title: Oral salmonella challenge and subsequent uptake by the peripheral lymph nodes in calves.
abstract: Previous attempts to infect peripheral lymph nodes (PLNs) with Salmonella via oral inoculation have been inconsistent. Therefore, we performed a series of experiments to determine whether multiple exposures to an oral challenge would result in Salmonella-positive PLN in cattle. In each of three experiments, calves were inoculated with Salmonella Montevideo. In the first experiment, calves were challenged with either no Salmonella (control), a single oral dose (∼10(10); PCON), or 10 consecutive doses in water (∼10(3); WAT). The positive control treatment resulted in an increase (P < 0.05) in the percentage of Salmonella-positive PLNs, compared with the WAT-treated and control animals. Experiments 2 and 3 were designed to additionally determine if the stress associated with feed and water deprivation influences the systemic spread of Salmonella from the gastrointestinal tract to PLNs. Following 14 days of oral inoculation (average 7.1 × 10(4) CFU/day) in experiment 1, Salmonella was recovered from one subiliac and one superficial cervical lymph node of calves that were deprived of feed and water (72 h). No treatment differences (P > 0.05) were observed between control and deprived calves. Based on the poor recovery of Salmonella from the PLNs in WAT-challenged calves in experiments 1 and 2, a higher challenge dose (average 1.2 × 10(7) CFU) was used in experiment 3. The increased dose resulted in the recovery of the challenge strain of Salmonella from the PLNs (70.8 and 75.0% of control and deprived calves, respectively). However, no treatment differences (P > 0.05) were observed between control and deprived calves. Results of this research demonstrated that a substantial oral challenge is required to produce Salmonella-positive PLNs. However, as the challenge periods examined herein were considerably shorter compared with the normal time spent by cattle in feedlots, increased exposure time to lower doses may produce the same effect observed in experiment 3.
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Food and Feed Safety Research Unit, 2881 F&B Road, College Station, Texas 77845, USA.
authors.forename: T R
authors.initials: TR
authors.lastname: Brown
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Food and Feed Safety Research Unit, 2881 F&B Road, College Station, Texas 77845, USA. tom.edrington@ars.usda.gov.
authors.forename: T S
authors.initials: TS
authors.lastname: Edrington
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Food and Feed Safety Research Unit, 2881 F&B Road, College Station, Texas 77845, USA.
authors.forename: K J
authors.initials: KJ
authors.lastname: Genovese
authors.affiliation: International Center for Food Industry Excellence, Department of Animal and Food Sciences, P.O. Box 42141, Texas Tech University, Lubbock, Texas 79409, USA.
authors.forename: G H
authors.initials: GH
authors.lastname: Loneragan
authors.affiliation: International Center for Food Industry Excellence, Department of Animal and Food Sciences, P.O. Box 42141, Texas Tech University, Lubbock, Texas 79409, USA.
authors.forename: D L
authors.initials: DL
authors.lastname: Hanson
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Food and Feed Safety Research Unit, 2881 F&B Road, College Station, Texas 77845, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Nisbet
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology* / Q000382:microbiology / Q000517:prevention & control; D008198:Lymph Nodes / Q000382:microbiology*; D012475:Salmonella / Q000276:immunology*; D012481:Salmonella Infections, Animal / Q000276:immunology*