Asymptomatic salmonellosis among children in day-care centers in Mérida, Yucatan, Mexico.

BACKGROUND: Child day-care centers (DCC) have become common in many lower and middle income countries, presenting new problems that may differ from those of DCC in more developed countries. Diarrhea is a common problem in DCC in the United States, but information on the prevalence of diarrhea or specific enteropathogens among children in DCC in tropical and developing countries is limited. METHODS: Because of preliminary data from newborns and DCC attendees in Mérida, Mexico, with high rates of Salmonella infection, we conducted a 12-month longitudinal surveillance study of enteropathogens in two Mérida DCC. Seventy-eight children ages 2 months to 4 years were evaluated with demographic and clinical data, and stools were cultured monthly. RESULTS: Salmonella sp. was the most common enteropathogen detected (46 of 683 specimens, 6.7%), with higher rates in children younger than 18 months (P < 0.02), but it was found in only 1 of 10 diarrhea episodes that coincided with sampling. Other common organisms identified included Giardia lamblia (21 of 683, 3.0%) and LT-producing enterotoxigenic Escherichia coli (16 of 683, 2.3%). Salmonella was recovered from as many as 19% of children in a single month, but the large multiplicity of serotypes recovered suggested multiple sources rather than a common source outbreak. Children with Salmonella tended to have more liquid stools during the preceding 2 weeks. Salmonella was also isolated from the stool of teachers in 1 of the 2 DCC in 10 of 94 specimens (10.6%), and again multiple serotypes were represented. CONCLUSION: These data indicate the presence of multiple sources of Salmonella infection in the DCC, posing a complex situation for infection control.

Four biochemical tests for identification of probable enteroinvasive Escherichia coli strains.

Enteroinvasive Escherichia coli (EIEC) share important features with Shigella spp., but EIEC strains are difficult to identify because their biochemical reactions are variable, and Sereny tests or other biological and molecular assays are expensive or hard to perform. The aim of this work was to detect probable enteroinvasive E. coli strains by using four biochemical tests, in children under 5 years of age with and without acute diarrhea. 330 strains of E. coli isolated from children with diarrhea, and 660 strains from children without diarrhea were studied. All strains were tested with the following tests: mucus , lysine and ornithine decarboxylase and motility. The strains which were negative to the four tests were tested by Sereny assay. Twelve strains (3.6%) isolated from children with diarrhea were negative to the tests proposed; eleven were lactose positive and only one was lactose negative. Three strains (0.5%) from children without diarrhea were negative to the tests proposed and were lactose positive. All the 15 strains (100%) were positive in Sereny assay. We recommend the use of these four biochemical tests for initial detection of EIEC strains, because their cost is very low and it is feasible carry out them in small diagnostic laboratories.

Frequency of adhesive factors and enterotoxins in strains of Escherichia coli isolated from piglets with diarrhea.

Neonatal colibacillosis is one of the most prevalent illnesses in pig farms. In order to examine the frequency of adherence factors and the production of enterotoxins in strains of E. coli, we collected stool specimens from 500 piglets between 1 and 10 days of age with diarrhea, including piglets from several different farms on the periphery of Mérida, Yucatán. One thousand and eighty (1080) strains of E. coli were isolated, of which 127 (11.76%) produced STa, and 62 (5.74%) produced adherence factors. Of these, 30 (48.39%) produced factor K88, 18 (29.03%) produced factor 987P, 12 (19.35%) produced K99, and 2 (3.23%) produced F41. Of the 62 strains which produced adherence factors, 42 (67.74%) also produced STa, and of these, 17 (40.84%) produced factor K88, 13 (30.95%) produced 987P, 10 (23.81%) produced K99, and 2 (4.76%) produced F41. In summary, of the 1080 strains isolated, 42 (3.89%) produced both STa toxin and adherence factors, 85 (7.87%) produced STa but did not produce adherence factors, and 933 (86.39%) produced neither STa or adherence factors. No LT-producing E. coli was detected in this study.

[Bacteriological quality of drinking water in the City of Merida, Mexico]. / Calidad bacteriológica del agua potable de la ciudad de Mérida, México.

With the aim of knowing the microbiological quality of drinking water in Merida, Yucatan, 383 paired samples of drinking water (two per house) were studied. Three hundred sixty four (95%) city water system samples and 283 (73.89%) tap water samples met the microbiological standards for drinking water. It was concluded that microbiological quality of drinking water from the city water system is satisfactory, except for the water system district Merida III, which has a significant aerobic plate count contamination level (21.7% of the samples). Domestic storage systems preserve water quality, with the exception of district Merida I, which has the highest level of contamination (4.8% of the samples) possibly from sewage water and fecal sources.

[Prevalence of enteropathogens in children with liquid diarrhea]. / Prevalencia de enteropatógenos en niños con diarrea líquida.

Between january 1 and october 31, 1991 148 samples of feces corresponding to the same number of children with acute diarrhea, aged 0-2 years, admitted to Hospital O'Horan of the Secretariat of Health in the city of Merida, Yucatan, Mexico, were studied. Stools from 105 (70.9%) patients were described as watery diarrhea; from these samples at least one enteric pathogen was detected in 49 (46.6%): a single pathogen was isolated in 37 (35.2%), and mixed infections were observed in 12 (11.4%). We isolated enterotoxigenic Escherichia coli in 18 (17.1%) samples; a predominance of strains producing only ST (11.4%) was observed. Rotavirus was detected in 14.3%, Shigella spp in 8.6%, Salmonella spp in 5.7%, Giardia lamblia in 4.8%, Campylobacter jejuni in 3.8%, enteroinvasive E. coli in 2.8%, Entamoeba histolytica in 2.8% and adenovirus in 1.9%. From watery samples, 80 (76.2%) were negative for fecal blood, and these were most frequently associated with enterotoxigenic E. coli (17.5%) and rotavirus (12.5%). E. coli LT+ and rotavirus association was observed in two patients, and E. coli ST+ and adenovirus association was observed in another one.

[Prevalence of enteropathogenic bacteria in children with acute bloody diarrhea]. / Prevalencia de bacterias enteropatógenas en niños con diarrea aguda con sangre.

Between January to October 1991, were studied 148 samples of feces corresponding to the same number of children with acute diarrhea. In 41 (27.7%) samples, were found macroscopic or microscopic blood. At least one associated bacterial pathogen capable to produce bloody diarrhea was isolated from 22 (53.7%) of these samples. Were isolated five (12.2%) Salmonella strains, all of them were S. enteritidis; nine (22.0%) Shigella: seven S. flexneri, one S. boydii, and other one S. sonnei; two (4.9%) enteroinvasive Escherichia coli strains, and six (14.6%) Campylobacter jejuni strains. A single associated invasive bacterial pathogen was isolated in 13 (31.7%) children. Mixed culture were found in nine children: five (12.2%) children had invasive pathogens association, and four (9.8%) children had invasive and no invasive pathogens association.

[Excretion of Salmonella in feces during the 1st 3 months of life]. / Excreción de Salmonella en las heces durante los tres primeros meses de vida.

30 children were followed up during their first three months of life, in order to determinate the moment for Salmonella excretion through feces. Five samples were taken during first month, and 3 samples in the next 2 months each. S. enteritidis was isolated in 10 children (33.3%), 4 of which were positive in 1 sample, and the others in more than one. From 330 samples (11 by child), in 24 (7.27%) Salmonella was isolated. We pointed out the fact of the isolation of the bacteria so early, and the role as a symptomatic carrier this child could play.

[The prevalence of Vibrio parahaemolyticus and its antibodies in seafood handlers in Mérida, Yucatán]. / Prevalencia de Vibrio parahaemolyticus y de sus anticuerpos en manipuladores de alimentos marinos en Mérida, Yucatán.

We report the prevalence of Vibrio parahaemolyticus and of antibodies against Vibrio parahaemolyticus in the feces and serum of fish and seafood handlers in the city of Mérida, Yucatán, Mexico. Between March 1 and August 31, 1989, we studied 81 feces samples and 81 serum samples from an equal number of handlers. Vibrio parahaemolyticus was not isolated in any of the feces studied. We found no statistically significant differences upon comparing our zero per cent isolation in feces samples with the highest percentages reported from available literature (3.85%): chi 2c = 0.36, p greater than 0.05. In two serum samples, we detected Vibrio parahaemolyticus antibodies to the degree of 2.47 per cent. We found no statistically significant differences upon comparing our 2.47 per cent prevalence of serum antibodies with the 10 per cent prevalence reported in a study done by Molina García, et al: chi 2c = 0.10, p greater than 0.05. The estimation interval with a confidence level of 95.00 per cent for the percentage in the population of fish and seafood handlers with Vibrio parahaemolyticus antibodies is 0.94% less than or equal to p less than or equal to 4.00%. We conclude that either the asymptomatic carrier stage does not exist, or that it is of a very short duration. On the other hand, based upon our 2.47 per cent serum-positive prevalence, we conclude that there exists both contact with, and infection from, Vibrio parahaemolyticus in fish and seafood handlers.