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Fraction-I (F-I) protein, the specific antigen of Pasteurella pestis, appears to be a series of molecular aggregates of identical subunits, all of which have serological reactivity with specific F-I antiserum.
A pseudolysogenic strain of Pasteurella pestis was isolated from a human in Vietnam. The culture contained a stable mixture of bacteriophage and phage-sensitive and phage-resistant P. pestis.
In the investigation of outbreaks of plague it is frequently more satisfactory to send specimens of suspected material collected in the field to a central laboratory, where usually better facilities for their more detailed examination are available. In the present study the authors have investigated the suitability of solid CO(2) (dry-ice) for the preservation of such material during transit. Three types of preparation were tested: broth suspensions of Pasteurella pestis, the livers and spleens of guinea-pigs dying after being infected with two different strains of P. pestis, and whole carcasses of mice and ground-squirrels infected with the organism. An additional test to ascertain the rate at which animal specimens became frozen and thawed was also carried out.These studies showed that (1) organisms in the various tissues frozen in dry-ice were not adversely affected by such treatment; (2) the survival of P. pestis cells did not depend on the number of organisms present in broth cultures or tissue suspensions, small numbers surviving equally well as large; and (3) plague bacilli contained in whole carcasses, even when present in small numbers, were also successfully preserved. It is concluded from these results, and also from the authors' practical use of the method over several years, that for the transport of plague-suspect materials from the field to the laboratory freezing with dry-ice can be confidently recommended.
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The effects of flea control on the prevalence of (Pasteurella) pestis antibody rates in the California vole, Microtus californicus, were studied in San Mateo County, California, USA. In this area, which had shown antibody prevalence rates of 50% or more during epizootics in previous years, continuous flea control measures reduced the antibody rate to virtually zero and held it at that level for 12 months, although a nearby area showed an incidence of 40-80% seropositive voles for 5 months during the same period. The striking correlation between the reduction of the flea population and the decline of Y. pestis antibody rates suggests that in the area studied there is no evidence that soil, or any factor other than the flea vector, was the agent of transmission of the infective agent in wild rodents.
Endotoxin containing 2.1% nitrogen, 1.6% phosphorus, 22.5% neutral hexose, 15% hexosamine, 25% esterified and amide-linked fatty acids, and 1.4% protein was isolated from Pasteurella pestis strain Alexander by slight modification of a method adapted by Tauber and Russell. The lipopolysaccharide exhibited classical endotoxic biological properties including: (i) toxicity in mice, guinea pigs, and rabbits; (ii) antigenicity in rabbits; (iii) capacity to evoke a biphasic pyrogenic response in rabbits; (iv) capacity to induce tolerance in mice to the lethal effect of endotoxin; (v) capacity to stimulate rapidly acquired resistance in mice to bacterial infection, and (vi) the capacity to produce the localized and generalized Shwartzman phenomena in rabbits. Findings obtained during the study concerning the occurrence, isolation, toxicity, and other biological properties of P. pestis endotoxin provide new evidence that endotoxin could contribute to death in plague.
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A method is described for the use of antiplague serum in Blood Agar Base plating media to detect fraction I-positive Pasteurella pestis. The antiserum was produced conveniently and in large volume in rabbits by use of Cutter plague vaccine combined with Freund's complete adjuvant. P. pestis colonies were specifically identified within 48 hr after plating by the presence of a precipitin ring surrounding each colony. The basis of the test was shown to be a precipitin reaction between fraction I antigen released from P. pestis colonies after chloroform vapor treatment and fraction I antibody present in the antiserum-agar medium.
The rate of oxidation of glucose by freshly harvested resting cells of P. pestis strain A-1122 was accelerated by 20 to 41 per cent in the presence of insulin. The stimulatory action was not noted when cell-free enzyme preparations were employed and was less marked after storage of cells for 3 days. Although insulin was not oxidized by the organism, the amount of oxygen consumed during the dissimilation of a unit weight of glucose was increased in the presence of the hormone.
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Electron microscopy examination of phiII-H deoxyribonucleic acid heteroduplexes, together with polyacrylamide gel electrophoretic analyses of phage ribonucleic acid species and proteins labeled in phiII or H-infected cells, demonstrates that Pasteurella pestis phage H is nearly identical to coliphage phiII.