Rhodococcus Flashcards
(26 cards)
What are the characteristics of rhodococcus organisms?
Aerobic, non-sporulating, not motile, gram +, mostly benign, only a few are pathogenic.
Organisms of the genus rhodococcus are closely related to what other organisms?
Mycobacteria and Corynebacteria.
Rhodococcus organisms thrive in what conditions?
Soil, water, and eukaryotic cells.
In what way is rhodococcus closely related to Mycobacteria?
Has some kind of waxy material in the cell wall.
Describe the shape of rhodococcus equi.
Coccobacillus: has the ability to exist as a coccus or bacillus or intermediate form.
Why is it called rhodococcus?
Ability to form a red, salmon-colored colony.
R. equi causes zoonotic infections in what species mainly?
Grazing animals mainly horses and foals.
R. equi rarely infects which individuals?
Immunocompetent humans.
What does it mean that R. equi is a facultative intracellular organism?
Prefers to be taken up by a macrophage so that they can prevent the lysosome from fusing with the phagosome.
What is the common name for R. equi?
Equine Foal Pneumonia.
How is R. equi transmitted?
Mainly through inhalation, but also ingestion of contaminated food or water.
What are the virulence factors of R. equi?
Virulence-assoc proteins (VapA), Exoenzymes (cholesterol oxidase and PLC), Mycolic acids in cell wall.
What is the role of virulence associated proteins (VapA) as virulence factors of R. equi?
Induce humoral immune response; antibodies enhance engulfment by membrane.
What is the role of exoenzymes as virulence factors of R. equi?
Membranolytic.
What is the role of cell wall mycolic acids as virulence factors of R. equi?
Inhibit lysosome-phagosome fusion.
Where does replication occur for R. equi?
In macrophages.
The death of macrophages results in what aspect of pathogenesis of R. equi?
Release of degradative enzymes.
Suppurative bronchopneumonia due to R. equi causes what?
Multiple abscesses.
Bacteremia due to R. equi causes what?
Dissemination of organisms to internal organs.
Ingestion of R. equi causes what?
Necrotizing enterocolitis.
Describe the clinical presentation of R. equi.
Not very obvious until the animal is very sick; foal not nursing well, fever and coughing; depressed and heavy breathing; some foals die suddenly without much warning.
Necropsy of an animal with R. equi will reveal what?
Large lung abscesses or ruptured abdominal abscesses.
How is the CAMP test used for R. equi?
Results in a spade-shaped area of hemolysis when inoculated at 90 degrees to Staph. aureus on blood agar.
R. equi in horses causes what infections?
Pleuropneumonia, abortion, etc.
