Submitted to: Microbial Pathogenesis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 3, 2013
Publication Date: October 11, 2013
Citation: Bearson, S.M., Bearson, B.L., Lee, I., Kich, J.D. 2013. Polynucleotide phosphorlyase (PNPase) is required for Salmonella enterica serovar Typhimurium colonization in swine. Microbial Pathogenesis. 65:63-66. Interpretive Summary: Intervention strategies against the foodborne pathogen Salmonella Typhimurium could target the function of Salmonella genes important in pathogen survival in the host. We determined that the pnp gene is required for Salmonella survival in the swine stomach. Furthermore, a mutation in the pnp gene dramatically decreased the ability of Salmonella Typhimurium to colonize pigs. The pnp gene product (PNPase) is involved in regulating numerous bacterial processes through degradation of the molecular building block, RNA. Thus, developing interventions that target the function of the pnp gene may cause the bacterium to be more susceptible to host defenses and environmental stress, thereby limiting swine colonization. Industry, university and government researchers investigating host-pathogen interactions should find this research interesting, especially those investigating control strategies of Salmonella in food production animals.
Technical Abstract: The pnp gene encodes polynucleotide phosphorylase, an exoribonuclease involved in RNA degradation. A mutation in the pnp gene was previously identified by our group in a signature-tagged mutagenesis screen designed to search for Salmonella enterica serovar Typhimurium genes required for survival in an ex vivo swine stomach content assay. In the current study, attenuation and colonization potential of the S. Typhimurium pnp mutant in the porcine host was evaluated. Following intranasal inoculation with 10**9 cfu of either the wild-type S. Typhimurium chi 4232 strain or an isogenic derivative lacking the pnp gene (n=5/group), a significant increase in rectal temperature (fever) was observed in the pigs inoculated with wild-type S. Typhimurium, but not in the pigs inoculated with the pnp mutant. Fecal shedding of the pnp mutant was significantly reduced during the 7-day study compared to the wild-type strain (p less than 0.05). Tissue colonization was also significantly reduced in the pigs inoculated with the pnp mutant compared to the parental strain, including the tonsils, ileocecal lymph nodes, Peyer’s Patch region of the ileum, cecum and contents of the cecum (p less than 0.05). The data indicate that the pnp gene is required for S. Typhimurium virulence and gastrointestinal colonization of the natural swine host.