The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform
Matthew K Waldor - One of the best experts on this subject based on the ideXlab platform.
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Autotransporters but not pAA are critical for Rabbit colonization by Shiga toxin-producing Escherichia coli O104:H4
2016Co-Authors: Diana Munera, Jennifer M Ritchie, Brigid M Davis, Sk Hatzios, Ee Schadt, Rod Bronson, Matthew K WaldorAbstract:The outbreak of diarrhea and hemolytic uremic syndrome that occurred in Germany in 2011 was caused by a Shiga toxin-producing enteroaggregative Escherichia coli (EAEC) strain. The strain was classified as EAEC due to the presence of a plasmid (pAA) that mediates a characteristic pattern of aggregative adherence on cultured cells, the defining feature of EAEC that has classically been associated with virulence. Here, we describe an Infant Rabbit-based model of intestinal colonization and diarrhea caused by the outbreak strain, which we use to decipher the factors that mediate the pathogen’s virulence. Shiga toxin is the key factor required for diarrhea. Unexpectedly, we observe that pAA is dispensable for intestinal colonization and development of intestinal pathology. Instead, chromosome-encoded autotransporters are critical for robust colonization and diarrheal disease in this model. Our findings suggest that conventional wisdom linking aggregative adherence to EAEC intestinal colonization is false for at least a subset of strains. Diarrheagenic E. coli is classified into six different ‘pathotypes ’ primarily based on the patterns and mechanisms by which these pathogens adhere to cultured human cells and o
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Current Protocols in Microbiology - Infant Rabbit Model for Diarrheal Diseases
Current protocols in microbiology, 2015Co-Authors: Sören Abel, Matthew K WaldorAbstract:Vibrio cholerae is the agent of cholera, a potentially lethal diarrheal disease that remains a significant threat to populations in developing nations. The Infant Rabbit model of cholera is the only non-surgical small animal model system that closely mimics human cholera. Following orogastric inoculation, V. cholerae colonizes the intestines of Infant Rabbits, and the animals develop severe cholera-like diarrhea. In this unit, we provide a detailed description of the preparation of the V. cholerae inoculum, the inoculation process and the collection and processing of tissue samples. This infection model is useful for studies of V. cholerae factors and mechanisms that promote its intestinal colonization and enterotoxicity, as well as the host response to infection. The Infant Rabbit model of cholera enables investigations that will further our understanding of the pathophysiology of cholera and provides a platform for testing new therapeutics.
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Infant Rabbit model for diarrheal diseases
Current protocols in microbiology, 2015Co-Authors: Matthew K Waldor, Sören AbelAbstract:Vibrio cholerae is the agent of cholera, a potentially lethal diarrheal disease that remains a significant threat to populations in developing nations. The Infant Rabbit model of cholera is the only non-surgical small animal model system that closely mimics human cholera. Following orogastric inoculation, V. cholerae colonizes the intestines of Infant Rabbits, and the animals develop severe cholera-like diarrhea. In this unit, we provide a detailed description of the preparation of the V. cholerae inoculum, the inoculation process and the collection and processing of tissue samples. This infection model is useful for studies of V. cholerae factors and mechanisms that promote its intestinal colonization and enterotoxicity, as well as the host response to infection. The Infant Rabbit model of cholera enables investigations that will further our understanding of the pathophysiology of cholera and provides a platform for testing new therapeutics.
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tn seq analysis of vibrio cholerae intestinal colonization reveals a role for t6ss mediated antibacterial activity in the host
Cell Host & Microbe, 2013Co-Authors: Matthew K Waldor, John J. MekalanosAbstract:Summary Analysis of genes required for host infection will provide clues to the drivers of evolutionary fitness of pathogens like Vibrio cholerae , a mounting threat to global heath. We used transposon insertion site sequencing (Tn-seq) to comprehensively assess the contribution of nearly all V. cholerae genes toward growth in the Infant Rabbit intestine. Four hundred genes were identified as critical to V. cholerae in vivo fitness. These included most known colonization factors and several new genes affecting the bacterium's metabolic properties, resistance to bile, and ability to synthesize cyclic AMP-GMP. Notably, a mutant carrying an insertion in tsiV3 , encoding immunity to a bacteriocidal type VI secretion system (T6SS) effector VgrG3, exhibited a colonization defect. The reduced in vivo fitness of tsiV3 mutants depends on their cocolonization with bacterial cells carrying an intact T6SS locus and VgrG3 gene, suggesting that the V. cholerae T6SS is functional and mediates antagonistic interbacterial interactions during infection.
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a double long polar fimbria mutant of escherichia coli o157 h7 expresses curli and exhibits reduced in vivo colonization
Infection and Immunity, 2012Co-Authors: Sonja J Lloyd, Jennifer M Ritchie, Jennifer L Greenwich, Matthew K Waldor, Maricarmen Rojaslopez, Carla A Blumentritt, Vsevolod L Popov, Alfredo G TorresAbstract:Escherichia coli O157:H7 causes food and waterborne enteric infections that can result in hemorrhagic colitis and life-threatening hemolytic uremic syndrome. Intimate adherence of the bacteria to intestinal epithelial cells is mediated by intimin, but E. coli O157:H7 also possess several other putative adhesins, including curli and two operons that encode long polar fimbriae (Lpf). To assess the importance of Lpf for intestinal colonization, we performed competition experiments between E. coli O157:H7 and an isogenic ΔlpfA1 ΔlpfA2 double mutant in the Infant Rabbit model. The mutant was outcompeted in the ileum, cecum, and midcolon, suggesting that Lpf contributes to intestinal colonization. In contrast, the ΔlpfA1 ΔlpfA2 mutant showed increased adherence to colonic epithelial cells in vitro. Transmission electron microscopy revealed curli-like structures on the surface of the ΔlpfA1 ΔlpfA2 mutant, and the presence of curli was confirmed by Congo red binding, immunogold-labeling electron microscopy, immunoblotting, and quantitative real-time reverse transcription-PCR (qRT-PCR) measuring csgA expression. However, deletion of csgA, which encodes the major curli subunit, does not appear to affect intestinal colonization. In addition to suggesting that Lpf can contribute to EHEC intestinal colonization, our observations indicate that the regulatory pathways governing the expression of Lpf and curli are interdependent.
Jennifer M Ritchie - One of the best experts on this subject based on the ideXlab platform.
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Infant Rabbit Model for Studying Shiga Toxin-Producing Escherichia coli.
Methods in molecular biology (Clifton N.J.), 2021Co-Authors: Jennifer M RitchieAbstract:Animal models represent part of the arsenal available to researchers studying the pathophysiology of potentially deadly human pathogens such as Shiga toxin-producing Escherichia coli (STEC). The optimal model may differ depending on what aspects of pathogen biology, disease progression, or host response are under study. Here, we provide detailed protocols for the Infant Rabbit model of STEC, which largely reproduces the intestinal disease seen following natural oral infection, and share insights from studies examining O157 and non-O157 serotypes.
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vibrio cholerae accessory colonisation factor acfc a chemotactic protein with a role in hyperinfectivity
Scientific Reports, 2018Co-Authors: Esmeralda Valiente, Jennifer M Ritchie, Cadi Davies, Dominic C Mills, Maria Getino, Brendan W WrenAbstract:Vibrio cholerae O1 El Tor is an aquatic Gram-negative bacterium responsible for the current seventh pandemic of the diarrheal disease, cholera. A previous whole-genome analysis on V. cholerae O1 El Tor strains from the 2010 epidemic in Pakistan showed that all strains contained the V. cholerae pathogenicity island-1 and the accessory colonisation gene acfC (VC_0841). Here we show that acfC possess an open reading frame of 770 bp encoding a protein with a predicted size of 28 kDa, which shares high amino acid similarity with two adhesion proteins found in other enteropathogens, including Paa in serotype O45 porcine enteropathogenic Escherichia coli and PEB3 in Campylobacter jejuni. Using a defined acfC deletion mutant, we studied the specific role of AcfC in V. cholerae O1 El Tor environmental survival, colonisation and virulence in two infection model systems (Galleria mellonella and Infant Rabbits). Our results indicate that AcfC might be a periplasmic sulfate-binding protein that affects chemotaxis towards mucin and bacterial infectivity in the Infant Rabbit model of cholera. Overall, our findings suggest that AcfC contributes to the chemotactic response of WT V. cholerae and plays an important role in defining the overall distribution of the organism within the intestine.
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Autotransporters but not pAA are critical for Rabbit colonization by Shiga toxin-producing Escherichia coli O104:H4
2016Co-Authors: Diana Munera, Jennifer M Ritchie, Brigid M Davis, Sk Hatzios, Ee Schadt, Rod Bronson, Matthew K WaldorAbstract:The outbreak of diarrhea and hemolytic uremic syndrome that occurred in Germany in 2011 was caused by a Shiga toxin-producing enteroaggregative Escherichia coli (EAEC) strain. The strain was classified as EAEC due to the presence of a plasmid (pAA) that mediates a characteristic pattern of aggregative adherence on cultured cells, the defining feature of EAEC that has classically been associated with virulence. Here, we describe an Infant Rabbit-based model of intestinal colonization and diarrhea caused by the outbreak strain, which we use to decipher the factors that mediate the pathogen’s virulence. Shiga toxin is the key factor required for diarrhea. Unexpectedly, we observe that pAA is dispensable for intestinal colonization and development of intestinal pathology. Instead, chromosome-encoded autotransporters are critical for robust colonization and diarrheal disease in this model. Our findings suggest that conventional wisdom linking aggregative adherence to EAEC intestinal colonization is false for at least a subset of strains. Diarrheagenic E. coli is classified into six different ‘pathotypes ’ primarily based on the patterns and mechanisms by which these pathogens adhere to cultured human cells and o
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a double long polar fimbria mutant of escherichia coli o157 h7 expresses curli and exhibits reduced in vivo colonization
Infection and Immunity, 2012Co-Authors: Sonja J Lloyd, Jennifer M Ritchie, Jennifer L Greenwich, Matthew K Waldor, Maricarmen Rojaslopez, Carla A Blumentritt, Vsevolod L Popov, Alfredo G TorresAbstract:Escherichia coli O157:H7 causes food and waterborne enteric infections that can result in hemorrhagic colitis and life-threatening hemolytic uremic syndrome. Intimate adherence of the bacteria to intestinal epithelial cells is mediated by intimin, but E. coli O157:H7 also possess several other putative adhesins, including curli and two operons that encode long polar fimbriae (Lpf). To assess the importance of Lpf for intestinal colonization, we performed competition experiments between E. coli O157:H7 and an isogenic ΔlpfA1 ΔlpfA2 double mutant in the Infant Rabbit model. The mutant was outcompeted in the ileum, cecum, and midcolon, suggesting that Lpf contributes to intestinal colonization. In contrast, the ΔlpfA1 ΔlpfA2 mutant showed increased adherence to colonic epithelial cells in vitro. Transmission electron microscopy revealed curli-like structures on the surface of the ΔlpfA1 ΔlpfA2 mutant, and the presence of curli was confirmed by Congo red binding, immunogold-labeling electron microscopy, immunoblotting, and quantitative real-time reverse transcription-PCR (qRT-PCR) measuring csgA expression. However, deletion of csgA, which encodes the major curli subunit, does not appear to affect intestinal colonization. In addition to suggesting that Lpf can contribute to EHEC intestinal colonization, our observations indicate that the regulatory pathways governing the expression of Lpf and curli are interdependent.
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an escherichia coli o157 specific engineered pyocin prevents and ameliorates infection by e coli o157 h7 in an animal model of diarrheal disease
Antimicrobial Agents and Chemotherapy, 2011Co-Authors: Jennifer M Ritchie, Jennifer L Greenwich, Brigid M Davis, Roderick T Bronson, Dana Gebhart, Steven R Williams, David W Martin, Dean Scholl, Matthew K WaldorAbstract:AvR2-V10.3 is an engineered R-type pyocin that specifically kills Escherichia coli O157, an enteric pathogen that is a major cause of food-borne diarrheal disease. New therapeutics to counteract E. coli O157 are needed, as currently available antibiotics can exacerbate the consequences of infection. We show here that orogastric administration of AvR2-V10.3 can prevent or ameliorate E. coli O157:H7-induced diarrhea and intestinal inflammation in an Infant Rabbit model of infection when the compound is administered either in a postexposure prophylactic regimen or after the onset of symptoms. Notably, administration of AvR2-V10.3 also reduces bacterial carriage and fecal shedding of this pathogen. Our findings support the further development of pathogen-specific R-type pyocins as a way to treat enteric infections.
Laurence J Carr - One of the best experts on this subject based on the ideXlab platform.
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the effect of acidosis on catecholamine responsiveness in isolated Infant Rabbit heart 260
Pediatric Research, 1996Co-Authors: Robert J Dimand, John M Spencer, Laurence J CarrAbstract:THE EFFECT OF ACIDOSIS ON CATECHOLAMINE RESPONSIVENESS IN ISOLATED Infant Rabbit HEART. † 260
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THE EFFECT OF ACIDOSIS ON CATECHOLAMINE RESPONSIVENESS IN ISOLATED Infant Rabbit HEART. † 260
Pediatric Research, 1996Co-Authors: Robert J Dimand, John M Spencer, Laurence J CarrAbstract:THE EFFECT OF ACIDOSIS ON CATECHOLAMINE RESPONSIVENESS IN ISOLATED Infant Rabbit HEART. † 260
John E Baker - One of the best experts on this subject based on the ideXlab platform.
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Mitochondrial big conductance KCa channel and cardioprotection in Infant Rabbit heart.
Journal of Cardiovascular Pharmacology, 2007Co-Authors: Ming Tao Jiang, William Hutchins, Eugene A. Konorev, Jidong Su, John E BakerAbstract:: Chronic hypoxia increases resistance to myocardial ischemia in Infants. Activation of the mitochondrial big conductance Ca(2+) -sensitive K channel (mitoBKCa) has been shown to be protective in adult hearts; however, its role in Infant hearts is unknown. Hearts from normoxic or hypoxic Infant Rabbits were perfused with a mitoKCa opener, NS1619, or blocker Paxilline before ischemia and reperfusion. Hypoxic hearts were more resistant to ischemia than normoxic hearts as manifested by a reduction in infarct size (9 +/- 5% versus 14 +/- 5%) and an increase in recovery of left ventricular developed pressure (LVDP) (69 +/- 7% versus 51 +/- 2%). NS1619 decreased infarct size in normoxic hearts from 14 +/- 5% to 10 +/- 5% and increased recovery of LVDP from 51 +/- 2% to 65 +/- 4%, but it had no effect on hypoxic hearts. Paxilline did not affect normoxic or hypoxic hearts. Activation of mitoBKCa protects normoxic Infant Rabbit hearts; however, cardioprotection by chronic hypoxia in Infant Rabbits does not appear involve mitoBKCa.
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Acute cardioprotective effects of erythropoietin in Infant Rabbits are mediated by activation of protein kinases and potassium channels
Basic Research in Cardiology, 2004Co-Authors: Parvaneh Rafiee, Jidong Su, Kirkwood A. Pritchard, James S. Tweddell, John E BakerAbstract:Erythropoietin is protective against cardiac ischemia, but the underlying mechanisms are unknown. We determined whether erythropoietin (0.5 – 10.0 U/ml) confers acute cardioprotection in Infant Rabbit hearts and the contribution of protein kinases, nitric oxide synthase and potassium channels to the underlying mechanism. Hearts from normoxic Infant New Zealand White Rabbits (n=8/group) were isolated and perfused in the Langendorff mode. Biventricular function was recorded under steady-state conditions prior to 30 min global no-flow ischemia and 35 min reperfusion. Administration of erythropoietin for 15 min immediately prior to ischemia resulted in a concentration-dependent increase in recovery of left and right ventricular developed pressure in Rabbit hearts following myocardial ischemia and reperfusion. The optimal concentration of erythropoietin that afforded maximum recovery of developed pressure was manifest at 1.0 U/ml. Erythropoietin (1.0 U/ml) treatment resulted in phosphorylation of PKC, p38 MAP kinase and p42/44 MAP kinase. The cardioprotective effects of erythropoietin were abolished by the protein kinase inhibitors SB203580 (p38 MAP kinase), PD98059 (p42/44 MAP kinase) and chelerythrine (PKC) as well as the potassium channel blockers glibenclamide, HMR 1098, 5-HD and Paxilline. Nitrite and nitrate release from hearts before (2.3 ± 0.9 nmol/min/g) and after (2.4 ± 1.9 nmol/min/g) 15 min treatment with erythropoietin (1.0 U/ml) were not different. L-NAME and L-NMA did not block the cardioprotective effect of erythropoietin. We conclude the rapid activation of potassium channels and protein kinases by erythropoietin represents an important new mechanism for increasing cardioprotection.
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Oxidative stress and adaptation of the Infant heart to hypoxia and ischemia.
Antioxidants & redox signaling, 2004Co-Authors: John E BakerAbstract:The potential contribution of oxidative stress to cardioprotection in Infants induced by adaptation to chronic hypoxia and by ischemic preconditioning is poorly understood. Under conditions of oxidative stress, reactive oxygen species and reactive nitrogen species may contribute to phenotypic changes in hearts adapted to chronic hypoxia and to the pathogenesis of myocardial injury during both ischemia/reperfusion and hypoxia/reoxygenation. Hearts from Infant Rabbits normoxic from birth can be preconditioned by brief periods of ischemia. In contrast, hearts from Infant Rabbits adapted to hypoxia from birth appear resistant to ischemic preconditioning. Chronically hypoxic Infant Rabbit hearts are already resistant to ischemia compared with age-matched normoxic controls, and thus additional cardioprotection by ischemic preconditioning may not be possible. Endothelial nitric oxide synthase (NOS3) protein and its product nitric oxide are increased, but not NOS3 message, in chronically hypoxic Infant hearts to protect against ischemia. Chronic hypoxia from birth also increases cardioprotection of Infant hearts by increasing association of heat shock protein 90 with NOS3. Normoxic Infant hearts also generate more superoxide by an N(omega)-nitro-L-arginine methyl ester-inhibitable mechanism than chronically hypoxic hearts. Thus, NOS3 appears to be critically important in adaptation of Infant hearts to chronic hypoxia and in resistance to subsequent ischemia by regulating the production of reactive oxygen and nitrogen species.
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direct effects of halothane and isoflurane in Infant Rabbit hearts with right ventricular hypertrophy secondary to chronic hypoxemia
Anesthesia & Analgesia, 1995Co-Authors: Barbara W Palmisano, John E Baker, Robert W Mehner, David F Stowe, Zeljko J Bosnjak, John P KampineAbstract:In this study we compared the direct myocardial effects of halothane and isoflurane between chronically hypoxemic and normoxemic Infant hearts with an isolated, perfused, nonworking Rabbit heart model. Anesthetic effects were measured on heart rate, atrioventricular time, coronary flow, O2 consumption and extraction, and left and right ventricular peak systolic and end-diastolic pressures, nd -dP/dtmax; and tau, the time constant of isovolumic relaxation. Control values were similar between chronically hypoxemic and normoxemic groups except for variables affected by right ventricular (RV) hypertrophy in chronically hypoxemic hearts. For these variables values were significantly larger in the chronically hypoxemic group (P < or = 0.05): coronary flow (12.3 +/- 0.4 vs 10.3 +/- 0.3 mL.min-1.g-1), RV peak systolic pressure (68 +/- 3 vs 53 +/- 4 mm Hg), RV + dP/dtmax (1.42 +/- 0.07 vs 1.03 +/- 0.08 mm Hg/ms), and RV -dP/dtmax (-0.99 +/- 0.04 vs -0.78 +/- 0.08 mm Hg/ms). (Values are mean +/- SEM.) With anesthesia, values were similar between chronically hypoxemic and normoxemic groups except for coronary flow, which was significantly greater in chronically hypoxemic hearts for both anesthetics (14.1 +/- 0.9 vs 11.3 +/- 0.7 mL.min-1.g-1 for halothane and 15.4 +/- 1.1 vs 12.2 +/- 0.6 mL.min-1.g-1 for isoflurane). The degree of depression of RV peak systolic pressure and RV + dP/dtmax by both anesthetics, and of RV - dP/dtmax by isoflurane, was significantly larger in chronically hypoxemic hearts because these hearts had greater control values but similar anesthetic values to normoxemic hearts.(ABSTRACT TRUNCATED AT 250 WORDS)
Matthew K Waldo - One of the best experts on this subject based on the ideXlab platform.
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an oral inoculation Infant Rabbit model for shigella infection
Mbio, 2020Co-Authors: Carole J Kuehl, Jonatha D Dgama, Matthew K WaldoAbstract:ABSTRACT Shigella species cause diarrheal disease globally. Shigellosis is typically characterized by bloody stools and colitis with mucosal damage and is the leading bacterial cause of diarrheal death worldwide. After the pathogen is orally ingested, it invades and replicates within the colonic epithelium through mechanisms that rely on its type III secretion system (T3SS). Currently, oral infection-based small animal models to study the pathogenesis of shigellosis are lacking. Here, we found that orogastric inoculation of Infant Rabbits with Shigella flexneri resulted in diarrhea and colonic pathology resembling that found in human shigellosis. Fasting animals prior to S. flexneri inoculation increased the frequency of disease. The pathogen colonized the colon, where both luminal and intraepithelial foci were observed. The intraepithelial foci likely arise through S. flexneri spreading from cell to cell. Robust S. flexneri intestinal colonization, invasion of the colonic epithelium, and epithelial sloughing all required the T3SS as well as IcsA, a factor required for bacterial spreading and adhesion in vitro. Expression of the proinflammatory chemokine interleukin 8 (IL-8), detected with in situ mRNA labeling, was higher in animals infected with wild-type S. flexneri versus mutant strains deficient in icsA or T3SS, suggesting that epithelial invasion promotes expression of this chemokine. Collectively, our findings suggest that oral infection of Infant Rabbits offers a useful experimental model for studies of the pathogenesis of shigellosis and for testing of new therapeutics. IMPORTANCEShigella species are the leading bacterial cause of diarrheal death globally. The pathogen causes bacillary dysentery, a bloody diarrheal disease characterized by damage to the colonic mucosa and is usually spread through the fecal-oral route. Small animal models of shigellosis that rely on the oral route of infection are lacking. Here, we found that orogastric inoculation of Infant Rabbits with S. flexneri led to a diarrheal disease and colonic pathology reminiscent of human shigellosis. Diarrhea, intestinal colonization, and pathology in this model were dependent on the S. flexneri type III secretion system and IcsA, canonical Shigella virulence factors. Thus, oral infection of Infant Rabbits offers a feasible model to study the pathogenesis of shigellosis and to develop and test new therapeutics.
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an oral inoculation Infant Rabbit model for shigella infection
bioRxiv, 2019Co-Authors: Carole J Kuehl, Jonatha D Dgama, Matthew K WaldoAbstract:Abstract Shigella species cause diarrheal disease globally. Shigellosis is typically characterized by bloody stools and colitis with mucosal damage and is the leading bacterial cause of diarrheal death worldwide. Following oral ingestion, the pathogen invades and replicates within the colonic epithelium through mechanisms that rely on its type III secretion system (T3SS). Currently, oral infection-based small animal models to study the pathogenesis of shigellosis are lacking. Here, we found that oro-gastric inoculation of Infant Rabbits with S. flexneri resulted in diarrhea and colonic pathology resembling that found in human shigellosis. Fasting animals prior to S. flexneri inoculation increased the frequency of disease. The pathogen colonized the colon, where both luminal and intraepithelial foci were observed. The intraepithelial foci likely arise through S. flexneri spreading from cell-to-cell. Robust S. flexneri intestinal colonization, invasion of the colonic epithelium, and epithelial sloughing all required the T3SS as well as IcsA, a factor required for bacterial spreading and adhesion in vitro. Expression of the proinflammatory chemokine IL-8, detected with in situ mRNA labeling, was higher in animals infected with wild-type S. flexneri versus mutant strains deficient in icsA or T3SS, suggesting that epithelial invasion promotes expression of this chemokine. Collectively, our findings suggest that oral infection of Infant Rabbits offers a useful experimental model for studies of the pathogenesis of shigellosis and for testing of new therapeutics. Importance Shigella species are the leading bacterial cause of diarrheal death globally. The pathogen causes bacillary dysentery, a bloody diarrheal disease characterized by damage to the colonic mucosa and is usually spread through the fecal-oral route. Small animal models of shigellosis that rely on the oral route of infection are lacking. Here, we found that oro-gastric inoculation of Infant Rabbits with S. flexneri led to a diarrheal disease and colonic pathology reminiscent of human shigellosis. Diarrhea, intestinal colonization and pathology in this model were dependent on the S. flexneri type III secretion system and IcsA, canonical Shigella virulence factors. Thus, oral infection of Infant Rabbits offers a feasible model to study the pathogenesis of shigellosis and to develop and test new therapeutics.