Exam 2 - (1) Chlamydiae, Rickettsiae, Ehrlichia Flashcards
What are some general features of Chlamydiae?
- Small (.25 - .8 um, just at light microscope limit)
- Gram negative (LPS outer membrane and cytoplasmic membrane
- No peptidoglycan (murein) in cell walls, has structure analogous to murein
- small genome (1-1.2 megabases)
Describe the class and defining features of Chlamydiae:
- obl. intracellular pathogens which only grow inside cells or on live tissues (animals, insects, protozoa)
- Energy parasites that depend on the host for ATP and certain amino acids
- complex developmental cycle
Formerly there were four species of Chlamydia recognized, what are they?
1- C. trachomatis (3 biovariants, multiple strains in each)
2- C. pneumoniae
3- C. psittaci
4- C. pecorum
Which Chlamydia species are primarily human pathogens?
- C. trachomatis
- C. pneumoniae
Which Chlamydia species are primarily animal pathogens but some are capable of causing disease in humans?
- C. psittaci
- C. pecorum
Chlamydial infections are the leading cause of preventable blindness world wide, T or F?
True
Chlamydia spp. are the second most common agents of sexually transmitted bacterial infections, T or F?
False, they are the MOST common
It is speculated that every living adult has had pneumonia caused by C. pneumoniae, what is the term for this?
Walking pneumoniae
What is the common route, initial target, and localization of a chlamydial infection?
- droplet or direct contact
- mucosal epithelial cells
- usually localized (eyes, lungs, genitalia; LGV is invasive, however)
How is chlamydial infections spread?
4 F’s: Fingers, Flies, Fomites, Fornication
What are the results of a C. trachomatis genital tract infection in males?
Prostatitis, epididymitis
What are the results of a C. trachomatis genital tract infection in females?
Cervicitis, PID, premature birth, pelvic pain, newborn eye/lung infections
What are the results of a C. trachomatis genital tract infection in both males and females?
Urethritis, infertility, proctitis, arthritis
C. trachomatis genital tract infections are usually ________ in females. Chronic and repeat infections can cause ______ and/or ______ pregnancy.
- asymptomatic
- sterility
- ectopic
C. trachomatis infections can be _____ or chronic. They involve a _____ ______ in which the organisms location is unknown.
- acute
- silent period
C. trachomatis asymptomatic carriage has no apparent adverse effects and is of little concern, T or F?
False: asymptomatic carriage results in the MOST damage and scarring
During birth, infants can contract a C. trachomatis infection which leads to:
- conjunctivitis
- pneumonia
What is the transit form of Chlamydia spp.?
Elementary bodies (EBs) which exist extracellularly.
How can EB’s enter into host cells?
they masquerade as nutrients, growth factors, and hormones which bind to specific receptors on the cells surface. They then are internalized by receptor mediated endocytosis.
EBs modify the endocytic vesicle which contains them in ways which ensure their survival while inside, describe them:
- maintain a favorable pH of above 6.2 which prevents vesicle’s fusion with lysosomes
- modify vesicles surface with host components (glycolipids) for camouflage
Infectious EBs transform into larger intracellular active organisms called ____. This form has the ability to ______ ______ using the host metabolites and ______ by binary fission.
- RBs
- synthesize molecules
- divide
The Chlamydial organisms (EB, RB) develop ____ within the host cells. There are usually ____ per cycle of division. Once ______ organisms are present, the ______ can be observed.
- slowly
- 2-3 days
- 200-1000
- inclusions
How do RBs accomplish nutrient uptake?
with tube-like structures or “drinking straws” that allow them to feed from the host cell without leaving the inclusion vacoule
how many drinking straws are typically present on an RB?
18 -23
Besides genital tract infection, what is another condition caused by C. trachomatis spp.?
Trachoma
Breifly describe trachoma:
it is an inflammation of the conjunctiva of the eye which can cause blindness or scarring of the cornea. It is spread by direct contact with eye, nose, and throat secretions from infected individuals OR contact with fomites such as towels and/or washcloths
What is an STD caused by a chlamydial infection?
LGV - Lymphogranuloma vererum
Describe LGV:
it is a sexually transmitted, systemic, invasive infection apparent in the lymph nodes that drain the genital tract.
Where is LGV most common?
in developing countries such as Africa, Asia, India, and South America (rare in the US 200-400 cases)
What is the most prevalent chlamydial pathogen in the human population?
Chlamydophila pneumoniae
___% of people up to the age of 20 have been infected by C. pneumoniae, and ____% in older adults.
- 50
- 80
Although C. pneumoniae infections are usually acute or ________, _______ respiratory infections have been associated with ______, ___, and _____ _____.
- asymptomatic
- chronic
- asthma
- CF
- lung cancer
C. pneumoniae infections can be directly observed in 40-100% of patients with what condition?
atherosclerotic heart lesions
What is the target of Chlamydial infection treatment?
the metabolically active RB forms
What four membranes must be penetrated in order to treat the Chlamydial RB forms?
1-host cell plasma membrane
2-inclusion membrane
3-chlamydial outer membrane
4-chlamydial cytoplasmic membrane
Why must antibiotics to treat Chlamydial infections must be maintained a long time?
because they grow slowly
What are some general characteristics of Rickettsiae?
- small gram(-) rods
- they don’t stain well
- obligate intracellular bacteria
- zoonoses (infections transmitted from animals to humans
Rickettsiae are energy parasites like Chlamydiae and cannot synthesize their own ATP, T or F?
False: Rickettsiae can synthesize ATP and are capable of independent metabolism
Rickettsiae, although they can achieve independent metabolism may still lack ______ necessary for growth.
metabolities
How must Rickettsiae be cultivated?
- within animals
- in embryonated eggs
- cell cultures in the lab
What are some Rickettsial diseases and their carriers?
- Rocky mountain spotted fever (ticks)
- Epidemic typhus, Recrudescent typhus (humans, flying squirrels)
- Murine typhus (fleas and rats)
- Scrub typhus (chiggers)
Only members of the hard tick family ______ are naturally infected with rocky mountain spotted fever. Some specific species include _________ and _________. Once infected a tick can carry the parasite for ______.
- Ixodidae
- Rocky mountain wood tick
- American dog tick
- life
Adult Ixodidae feed on ______, larval and nymph forms feed on _______. Before developing to the next stage most tick spp. require a ______ ______.
- large mammals (e.x. humans)
- small rodents
- blood meal
Describe the course of a Rickettsial infection via tick:
During feeding as a larvae or nymph ticks become infected with R. rickettsii -> bacteria pass to humans as adult ticks during bloodmeal -> bacteria spreads through bloodstream
describe Rickettsiae systemic entry:
1-attach to vascular endothelial cells
2-induce endocytosis
3-once inside, they lyse the phagosome (phospholipase) and enter the cytosol
All Rickettsial species exit the the host cell in the same manner, T or F?
False, their mode of exit from host cells varry
How does R. prowazekii exit the host cell?
lysis
How does R. rickettsii exit the host cell?
it gets excluded through local projections known as filopodia (host actin filaments help push it out)
How does R. tsutsugamushi exit the host cell?
budding through the host cell membrane, it retains the membrane as it infects other cells.
describe the injury to the host of a Rickettsial infection:
proportional to the number of intracellular bacteria, cells lyse and cause leakage of blood which presents as a rash (hemorrhagic spots). Although the organism can travel to critical vessels such as those in the heart and brain 75% of patients will clear the infection before antimicrobial treatment
What are three types of Rickettsial typhus group fevers? which organisms cause them?
1-Typhus fever/Recrudescent typhus (R. prowazekii)
2-Murine typhus (R. typhi)
3-Scrub typhus (Orienta tsutsugamushi)
What is recrudescent typhus?
reactivation of the the dormant agent seen in the U.S.
how is typhus and recrudescent typhus spread?
human lice on humans and flying squirrels
Murine typhus (R. typhi) is more prevalent and widespread than typhus. it is carried by _________.
rats and fleas
Which type of typhus (O. tsutsugamushi) causes no rash?
Scrub typhus
When was Ehrlichia discovered?
1987
