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Biomedical subjects

S B Formal

Publications and source records attributed to S B Formal.

At least 127 records · Page 7Linked to original sources
PubMed1970

Genetic Transfer of Shigella flexneri Antigens to Escherichia coli K-12.

The genes controlling synthesis of Shigella flexneri group- and type-specific antigens were transferred to Escherichia coli K-12 recipients by conjugation with an S. flexneri Hfr. After mating E. coli with an Hfr strain of S. flexneri 2a and selecting for his(+) recombinants, a high proportion of the E. coli hybrids agglutinated in S. flexneri grouping serum. None of these hybrids expressed S. flexneri type-specific antigen II. When an E. coli his(+) hybrid possessing the S. flexneri group antigen was remated with the same Hfr with selection for pro(+) hybrids, a high proportion now expressed the type-specific antigen as well as the previously inherited group antigen. If such crosses were performed in reverse order (i.e., pro(+) followed by his(+) selection), a different pattern of serological behavior was observed. None of the pro(+) hybrids showed the type-specific antigen. Subsequent mating for his(+) resulted in hybrids with both the group- and type-specific antigens. These results show that genes controlling the synthesis of S. flexneri group antigen (linked to the his locus) and type-specific antigen (linked to the pro locus) are widely separated on the chromosome. Expression of the type-specific antigen II depends on the presence of the group antigen.

Journal Article↗
PubMed1968

Freeze-drying various strains of Shigella.

Of six candidate strains of Shigella prepared in Brain Heart Infusion broth as freeze-dried vaccine, low survival rates were obtained with two of the most promising strains. Survival rates with these two strains were increased to acceptable levels when the organisms were suspended in a medium consisting of 8.2% sucrose, 0.01 M phosphate, 0.07% monosodium glutamate, and 2.5% human serum albumin. Alteration of the freezing temperature did not improve the recovery rates significantly.

Bacterial Vaccines↗
PubMed1966

Fluorescent-antibody and histological study of vaccinated and control monkeys challenged with Shigella flexneri.

Formal, Samuel B., (Walter Reed Army Institute of Research, Washington, D.C.), T. H. Kent, S. Austin, and E. H. LaBrec. Fluorescent-antibody and histological study of vaccinated and control monkeys challenged with Shigella flexneri. J. Bacteriol. 91:2368-2376. 1966.-Groups of monkeys were fed four doses of a living Escherichia coli-Shigella flexneri 2a hybrid strain, and, together with control animals, were challenged with virulent S. flexneri 2a. Two experiments were carried out; in the first, the animals were challenged 10 days after and in the second, 1 month after the last vaccine dose was administered. At 48 hr after challenge, tissues were removed from the vaccinated and control animals, and examined by use of histological and fluorescent-antibody techniques. The results of this study demonstrate that the animals receiving the vaccine were protected from the tissue damage ordinarily observed after experimental challenge with virulent dysentery bacilli. The virulent challenge strain appeared to be unable to penetrate into the intestinal mucosa of immunized animals.

Animals↗
PubMed1966

Protection of monkeys against experimental shigellosis with a living attenuated oral polyvalent dysentery vaccine.

Formal, Samuel B. (Walter Reed Army Institute of Research, Washington, D.C.), T. H. Kent, H. C. May, A. Palmer, and E. H. LaBrec. Protection of monkeys against experimental challenge with a living attenuated oral polyvalent dysentery vaccine. J. Bacteriol. 91:17-22. 1966.-Virulent strains of Shigella flexneri 1b, S. flexneri 3, and S. sonnei I were mated with an Hfr strain of Escherichia coli K-12, and hybrids were selected for the xylose marker. One hybrid strain of each of the serotypes was chosen for study of their biological characteristics. Their capacity to cause a fatal enteric infection in starved guinea pigs was reduced, they failed to cause dysentery when fed to monkeys, they caused keratoconjunctivitis in the guinea pig eye, and they penetrated HeLa cells. Two doses of a polyvalent oral vaccine composed of S. flexneri 1b, 2a, and 3, and S. sonnei I hybrid strains were fed to groups of monkeys at an interval of 4 to 7 days, and they, together with controls, were challenged 10 days after the last dose with one or another of the virulent parent dysentery strains. A significant degree of protection was afforded in all vaccinated groups with the exception of one group challenged with S. flexneri 6, a component not included in the vaccine. When animals were challenged with virulent S. flexneri 2a 1 month after oral vaccination, they were also protected. The vaccine produced a rise in serum antibody, but we were not able to detect coproantibody in saline extracts of feces from animals which received the vaccine.

Animals↗
PubMed1965

Protection of Monkeys Against Experimental Shigellosis with Attenuated Vaccines.

Formal, Samuel B. (Walter Reed Army Institute of Research, Washington, D.C.), E. H. LaBrec, Amos Palmer, and Stanley Falkow. Protection of monkeys against experimental shigellosis with attenuated vaccines. J. Bacteriol. 90:63-68. 1965.-Two Shigella flexneri 2a strains of reduced virulence were used as oral vaccines to protect monkeys against experimental challenge. One strain, a spontaneous mutant, had lost its ability to cause disease and was unable to penetrate the intestinal epithelium and reach the lamina propria. The other strain was a hybrid obtained by mating virulent S. flexneri 2a with Escherichia coli. This hybrid strain retained the capacity to penetrate the intestinal epithelium but was not able to maintain itself in the lamina propria. Five oral doses of the nonpenetrating mutant strain were required to render monkeys resistant to experimental challenge, but a single dose of the hybrid strain sufficed to protect the animals. There was some evidence that a degree of specificity was involved in the induced resistance, although neither vaccine evoked a consistent serum antibody or a detectable coproantibody response.

Journal Article↗