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Biomedical subjects

R B Sack

Publications and source records attributed to R B Sack.

At least 181 records · Page 10Linked to original sources
PubMed1979

Cytotoxic enterotoxin produced by Aeromonas hydrophila: relationship of toxigenic isolates to diarrheal disease.

Ninety-six Aeromonas hydrophila isolates were tested for cytotoxin and hemolysin production. Sixty-six (69%) of the isolates were both cytotoxic and hemolytic, whereas the rest produced neither cytotoxin nor hemolysin. No evidence of a separate cytotonic activity could be found in any of the isolates. Cytotoxin activity correlated with enterotoxic activity. Of four cytotoxin-producing strains tested in the isolated rabbit ileal loop, three were definitely positive and one was borderline, whereas two nontoxigenic strains were negative. Cytotoxin activity appeared to be a stable property and could not be assoicated with any common identified plasmid; only 10 of 21 cytotoxin-producing strains could be shown to have any plasmid by agarose gel electrophoresis. Cytotoxin production correlated with a positive lysine decarboxylase phenotype (98%) or a positive Voges-Proskauer phenotype (94%), compared to 27% lysine decarboxylase-positive and 23% Voges-Proskauer-positive, cytotoxin-negative isolates (P less than 0.001 for both). In fecal samples, cytotoxin production correlated with diarrheal disease; of 40 diarrheal isolates, 32 (80%) were toxigenic compared to 9 (41%) of 22 nondiarrheal isolates (P = 0.004). It appears that A. hydrophila can be a cause of diarrhea and that this enteropathogenic potential is mediated by a cytotoxic enterotoxin.

Aeromonas↗
PubMed1979

Use of colony pools for diagnosis of enterotoxigenic Escherichia coli diarrhea.

Diagnosis of enterotoxigenic Escherichia coli diarrhea was made in 109 adult males with an acute dehydrating cholera-like syndrome in Dacca, Bangladesh, by testing 10 colonies isolated from admission stool specimens for production of heat-labile and heat-stable toxins. Toxin testing of one colony yielded a diagnosis in 92% of the cases, testing of two colonies yielded a diagnosis in 95% of the cases, testing of a pool of 5 colonies yielded a diagnosis in 95% of the cases, and testing of a pool of 10 colonies yielded a diagnosis in 96% of the cases. From stool cultures obtained on subsequent days, toxin testing of individual colonies and pools revealed diminished efficacy of pooling with decreasing numbers of enterotoxin-positive isolates in the pool. To detect the presence of enterotoxigenic E. coli in stools, toxin testing of 5 individual isolates and a pool of 10 colonies was found to be almost as effective as the testing of 10 individual isolates.

Bacteriological Techniques↗
PubMed1979

Prophylactic doxycycline for travelers' diarrhea: results of a prospective double-blind study of Peace Corps volunteers in Morocco.

A second randomized double-blind study to determine the efficacy of doxycycline, 100 mg daily, for the prevention of travelers' diarrhea was carried out among 50 Peace Corps Volunteers during their first 10 wk in Morocco. The volunteers took either doxycycline or placebo for 3 wk, and were observed for an additional 7 wk. Eleven of 24 taking the placebo and 2 of 26 taking doxycycline had travelers' diarrhea during the treatment period (P less than 0.01). One week after cessation of the doxycycline, however, persons in that group developed an increase in frequency of travelers' diarrhea (P less than 0.05) so that by 3 wk after the drug was stopped, there were no differences between groups. Enterotoxigenic E. coli, most of which were sensitive to doxycycline, were the most frequently isolated pathogens during the entire study. This study corroborates the effectiveness of doxycycline prophylaxis for travelers' diarrhea.

Adult↗
PubMed1978

Prophylactic doxycycline for travelers' diarrhea. Results of a prospective double-blind study of Peace Corps volunteers in Kenya.

We performed a randomized double-blind study to determine the efficacy of doxycycline (100 mg daily) in preventing travelers' diarrhea among 39 Peace Corps volunteers during their first five weeks in Kenya. The volunteers took either doxycycline or placebo for three weeks and were observed for an additional two weeks. Nine of 21 taking placebo and one of 18 taking doxycycline had travelers' diarrhea during the treatment period (P = 0.012). The protection seemed to persist for at least one week after the drug was stopped. Enterotoxigenic Escherichia coli was the only pathogen isolated from the placebo group, but was not detected in persons taking doxycycline. None of these organisms were resistant to doxycycline or tetracycline, whereas resistance to tetracyclines and other antibiotics was common among the nonenterotoxigenic Esch. coli. We conclude that doxycycline effectively prevented most episodes of travelers' dirrhea.

Adult↗
PubMed1978

Purification of heat-labile enterotoxin from four Escherichia coli strains by affinity immunoadsorbent: evidence for similar subunit structure.

A single-step method for the purification of heat-labile enterotoxin of Escherichia coli is described. The method involves an affinity immunoadsorbent made with antiserum to cholera toxin. Crude toxin preparations of three human and one porcine enterotoxinogenic strains of E. coli were purified on this immunoadsorbent, and the elution products suggest that the toxin molecule is composed of subunits. One kind of subunit shared by these four strains showed similar mobility of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, close antigenic relationship, and an antigen in common with cholera enterotoxin.

Antigens, Bacterial↗
PubMed1977

Enterotoxigenic Escherichia coli isolated from patients at a hospital in Dacca.

Enterotoxigenic strains of Escherichia coli, a significant cause of acute, watery, cholera-like diarrhea, were isolated from 23 of 65 patients with diarrhea in whom no other enteric pathogens were found during one week (November 1974) at the Cholera Research Hospital, Dacca, Bangladesh. Diarrhea associated with enterotoxigenic strains of E. coli occurred primarily in adults but affected persons of all age groups and could not be distinguished from cholera or from other cholera-like diarrhea on clinical grounds. Routine bacteriologic methods were inadequate for identification of enterotoxigenic E. coli as the etiologic agent of the diarrhea. The enterotoxigenic E. coli, producing heat-stable and/or heat-labile enterotoxin, were detected by use of assays in the Y1 adrenal cell, the Chinese hamster ovary cell, the rabbit ileal loop, and the infant mouse. The two tissue culture assays yielded comparable results in tests with 640 (193 positive, 447 negative) of 643 isolates of E. coli. The results of this study support the idea that enterotoxigenic E. coli play a significant role as pathogens in the etiology of acute watery diarrhea.

Adolescent↗
PubMed1977

Enterotoxigenic Escherichia coli isolated from food.

Approximately 8% of 240 isolates of Escherichia coli obtained from food of animal origin in the United States were found to be enterotoxigenic, as determined in adrenal cells, rabbit ileal loops, and assays in infant mice. These organisms were of diverse serotypes that are not included among the so-called enteropathogenic serotypes and would not have been identified by usual laboratory methods. These enterotoxigenic E. coli are of potential importance to public health.

Animals↗
PubMed1977

Immunity to experimental cholera. III. Enhanced duration of protection after sequential parenteral-oral administration of toxoid to dogs.

Protection against experimental cholera after immunization with a purified glutaraldehyde toxoid given subcutaneously (sc), orally, or by a combined sc-oral sequence was compared in dogs. The protection induced by toxoid appeared to be entirely due to antitoxin. Repeated sc immunization with precipitated toxoid resulted in 77% protection at two weeks but no protection at four months. Protection after sc immunization correlated with titers of antitoxin in serum and appeared to result entirely from serum-derived antibody. In contrast, immunization by the sc-oral sequence resulted in prolonged protection (74% at two weeks, P=0.04; 100% after four months, P=0.004; and 57% after eight months, P=0.01) that was not related to the low serum antitoxin titers achieved. This sequence was effective only if the oral booster was given in divided doses. Immunization by oral priming and boosting was ineffective. These results suggest that the sc-oral sequence of immunization is an efficient means of stimulating the enteric immune response to nonreplicating protein antigens and may provide an improved approach to immunization against cholera.

Administration, Oral↗
PubMed1977

Immune response of the intestinal mucosa to cholera toxoid.

The intestinal immune response to cholera toxoid was studied in dogs and rats. Oral or intraperitoneal priming followed by duodenal boosting with toxoid reulted in antitoxin-containing plasma cells (ACC) in jejunal lamina propria of rats. Priming and boosting by the intraperitoneal route alone induced almost no jejunal response. Lamina propria ACC were derived largely from migrating immunoblasts, which appeared earlier among thoracic duct lymphocytes. Protection of dogs after repeated subcutaneous immunization with toxoid was mediated largely, or entirely, by serum-derived antibody. The sequence of subcutaneous priming and repeated oral boosting induced longer lasting protection mediated almost entirely by the local intestinal immune mechanism. The results suggest that cholera immunization should be specifically designed to stimulate the intestinal immune mechanism and that the subcutaneous oral immunizing sequence may be an efficient way to do this.

Administration, Oral↗
PubMed1977

Microtiter solid-phase radioimmunoassay for detection of Escherichia coli heat-labile enterotoxin.

The development of a microtiter solid-phase radioimmunoassay for the detection of Vibrio cholerae enterotoxin and heat-labile Escherichia coli enterotoxin is described. The test is based on the immunological similarity between V. cholerae toxin and E. coli heat-labile toxin. The assay is easy to perform, quantitative, and at least as sensitive and specific as the Y-1 adrenal cell system.

Adrenal Glands↗
PubMed1977

Antigenic similarity of heat-labile enterotoxins from diverse strains of Escherichia coli.

With use of the rabbit intestinal loop model, heat-labile enterotoxins from 21 Escherichia coli strains isolated from a wide spectrum of patients with diarrheal diseases were all neutralized to high titer by two antisera prepared against enterotoxins of either E. coli or Vibrio cholerae. These findings suggest marked immunological similarity among heat-labile enterotoxins from a heterogenous group of E. coli.

Adult↗
PubMed1977

Enzyme-linked immunosorbent assay for detection of Escherichia coli heat-labile enterotoxin.

The development of an enzyme-linked immunosorbent assay (ELISA) for the detection of heat-labile Escherichia coli enterotoxin is described. The assay, which is based on the immunological similarity between Vibrio cholerae toxin and heat-labile E. coli enterotoxin, is similar in design to a radioimmunoassay but utilizes enzyme-labeled rather than radioactive isotope-labeled reagents. The ELISA system is as sensitive as both radioimmunoassay and the y-1 adrenal cell assay for the detection of heat-labile E. coli enterotoxin but requires neither radioactive reagents nor tissue culture techniques. The ELISA is easy to perform and is adaptable for use in small laboratories.

Drug Stability↗
PubMed1977

Enterotoxigenic Escherichia coli diarrhea of travelers: a prospective study of American Peace Corps volunteers.

Travelers' diarrhea was studied prospectively in a group of 39 American Peace Corps Volunteers (PCVs) during their first five weeks in Kenya. Twenty-seven developed diarrheal disease and 12 remained well. Multiple episodes were documented in 11 of the symptomatic volunteers. Enterotoxigenic Escherichia coli of many serotypes producing heat-labile and/or heat-stable enterotoxin were isolated from 17 of the 27 volunteers with diarrhea and from 1 of the 12 well volunteers. The enterotoxigenic E. coli were more likely to be antibiotic sensitive than the non-enterotoxigenic E. coli. A serum antibody rise to the heat-labile toxin (LT) was detected in six symptomatic volunteers, five of whom had a positive culture for LT-producing E. coli, and from one asymptomatic, culture negative volunteer. Salmonella cubana was isolated from two volunteers, and three volunteers had serologic evidence of infection with human reovirus-like (rotavirus) agent. This study confirms the role of enterotoxigenic E. coli as a major cause of travelers' diarrhea and suggests that the disease is similar in widely separated geographic areas.

Adult↗