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Biomedical subjects

R B Sack

Publications and source records attributed to R B Sack.

232 records · Page 13Linked to original sources
PubMed1969

Progressive changes of Vibrio serotypes in germ-free mice infected with Vibrio cholerae.

Germ-free mice inoculated with Vibrio cholerae became colonized with vibrios throughout the gastrointestinal tract, but they did not become ill. High vibrio concentrations in the feces were observed throughout the 3 months of observation in spite of the presence of serum antibody. Reciprocal conversions of both Inaba and Ogawa serotypes occurred regularly after inoculation and could be correlated temporally with the appearance of serum-agglutinating antibody. Both of these smooth serotype were later progressively replaced by rough vibrios. Rough to smooth serotype reversions were also found in mice inoculated with a rough vibrio strain. Studies employing immunosuppression and selective vaccination suggested that such serotypic changes were a result of the selective effect of antibody within the intestinal lumen.

Agglutination↗
PubMed1968

Site and characteristics of electrolyte loss and effect of intraluminal glucose in experimental canine cholera.

The site and characteristics of gastrointestinal electrolyte loss were investigated in eight dogs with experimental cholera induced by orogastric administration of 6-hr broth cultures of Vibrio cholerae, strain Ogawa 395. In these animals, all electrolyte losses originated in the small bowel, predominantly from the jejunum and ileum. The bicarbonate concentration of the small bowel fluid showed a progressive increase from duodenum, where it was less than that of plasma, to the terminal ileum, where it was significantly greater than that of simultaneously obtained plasma. Studies of the responses of chronic Thiry-Vella jejunal loops (five dogs) and chronic Thiry-Vella ileal loops (five dogs) to intraluminal challenge by cholera exotoxin demonstrated that all loops exhibited isotonic electrolyte loss for a 14-18 hr period after challenge. The bicarbonate concentration of fluid produced by exotoxin-challenged jejunal loops was not significantly different from that of plasma, whereas the ileal loops produced fluid with a bicarbonate concentration approximately three times that of plasma. The effect of intraluminal glucose on the response of canine gut to cholera exotoxin was investigated by perfusion studies in 12 dogs with chronic Thiry-Vella fistulae. Intraluminal glucose significantly enhanced isotonic fluid absorption in both jejunal and ileal loops. The net effects of glucose on isotonic fluid absorption were equal before and after intraluminal administration of crude cholera exotoxin. These data suggest that cholera exotoxin causes gut electrolyte loss by a mechanism independent of that by which glucose enhances sodium absorption.

Animals↗
PubMed1965

Clinical and physiological observations during an epidemic outbreak of non-vibrio cholera-like disease in Calcutta.

During March through June 1964, an epidemic of acute non-vibrio diarrhoeal disease, closely simulating cholera, occurred in Calcutta. To clarify the etiology and pathophysiology and improve the therapy of this illness, bacteriological and metabolic studies were performed on 145 consecutive hypotensive adult male patients admitted with acute diarrhoeal disease to the Calcutta Infectious Disease Hospital. Bacteriological and serological studies clearly demonstrated that the majority of patients with acute diarrhoeal disease admitted during this period of time were not suffering from V. cholerae infection; no known pathogen could be recovered from 86% of such patients. Biochemical studies indicated that, in contrast to the findings in cholera, factors other than saline depletion contributed to hypotension in many of the patients with non-vibrio diarrhoeal disease. Although the majority of the acute diarrhoeal patients responded well to the 2: 1 saline: lactate regimen which is consistently successful in treating adult cholera patients, six of the non-cholera patients required prolonged administration of vasopressor drugs as an adjunct to fluid and electrolyte repletion therapy.

Cholera↗
PubMedDate not supplied

Association of Vibrio cholerae O1 with the cyanobacterium, Anabaena sp., elucidated by polymerase chain reaction and transmission electron microscopy.

It has been hypothesized that Vibrio cholerae is an autochthonous flora of the estuarine and brackish water environment. Zooplankton and phytoplankton have been considered as possible reservoirs. The present study was carried out in microcosms to confirm the role of a cyanobacterium, Anabaena sp., as a reservoir of V. cholerae O1 using culture, polymerase chain reaction (PCR) and immunoelectron microscopy. Survival of culturable V. cholerae in microcosms was monitored by using tellurite taurocholate gelatin agar. Culturable V. cholerae were detected for up to 1 h in association with Anabaena sp. from a microcosm. However, viable but nonculturable (VBNC) V. cholerae O1 were detected for up to 25 months using PCR and immunoelectron microscopy. Results also showed that VBNC V. cholerae can multiply and maintain their progeny in the mucilaginous sheath of Anabaena sp. This is the first time that PCR and immunoelectron microscopy have been used to detect nonculturable V. cholerae in association with Anabaena sp. This study further clarifies the role of Anabaena sp. as a possible reservoir of cholera.

Anabaena↗
PubMedDate not supplied

Travelers' diarrhea: microbiologic bases for prevention and treatment.

The microbiology of travelers' diarrhea has become reasonably well defined, although new bacterial agents are probably yet to be described. The most common etiologic agent, enterotoxigenic Escherichia coli (ETEC), has been studied extensively and, because of the importance of this etiology, strategies for prevention and treatment of ETEC diarrhea with antimicrobial agents have been devised. The prevention of travelers' diarrhea by immunization will, to a large extent, depend on the development of vaccines against ETEC. Because the etiologic agents that cause travelers' diarrhea are the same ones (with the exception of rotavirus) that cause acute diarrhea in small children living in the developing world that tourists visit, any advances in prevention and treatment of diarrhea in travelers will be directly applicable to the worldwide problem of diarrhea in children, which is far more important on a global scale.

Anti-Bacterial Agents↗
PubMedDate not supplied

Antimicrobial prophylaxis of travelers' diarrhea: a selected summary.

This paper summarizes the published controlled studies of the prophylaxis of travelers' diarrhea in which the following drugs have been used: neomycin, nonabsorbable sulfonamides, Streptotriad, doxycycline, erythromycin, and mecillinam. These studies have shown that antimicrobial prophylaxis can be highly effective in preventing episodes of travelers' diarrhea. The protection, however, lasts only as long as the drugs are being taken; there is no evidence that subclinical infections occur while the drug is being taken. None of the data suggest that antimicrobial prophylaxis increases the probability of infection with drug-resistant enteric pathogens. In these studies few subjects have experienced adverse drug reactions; however, the number of subjects has been too small to allow determination of accurate incidence data. Antimicrobial prophylaxis for travelers' diarrhea can be effectively and safely used on an individualized basis for persons traveling to areas of high risk.

Amdinocillin↗