Disseminated<i>Rhodococcus equi</i>Infection in Two Goats

Davis, Wendell; Steficek, Barbara A.; Watson, G. L.; Yamini, B.; Madarame, Hiroo; Takaı̈, Shinji; Render, James A.

doi:10.1354/vp.36-4-336

Cited by 25 publications

(37 citation statements)

References 17 publications

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“…In the human host the infection presents usually as tuberculosis-like cavitary pneumonia or bacteremia (2,36). R. equi is also being increasingly reported in other animal species, mainly associated with extrapulmonary, purulent, caseating infections (5,33). In cattle the organism is typically isolated from chronic retropharyngeal, bronchial, or mediastinal pyogranulomatous lymphadenitis (6) and in pigs from submaxillary lymph nodes (18).…”

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Internally Controlled Real-Time PCR Method for Quantitative Species-Specific Detection and vapA Genotyping of Rhodococcus equi

Rodrı́guez-Lázaro

Lewis

Ocampo-Sosa

et al. 2006

Appl Environ Microbiol

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We developed a novel quantitative real-time PCR (Q-PCR) method for the soil actinomycete Rhodococcus equi, an important horse pathogen and emerging human pathogen. Species-specific quantification was achieved by targeting the chromosomal monocopy gene choE, universally conserved in R. equi. The choE Q-PCR included an internal amplification control (IAC) for identification of false negatives. A second Q-PCR targeted the virulence plasmid gene vapA, carried by most horse isolates but infrequently found in isolates from other sources. The choE-IAC and vapA assays were 100% sensitive and specific as determined using 178 R. equi isolates, 77 nontarget bacteria, and a panel of 60 R. equi isolates with known vapA ؉ and vapA-negative (including vapB ؉ ) plasmid genotypes. The vapA ؉ frequency among isolate types was as follows: horse, 85%; human, 20%; bovine and pig, 0%; others, 27%. The choE-IAC Q-PCR could detect up to one genome equivalent using R. equi DNA or 100 bacteria/ml using DNA extracted from artificially contaminated horse bronchoalveolar lavage (BAL) fluid. Quantification was linear over a 6-log dynamic range down to Ϸ10 target molecules (or 1,000 CFU/ml BAL fluid) with PCR efficiency E of >0.94. The vapA assay had similar performance but appeared unsuitable for accurate (vapA ؉ ) R. equi quantification due to variability in target gene or plasmid copy number (1 to 9). The dual-reaction Q-PCR system here reported offers a useful tool to both medical and veterinary diagnostic laboratories for the quantitative detection of R. equi and (optional) vapA ؉ "horsepathogenic" genotype determination.

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Internally Controlled Real-Time PCR Method for Quantitative Species-Specific Detection and vapA Genotyping of Rhodococcus equi

Rodrı́guez-Lázaro

Lewis

Ocampo-Sosa

et al. 2006

Appl Environ Microbiol

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“…15 However, in humans, goats, and occasionally, foals, R. equi strains lacking this virulence factor can also produce disease. 4,14,15 R. equi causes pyogranulomatous pneumonia, lymphadenitis, polyarthritis, and ulcerative enteritis in 2-6 month old foals. 5 Sporadically, it produces numerous other lesions in horses, such as peritonitis, pleuritis and pericarditis, renal infarction, septicemia, retrobulbar abscess formation, suppurative osteomyelitis, nephritis and hepatitis with abscesses, ulcerative lymphangitis, and dermatitis with abscesses.…”

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Two Cases of Equine Abortion Caused by Rhodococcus equi

Szeredi¹,

Molnár²,

Glávits³

et al. 2006

Vet Pathol

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Abstract. Rhodococcus equi was isolated from lung, liver, spleen, and stomach content of two aborted equine fetuses of 7 and 8 months gestation from two different farms. Lesions included diffuse pyogranulomatous pneumonia with numerous Gram-positive coccobacilli within the cytoplasm of macrophages, multinucleated Langhans giant cells and neutrophils, and enhanced extramedullary hematopoiesis with megakaryocytosis within the liver and spleen. Detection of R. equi was made by bacteriology and immunohistochemistry for R. equi and VapA, the virulence factor of R. equi. R. equi and VapA were identified within the lungs of both fetuses, and its distribution correlated with lesions. Fetal lesions were similar to those observed in foals. We speculate that the fetuses contracted infection from the placenta by normal breathing movements or by swallowing of the amniotic fluid contaminated with R. equi.

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“…The vapA gene was expressed in a plasmid-cured isogenic strain of R. equi, but this was not sufficient to restore the capacity to proliferate in macrophages and to colonize the lungs of experimentally infected foals (10), questioning a role for VapA in virulence. The virulence plasmid itself does not appear to be essential for pathogenesis in non-horse hosts, as it is not always detected in clinical isolates from humans and other animal species (4,7,33,48,49,52). This suggests that chromosomally determined factors are involved in R. equi pathogenicity.…”

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Identification and Mutagenesis by Allelic Exchange ofchoE, Encoding a Cholesterol Oxidase from the Intracellular PathogenRhodococcus equi

et al. 2001

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The virulence mechanisms of the facultative intracellular parasite Rhodococcus equi remain largely unknown. Among the candidate virulence factors of this pathogenic actinomycete is a secreted cholesterol oxidase, a putative membrane-damaging toxin. We identified and characterized the gene encoding this enzyme, the choE monocistron. Its protein product, ChoE, is homologous to other secreted cholesterol oxidases identified in Brevibacterium sterolicum and Streptomyces spp. ChoE also exhibits significant similarities to putative cholesterol oxidases encoded by Mycobacterium tuberculosis and Mycobacterium leprae. Genetic tools for use with R. equi are poorly developed. Here we describe the first targeted mutagenesis system available for this bacterium. It is based on a suicide plasmid, a selectable marker (the aacC4 apramycin resistance gene from Salmonella), and homologous recombination. The choE allele was disrupted by insertion of the aacC4 gene, cloned in pUC19 and introduced by electroporation in R. equi. choE recombinants were isolated at frequencies between 10 ؊2 and 10 ؊3 . Twelve percent of the recombinants were double-crossover choE mutants. The choE mutation was associated with loss of cooperative (CAMP-like) hemolysis with sphingomyelinase-producing bacteria (Listeria ivanovii). Functional complementation was achieved by expression of choE from pVK173-T, a pAL5000 derivative conferring hygromycin resistance. Our data demonstrate that ChoE is an important cytolytic factor for R. equi. The highly efficient targeted mutagenesis procedure that we used to generate choE isogenic mutants will be a valuable tool for the molecular analysis of R. equi virulence.

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DisseminatedRhodococcus equiInfection in Two Goats

Cited by 25 publications

References 17 publications

Internally Controlled Real-Time PCR Method for Quantitative Species-Specific Detection and vapA Genotyping of Rhodococcus equi

Internally Controlled Real-Time PCR Method for Quantitative Species-Specific Detection and vapA Genotyping of Rhodococcus equi

Two Cases of Equine Abortion Caused by Rhodococcus equi

Identification and Mutagenesis by Allelic Exchange ofchoE, Encoding a Cholesterol Oxidase from the Intracellular PathogenRhodococcus equi

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