DISSERTATION LABORATORY MOUSE MODELS FOR BARTONELLA BACTERIAL INFECTION: BACTEREMIA, HOST SPECIFICITY, AND PATHOLOGY Submitted by Leah Colton Department of Microbiology, Immunology, and Pathology In partial fulfillment of the requirements for the Degree of Doctor of Philosophy Colorado State University Fort Collins, Colorado Fall 2011 Doctoral Committee: Advisor: Brian Foy Co-Advisor: Michael Kosoy Richard Bowen Kenneth L. Gage ABSTRACT LABORATORY MOUSE MODELS FOR BARTONELLA BACTERIAL INFECTION: BACTEREMIA, HOST SPECIFICITY, AND PATHOLOGY Bartonella bacterial species are globally distributed in a diverse variety of mammalian reservoir hosts. Natural host infections are generally characterized by persistent bacteremias of long duration, seemingly without adverse host effect, whereas non-natural host infections can produce mild, self-limiting illnesses or more severe disease such as endocarditis. Incidental host infections seem to most closely resemble natural host infections when the taxonomic distance between the two hosts is small. The greater the taxonomic distance between the host of origin and the incidental host, the more likely it seems that the incidental host will either clear the bacteria or develop pathology following exposure. This level of bacterial host specificity has been demonstrated consistently and presents an enormous obstacle to the development of animal models, particularly murine models that reproduce characteristics of natural host infection or pathology consistent with human incidental infections. ii In this dissertation laboratory mouse models for bartonella infection are described following the introduction and literature review (Chapter 1). Chapter 2 reports infection of mice with bartonella strains from wild Mus species, simulating a cross-species host switch for the bacteria. Infected mice exhibited characteristics consistent with reports of natural rodent host infection. Chapter 3 reports on a mouse infection study using four rat bartonella strains, simulating a cross-genus host switch for the bacteria. Only one of the strains infected mice and alterations in bacteremia duration and magnitude were observed relative to those reported for natural host infections. Mice also displayed organ pathology following bacteremia resolution. Chapter 4 presents a mouse infection study using an Asian house shrew Bartonella elizabethae strain inoculated into three different laboratory mouse stocks. Mice of all three stocks developed bacteremia following bacterial exposures, a demonstration of cross-order host switching by the bacteria. No obvious differences in infection response were observed among the mice despite differences in their genetic backgrounds. Chapter 5 describes inoculation of aged mice with either a mouse bartonella strain or human Bartonella tamiae strains. Mice infected with the mouse strain developed bacteremia, whereas mice infected with B. tamiae did not, consistent with the idea that taxonomic distance between host of origin and incidental host can be a predictor of infection outcome. iii Chapter 6 details results of a study where aged mice were exposed to three different B. tamiae strains. The mice developed disease consistent with reports of human illness symptomatology. In summary (Chapter 7), these laboratory mouse models are presented as defined, scientific resources for research on Bartonella species host ecology, bacteria: host interactions, and transmission dynamics. iv TABLE OF CONTENTS ABSTRACT .......................................................................................... ii CHAPTER 1 ........................................................................................... BACKGROUND AND LITERATURE REVIEW .......................................... 1 THE GENUS BARTONELLA .................................................................... 1 BACTERIOLOGY ................................................................................. 6 Interactions with eukaryotic host cells ................................................ 7 Genetic and geographic diversity of bartonella strains ........................ 12 ECOLOGY OF ZOONOTIC BARTONELLAE .............................................. 14 Natural history of bartonellae infections in rodents ............................ 15 Rodent responses to naturally acquired bartonella infections ............... 22 Vector transmission of bartonellae among hosts ................................ 24 EPIDEMIOLOGY OF HUMAN BARTONELLA INFECTIONS ......................... 28 Human infections with zoonotic bartonellae ...................................... 32 Seroprevalence surveys for human exposures to zoonotic bartonellae .. 40 LABORATORY MOUSE MODELS FOR BARTONELLA INFECTION ................ 43 CHAPTER 2 ........................................................................................... EXPERIMENTAL INFECTION OF LABORATORY MICE WITH BARTONELLA STRAINS FROM WILD MUS SPECIES: A HOMOLOGOUS HOST-BACTERIA MODEL SYSTEM AT THE GENUS LEVEL ................... 51 INTRODUCTION ............................................................................... 51 MATERIALS AND METHODS ............................................................... 53 Mice and bacteria .......................................................................... 53 v Experimental design and blood collections ........................................ 54 Urine collections ............................................................................ 55 Testing samples for viable bartonella bacteria ................................... 56 RESULTS ......................................................................................... 56 Bacteremia kinetics in mice ............................................................ 56 Bacteria in urine ............................................................................ 61 DISCUSSION ................................................................................... 61 CHAPTER 3 ........................................................................................... EXPERIMENTAL INFECTION OF LABORATORY MICE WITH RAT BARTONELLA STRAINS: HOST SPECIFICITY, BACTEREMIA KINETICS, DOSE DEPENDENT RESPONSE AND PATHOLOGY .............................. 69 INTRODUCTION ............................................................................... 69 MATERIALS AND METHODS ............................................................... 71 Mice ............................................................................................ 71 Bacteria ....................................................................................... 71 Inoculation of mice and experimental design for the study .................. 73 Blood collections ........................................................................... 75 Testing for bacteremia ................................................................... 76 Histopathology .............................................................................. 76 RESULTS ......................................................................................... 77 Bacteremias in inoculated mice ....................................................... 77 Histopathological observations ........................................................ 81 DISCUSSION ................................................................................... 84 vi CHAPTER 4 ........................................................................................... EXPERIMENTAL INFECTION OF THREE LABORATORY MOUSE STOCKS WITH A SHREW ORIGIN BARTONELLA ELIZABETHAE STRAIN: HOST SPECIFICITY AND ZOONOTIC POTENTIAL ........................................ 89 INTRODUCTION ............................................................................... 89 MATERIALS AND METHODS ............................................................... 91 Mice and bacteria .......................................................................... 91 Experimental design ...................................................................... 92 Testing for bacteremia ................................................................... 92 RESULTS ......................................................................................... 93 Infection of SW mice ...................................................................... 94 Infection of BALB/c mice ................................................................ 94 Infection of C57BL/6 mice .............................................................. 95 DISCUSSION ................................................................................... 96 CHAPTER 5 ........................................................................................... EXPERIMENTAL INFECTION OF AGED LABORATORY MICE WITH A MOUSE ORIGIN BARTONELLA STRAIN AND THREE HUMAN ORIGIN BARTONELLA TAMIAE STRAINS: TAXONOMIC DISTANCE AS A PREDICTOR OF INFECTION OUTCOME ............................................ 101 INTRODUCTION ............................................................................. 101 MATERIALS AND METHODS ............................................................. 105 Mice and bacteria ........................................................................ 105 Blood collections and bacteremia testing ........................................ 106 vii RESULTS ....................................................................................... 107 DISCUSSION ................................................................................. 107 CHAPTER 6 ..........................................................................................