2007 Annual Report
1a.Objectives (from AD-416)
1) Identify environmental influences and management practices that contribute to the colonization of food-borne pathogens in pre-harvest poultry.
2) Identify environmental influences and management practices that contribute to Clostridium spp. colonization and the onset of necrotic enteritis (NE) in pre-harvest poultry.
3) Identify prebiotics and symbiotics (lactose, cottonseed, etc.) that can be utilized as pre-harvest intervention strategies, and determine how chlorate and feed additives such as alfalfa control poultry enteropathogen colonization.
4) Identify environmental or management practices that contribute to antibiotic resistance acquisition and dissemination among and between the various pathogenic and commensal microorganisms found in commercial poultry.
5) Characterize the complex interactions between the innate immune and endocrine systems and develop a more fundamental understanding of the role of gastrointestinal endocrinology on the microbial ecology of the gut of food-producing animals.
1b.Approach (from AD-416)
1) Using a newly constructed (i.e., naive) commercial broiler production facility, we will follow bacterial, viral, protozoan, and fungal movement within the facility from prior to the first placement of birds through several successive production cycles. The movement of these organisms within the environment will be mapped using genetic identification and traditional culture methods.
2) Using a necrotic enteritis (NE) in vivo model developed in our laboratory and a primary cell culture model, we will investigate the interactions of Clostridium with other bacterial populations within the gastrointestinal tract of broilers and the development of NE. We will evaluate these bacterial populations using molecular-based techniques (DGGE, PFGE) in order to determine the dynamics between commensal gut bacterial populations and Clostridium. Additionally, we will examine the toxins produced by Clostridium using tissue culture techniques and Multiplex Polymerase Chain Reactions (PCR).
3) The efficacy of lactose, cottonseed and similar prebiotics and symbiotics will be evaluated under commercial conditions for their ability to reduce food-borne pathogens in poultry. Practical feeding trials will be performed to ascertain the ability of chlorate and alfalfa as alternatives to traditional antimicrobials, and the mode of action of these compounds will be determined. We will also study different quorum sensing autoinducers to determine the effects of biological and synthetic bacterial autoinducer inhibitors on poultry enteropathogens.
4) Utilizing an in vitro bacterial conjugation assay, we will identify flavophospholipol-like compounds (flavophospholipol has been shown to reduce horizontal gene transfer between Enterococci in vitro), that inhibit bacterial conjugation and resistance gene acquisition among gut bacteria.
5) We will characterize specific interactions between the immune and endocrine systems that influence enteropathogen colonization in the gastrointestinal tract of poultry. Microarrays will be utilized to assess fluctuations in key avian hormones that correspond to cytokine expression.
Necrotic Enteritis Controlled by Dietary Lactose:
Necrotic enteritis (NE) is a serious poultry disease that affects a significant component of the U.S. poultry production industry. Unfortunately, ongoing efforts by poultry producers to minimize the use of antibiotic growth promoters in poultry production tends to result in higher incidences of NE because the bacterium Clostridium perfringens is a causative agent of NE and is effectively controlled by antibiotics. Effort is needed to develop effective, non-antibiotic methods for NE control. Scientists in the Food and Feed Safety Research Unit at the Southern Plains Agricultural Research Center, College Station, TX, demonstrated that lactose (milk sugar), when added to the diet, reduces the incidence of NE in birds that are not receiving common antibiotic growth promoters. This accomplishment is important because it demonstrates that a common, widely available, and inexpensive sugar may have practical use in facilitating the goal of minimizing antibiotic use in poultry production while assuring that necrotic enteritis is managed in an effective manner. (NP 108, Component 1.1, Problem Statement 1.1.4)
Management of Antibiotic Resistance in Pathogenic Bacteria:
The use of antibiotics in the production of livestock and poultry is believed by many to have created a reservoir of antimicrobial-resistant bacteria. One of the problematic issues related to antimicrobial resistance in bacteria is that the organisms can share or transfer antibiotic resistance genetic elements by a process called conjugation; more needs to be known about this phenomenon and its significance in the potential spread of antibiotic-resistant microorganisms. Scientists in the Food and Feed Safety Research Unit at the Southern Plains Agricultural Research Center, College Station, TX, determined the capability of a common poultry feed additive (known as flavophospholipol) to inhibit the spread of genetic information from one E. coli bacterium to another in living poultry. The studies used day-of-hatch chicks inoculated with E. coli, and firmly established that the additive did not prevent the bacteria from sharing genetic information. Although flavophospholipol demonstrated no useful biochemical actions, the work is nonetheless important because it provides solid scientific information on the dynamics of feed additive interactions with poultry gut microorganisms; ongoing work may be successful in identifying practical means to inhibit bacterial conjugation in living animals and thus reduce the threat posed by the antibiotic resistance phenomenon. (NP 108, Component 1.1, Problem Statement 1.1.5)
New Molting Diet for Laying Hens Reduces Stress and Salmonella Levels:
Salmonella is a significant food-poisoning bacterium in humans; infections are often acquired by consumption of contaminated poultry products. With laying hens, producers periodically induce hen molting (feather replacement) which results in subsequent increased egg laying by the newly molted birds. However, molting is a stressful process for poultry, and it is known that these stresses can result in the birds becoming very susceptible to Salmonella infections which can result in Salmonella-contaminated eggs. New protocols are needed that will allow molting to be accomplished without the resulting bird stress and egg-contamination potential. Scientists in the Food and Feed Safety Research Unit at the Southern Plains Agricultural Research Center, College Station, TX, in collaboration with scientists at Texas A&M University, developed an alfalfa diet for use during a forced molt that effectively reduces Salmonella levels in the birds during and after the molt and that greatly reduces the likelihood of the birds producing Salmonella-contaminated eggs. This accomplishment is important because implementation of the alfalfa molting diet will enhance the microbiological safety of raw egg products reaching the consumer, and it will provide producers with a much less stressful method for accomplishing a necessary bird management practice. (NP 108, Component 1.1, Problem Statement 1.1.4)
Immune System Modulation to Control Pathogenic Bacteria in Livestock and Poultry:
The colonization of livestock and poultry by pathogenic or food-poisoning bacteria is a serious problem in food animal production. One potential way to manage this problem is to exploit the animals’ own immune systems to increase their ability to fight off colonization by the pathogens. Scientists in the Food and Feed Safety Research Unit at the Southern Plains Agricultural Research Center, College Station, TX, defined critical parameters in poultry that are related to the production of nitric oxide which is a major mechanism used by the body’s immune system to defend against bacterial invasion. The work focused on identification of critical components of the nitric oxide pathway in a type of chicken white cell known as a macrophage, and as affected by chemicals that inhibit the production of signals that normally result from macrophage interactions with bacteria or viruses. This accomplishment is important because it demonstrated that the signaling process in birds is very similar to that known to occur in mammals. Thus, the full body of research on the nitric oxide signaling pathway, across higher animal types, can likely be exploited to hasten the success of ongoing efforts to develop effective pathogen management strategies in both livestock and poultry for animal disease control and to enhance human food safety. (NP 108, Component 1.1, Problem Statement 1.1.5)
|Number of active CRADAs and MTAs||2|
|Number of new commercial licenses granted||1|
|Number of non-peer reviewed presentations and proceedings||18|
Byrd II, J.A., Bailey, R.H., Wills, R.W., Nisbet, D.J. 2007. Recovery of Campylobacter from commercial broiler hatchery trayliners. Poultry Science. 86:26-29.
McReynolds, J.L., Byrd II, J.A., Genovese, K.J., Poole, T.L., Duke, S.E., Farnell, M.B., Nisbet, D.J. 2007. Dietary lactose and its effect on the disease condition of necrotic enteritis. Poultry Science. 86:1656-1661.
Poole, T.L., McReynolds, J.L., Edrington, T.S., Byrd II, J.A., Callaway, T.R., Nisbet, D.J. 2006. Effect of flavophospholipol on conjugation frequency between Escherichia coli donor and recipient pairs in vitro and in the chicken gastrointestinal tract. Journal of Antimicrobial Chemotherapy. 58:359-366.
Crippen, T.L., Sheffield, C.L. 2006. External surface disinfection of the lesser mealworm (Coleoptera: Tenebrionidae). Journal of Medical Entomology. 43:916-923.
Sheffield, C.L., Andrews, K., Harvey, R.B., Crippen, T.L., Nisbet, D.J. 2006. Dereplication by automated ribotyping of a competitive exclusion culture bacterial isolate library. Journal of Food Protection. 69:228-232.
Dunkley, K.D., McReynolds, J.L., Hume, M.E., Dunkley, C.S., Callaway, T.R., Kubena, L.F., Nisbet, D.J., Ricke, S.C. 2007. Molting in Salmonella enteritidis-challenged laying hens fed alfalfa crumbles. I. Salmonella enteritidis colonization and virulence gene hilA response. Poultry Science. 86:1633-1639.
Crippen, T.L. 2006. The selective inhibition of nitric oxide production in the avian macrophage cell line HD11. Veterinary Immunology and Immunopathology. 109:127-137.