Guinea pig infection with the intracellular pathogen Rhodococcus equi

Guinea pig infection with the intracellular pathogen Rhodococcus equi

•Guinea pigs tolerate R. equi airway infection without clinical signs of pneumonia.•R. equi can be detected in lungs of infected guinea pigs until day 7 PI.•Low- and high-dose infection induced similar lung cellularity and no lesions. Rhodococcus equi is an opportunistic, intracellular pathogen that...

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Bibliographic Details
Published in:Veterinary microbiology Vol. 215; pp. 18 - 22
Main Authors: Bordin, Angela I., Gressler, Leticia T., Alexander, Ellen Ruth C., Sule, Preeti, Cirillo, Jeffrey D., Edwards, John F., Cohen, Noah D.
Format: Journal Article
Language:English
Published: Netherlands Elsevier B.V 01-02-2018
Elsevier BV
Subjects:
Animal diseases
Animal model
Experimental infection
Guinea pigs
Histology
Infection
Inflammation
Inoculum
Intracellular
Juveniles
Lung
Lungs
Lymphocytes B
Lymphocytes T
Macrophages
Opportunist infection
Pathogens
Pneumonia
Respiratory pathogen
Rhodococcus
Rhodococcus equi
Infection
Animal model
Respiratory pathogen
Pneumonia
Lung
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Summary:•Guinea pigs tolerate R. equi airway infection without clinical signs of pneumonia.•R. equi can be detected in lungs of infected guinea pigs until day 7 PI.•Low- and high-dose infection induced similar lung cellularity and no lesions. Rhodococcus equi is an opportunistic, intracellular pathogen that causes pyogranulomatous pneumonia in foals and immunocompromised people. Currently, there is no experimental model of R. equi pneumonia other than intra-bronchial experimental infection of foals with R. equi, which is labor-intensive and costly. This study’s objective was to develop a guinea pig (GP) model of R. equi pneumonia that would facilitate development of novel approaches for controlling and preventing this disease. Guinea pigs were infected with either 101, 102, 103, or 104 colony forming units (CFUs) of a virulent strain of R. equi using a Madison aerosol chamber, or 106 or 107 CFUs of this strain intratracheally. Animals were monitored daily for clinical signs of pneumonia, and were euthanized and necropsied on days 1, 3, 7, or 35 post-infection (PI). Lung homogenates were plated onto selective agar to determine bacterial load. No clinical signs of disease were observed regardless of the inoculum dose or infection method. No bacteria were recovered from GPs euthanized at 35 days PI. Histology and immunostaining of T-cells, B-cells, and macrophages in lungs showed that inflammatory responses in infected GPs were similarly unremarkable irrespective of dose or route of infection. Guinea pigs appear to be resistant to pulmonary infection with virulent R. equi even at doses that reliably produce clinical pneumonia in foals.
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ISSN:0378-1135
1873-2542
DOI:10.1016/j.vetmic.2017.11.019