Abstract: A fluorescent DNA probes specific to the conserved terminal 3′-noncoding region (nucleotides 10653-10678) of dengue virus and a pair of flanking primers are designed to formulate a dengue specific fluorogenic polymerase chain reaction (PCR). Optimal assay conditions with zero background are disclosed which permit the detection of low levels of dengue virus from clinical specimens. Dengue virus isolates from different geographic regions can be universally detected and identified by the fluorogenic RT-PCR assay. Moreover, the assay is specific for dengue 2 virus and does not recognize other related flaviviruses, including dengue serotypes Louis encephalitis, yellow fever, and Kunjin viruses. The ) 3, and 4, Japanese encephalitis, St. assay also efficiently detected immunocomplexed dengue viruses. The fluorogenic RT-PCR assay readily detected viremia in sera collected from individuals ill with dengue fever.

Abstract: A simple polymerase chain reaction procedure is described for the detection and differentiation of Shigella from other pathogenic Escherichia coli isolates, such as EIEC and EPEC. Serotype specific primers derived from the rfc genes of different Shigella strains are used to identify the most prominents Shigella serotypes, such as S. sonnei, S. flexneria 1 through 5, and S dysenteriae 1. More than 95% of Shigellosis cases reported could be identified by the serotype specific primers described.

Abstract: The vaccines are prepared by isolating the Brucella genes complementing mutations in the purEK genes of Escherichia coli, physically mapping, determining the DNA sequence, constructing a defined deletion mutation by polynucleotide chain reaction (PCR), introducing a selectable marker into the deletion, and then selecting a purE mutant in Brucella arising by allelic exchange. The resulting Brucella require purines for growth because they lack the purE gene product that is required for the carboxylation of 5'-phosphoribosyl-5-aminoimidazole.