Oligonucleotide primers for the polymerase chain reaction (PCR) that enable genus-specific detection of members of the genus Salmonella were developed. The primers amplify a 496-bp genetic sequence of members of the genus Salmonella. Amplification of DNA extracted from all other genera of the family Enterobacteriaceae and various other gram-positive aerobic and anaerobic bacteria yielded negative results. Applications of the PCR using these genus-specific primers are discussed.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a member of the positive-strand RNA virus family Arteriviridae. Although considerable research has focused on this important pathogen, little is known about the function of most PRRSV proteins. To examine characteristics of putative nonstructural proteins (nsp) encoded in ORF1b, which have been identified by nucleotide similarity to domains of equine arteritis virus, defined genomic regions were cloned and expressed in the pRSET expression system. One region, nsp10, encoded a protein with a putative helicase domain and was further examined for functional helicase-like activities. PRRSV nsp10 was found to possess a thermolabile and pH-sensitive NTPase activity that was modulated by polynucleotides and to unwind dsRNA in a 5' to 3' polarity. These results provide the first evidence of the functional properties of PRRSV helicase and further support the finding that nidovirus helicases possess properties that distinguish them from other viral helicases.

We have previously shown that increased resistance to Salmonella enteritidis organ infectivity in day-old chicks was conferred by the immunoprophylactic administration of S. enteritidis-immune lymphokines (ILK). This resistance was associated with a significant increase in the number of circulating heterophils 4 h after ILK injection. The objective of the present study was to evaluate heterophil function following the administration of ILK in day-old chicks. Significant increases (P < 0.001) in adherence, chemotaxis, and phagocytosis of S. enteritidis were found with heterophils isolated from ILK-injected chickens compared to the heterophils isolated from birds injected with either pyrogen-free saline or lymphokines from non-immune T cells. After phagocytosis, the heterophils from the ILK-injected chickens were also able to kill significantly greater numbers of S. enteritidis more rapidly than did the heterophils from the saline-injected control birds (within 30 min, control cells killed 21.89% of the bacteria whereas ILK-treated cells killed 88.22%). We also found that the heterophils from the ILK-injected birds were more efficient killers of S. typhimurium, S. gallinarum, and E. coli. These results strongly suggest that the protection against S. enteritidis organ invasion induced by the prophylactic treatment of day-old chicks with ILK involves activated heterophils which migrate rapidly to the inflammatory stimulus where they phagocytize and kill the bacteria.

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