SALMONELLA IN THE LYMPH NODES OF CATTLE PRESENTED FOR HARVEST By Sara Elizabeth Gragg, M.S. A Dissertation In ANIMAL SCIENCE Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Approved Dr. Mindy Brashears Chair of Committee Dr. Guy H. Loneragan Dr. J. Chance Brooks Dr. Mark Miller Dr. Michael San Francisco Dominick Casadonte Dean of the Graduate School December, 2012 Copyright 2012, Sara Elizabeth Gragg Texas Tech University, Sara Elizabeth Gragg, December 2012 ACKNOWLEDGEMENTS To my advisor, Dr. Mindy Brashears, I thank you for the opportunity to learn from you both personally and professionally over the previous fifteen years. You have provided me with amazing opportunities and have been an outstanding role model. I have the utmost respect for you and am truly blessed to call you my mentor and my friend. To my committee, Drs. Mindy Brashears, Guy Loneragan, Chance Brooks, Mark Miller and Michael San Francisco, I look up to each of you and appreciate the guidance and support you have provided throughout my education at Texas Tech University. Thank you, Drs. Guy Loneragan and Kendra Nightingale, for the expertise and opportunities that you have shared with me. I have learned a great deal from each of you and consider you both great mentors of mine. I gratefully acknowledge the numerous graduate students, staff members and student workers who contributed significantly to the success of my research and made my graduate education memorable. Your friendship and support have been invaluable. A special thank you to Dr. Angela Laury-Shaw, Rebecca McCarthy, Amy Parks, Max Wolf, Kathleen Fermin, Tanya Jackson, Martha Maradiaga, Ashley Hartzog-Hawkins, Alexandra Calle, Jake Elder and Tyson Brown who devoted a great deal of time to my project. I appreciate each of you and your dedication was invaluable. ii Texas Tech University, Sara Elizabeth Gragg, December 2012 I thank Texas Tech University for the financial assistance provided throughout my program. My educational and personal experiences at Texas Tech University have been superb and I will always remember my graduate school years fondly. To Dr. Dayna Brichta-Harhay, you have been an excellent mentor and friend throughout our collaborative research efforts. Thank you for going above and beyond and having my best interest in mind at all times. Your support and guidance is greatly appreciated. I recognize the important role the United States Meat Animal Research Center scientists played in the completion of my research and I specifically thank Drs. Terry Arthur, Joseph “Mick” Bosilevac, Norasak Kalchayanand, Rong Wang, John Schmidt, Steven Shackelford and Tommy Wheeler for their efforts. I also thank Dr. Tom Edrington at the Southern Plains Agricultural Research Center for his assistance. I thank the numerous commercial abattoirs and industry personnel who made my research possible. Their assistance and cooperation was instrumental throughout my project. To Dr. Todd Brashears, you have been an important mentor since high school and I appreciate the impact you have had on my life. My family has been a constant source of encouragement and I am thankful for their unwavering support. I specifically acknowledge the iii Texas Tech University, Sara Elizabeth Gragg, December 2012 unconditional love and continual praise from my mother, Arnita Endacott. Thank you for being a wonderful role model and one of my biggest fans. To my husband, J.D. Gragg, I thank you for wholeheartedly embracing my career goals and playing an integral role in achieving them. Your steadfast support has made every challenge easier and each success more joyful. Thank you for happily adjusting your life and traversing this journey with me. I thank my son, Barrett Gragg, for providing a continual source of joy and inspiration. You joined our family in the midst of my doctoral education and brought a new depth to my passion for improving food safety and public health. I am proud to be your mother and am so thankful for the daily encouragement you provide. I praise God for the blessings He has bestowed upon me and the love He reveals on a daily basis. May He be glorified in all of my endeavors. iv Texas Tech University, Sara Elizabeth Gragg, December 2012 TABLE OF CONTENTS ACKNOWLEDGEMENTS ......................................................................................ii ABSTRACT ........................................................................................................ viii LIST OF TABLES ................................................................................................. x LIST OF FIGURES .............................................................................................. xii CHAPTER I: INTRODUCTION ............................................................................. 1 Literature Cited .................................................................................................. 5 CHAPTER II: REVIEW OF THE LITERATURE .................................................... 7 Salmonella species ........................................................................................... 7 Introduction .................................................................................................... 7 Classification .................................................................................................. 8 Salmonella-Associated Diseases ................................................................... 9 Antimicrobial Susceptibility........................................................................... 15 Salmonella Epidemiology ................................................................................ 21 Host Adaptation of Salmonella Serotypes .................................................... 21 Salmonella Habitat and Environmental Distribution ..................................... 22 Burden of Salmonellosis .............................................................................. 24 Economic Burden of Salmonellosis ................................................................. 26 Salmonella in Cattle ........................................................................................ 27 Salmonellosis ............................................................................................... 27 Prevalence, S. enterica Serotypes and Antimicrobial Susceptibility ............. 28 Prevalence in Beef Products and Antimicrobial Susceptibility...................... 37 Prevalence in Lymph Nodes and Antimicrobial Susceptibility ...................... 39 The Lymphatic System .................................................................................... 42 v Texas Tech University, Sara Elizabeth Gragg, December 2012 Literature Cited ................................................................................................ 46 CHAPTER III: OBJECTIVE I SALMONELLA ENTERICA CARRIAGE IN SUBILIAC LYMPH NODES OF CULL AND FEEDLOT CATTLE AT HARVEST ............................................................ 60 Introduction ..................................................................................................... 60 Materials and Methods .................................................................................... 61 Sample collection ......................................................................................... 61 Lymph node sample processing and Salmonella detection ......................... 62 Antimicrobial susceptibility testing ................................................................ 63 Salmonella enumeration .............................................................................. 63 Statistical analysis ........................................................................................ 64 Results ............................................................................................................ 65 Salmonella prevalence and enumeration ..................................................... 65 Salmonella serotypes and antimicrobial susceptibility phenotypes .............. 67 Discussion ....................................................................................................... 68 Conclusions ..................................................................................................... 71 Literature Cited ................................................................................................ 72 CHAPTER IV: OBJECTIVE II PREVALENCE AND CHARACTERIZATION OF SALMONELLA ISOLATES RECOVERED FROM THE LYMPH NODES, FECES AND HIDES OF CATTLE PRESENTED FOR HARVEST AT A SLAUGHTER FACILITY IN MEXICO ....... 81 Introduction ..................................................................................................... 81 Materials and Methods .................................................................................... 84 Sample collection ......................................................................................... 84 Lymph node analysis ................................................................................... 84 vi Texas Tech University, Sara Elizabeth Gragg, December 2012 Fecal and hide analysis................................................................................ 85 Pulsed-field gel electrophoresis (PFGE) ...................................................... 85 Salmonella serotyping .................................................................................. 86 Antimicrobial susceptibility ..........................................................................