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Biomedical subjects

A Shirai

Publications and source records attributed to A Shirai.

At least 109 records · Page 6Linked to original sources
PubMed1975

Serologic classification of scrub typhus isolates from Pakistan.

Detailed serologic characterization of 79 isolates of Rickettsia tsutsugamushi from Pakistan was performed by using complement fixation and direct immunofluorescence techniques for comparison with three prototype strains. Seventy-one were of the Karp serotype and one was of a Gilliam serotype. Seven isolates were multiply-reactive: one with Karp and Gilliam, 3 with Karp and Kato, and 3 with Karp, Gilliam and Kato, No strain failed to react with at least 1 of the 3 prototype antisera. No correlation of antigenic types with local geographic factors, animal hosts, vecotr mites, or specific strain virulence was observed. These findings suggest the possibility that antigenic heterogeneity may be more restricted in areas peripheral to the geographic epicenter of scrub typhus endemicity, that the serotypes are relatively stable genetically and that new geographic variants are probably infrequent. The importance of these findings to the practical problems of immunoprophylaxis and serodiagnosis are discussed.

Animals↗
PubMed1967

Experimental infection of the cotton rat Sigmodon hispidus with Rickettsia rickettsii.

Studies of experimental infection of the cotton rat, Sigmodon hispidus, with the virulent Sheila Smith (R type) and the avirulent Si 7 (U type) strains of Rickettsia rickettsii were undertaken to evaluate the role of this native wild mammal in the ecology of Rocky Mountain spotted fever. The Sheila Smith strain, which was highly lethal for guinea pigs, was nonpathogenic for cotton rats. Serial passage of the R-type strain in the cotton rat did not alter the virulence of the agent for cotton rats or guinea pigs. The U-type strain, which was originally recovered from a wild cotton rat, could not be maintained beyond the first passage in this animal host. Rickettsemia in the cotton rat occurred over a 24-hr period after inoculation of the virulent strain but was detected only 1 hr after inoculation of the avirulent strain. The short period of rickettsemia suggests that the cotton rat probably is not an important reservoir of R. rickettsii. Specific complement-fixing antibodies developed rapidly after infection with either strain, but the antibodies evoked by the R strain attained higher titers and persisted longer. Cotton rats previously infected with the Sheila Smith strain developed rickettsemia after reinfection with the same strain, even though relatively high levels of antibody were still present.

Animals↗