Composition of cell wall and plasma membrane of standard strains of Salmonella typhosa.
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An investigation of the immunogenicity of vaccines prepared from closely related virulent and avirulent strains of S. typhosa is reported. No evidence was obtained of any essential relationship between the virulence of the strains employed and their immunogenicity, as determined by active-immunity mouse-protection tests and by the agglutinin and mouse-protective antibody response in human beings.
Quantitative determinations, employing turbidimetric growth assays, have been made of the inhibitory actions of choramphenicol, and of specific antibody plus complement, separately, and in combination. In experiments with the Ty2 strain of S. typhosa the combined activities of the two groups of reagents have been predicted, within 3 per cent, from the activities of the separate components, on the hypothesis of joint, independent action (additive inhibitions). A fourfold increase in resistance to chloramphenicol of the 0901 strain of S. typhosa has been shown to have little, if any, effect on its susceptibility to the bactericidal action of anti-O antibody and complement. Indirect evidence indicates that the latter may not be a general effect but may vary with the particular strain.
An investigation is reported of a comparison by three methods of the degree and certainty of differentiation of strains of S. typhosa of different virulence for mice. These methods were (a) intracerebral injection, (b) intraperitoneal injection of saline suspensions, and (c) intraperitoneal injection of mucin suspensions of the test organisms. With the strains of S. typhosa employed, differentiation was questionable by the intracerebral method, somewhat more marked by the intraperitoneal-saline suspension method, and most definite by the intraperitoneal-mucin suspension method. Differentiation of the strains employed was found to be independent of the presence or absence of Vi antigen and apparently was more dependent upon the method of testing than upon any known differences in biological characteristics of the organisms.
Rabbits receiving three injections of PFA intravenously in ear, after that first treatment gave a weak antibody response, after the second one a rapid and copious increase of agglutination titre; the third injection induced a very small increase. In rabbits injected with PFA in superior mesenteric vein the first injection produced a little effect, the second induced a little effect too; the third injection performed in auricular vein, gave a substancial rapid and copious antibody response. This behaviour is similar to that obtained after the second injection in the first set of experiments. The PFA injected two times in mesenteric vein caused certainly a massive phagocytosis of antigen by Kupffer cells. Nevertheless this copious phagocytosis can exercise only an action of "priming", not a response of secondary type. For this purpose it is necessary an injection in the ear vein to provoke a direct intervention of lymphonodal reticular phagocytes. The phenomenon can be related to the proteic nature of the antigen.
The antibacterial effects of 24-h exposures to high-pressure oxygen in relation to environmental CO(2) were studied at 3 atm absolute (ata) and at 1 ata. Eight gram-negative, aerobic and facultatively aerobic, pathogenic enteric bacteria (Salmonella typhosa, Salmonella paratyphi, Salmonella schottmuelleri, Shigella dysenteriae, Shigella flexneri, Proteus vulgaris, Pseudomonas aeruginosa, and Escherichia coli) were exposed as shallow-broth cultures and agar surface cultures. Although broths supplemented with 0.2% glucose permitted some growth of Salmonella typhosa, Salmonella schottmuelleri, Shigella dysenteriae, and Shigella flexneri during exposure to high-pressure oxygen in the presence of CO(2), the other species grew only after the exposure, indicating a bacteriostatic effect. Both bacteriostatic and bactericidal effects were demonstrated on the surface of Trypticase soy agar, where killing of Salmonellea typhosa, Proteus vulgaris, and Pseudomonas aeruginosa was significantly greater after exposure to pure O(2) at 3 ata than at 1 ata. At 3 ata, significantly more killing occurred upon exposure of all species (except Shigella dysenteriae and S. flexneri) on an agar surface to 100% O(2) as compared with exposure to a mixture of 95% O(2) + 5% CO(2). Thus, deprivation of CO(2) during exposure to pure O(2) enhanced the bactericidal effect of high-pressure oxygen.
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FIVE TEST ORGANISMS WERE USED: Escherichia coli, Salmonella typhosa, Salmonella schottmuelleri, Salmonella enteritidis, and Shigella paradysenteriae. Even when large inocula of these test cultures were introduced into fresh passionfruit nectar base, all test organisms were killed within 1 to 2 hr, provided the nectar base was held at room temperature for more than 1 hr before freezing. If the nectar base was frozen immediately after inoculation, four of the five test organisms were eliminated almost as quickly. But the fifth, Salmonella enteritidis, proved to be exceptional: it was being recovered after 90 days of storage at -20 C, when the last available sample was analyzed.
The results of the study on the antimicrobial activity of 12 chlorine-substituted 4-alkyl- and arylphenols against Staphylococcus, Streptococcus, E. coli, Salmonella typhosa, Salmonella typhimurium, Shigella dysenteriae, Proteus, Klebsiella rhinoscleromatis, Candida, Trichophyton gypseum and Microsporum lanosum are presented. It was found that introduction of the alkyl substitute to position 4 of orthochlorphenol increased the activity of the substances against the majority of test microbes. The antimicrobial effect of the substances depended on the length and structure of the alkyl radical. With an increase in the number of the carbon atoms in the alkyl radical from 3 to 7 and in the presence of the cyclic radical C5 - C6 the antimicrobial activity of the substances increased.