Rhodococcus Flashcards
What color is rhodococcus?
Red colored- after 24 hours produce pink colonies in the agar
Who are the main host for this bacteria?
Horses- Especially foals 1-6 months old
mainly associated with what types of lesions?
granulose and pyogranulous
What kind of cell wall does this bacteria have?
very Lipid rich!
Is rhodococcus acid fast positive or negative?
Acid fast positive- rich in mycolic acid
Rhodococcus is a facultative _____ organism
intracellular
What cells do Rhodococcus live in?
Macrophages- develop granulomas
What kind of immune response do we want for Rhodococcus?
cell mediated immune response- Th1
Is rhodococcus aerobic or anaerobic?
Aerobic
Rhodococcus is: catalase _____ oxidase ______ CAMP ______
positive, negative, positive
True or False: Rhodococcus is spore forming and non motile
FALSE- non- spore forming and non motile
Rhodococcus are gram positive ____
bacilli- (very small and can look like cocci) also can be pleomorphic with rods and cocci
Does Rhodococcus have a capsule?
Yes, they are encapsulated
Picture of Gram stain for Rhodococcus
Pleomorphic gram stain
Would Rhodococcus be positive or negative on the Ziehl-Neelsen stain?
positive, because this is the acid fast stain
What is the only pathogenic species of Rhodococcus?
Rhodococcus Equi
What does rhodococcus equi cause in foals?
pneumonia
The antibiotic that you use needs to ____ the cell
penetrate
What are the virulence factors of Rhodococcus?
Capsule, cell wall, and Vaps
Why does Rhodococcus want C3b to bind to them?
They want to be opsonized so that the macrophages will take them in. Once inside the macrophage, they will replicate
Does Rhodococcus want to be uptaken by the FC receptor?
no- they will get killed via this pathway
Is the capsule anti-phagocytic?
not in Rhodococcus! They want to be taken up by the macrophages
What are Vaps?
virulence associated proteins
Rhodococcus equi that has lost its plasmid and do not produce Vaps are ____ in virulence
lower
______ have genes that will code for the virulence associated proteins
Pathogenicity islands
What is the role of pathogenicity islands?
- intracellular survival 2. down regulation of IFN gamma 3. Temperature regulation
Why does Rhodococcus down regulate IFN gamma?
IFN gamma is one of the key cytokines necessary for Th1 activation of the cell mediated immunity
Does Rhodococcus survive in the environment for long periods of time?
YES- it can persist in dry environments
What environment does Rhodococcus persist in?
Soil and animal manure
Does Rhodococcus have high variability?
yes!- many different antigens present in the capsules
How is Rhodococcus transmitted?
inhalation, ingestion or congenitally
Pathogenesis of Rhodococcus
- Opsonization by C3b and will be taken in by macrophages
- Induces Vaps and survives inside the phagolysosome
- Down regulates IFN gamma
- Causes pyogranulomatose to granulomatose lesions
What will the prognosis of foals depend on?
The passive immunity and the amount of maternal anitbodies in the foal. Also, if the bacteria have the plasmid that encode for the pathogenicity island then the Vaps will be more virulent
What are the elements of the granulomatous inflammation?
macrophages, giant cells and neutrophils
What is the main manifestation in Foals?
Pneumonia- produces large abscesses in the lungs and lymph nodes
What happens if Rhodococcus is swallowed and gets into the GI tract?
Ulcerative intestinal lesions
What is the fatality rate in foals?
50%
Rhodococcus equi causes what in the lungs?
Pyogranulomatous Bronchopneumonia
What does Rhodococcus equi cause in the GI tract?
enteritis
Does Rhodococcus affect Humans?
It can cause pneumonia in immunocompromised individuals. Mortality can reach 50%
What does Rhodococcus cause in swine?
Nasty lesions of the lymph node
When is the seasonal peak for Rhodococcus?
Summer- heat and dust
What kind of immunity do you want?
Both cell mediated and Humoral immunity, however cell mediated is much more important. Antibodies for the foals are extremely important
Is there a vaccine for Rhodococcus?
No
What will you see in stains of infected tissue?
Intracellular and extracellular clusters of Gram positive cocci or rods. Completely packed macrophages
What will the media show with Rhodococcus growth?
non hemolytic mucoid colonies
This bacteria has a positive CAMP test with _____
Staph aureus or C. pseudotuberculosis- when cultured with these bacteria it produces complete hemolysis
What is the treatment?
Sick foal should be isolated and treated with antimicrobials (drug needs to penetrate the macrophages).
PREVENTION is key
- good colostrum is very important
- dust control
Do foals have a good or bad prognosis?
Bad
