Coxiella burnetii Flashcards
What does Coxiella burnetii cause?
Q (Query, Queensland) fever - occupational zoonotic disease categorized as a bioterrorism agent by the CDC
What are 4 reasons that Coxiella burnetii is recorded as a bioterrorism agent?
- causes disability, fever outbreaks, and epidemics of abortion in ruminants (huge economic loss)
- airborne transmission up to 20 km away
- highly infectious with low infective dose of 1-10 cells
- viable in the environment for years using a pseudo-spore-life life form (small cell variant)
What kind of bacteria is Coxiella burnetii? How does it differ from other of the same bacteria?
Gram-negative with an outer membrane composed of LPS and surface proteins and peptidoglycan
better stained with the Gimenez method
How does Coxiella burnetii differ from Chlamydia, Anaplasma, Ehrlichia, and Rickettsia?
not an ATP parasite on host cells
- cell envelop does not transport ATP across its membranes
- able to synthesize its own ATP
Why is Coxiella burnetii an obligate intracellular pathogen?
cannot synthesize its own amino acids, like cysteine and arginine and must steal it from the host cytoplasm
What are the 2 morphotypes of Coxiella brunetii?
- small cell variant (SCV) = extracellular
- large cell variant (LCV) = intracellular
What are the 4 major characteristics of the small cell variant of Coxiella burnetii?
- hardy form taken when it is in the environment, outside of the host cell, or when conditions are not favorable
- infectious and transmissible form
- electron-dense
- can remain in the environment for decades
What are the 3 major characteristics of the large cell variant of Coxiella burnetii?
- vegetative/replicative form
- activated when it enters the cytoplasm of the host cell
- metabolically active
What are the primary reservoirs of Coxiella burnetii? What species does it infect?
cattle, sheep, goats (ruminants!)
- wildlife
- marine mammals
- domestic mammals
- birds
- reptiles
- ticks
- humans
Other than the environment, where can the small cell variant of Coxiella burnetii be found?
free living amoeba
What are the 4 entry routes of Coxiella burnetii? 5 exit routes?
ENTRY
1. inhalation**
2. ingestion
3. contact
4. ticks
EXIT = feces, abortion, urine, sexual activity, milk, ticks
Coxiella burnetii tranmission:
How are people, ruminants, dogs/cats, and ticks commonly infected with Coxiella burnetii?
PEOPLE: inhalation, direct/indirect contact with infected animals during parturition, ingestion of infected milk
RUMINANTS: reservoirs
DOGS/CATS: contact/ingestion of wildlife species
TICKS: harbor microorganism and maintain transmission to wildlife species, especially rodents, rabbits, and birds
What are the main 4 ways that Coxiella is transmitted transovarially?
- between wildlife
- between wildlife and domestic animals
- from wildlife to humans
- reservoir for maintenance in sylvatic environment
How is Coxiella burnetii able to survive in microbicidal cells, like monocytes and macrophages?
- uses atypical LPS lacking sugars via genetic deletion to become avirulent (docile) by acquiring a rough surface and avoiding immune cells
- enters cells in its non-replicative SCV form and resides in membrane-bound Coxiella-containing vacuoles and exponentially replicated
What is the function of Coxiella LPS?
protection for its optimal growth in phagocytes, non-phagocytic cells, and in cell-free culture media
What is another name for the pili of Coxiella? What are 3 functions?
type 4 secretion system
- attachment
- injection of effector proteins into host cell
- promotes intracellular survival and replication
How does Coxiella survive in vacuoles?
vacuole acidification by colliding with cell lysozyme using EEA1 and Rab5 (pH 5.4 to 4.5) —> allows for development and replication inside vacuole and protects it from damage from phagolysosome
What are the 2 phases of the large cell variants of Coxiella?
VIRULENT PHASE I = LPS has intact O-antigen (smooth)
AVIRULENT PHASE II = LPS lost its O-antigen (rough)
What are the 3 tropisms of Coxiella?
- MONOCYTES and MACROPHAGES of birds, mammals, and humans** - cells disseminate it into blood vessel endothelial cells
- ENDOTHELIAL CELLS of vital body parts of birds, mammals, and humans - localizes in lung, placenta, reproductive tract, liver, mammary glands, lymph nodes, heart, joints, bones, and brain
- MIDGUT and SALIVARY GLAND CELLS of ticks
What are the 2 forms of clinical signs of Coxiella infection?
- ACUTE = fever + pneumonia, abortion and stillbirth, jaundice and granulomatous hepatitis, mastitis, lymphadenitis linked with lymphoma, vasculitis, rash/hemorrhage
- CHRONIC = endocarditis/heart failure (heart valves), osteoarthritis, brain
(60% are asymptomatic)
What 6 specimens can be taken for Coxiella isolation?
- vaginal discharge
- abortion remains
- milk
- nasal discharge
- blood
- serum
What is the gold standard of serological tests for Coxiella identification? What titers suggest primary Q fever infection?
indirect immunofluorescence assay
- ELISA can also be done
IgG > 200
IgM > 50
What genes are targeted for PCR and sequencing for Coxiella identification?
16S-23S RNA, ompA, com1, superoxide dismutase gene, plasmids, mobile genetic repetitive insertion elements
What are the 2 major methods of Coxiella culturing?
- on cell lines of chick fibroblasts
- broth or agar media using acidified citrate cysteine
(in a BSL3 containment laboratory)
What is the sole example of an obligate intracellular bacterial pathogen for which specific axenic culture medium has been developed?
Coxiella burnetii
What are 6 possible treatments of Coxiella burnetii infection? What is the safest option?
- Doxycycline
- Oxytetracycline
- Doxycycline + Hydroxychloroquine
- Chloramphenicol
- Erythromycin
- Fluoroquinolones
trimethoprim-sulfamethoxazole
What are the 4 major ways to control/prevent Coxiella burnetii infection?
- whole-cell killed vaccine licensed in Australia and Europe used in cattle to lower the risk of spreading and in goats to reduce abortion/spreading
- tick control
- BSL 3 - PPE during isolation, N95 while performing Q fever positive autopsies/parturition
- clean the environment with quaternary ammonium detergent or household bleach to decontaminated surfaces from spore-like form
