Genomic subtractive hybridization of closely relatedPasteurella multocida isolates has generated clones useful in distinguishing hemorrhagic septicemia-causing type B strains from other P. multocida serotypes. Oligonucleotide primers designed during the sequencing of these clones have proved valuable in the development of PCR assays for rapid species- and type-specific detection of P. multocida and of type B:2 in particular. This study demonstrated that the primer pair designed from the sequence of the clone 6b (KTT72 and KTSP61) specifically amplified a DNA fragment from types B:2, B:5, and B:2,5P. multocida and that the primers KMT1T7 and KMT1SP6 produced an amplification product unique to all P. multocida isolates analyzed. It was also shown that PCR amplification performed directly on bacterial colonies or cultures represents an extremely rapid, sensitive method of P. multocida identification.

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Age-related macular degeneration (AMD), a disease of the area centralis or macula, is the leading cause of blindness in the elderly population of the developed world.

Mice homozygous for the beige gene (bg/bg) are a homologue of the Chediak-Higashi syndrome of man and are known to be selectively defective in natural killer (NK) cells. We have compared the susceptibility of bg/bg and bg/+ C57BL/6J mice to infection with murine cytomegalovirus (MCMV). Beige mice are more susceptible to lethal infection and develop 33-to 43-fold higher virus titers in the liver, spleen, and kidney than do bg/+ mice after a sublethal infection, although virus replication is the same in vitro in cultured fibroblasts or epithelial cells from these mice. Inoculation with a sublethal dose of virus stimulates a NK cell response, although this is lower in bg/bg mice despite higher titers of interferon type 1 than in bg/+. A dose of MCMV that is lethal only to bg/bg augments cytotoxicity within 12 hr in bg/+ mice, whereas cytotoxicity in bg/bg remains very low. In bone marrow chimeras, recipients of bg/bg marrow were more susceptible to MCMV and had lower NK cell responses after virus inoculation than did recipients of marrow from bg/+ donors. The greater susceptibility of beige mice to the virus suggests that NK cells may contribute to resistance early in MCMV infection.The Ch6diak-Higashi syndrome and its animal homologues are associated with defective granule formation in a range of cell types (1) and with predisposition to bacterial infection resulting from the decreased bactericidal capacity of granulocytes (2). In man and beige mutant mice there is also a defect in cytolysis mediated by natural killer (NK) cells (3, 4), which spontaneously lyse tumor or virus-infected cells in vitro without prior immunization (5, 6). The increased growth of implanted tumors in beige mice has suggested that NK cells carry out tumor surveillance in normal individuals (7,8), but little is known about the role of NK cells in virus infections.We are interested in the possibility that NK cells contribute to resistance to murine cytomegalovirus (MCMV) early in infection and may account at least in part for genotype-related differences in susceptibility to this virus. Whilst adoptive protection against infection with MCMV can be conferred by T cells from immune mice (9, 10), the primary cytotoxic T cell response is difficult to detect (10) and significant cytotoxicity is not observed before the fourth day of infection (11). Thus, because at an appropriate virus dose susceptible mice die within 3-4 days of infection whereas mice of resistant strains survive (12), protection of resistant mice by an early non-T cell mechanism appears likely. In support of an early protective role for NK cells, it has been shown that their cytotoxicity is rapidly enhanced during MCMV infection and that they lyse MCMV-infected cells in vitro (13,14). A significant positive correlation between resistance to lethal MCMV infection and the level of NK cytotoxicity has been demonstrated at 1 day after infection in a number of mouse strains (14, 15). We here report that NK-deficient beige mice are also more susceptible to MCMV than are thei...