Copyright (c) 2009 University of Nebraska - Lincoln All rights reserved. http://digitalcommons.unl.edu/vetscipapers Recent documents in Papers in Veterinary and Biomedical Science en-us Sat, 14 Nov 2009 23:17:59 PST 3600 http://digitalcommons.unl.edu/vetscipapers/113 http://digitalcommons.unl.edu/vetscipapers/113 Fri, 13 Nov 2009 12:45:03 PST The present invention is directed to D-alanine racemase mutants of mycobacterial species. The D-alanine racemase gene (alrA) is involved in the systhesis of D-alanine, a basic component of peptidoglycan that forms the backbone of the bacterial cell wall. The vresent invention is also directed to methods of making live-attenuated vaccines against pathogenic mycobacteria using such alrA mutants and to the vaccines made according to such methods. The present invention is further directed to use of alrA mutants in methods for screening antimycobacterial agents that are synergistic with peptidoglycan inhibitors. Finally, the present invention is directed to methods to identify new pathways of D-alanine biosynthesis for use in developing new drugs targeting peptidoglycan biosynthesis in mycobacteria and to identify vaccines useful against pathogenic mycobacteria. Raul G. Barletta http://digitalcommons.unl.edu/vetscipapers/112 http://digitalcommons.unl.edu/vetscipapers/112 Fri, 13 Nov 2009 12:42:25 PST Recombinant mycobacterial strains which overproduce essential biosynthetic enzymes of pathogenic mycobateria are provided. These strains overproduce enzymes involved in the synthesis and incorporation of D-alanine into mycobacterial peptidoglycan, the backbone of the mycobacterial cell wall. These overproducing strains may be used as reference strains in in vitro screening methods to identify antimycobacterial agents. Raul G. Barletta http://digitalcommons.unl.edu/vetscipapers/111 http://digitalcommons.unl.edu/vetscipapers/111 Fri, 13 Nov 2009 12:37:47 PST The present invention provides methods and compositions for preventing or inhibiting human food-borne pathogens in animals, and methods for increasing feed efficiency in animals by administering to the animal effective amounts of probiotic lactic acid producing bacteria. Further provided are feed compositions comprising probiotic lactic acid producing bacteria. A preferred probiotic lactic acid producing bacteria is Lactobacillus acidophilus strain ATCC accession number PTA-5249. This bacterial strain inhibits nalidixic acid-resistant Escherichia coli 0157:H7. Mindy M. Brashears http://digitalcommons.unl.edu/vetscipapers/110 http://digitalcommons.unl.edu/vetscipapers/110 Wed, 14 Oct 2009 10:37:44 PDT Johne's disease is a chronic diarrhea affecting all ruminants. Mycobacterium avium subsp. paratuberculosis (MAP), a slowly growing mycobacteria, is the etiologic agent. There is also a concern that MAP might be a causative agent of some cases of inflammatory bowel disease in humans, especially Crohn's disease. Food products including pasteurized bovine milk have been suggested as potential sources of human infection. This review addresses microbial factors that may contribute to its pathogenicity. In addition, the experimental evidence defining MAP as the cause of Johne's disease and the issues and controversies surrounding its potential pathogenic role in humans are discussed. Ofelia Barletta-Chacon http://digitalcommons.unl.edu/vetscipapers/109 http://digitalcommons.unl.edu/vetscipapers/109 Fri, 31 Jul 2009 08:08:47 PDT Bovine herpesvirus type 1 (BHV-1) is an important pathogen that can initiate bovine respiratory disease complex. Like other members of the subfamily Alphaherpesvirinae, BHV-1 establishes latency in sensory neurons. The latency-related (LR) gene expresses a family of alternatively spliced transcripts in infected sensory neurons that have the potential to encode several LR proteins. An LR mutant virus that contains three stop codons near the 5' terminus of the first open reading frame in the LR gene does not express two LR proteins or reactivate from latency. In addition, the LR mutant virus induces higher levels of apoptosis in trigeminal ganglionic neurons and grows less efficiently in certain tissues of infected calves. In spite of the reduced pathogenesis, the LR mutant virus, wild-type BHV-1, and the LR rescued virus exhibit identical growth properties in cultured bovine cells. In this study, we demonstrated that during early phases of productive infection the LR mutant virus expressed higher levels of LR-RNA relative to the LR rescued virus or wt BHV-1. Bovine kidney cells infected with the LR mutant virus also induced higher levels of beta interferon RNA and interferon response genes. These results suggest that inappropriate expression of LR-RNA, in the absence of LR protein expression, may influence the latency-reactivation cycle and pathogenic potential of BHV-1. Sandra Perez http://digitalcommons.unl.edu/vetscipapers/108 http://digitalcommons.unl.edu/vetscipapers/108 Thu, 09 Jul 2009 08:07:49 PDT The objective of this study was to investigate coliform counts in feedlot cattle water and feed rations and their associations with management, climate, fecal material, and water Escherichia coli O157 using a cross-sectional study design. Coliform counts were performed on feed samples from 671 pens on 70 feedlots and on water samples from 702 pens on 72 feedlots in four U.S. states collected between May and August 2001. Management and climate factors were obtained by survey and observation. Month of sampling (higher in May and June), presence of corn silage in the ration (negative association), temperature of the feed 1 in. (ca. 2.5 cm) below the surface at the time of sampling (negative association), and wind velocity at the time of sampling (positive association) were significantly associated with log10 coliform levels in feed. Month of sampling (lower in May versus June July and August), water pH (negative association), and water total solids (positive association) were significantly associated with log10 water coliform levels. Coliform counts in feed and water were not associated with prevalence of E. coli O157 in cattle feces or water. Management risk factors must be interpreted with caution but the results reported here do not support the use of coliform counts as a marker for E. coli O157 contamination of feed or water. Michael W. Sanderson http://digitalcommons.unl.edu/vetscipapers/107 http://digitalcommons.unl.edu/vetscipapers/107 Thu, 09 Jul 2009 08:03:16 PDT Ileocolitis associated with spiral bacteria identified as an Anaerobiospirillum sp. was found in six cats. Two cats had acute onset of gastrointestinal signs characterized by vomiting and diarrhea in one cat and vomiting in another cat, one cat had chronic diarrhea that was refractory to medical therapy; one cat had acute onset of anorexia and lethargy, and two cats had clinical signs that were not related to the gastrointestinal tract. The presence of an Anaerobiospirillum sp. was demonstrated on the basis of ultrastructural morphology of spiral bacteria associated with intestinal lesions and PCR amplification of a genus-specific 16S rRNA gene from affected tissues from each cat. The colons of three clinically healthy cats without lesions and one cat with mild colitis not associated with spiral bacteria were negative for Anaerobiospirillum spp. in the same assay. Comparative nucleotide sequence analysis of cloned PCR products from three affected cats further suggested that the spiral bacteria were closely related to Anaerobiospirillum succiniciproducens. H. E. V. De Cock http://digitalcommons.unl.edu/vetscipapers/106 http://digitalcommons.unl.edu/vetscipapers/106 Wed, 27 May 2009 09:47:30 PDT A selective trans-packaging system was developed to produce and isolate bovine viral diarrhea virus (BVDV) pseudo-particles with complementing reporter replicons and their packaging proteins expressed in trans with recombinant vaccinia virus. The encapsidation of replicon rNS3-5B was dependent not only on the in trans expression of structural proteins C, Erns, E1 and E2, but also the nonstructural proteins, p7 and contiguous precursor NS2-3-4A. Nonstructural p7, NS4B, NS5A or NS5B could be expressed in cis and in trans with precursor NS2-3-4A without significantly affecting virion assembly efficiency. NS2-3-4A was identified as an in trans functional precursor in virion assembly. BVDV genomes with mutant NS5B, which did not undergo active replication, were packaged 5-fold less efficiently than the intact genomes demonstrating the importance of replication in virion packaging. These results suggest that genome replication and assembly are closely associated, consistent with a model in which these two steps are coupled for maximum efficiency. Delin Liang http://digitalcommons.unl.edu/vetscipapers/105 http://digitalcommons.unl.edu/vetscipapers/105 Wed, 13 May 2009 10:11:27 PDT Mycobacterium avium subsp. paratuberculosis is the etiologic agent of Johne's disease, a chronic intestinal infection in ruminants. Adenosine 5′-Triphosphate (ATP) has been reported to induce killing of several Mycobacterium species in human and murine macrophages. We investigated whether ATP secreted from M. avium subsp. paratuberculosis-infected bovine monocytes affects intracellular survival of the bacilli. Bovine monocytes constitutively secreted ATP during an 8-day incubation period in vitro; however, M. avium subsp. paratuberculosis infection did not enhance ATP release. Removal of extracellular ATP by the addition of apyrase increased the viability of infected monocytes, but surprisingly decreased the number of viable intracellular bacilli. In contrast to previous reports, addition of extracellular ATP (1 mM) increased intracellular survival of M. avium subsp. paratuberculosis in bovine monocytes. Neither apyrase nor ATP altered production of reactive oxygen intermediates (ROI) or reactive nitrogen intermediates (RNI) by bovine monocytes. These results suggest that ATP release from infected bovine monocytes improves, rather than decreases, the intracellular survival of M. avium subsp. paratuberculosis. Seng-Ryong Woo http://digitalcommons.unl.edu/vetscipapers/104 http://digitalcommons.unl.edu/vetscipapers/104 Wed, 29 Apr 2009 12:36:42 PDT Background: We analyzed the claim "mammography saves lives" by calculating the life-saving absolute benefit of screening mammography in reducing breast cancer mortality in women ages 40 to 65. Methods: To calculate the absolute benefit, we first estimated the screen-free absolute death risk from breast cancer by adjusting the Surveillance, Epidemiology and End Results Program 15-year cumulative breast cancer mortality to account for the separate effects of screening mammography and improved therapy. We calculated the absolute risk reduction (reduction in absolute death risk), the number needed to screen assuming repeated screening, and the survival percentages without and with screening. We varied the relative risk reduction from 10%-30% based on the randomized trials of screening mammography. We developed additional variations of the absolute risk reduction for a screening intervention, including the average benefit of a single screen, as well as the life-saving proportion among patients with earlier cancer detection. Results: Because the screen-free absolute death risk is approximately 1% overall but rises with age, the relative risk reduction from repeated screening mammography is about 100 times the absolute risk reduction between the starting ages of 50 and 60. Assuming a base case 20% relative risk reduction, repeated screening starting at age 50 saves about 1.8 (overall range, 0.9-2.7) lives over 15 years for every 1000 women screened. The number needed to screen repeatedly is 1000/ 1.8, or 570. The survival percentage is 99.12% without and 99.29% with screening. The average benefit of a single screening mammogram is 0.034%, or 2970 women must be screened once to save one life. Mammography saves 4.3% of screen-detectable cancer patients' lives starting at age 50. This means 23 cancers must be found starting at age 50, or 27 cancers at age 40 and 21 cancers at age 65, to save one life. Conclusion: The life-saving absolute benefit of screening mammography increases with age as the absolute death risk increases. The number of events needed to save one life varies depending on the prospective screening subset or reference class. Less than 5% of women with screen-detectable cancers have their lives saved. James E. Keen