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78 Cards in this Set

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common characteristics of what two obligate intracellular bacteria?
-small size (~300 nm)
-obligate intracellular growth
evidence that obligate intracellular bacterium (RICKETTSIA and CHLAMYDIA) are NOT viruses
1) contain both DNA and RNA
2) multiply by binary fission
3) susceptible to antibiotics, esp. tetracyclines
4) have their own protein synthetic machinery (ribosomes, etc..)
5) bacteria-like cell walls (most closely related to gram-negative bacteria)
how are mycobacterium leprae different from other oblicate intracellular bacteria (chlamydia and rickettsia) ?
though they are often intracellular during infection, Mycobacterium leprae can grow extracellularly both in vivo and in vitro
chlamydia that cause human disease are normally parasites of what species?
(not arthropots as in rickettsia)
stages in CHLAMYDIA developmental cycle
a) ELEMENTARY BODIES enter by inducing host cell to phagocytose them
b) w/in 24hrs elementary bodies lose cell wall, double in diameter and synthesize RNA to yield INITIAL BODIES
c) INITIAL BODIES divide by binary fission and some of the progeny are converted back to the original smaller, highly infectious ELEMENTARY BODIES
compare the ELEMENTARY and INITIAL bodies of CHLAMYDIA
ELEMENTARY BODIES: small, non-multiplying, rigid bacterial-like cell wall (Transmits the infection from cell to cell and from person to person)
INITIAL BODIES (aka reticulate): larger, actively multiplying, lacks rigid wall, noninfectious
why do CHLAMYDIA exhibit obligate intracellular growth?
cannot make ATP and thus depends on host cell ATP
3 known species of CHLAMYDIA
a) Chlamydia psittaci (1 serotype): causes psittacosis
b) Chlamydia pneumoniae (1 serotype): pneumonia, mostly in adults
c) Chlamydia trachomatis: multiple serotypes cause trachoma, lymphogranuloma venereum, and a complex array of clinical presentations including inclusion conjunctivitis, newborn infant pneumonia, and urethritis
causes trachoma, lymphogranuloma venereum, and a complex array of clinical presentations including inclusion conjunctivitis, newborn infant pneumonia, and urethritis
Chlamydia trachomatis
Chlamydia psittaci naturally a parasite of what species?

can produce a chronic subclinical infection, with constant fecal excretion increased with stress
How is Chlamydia psittaci transmitted to humans?
human infection is most commonly acquired by inhaling infected bird feces (mostly from contact with parrots, parakeets, and pigeons)
pathogenesis of Chlamydia psittaci
PSITTACOSIS: generalized infection, agent can be recovered from blood or sputum, most patients have feber and headach, most distinctive and severe sign of infection is extensive interstitial pneumonia
Chlamydia pneumoniae causes a significant fraction of what disease in adults?
how is Chlamydia pneumoniae transmitted to humans?
spread directly from person to person as respiratory aerosols (w/o involvement of birds as in Chlamydia psittaci)
several serotypes of Chlamydia trachomatis cause what common venereal disease?
symptoms in male infected with Chlamydia trachomatis
many are asymptomatic, those who are present with a purulent urethral discharge
symptoms in female infected with Chlamydia trachomatis
freqently asymptomatic, though bacteria are grwoing in the cervical cells and elsewhere
infection with Chlamydia trachomatis increases the likelihood of transmission of what virus?
What are the consequences of chronic Chlamydia trachomatis in females?
sterility, ectopic pregnancy
How is Chlamydia trachomatis screened in at-risk women of child bearing years?
PCR of urine
How are infections of Chlamydia trachomatis best treated?
with a single dose of AZITHROMYCIN (best bet for compliance in asymptomatic patient)
serotypes of Chlamydia trachomatis can produce what diseases?



How might a neonate be infected with inclusion conjunctivits (from C. trachomatis)
VERTICAL TRANSMISSION from infected mom (symptomatic or asymptomatic)
How are C. trachomatis serotypes that cause TRACHOMA different from the others?
more invasive
How is Trachoma transmitted?
finger to eye and by flies
Where is trachoma prevalent
in tropical africa and asia (particularly arid regions)
Pathogenesis of trachoma
chronic reinfection of the conjunctiva causes an infolding of the eyelashes that results in corneal scarring and blindness
2nd Major cause of blindness worldwide
TRACHOMA (caused by chlamydia trachomatis)
Effective public health effort against trachoma
annual universal treatment with azithromycin
Lymphogranuloma Venereum is caused by serotypes of what?
C. trachomatis that are transmitted venerally but are more invasive than those causing nongonococcal urethritis
characteristic symptom of lymphogranuloma venereum
painless papule, pregoressing to an ulcerating vesicle (first appearing 2 weeks after exposure)
what sometimes happens 4 weeks after exposure to Chlamydia trachomatis causing lymphogranuloma venereum infection?
infection will progress to a painful suppurative disease of regional lymph nodes
what test is used to detect prior or current Lymphogranuloma venereum
FREI TEST: a delayed hypersensitivity to heat-killed LGV injected intradermally
treatments of Chlamydial infections:
tetracyclines work well in all chlamydial infections, but azithromycin may be preferred
lab Dx of Chlamydial infections
PCR is method of choice

all share a group Ag, but are distinguished from one another by specific Ags

compare acute and convalescent Ab titers

Chlamydia can be isolated by inoculation of cultured cells and detecting characteristic cytoplasmic inclusion bodies by staining or, more specifically, by fluorescent Ab
Most rickettsia that cause human disease are normally parasites of...
describe intracellular growth of rickettsia

and how it differs from that of chlamydia
1) enters human or arthropod cell by inducing its own phagocytosis
2) slow multiplication by binary fission (1 division per day)
3) progeny are released by lysis of host cell

do not have distinct elementary and initial body morphology

also no good explanation for obligate intracellular parasitism (since they can take up ATP, NAD and make their own ATP)
Rickettsie prowazekii causes what disease?

(recrudescently causes Brill-Zinser Disease)
incubation of Primary Epidemic Typhus (caused by Rickettsia prowazekii)
10 day incubation period,
abrupt onset of fever and severe headache

rash follows 4-7 days later
symptoms of Primary Epidemic Typhus (caused by Rickettsia prowazekii)
abrupt onset of fever and severe intractable headache

rash follows 4-7 days later
transmission patter of R. prowazekii in primary epidemic typhus
--> human --> body louse --> human --> body louse
how does the body louse transmit R. prowazekii to humans?
punctures skin to get a blood meal and defecates at the same time, scratching drives the fecal material and rickettsie into the bite wound
effective treatment for primary epidemic typhus
prevention of primary epidemic typhus involves what?
louse control (DDT or adequate bath/laundry facilities)
Dx of primary epidemic typhus
usually by rise in Ab titer (acute vs. convalescent serum samples)

WEIL-FELIX REACTION {agglutination of Proteus (w/ cross-reacting Ag)} highly sensitive, but lousy specificity (saved a jewish town!)
Brill-Zinsser Disease is caused by what bacteria?
secondary infection of R. prowazekii
How is R. prowazekii stabily maintained in the US?
in a cycle involving the southern flying squirrel

flying squirrel --> squirrel louse --> squirrel louse --> human (sporadic case)
What ZOONOSIS is caused by Rickettsie typhi?
Endemic murine typhus
What are the usual animal hosts of Rickettsie typhi?
rats and ground squirrels
Pattern of transmission of Rickettsie typhi
--> ground squirrel --> ground squirrel flea --> {humans} or ground squirrel --> ground squirrel flea
milder and does not have high mortality rate of epidemic typhus
Endemic Murine Typhus foci with rat as host in what regions?
Atlantic and Gulf of Mexico seaboard in the SE USA
Endemic Murine Typhus in the SW USA involves what vertebrate host?
the ground squirrel
Tx and Rx for Primary epidemic typhus
same as for primary epidemic typhus

R. rickettsii causes what disease
fever, headache, arthritic pains and abdominal pain with nausea and vomiting follow an incubation period of 1 week or less

rash begins on hands and feet and spreads rapidly to trunk (usually not on palms or soles)
1 week or less
mortality of untreated ROCKY MOUNTAIN SPOTTED FEVER
patterns of tranmission of ROCKY MOUNTAIN SPOTTED FEVER
tick--(transovarian)--> tick
tick--> mammal --> tick ---> humans
Dx Rocky Mountain spotted Fever
fluorescent Ab tests on skin biopsy give immediate Dx
tetracyclines effective
mostly clothing to avoid ticks

several tick species are involved {forest tick in W. US; dog tick in Eastern US}
Most cases of ROCKY MOUNTAIN SPOTTED FEVER are aquired in what region?
the EASTERN half of the US
Rickettsial pox is caused by what species?
Rickettsia akari
symptoms of Rickettsial pox
primary skin lesion appears at site of arthropod vector bite
1 week later systemic disease is seen (fever, chils, headache, rash)
rash resembles that of chicken pox
(benign nonlife-threatening disease)
transmission pattern of Rickettsial pox
--> mouse mite --> mouse ---> mouse mite --> {humans} or mouse
outbreaks of Rickettsial pox are often confined to...?
a single building, i.e. large apartment houses
Q fever is caused by what bacteria?
Coxiella burnetii
How are humans infected by Q fever?
by inhaling C. burnetii (not through bite of an arthropod)
what type of tissue contains a very high titer of infectious C. burnetii?
placental tissue of infected sheep and of other animals
How is Q fever infectious agent transmitted
in a spore-like stage, inhaled by humans

unique to C. burnetii, not in other rickettsia
Pattern of transmission of Q fever

see M9
--> {sheep, goat, cow, cat} --> tick --> {sheep, goat, cow, cat} ---> tick or {placental tissue --> (spore like stage to humans or back to {sheep, goat, cow, cat} )}
disease characterized by INTERSTITIAL PNEUMONIA, fever, headache, elevated LFTs, some patients have a rash
{think of animal (esp. occupational exposure)}
(Coxiella burnetii)
Ehrlichiosis can be caused by what two different obligate intracellular bacteria?
Ehrlichia chaffeensis (MONOCYTIC EHRLICHIOSIS)

or Anaplasma phagocytophilium (GRANULOCYTIC EHRLICHIOSIS)
EHRLICHIOSIS infections are characterized by:
feber, lymphocytopenia (think of white cells destroyed through being infected) and LFTs due to liver damage
best treatment of EHRLICHIOSIS is:
tick-borne disease that infects monocytes
tick-borne disease that infects granulocytes