Lecture 11 Rickettsia, Chlamydia & Mycoplasma Flashcards
How is Rickettsia spread and what does it cause?
It is spread by an Arthropod and causes a variety of related LPS -driven fevers!
What do Rickettsia, Chlamydia, and Mycoplasma all have in common?
They are all very small gram negative bacteria that cause human disease. They also all steal from their host
What is Chlamydia and what does it cause?
- Obligate intracellular parasite that steals a.a and ATP.
- Causes LOCAL infection in mucosal epithelium, with LPS induced inflammation causing epithelial damage and scarring.
- No cell wall
- Lysis of cells
- It causes:
1) millions of cases of blindness
2) 500,000 cases of PID and
3) non-gonoccocal urethritis (NGU),
4) eye infections
5) pneumonia
6) Psittocosis - Is sexually transmitted more than Gonococcal disease
How is C. psittaci spread?
Spread by powdered bird feces (yes, we eat and breath it ) and it causes pneumonia
What is Mycoplasma?
The smallest Extracellular known free-living cells.
- Causes LOCAL infection ON epithelium and releases a super-Ag that is the main cause of epithelial damage.
- Steals lipids and cholesterol to “strengthen” its membrane.
- NO LPS or CELL WALL
- Mycoplasma causes pneumonia, urogenital disease and vascular disease.
What is Rickettsia?
- Obligate Gram negative intracellular parasite that steals a.a and ATP
- Causes systemic infections by infecting endothelial cells, with capillary blockage (rash) and fever cause by LPS
- Causes many LPS-related fevers
- Cause of enormous morbidity and mortality
Why must Rickettsia grow inside the cells?
They lack many of the enzymes required to produce amino acids and depend on host-derived amino acids.
Where is Rickettsia maintained?
In animal and arthropod reservoirs and are transmitted by arthropod vectors. (e.g ticks, mites, lice, fleas)
Explain why humans are accidental hosts
Accidental hosts are not the primary host of a microorganism and are often poorly adapted to infection. Disease can be more severe in poorly adapted, accidental hosts.
How do people become infected with Rickettsia?
- When an infected tick, mite, louse, or flea defecates as it eats its blood meal, and the person itches the site, which brings the feces and bacteria in contact with the wound.
- **Bacteria enter blood stream and infect endothelial cells throughout the body.
- They infect endothelial cells by mobilizing actin *similar to Shigella)
- kills host endothelial cells= typical rash
- LPS produces both local and systemic inflammation
What do all Rickettsia bacteria cause?
All cause similar clinical diseases in humans–>fevers (chills), rash, and headache.
*Much of the pathologies are associated to LPS flooding the blood steam. (severe cases cause vascular damage in organs/tissues)
What is the most common and important Rickettsial disease?
Rickettsia-caused Typhus
- Epidemic Typhus (Louse-borne)
- Endemic Murine Typhus (flea-borne)
- Scrub Typhus (Mite-borne)
* Each has different arthropod vector
What is the only Rickettsial disease that can cause explosive epidemics in humans?
Louse- borne Typhus.
- It is commonly associated with wars and human disasters
- Endemic in the highlands and cold areas of Africa, Asia, and Central and South America.
What is the causative agent for Louse-borne Epidemic Typhus? And how is it transmitted?
R. prowazekii
-Transmitted by the human body louse, which is infected while feeding on the blood of patients with acute typhus fever.
(Lice proliferate rapidly in refugee camps and other crowded, unsanitary conditions)
* Head and pubic lice may no role in transmission.
How is infected lice excrete Rickettsia?
Excretes it when feeding on a second host. Rubbing louse fecal matter or crushed lice into the bite wound or through scratching, infects people.
*Untreated mortality is 10-50%
What is the most severe and frequently reported Rickettsial illness in the US?
Rocky Mountain spotted fever
