from food produced enterotoxin. Only one isolate, which was nontoxigenic, was resistant to trimethoprim, and no coliforms were resistant to trimethoprim-sulfamethoxazole; however, 16 isolates demonstrated multiple drug resistance. Of 235 gram-negative organisms recovered from frozen food samples grown on antibiotic-containing media and tested for enterotoxin production, no isolates were enterotoxigenic. Thirty-four isolates were resistant to trimethoprim, 15 were resistant to trimethoprim-sulfamethoxazole, and 33 demonstrated multiple resistance. Multiple drug resistance was demonstrated among gram-negative organisms isolated from patients' stools and foods in Mexico.(ABSTRACT TRUNCATED AT 250 WORDS)

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We examined food consumption patterns of U.S. students temporarily living in Guadalajara, Mexico. Consumption of foods prepared in Mexican homes was associated with an increased risk of acquisition of diarrhea. Foods from commercial sources and private Mexican homes in Guadalajara were subsequently examined for contamination with coliforms, fecal coliforms, and bacterial enteropathogens. For comparison, selected restaurant foods were obtained in Houston, Tex. Food obtained from Mexican homes showed generally higher counts of coliforms and fecal coliforms than those obtained from commercial sources in Mexico and Houston. The foods in Mexico, both from homes and commercial sources, commonly contained Escherichia coli and occasionally enterotoxigenic E. coli. Foods in Houston were not contaminated with E. coli or enterotoxigenic E. coli. Salmonella (17 isolates), Shigella (4 isolates), and Aeromonas hydrophila (1 isolate) were found only in the foods obtained from Mexican homes. Enterotoxigenic non-E. coli Enterobacteriaceae was recovered with approximately equal frequency from all food sources.

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We conducted a double-blind treatment study of 110 adults from the United States who were attending summer classes in Guadalajara, Mexico, and had diarrhea (four or more unformed stools in 24 hours, or three or more unformed stools per eight-hour period plus one or more additional clinical indicators of enteric infection). Thirty-seven patients received trimethoprim/sulfamethoxazole (TMP/SMX) (160 mg of TMP and 800 mg of SMX), 38 were given TMP alone (200 mg), and 35 took a placebo twice daily for five days. By the end of the first 24 hours of treatment, patients taking either TMP/SMX or TMP alone passed fewer unformed stools than did patients given placebo (P = 0.0002 and P = 0.01, respectively). Abdominal pain and nausea were reduced in both treatment groups. The beneficial effect was seen in treatment of Escherichia coli-induced diarrhea, shigellosis, and diarrhea not associated with an enteropathogen. Five per cent of patients given TMP/SMX, 8 per cent of those given TMP, and 49 per cent of those given placebo were considered treatment failures (P less than 0.001 for both active drugs as compared with placebo). Early treatment with TMP/SMX or TMP is an alternative to prophylactic use of drugs for travelers' diarrhea.

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