Section IV Lecture 4: Rickettsia, Bartonella, Borrelia and Treponema
Medical Microbiology 3200 with Thai at University of Missouri- Columbia
About this deck
By: Megan Manuel
Created: 2011-11-01
Size: 33 flashcards
Views: 14
Created: 2011-11-01
Size: 33 flashcards
Views: 14
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Rickettsias general characteristics
small size
rod-shaped or coccobacilli
non-motile (no flagella)
G- (poorly)
many are transmitted by insects and ticks
obligate intracellular parasites
R. rickettsiae general characteristics
disease: Rocky Mountain spotted fever
vector: tick
reservoir: ticks and rodents
R. rickettsiae symptoms
age distribution: 70% cases are in children/teenagers < 15 years
initially: (5-10 days after tick bite) fever, chills, headache, muscle pain, nausea/vomiting, lack of appetite
later signs: (2-5 days after fever) rash, abdominal pain, joint pain, diarrhea
rash starts at extremities and spreads to trunk
--small, non itchy spots (most patients), red spotted rash (35-60% of patients)
R. rickettsiae pathogenesis
replication in endothelial cells
leakage of blood vessels
complications: GI tract problems, respiratory failure, kidney failure, heart problems
mortality of 20% if untreated
R. rickettsiae diagnosis
culture not useful
IFA
immunostaining of skin biopsy of rash
R. rickettsiae treatment and prevention
tetracyclines, chloramphenicol
limit tick exposure, remove ticks, tick repellant
no vaccine currently
Ehrlichiosis general characteristics
Ehrlichia species
first identified in 1986
obligately intracellular
G- cocci
grow as characteristic vacuole bound Morulae
Two different species that cause similar disease in humans
- E. chaffeensis – monocytic disease
- Human Granulocytic Ehrlichiosis is actually caused by Anaplasma phagocytophilum—not covered by lecture
Ehrlichiosis symptoms
may be asymptomatic
clinical signs resemble RMSF--fever, headache, malaise, muscle ache
a rash develops in < 20% of cases
rash is most common in children (adults get disease more often)
mortality is less than 5%
Ehrlichiosis diagnosis and treatment
difficult
clinical tests: low WBC counts
IFA
PCR
gold standard = isolation
--difficult, time consuming
tetracyclines
summary of cellular and subcellular location
Rickettsia
- host target cell: endothelium
- cellular location: cytosol
- host target cell: leukocyte
- cellular location: cytoplasmic membrane
Bartonella henselae general characteristics
cat scratch disease
G- bacilli
fastidious growth requirements
- enriched blood agar
- carbon dioxide
- several weeks needed
Bartonella henselae epidemiology and transmission
22, 000 cases per year
80-90% patients are < 21 years old
serology: cats from warm climates 30-50%, cats from cooler climates 5-7%
cats usually asymptomatic...uveitis?
Bartonella henselae symptoms
papule/pustule
regional adenopathy
in immunocompromised patients:
- bacillary angiomatosis-vascular proliferative disease
- bacillary peliosis hepatitis (blood-filled cavities in the liver
- endocarditis
Bartonella henselae diagnosis and treatment
history of cat contact
positive skin test response to CSD-skin test antigen
no evidence of other infectious causes for condition
histopathology of nodes
efficacy? azithromycin
90% infections resolve without therapy
Spirochetes general characteristics
G-
motile (flagella are beneath outer membrane)
spiral shaped
extracellular pathogens
Borrelia burgdorferi Lyme disease
vector: black-legged/deer ticks
reservoir: rodents and deer
deer provide ideal package!
- dining
- meeting
- mating
- travel
replication, surface changes promote spread in tick
no human-human transmission
Lyme disease stage 1
- 3-14 days after tick bite, typical bulls eye rash (80% of patients)
- local spread in skin as bacteria multiply
- may get fever, muscle pain, joint pain
- resolves within weeks
Lyme disease stage 2
- weeks to months after initial infection
- disseminated infection: joint/muscle pain, multiple tissues and organs affected
- irregular heartbeat, facial paralysis/neurological conditions, conjunctivitis
Lyme disease stage 3
- may develop months to years after infection
- arthritis, often longer episodes as years pass by
- immune disorder, high antibodies to Borrelia surface antigens, cross-reactivity with human proteins
- advanced neurological disorders: disabling fatigue, memory loss, dementia, paralysis
Lyme disease diagnosis
clinical signs (bulls eye rash)
prevalence of ticks in area
culture from skin lesions
serological tests: (many false negatives during stage 1) ELISA, Western blot analysis
polymerase chain reaction--not standardized yet
Lyme disease treatment
antibiotics are effective early
- tetracycline, erythromycin for 10-30 days
some arthritis is treatment resistant: bacterium eliminated, damaging antibodies still in circulation
vaccines were available, since withdrawn
Treponema pallidum syphilis
difficult to see under light microscope
prolonged staining yields a pale pink (pallid) appearance
Treponema pallidum growth and metabolism
very difficult to grow in vitro (only 2-3 log increase)
co-cultivation has been reported with tissue culture cells
reliable serial subculture is difficult
impossible to grow cell-free, despite exhaustive efforts
rabbit testis is used to produce large numbers of treponemes
long doubling times (~30 hours)
genome sequence useful to determine nutrient demands
syphilis
humans are only reservoir
organism is labile (heat, desiccation, oxidants and disinfectants)
typically transmitted by all forms of sexual contact
about 30% transmission rate from single sexual contact
also by contact (touching/kissing) of infected regions
- small abrasions in the skin
- can penetrate mucous membranes
- no evidence for colonization prior to penetration
syphilis primary lesions
occurs 2-10 days post infection
small, hard chancre at site of infection
- painless ulcerated papule of crusted erosion
- very infectious (many treponemes present)
within 3-8 weeks, chancre erodes
no further symptoms for 2-10 weeks
- bacteria are disseminating through blood/lypmh
secondary syphilis
occurs 2-12 weeks after infection
widely disseminated bacteria, many clinical manifestations
skin rash (often starts on trunk) in 90% of cases
mucous patches/erosions in mouth and throat (30%)
fever, malaise, joint pain, hair loss, weight loss (70%)
CNS involvement (40%): headache, ocular disease
lesions contain many spirochetes (infections)
lasts several weeks and subsides (end of disease in most)
secondary syphilis clinical manifestations
skin rash may be macular (stain or spot), papular (small solid elevation), pustular (pus containing)
condyloma lata: wart-like lesions occur at moist sites (genital, perianal), coalescence and erosion of papules
syphilis latency
no symptoms (< 30 years) but serologic tests are positive
after 2-4 years, not infectious (except to fetus)
even if untreated, this is often the end of the disease
tertiary syphilis
occurs in less than half of untreated patients
may begin 10-30 years after start of latent period
- not known where the bacteria are hiding
inflammatory response to pathogen components
gummas (rubbery) may occur in many organs/bone/skin
- necrotic (palate, tongue perforations)
- weaken aorta
- few organisms in lesions; not highly contagious
congenital syphilis
transmitted from mother to fetus (placenta or birth canal)
pregnancies in primary/secondary stages lead to still-birth
most common when pregnancy occurs in latent phase
- child is born without symptoms
- rash develops
- multi organ malformations, cardiovascular problems
- bone destruction and mental developmental problems
syphilis standard tests
culture is not possible
dark field microscopy if fresh sample from skin lesions
serology is usual means of diagnosis
- non treponemal tests (detect 70-90%)
- tests use cardiolipin as antigen and test for reagin antibodies that react with host lipids that are released during disease
- RPR (rapid plasma region)
- cardiolipin on carbon particles, serum causes clumping
- VDRL (venereal disease research laboratory)
- slide flocculation test (clumping)
- Complement fixation
syphilis detection and treatment
direct test: use treponemal antigens
- fluorescent treponemal antibody absorption test
- serum and antigens react on microscope slde
- fluorescence when positive
- used for confirmation
treatment: penicillins (tetracyclines if allergic), single shot of benzathine penicillin may be enough (slow acting, 2 weeks)
About this deck
By: Megan Manuel
Created: 2011-11-01
Size: 33 flashcards
Views: 14
Created: 2011-11-01
Size: 33 flashcards
Views: 14
About StudyBlue
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