Rhodococcus equi

Rhodococcus equi
Scientific classification
Domain:	Bacteria
Phylum:	Actinomycetota
Class:	Actinomycetia
Order:	Mycobacteriales
Family:	Nocardiaceae
Genus:	Rhodococcus
Species:	R. equi
Binomial name
Rhodococcus equi (Magnusson 1923) Goodfellow and Alderson 1977 (Approved Lists 1980)

Rhodococcus equi is a

• Pigs (wild and domestic)
• Goats
• Horses
• Sheep
• Cattle
• Humans
• Cats may become infected if wound is exposed. ^{[citation needed]}

Virulence

The most common route of infection in horses is likely via inhalation of contaminated dust particles. Inhaled

The variable region of the virulence plasmid contain genes that are highly expressed following phagocytosis of R. equi by macrophages.[11] This variable region is believed to be a pathogenicity island that contains genes essential for virulence.

A hallmark of the pathogenicity island (PAI) is that many genes within it do not have homologues in other species. The most notable of these are the virulence-associated protein (vap) genes. All foals infected with R. equi produce high levels of antibodies specific for vapA, the first vap gene to be characterised. Deletion of vapA renders the resulting strain avirulent.^[12] In addition to vapA, the PAI encodes a further five full-length vap homologues, one truncated vap gene, and two vap pseudogenes. The porcine PAI contains five full-length vap genes, including the vapA homologue, vapB. In addition to these unique genes, the PAI contains genes that have a known function, in particular two regulatory genes encoding the LysR-type regulator VirR and the response regulator Orf8. These two proteins have been shown to control expression of a number of PAI genes including vapA.^[13] Other genes have homology to transport proteins and enzymes. However, the functionality of these genes or how the proteins encoded within PAI subvert the macrophage has not yet been established.^{[citation needed]}

Taxonomic debate

While this organism is generally known as Rhodococcus equi, there has been taxonomic debate since the 1980s^[14] about whether this name is the valid name, with Rhodococcus hoagii and Prescottella equi both proposed as official alternative names.^[15] Other names used in literature include Nocardia restricta,^[14] Corynebacterium equi,^[16] Bacillus hoagii,^[16] Corynebacterium purulentus,^[16] Mycobacterium equi,^[16] Mycobacterium restrictum,^[16] and Proactinomyces restrictus.^[16]

References