The effect of bacterial dose and foal age at challenge on Rhodococcus equi infection.
Abstract: While Rhodococcus equi remains the most common cause of subacute or chronic granulomatous bronchopneumonia in foals, development of a relevant model to study R. equi infection has proven difficult. The objective of this study was to identify a challenge dose of R. equi that resulted in slow progressive disease, spontaneous regression of lung lesions and age-dependent susceptibility. Foals less than one-week of age were challenged intratracheally using either 10(6), 10(5), 10(4), 10(3) or 10(2) cfu of R. equi. Two doses (10(3) cfu and 10(5) cfu) were used to challenge 2 and 3-week-old, and 3 and 6-week-old foals, respectively. Physical examination, thoracic ultrasound and blood work were performed. Foals were euthanized at the end of the study or when clinical signs of pneumonia developed. All foals were necropsied and their lung lesions scored. Foals challenged with low concentrations of R. equi developed slow progressive pneumonia and approximately 50% of the foals recovered spontaneously. Likewise, macroscopic (>1cm diameter) pyogranulomatous lesions were only observed when low doses of R. equi were used. Clinical pneumonia was not seen after low dose challenge in the 3-week-old foals or in the 6-week-old foals. This study demonstrates that the use of low doses of R. equi to challenge neonatal foals provides an improved model for studying this disease. Furthermore, susceptibility to R. equi infection was shown to diminish early in the foal's life, as has been reported in the field.
Copyright © 2013 Elsevier B.V. All rights reserved.
Publication Date: 2013-09-24 PubMed ID: 24139178DOI: 10.1016/j.vetmic.2013.09.018Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research aimed to develop a improved model for studying Rhodococcus equi infection in foals, a common cause of severe pneumonia. By varying the bacterial dose and the age of the foals, the study revealed that lower doses resulted in delayed development of disease and spontaneous recovery in approximately half of the cases, and that susceptibility to infection diminishes early in a foal’s life.
Research Objective
- The primary goal of the study was to establish a challenge dose of R. equi that leads to slow disease progression, self-healing of lung lesions, and age-dependent vulnerability. The research also aimed to understand the effect of bacterial dose and the age of the foal at the time of infection on the nature and progression of the disease.
Methodology
- Foals that were under one week of age were given doses of R. equi bacteria intratracheally at varying concentrations.
- Options for the dosage were 10(6), 10(5), 10(4), 10(3) or 10(2) cfu of R. equi, with the middle to lower ranges also used to infect foals of 2-3 weeks and 3-6 weeks of age.
- Physical examination, thoracic ultrasound, and blood work were conducted on the foals.
- Once clinical signs of pneumonia developed, or at the end of the study, the foals were euthanized, necropsied, and lung lesions were scored to determine the severity of the disease.
Findings
- Lower dosage levels of R. equi resulted in slower disease progression and in almost 50% of these cases, the foals recovered on their own.
- Macroscopic pyogranulomatous lesions, which are a characteristic of R. equi infection, only occurred with the administration of lower doses.
- In foals challenged with a low dose at 3 and 6 weeks of age, pneumonia symptoms were not detected.
- The susceptibility to R. equi infection decreased as the foals got older, corroborating field observations.
Significance of the Study
- The study offers an improved research model for studying R. equi infection in foals by introducing low doses to neonatal foals.
- The findings validate field observations, contributing to a more extensive understanding of the disease and how to prevent or treat it effectively.
Cite This Article
APA
Sanz M, Loynachan A, Sun L, Oliveira A, Breheny P, Horohov DW.
(2013).
The effect of bacterial dose and foal age at challenge on Rhodococcus equi infection.
Vet Microbiol, 167(3-4), 623-631.
https://doi.org/10.1016/j.vetmic.2013.09.018 Publication
Researcher Affiliations
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546-0099, United States.
MeSH Terms
- Actinomycetales Infections / complications
- Actinomycetales Infections / mortality
- Actinomycetales Infections / veterinary
- Age Factors
- Animals
- Animals, Newborn
- Bacterial Load
- Erythrocyte Count
- Hemoglobins / analysis
- Horse Diseases / diagnostic imaging
- Horse Diseases / microbiology
- Horse Diseases / mortality
- Horse Diseases / pathology
- Horses
- Lymphocytes
- Pneumonia / diagnostic imaging
- Pneumonia / etiology
- Pneumonia / mortality
- Pneumonia / veterinary
- Rhodococcus equi / physiology
- Survival Analysis
- Ultrasonography
Citations
This article has been cited 14 times.- Rivolta AA, Bujold AR, Wilmarth PA, Phinney BS, Navelski JP, Horohov DW, Sanz MG. Comparison of the broncoalveolar lavage fluid proteomics between foals and adult horses.. PLoS One 2023;18(9):e0290778.
- Cohen ND, Kahn SK, Bordin AI, Gonzales GM, da Silveira BP, Bray JM, Legere RM, Ramirez-Cortez SC. Association of pneumonia with concentrations of virulent Rhodococcus equi in fecal swabs of foals before and after intrabronchial infection with virulent R. equi.. J Vet Intern Med 2022 May;36(3):1139-1145.
- Rivolta AA, Pittman DC, Kappes AJ, Stancil RK, Kogan C, Sanz MG. The type of anticoagulant used for plasma collection affects in vitro Rhodococcus equi assays.. BMC Res Notes 2022 Feb 14;15(1):50.
- Cohen ND, Kahn SK, Cywes-Bentley C, Ramirez-Cortez S, Schuckert AE, Vinacur M, Bordin AI, Pier GB. Serum Antibody Activity against Poly-N-Acetyl Glucosamine (PNAG), but Not PNAG Vaccination Status, Is Associated with Protecting Newborn Foals against Intrabronchial Infection with Rhodococcus equi.. Microbiol Spectr 2021 Sep 3;9(1):e0063821.
- Bordin AI, Cohen ND, Giguère S, Bray JM, Berghaus LJ, Scott B, Johnson R, Hook M. Host-directed therapy in foals can enhance functional innate immunity and reduce severity of Rhodococcus equi pneumonia.. Sci Rep 2021 Jan 28;11(1):2483.
- Harvey AB, Bordin AI, Rocha JN, Bray JM, Cohen ND. Opsonization but not pretreatment of equine macrophages with hyperimmune plasma nonspecifically enhances phagocytosis and intracellular killing of Rhodococcus equi.. J Vet Intern Med 2021 Jan;35(1):590-596.
- Rakowska A, Cywinska A, Witkowski L. Current Trends in Understanding and Managing Equine Rhodococcosis.. Animals (Basel) 2020 Oct 18;10(10).
- Arencibia A, Corbera JA, Ramírez G, Díaz-Bertrana ML, Pitti L, Morales M, Jaber JR. Anatomical Assessment of the Thorax in the Neonatal Foal Using Computed Tomography Angiography, Sectional Anatomy, and Gross Dissections.. Animals (Basel) 2020 Jun 17;10(6).
- Rampacci E, Marenzoni ML, Giovagnoli S, Passamonti F, Coletti M, Pietrella D. Phenotypic Characterization of Rhodococcus equi Biofilm Grown In Vitro and Inhibiting and Dissolving Activity of Azithromycin/Rifampicin Treatment.. Pathogens 2019 Dec 4;8(4).
- Bujold AR, Lani NR, Sanz MG. Strain-to-strain variation of Rhodococcus equi growth and biofilm formation in vitro.. BMC Res Notes 2019 Aug 19;12(1):519.
- Tallmadge RL, Wang M, Sun Q, Felippe MJB. Transcriptome analysis of immune genes in peripheral blood mononuclear cells of young foals and adult horses.. PLoS One 2018;13(9):e0202646.
- Cywes-Bentley C, Rocha JN, Bordin AI, Vinacur M, Rehman S, Zaidi TS, Meyer M, Anthony S, Lambert M, Vlock DR, Giguère S, Cohen ND, Pier GB. Antibody to Poly-N-acetyl glucosamine provides protection against intracellular pathogens: Mechanism of action and validation in horse foals challenged with Rhodococcus equi.. PLoS Pathog 2018 Jul;14(7):e1007160.
- Rocha JN, Cohen ND, Bordin AI, Brake CN, Giguère S, Coleman MC, Alaniz RC, Lawhon SD, Mwangi W, Pillai SD. Oral Administration of Electron-Beam Inactivated Rhodococcus equi Failed to Protect Foals against Intrabronchial Infection with Live, Virulent R. equi.. PLoS One 2016;11(2):e0148111.
- Whitfield-Cargile CM, Cohen ND, Suchodolski J, Chaffin MK, McQueen CM, Arnold CE, Dowd SE, Blodgett GP. Composition and Diversity of the Fecal Microbiome and Inferred Fecal Metagenome Does Not Predict Subsequent Pneumonia Caused by Rhodococcus equi in Foals.. PLoS One 2015;10(8):e0136586.
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