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Biomedical subjects

R B Sack

Publications and source records attributed to R B Sack.

At least 199 records · Page 11Linked to original sources
PubMed1976

Travelers' diarrhea in Mexico. A prospective study of physicians and family members attending a congress.

We conducted a prospective study of travelers' diarrhea on 73 physicians and 48 family members attending a medical congress in Mexico City, in October, 1974. Fecal and blood specimens were collected before, during and after their visit and examined for enteric bacterial pathogens, viruses and parasites. In 59 (49 per cent) participants travelers' diarrhea developed. Median duration of illness was five days. Onset occurred a median of six days after arrival. An etiologic agent was found in 63 per cent of ill participants. Enterotoxigenic Escherichia coli of different, non-"enteropathogenic" serotypes was the most common cause; other responsible pathogens included salmonellae, invasive Esch. coli., shigellae, Vibrio parahaemolyticus, Giardia lamblia and the human reovirus-like agent. Consumption of salads containing raw vegetables was associated with enterotoxigenic Esch. coli infection (P = 0.014). Travelers' diarrhea in Mexico is a syndrome caused by a variety of pathogens, the most common of which is enterotoxigenic Esch. col.

Diarrhea↗
PubMed1976

Special Escherichia coli serotypes among enterotoxigenic strains from diarrhoea in adults and children.

106 enterotoxigenic Escherichia coli strains from children and adults from many parts of the world were serotyped for O and H antigens. Some O:H types, i.e. O6:H16, 08:H9, O15:H11, O25:H42, O78:H11 and O78:H12, were found repeatedly from different geographical locations. Some of these O:H serotypes were only found rarely among more than 20000 E. coli strains collected over many years from different locations and sources. It is suggested that these special O:H serotypes represent clones which have been selected to the special conditions in the small intestine and selected to carry the plasmids necessary to provoke diarrhoea.

Adult↗
PubMed1976

Challenge of dogs with live enterotoxigenic Escherichia coli and effects of repeated challenges on fluid secretion in jejunal Thiry-Vella loops.

Dogs were evaluated as experimental models for the study of diarrheal disease produced by enterotoxigenic Escherichia coli. Although a suitable whole model for orogastric bacterial challenge could not be developed, chronic jejunal Thiry-Vella loops were used to study the secretory effects of multiple jejunal challenges with enterotoxin of either Vibrio cholerae or E. coli. The heat-stable and heat-labile E. coli enterotoxins could be differentiated clearly in this model. Sequential weekly challenges over a four-week period showed a significant decrease in loop secretory response to homologous enterotoxin, although levels of antitoxin in serum remained unchanged, a finding suggesting a local immune response. Dogs challenged with E. coli enterotoxin were markedly protected against subsequent challenge with V. cholerae enterotoxin; the converse was not true. Histologic studies of the loops showed only minimal atrophy, and results of absorption studies in the loops were normal. These studies suggest that mongrel dogs are resistant to colonization by enterotoxigenic E. coli and partially resistant to challenge with enterotoxin, perhaps on an immune basis due to prior antigenic exposure. Multiple challenges with enterotoxin effect a decreased secretory response; this finding also suggests a local immune mechanism.

Animals↗
PubMed1976

Laboratory investigation of diarrhea in travelers to Mexico: evaluation of methods for detecting enterotoxigenic Echerichia coli.

A laboratory investigation was conducted on cultures collected from travelers before, during, and after a trip to Mexico to characterize the etiology of traveler's diarrhea. Four laboratory methods for detecting enterotoxigenicity of Escherichia coli were evaluated: the infant mouse assay, the Chinese hamster ovary (CHO) cell assay, the Y1 adrenal cell assay, and the rabbit ileal loop. Although a number of common enteric pathogens were identified as a cause of traveler's diarrhea, including six serotypes of Salmonella, two serotypes of Shigella, Vibrio parahaemolyticus, Giardia lamblia, and Entamoeba histolytica, enterotoxigenic Escherichia coli was most commonly isolated. Strains were identified that produced only heat-labile enterotoxin (LT), only heat-stable enterotoxin (ST), or both LT and ST. The infant mouse assay yielded results falling into two distinct groups, providing a clear separation of positive and negative cultures. The CHO assay also formed two groups, with positive cultures producing 11% or more of the elongated cells. There was good agreement between the CHO and the Y1 adrenal cell assays for detection of LT. The adrenal cell system for detection of LT was more suitable than the CHO assay for processing large numbers of specimens because of the miniculture modification of this method utilized in this study. The infant mouse method was a simple and reliable method for detecting ST.

Animals↗
PubMed1975

Diarrhoea associated with heat-stable enterotoxin-producing strains of Escherichia coli.

Five patients who developed acute watery diarrhoea while travelling in Mexico in October, 1974, were found to have enterotoxigenic Escherichia coli in their stool which produced heat-stable enterotoxin (S.T.) without producing heat-labile enterotoxin (L.T.). These S.T.-only E. coli, which have previously been described as causing diseases in animals, must now be regarded as pathogenic for humans as well.

Adult↗
PubMed1975

Enterotoxigenic Escherichia-coli-associated diarrheal disease in Apache children.

A search for intestinal enterotoxigenic Escherichia coli was made in 59 Apache children hospitalized with 64 episodes of acute diarrhea. Esch. coli isolates from acute-phase and convalescent-phase specimens of small-bowel fluid and stool were tested in three currently recognized models: the adult-rabbit ileal loop; infant rabbit; and the adrenal-cell assay. Enterotoxigenic strains were isolated from 10 children during acute diarrheal episodes (16 per cent); none were isolated from convalescent-phase specimens. None of 64 "enteropathogenic" serotypes of Esch. coli from 43 children with diarrhea, however, caused fluid production in the ileal-loop model. These results suggest that enterotoxigenic Esch. coli may be the cause of considerable diarrhea in this population and that the term "enteropathogenic" as applied to serotypes of Esch. coli needs to be redefined.

Acute Disease↗
PubMed1975

Test for enterotoxigenic Escherichia coli using Y-1 adrenal cells in miniculture.

A rapid, potentially clinically useful test for detection of enterotoxigenic Escherichia coli is described. Whole bacterial cultures of enterotoxigenic E. coli, when briefly exposed to Y1 adrenal cells in tissue miniculture, effect a rounding response in the tissue culture that can be discerned at 18 to 24 h. The tissue culture technique agreed with the rabbit ileal loop in all 58 enterotoxigenic and 52 non-enterotoxigenic E. coli strains tested.

Adrenal Glands↗
PubMed1975

Antibodies to heat-labile Escherichia coli enterotoxin in Apaches in Whiteriver, Arizona.

Antitoxin titers to heat-labile Escherichia coli enterotoxin were measured in Apache children hospitalized with acute diarrhea and in Apaches of different age groups without diarrhea in Whiteriver, Ariz. The study suggests that in this locale, exposure to enterotocigenic E. coli is probably widespread and occurs early in life. Antitoxin titer rises after idarrheal disease associated with enterotocigenic E. coli infection, however, were not regulary found.

Antitoxins↗
PubMed1975

Attempted prevention of diarrheal disease in Apache children with a non-absorbable broad-spectrum antimicrobial.

A double-blind study was conducted to test the prophylactic effect of a non-absorbable broad-spectrum antimicrobial (oral colistin sulfate) against acute diarrhea in Apache children. Children 1 to 6 months old had over twice the morbidity from diarrhea if assigned to the antimicrobial group as compared to placebo, while the toddler group (7-30 months) taking the antimicrobial had somewhat less diarrhea. Enteropathogenic E. coli were significantly more often isolated from the antimicrobial group (but only in well children). No special effect on the children's growth by the antimicrobial was discerned.

Age Factors↗