RickettsiaRocky Mountain spotted fever

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Rickettsia Rocky Mountain spotted
fever Rickettsialpox Epidemic and sporadic
typhus Oral Vesicles in the oral cavity -
R. akari Macular rash, swollen tissue - R.
rickettsii Orientia Scrub typhus Ehrlichia Ehrli
chiosis Coxiella Q fever
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Aerobic, Gram-negative bacilli (but stain
poorly) Obligate intracellular
parasites Coxiella Ehrlichia multiply in
vacuoles Rickettsia and Orientia are found free
in the cytoplasm Utilize the host cell's ATP,
coenzyme A and NAD as long as they are available
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The growth of Ehrlichia in an infected cell
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Proliferate at the site of infection The
organisms eventually lyse the cell Spread to the
endothelial cells lining small blood
vessels Focal hyperplasia, inflammation
Formation of microthrombi, with localized
infarction of organs and tissues
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Can grow in the nucleus Causes Rocky Mountain
Spotted Fever Damages endothelial cells and
causes leakage of blood vessels Transmitted by
wood ticks, dog ticks or Lone Star ticks
Incidence highest in children and
teenagers Abrupt onset Fever, chills, headache,
myalgia
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Macular rash on hands, wrists, feet and ankles,
then covers the entire body Sometimes found on
oral mucosa Causes swollen throat and
tongue Complications splenomegaly, neurologic
disturbances, thrombocytopenia, disseminated
intravascular coagulation, and heart
failure Mortality is 20 if not treated
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Causes Epidemic Typhus (louse-borne
typhus) Associated with crowded, unsanitary
conditions that favor the spread of body
lice Abrupt onset, with fever, chills, myalgias,
and severe headache Maculopapular rash develops
on day 5 and spreads Complications myocarditis,
CNS dysfunction. Mortality can be as high as 60
if untreated.
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Causes Scrub typhus Fever develops suddenly, and
increases to 104F in a few days A macular to
papular rash develops on the trunk in less than
half the cases Generalized lymphadenopathy,
splenomegaly, CNS complications and heart failure
can occur The viral load of HIV patients is
lower if they are also infected with O.
tsutsugamushi
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Causes rickettsialpox Papular skin lesion at the
site of the mite bite (mouse mite),
lymphadenopathy, fever, chills, headache, and a
generalized papulovesicular rash In some cases
vesicles develop on the palate, tongue, buccal
mucosa, pharynx and lips.
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Infect lymphocytes, neutrophils monocytes, and
capillary endothelial cells High fever, malaise,
headache and myalgia Only 20 of the patients
present rashes (thus difficult to diagnose)
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Resistant to desiccation, and can remain in the
environment Q fever is most commonly caused by
inhalation of airborne particles Proliferates in
the respiratory tract, with subsequent
dissemination
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In severe cases it may cause necrotizing
hemorrhagic pneumonia The most common clinical
manifestation is endocarditis Sudden onset with
severe headaches, high-grade fever, chills and
myalgias Respiratory symptoms are generally
mild, but can be severe.
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Tetracycline and chloramphenicol Prompt
diagnosis and initiation of therapy results in
good prognosis Vaccines are available against
epidemic typhus and Q fever Hygiene, and
de-lousing sprays can control the human body
louse
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They were initially thought to be viruses since
they are small enough to pass through 0.45 µm
filters and are obligate intracellular
parasites They have an inner outer membrane,
like Gram-negative organisms, but no
peptidoglycan layer and no muramic acid Cause
psittacosis, trachoma and lymphogranuloma venereum
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They exist in 2 morphologically distinct
forms 1. Extracellular, infectious elementary
body (300-400 nm) 2. Intracellular,
metabolically active, replicating, but
non-infectious, reticulate body (800-1000 nm)
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Chlamydia replicate in phagosomes, forming an
inclusion The intact cell envelope inhibits
phagosome-lysosome fusion If the outer membrane
is damaged or the chlamydiae are heat-inactivated
or coated with antibodies, phagolysosome fusion
proceeds
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Iodine-stained Chlamydia trachomatis inclusion
bodies
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Fluorescent-stained elementary bodies in a
clinical sample
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Infects epithelial cells of mucosal surfaces
conjunctivae, endocervix, urethra, rectum,
endometrium, fallopian tubes, respiratory tract
and conjunctivae The lymphogranuloma venereum
(LGV) biovar infects lymphoid tissue and
replicates in mononuclear phagocytes Trachoma
strains infect epithelial cells Clinical
manifestations arise from cell destruction and
the host inflammatory response Granuloma
formation is typical
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Infection leads to formation of antibodies and
cell-mediated immune reactions but not to
resistance to reinfection or elimination of the
organism Re-infection induces a vigorous
inflammatory response with subsequent tissue
damage This response produces the vision loss in
patients with eye infections, and scarring with
sterility and sexual dysfunction in patients with
genital infections
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C. trachomatis is the one of the most common
sexually transmitted bacteria in the US (4
million new cases per year) It is estimated that
50 million new cases occur per year
worldwide Most urogenital infections in women
are asymptomatic, but may become symptomatic
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Clinical syndromes include cervicitis endometrit
is urethritis salpingitis pelvic inflammatory
disease (PID) 1 million women/year in the
US Can cause scarring of fallopian tubes,
preventing fertilization Most genital
infections in men are symptomatic
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Time course of untreated chlamydial urethritis
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Treatment and Prevention Ocular and genital
infections in adults One dose of
azithromycin doxycycline for 7 days ofloxacin
for 7 days Sanitation is important in areas
where trachoma is endemic Neonatal
conjunctivitis Erythromycin for 10-14 days.
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Transmitted to humans from infected birds via the
inhalation of dried bird excrement Spreads to
the liver, spleen, lungs causes lymphocytic
inflammation, edema, thickening of the alveolar
wall, infiltration of macrophages
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Causes psittacosis (parrot fever) characterized
by headache, high fever and chills. Other
symptoms may include malaise, anorexia, myalgia,
arthralgia, nonproductive cough Infections are
treated with tetracycline and erythromycin
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Time course of Chlamydophila psittaci infection
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First isolated from the conjunctiva of a child in
Taiwan, and was initially considered to be a
psittacosis strain It was found to be
serologically related to strain AR, which led to
the designation TWAR strain DNA homology
studies have indicated that it is a species
distinct from both Chlamydia trachomatis and
Chlamydia psittaci
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Transmitted by respiratory secretions Causes
pneumonia, bronchitis, pharyngitis, sinusitis and
flu-like illness Most common in the age group
60-79
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C. pneumoniae infection is strongly associated
with coronary artery disease atherosclerosis
of the carotid artery, aorta, and peripheral
arteries
C. pneumoniae in atherosclerotic plaque
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Treatment Macrolides (erythromycin,
azithromycin, clarithromycin) before
identification of the cuase of pneumonia Doxycycl
ine or levofloxacin administered for 10-14 days