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Title:   Author  item
                                            Brown, Tysonitem
                                            Edrington, Thomasitem
                                            Genovese, Kenneth

                                                         - *Ken*item
                                            LONGERAGAN, GUY - Texas Tech Universityitem
                                            HANSON, D - Texas Tech Universityitem
                                            Nisbet, David
  Submitted to: Journal of Food Protection
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 10/28/2014
                                    Publication  Date: 3/1/2015
                                    Publication URL: http://handle.nal.usda.gov/10113/60558Citation: Brown, T.R., Edrington, T.S., Genovese, K.J., Longeragan, G., Hanson, D.L., Nisbet, D.J. 2015. Oral Salmonella challenge and subsequent uptake by the peripheral lymph nodes in calves. Journal of Food Protection. 78:573-578.Interpretive Summary: Cattle may contain the bacteria Salmonella that can make people sick.  Peripheral lymph nodes in these cattle have been shown to contain Salmonella.  Pre-harvest interventions are needed to control Salmonella in cattle; however, not much is known about what causes Salmonella to spread from the gastrointestinal tract to peripheral lymph nodes. This research was conducted to specifically evaluate if multiple oral exposures of Salmonella causes uptake by the peripheral lymph nodes.  Results indicate that these lymph nodes will become infected with Salmonella following a substantial oral inoculation.  By better understanding routes of infection of human food safety pathogens novel intervention strategies can be developed.
                                Technical Abstract: Because previous attempts to infect peripheral lymph nodes (PLNs) with Salmonella via oral inoculation have been inconsistent, we performed a series of experiments to determine whether multiple exposures to an oral challenge resulted 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 (~1010; PCON), or 10 consecutive doses in water (~103; WAT). The PCON treatment resulted in an increase (P < 0.05) in the percentage of Salmonella-positive PLNs, when compared to the WAT treated and control animals.  Experiments II and III 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 × 104 CFU/d) in Experiment I, 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 water-challenged calves in experiments I and II, a higher challenge dose (average 1.2 × 107 CFU) was used in Experiment III. 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 to the normal time spent by cattle in feedlots, it is reasonable to assume increased exposure time to lower doses may produce the same effect observed in Experiment III.


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