18_Chlamydia, Rickettsia, Ehrlichia Flashcards
what do the following have in common?
- chlamydia
- rickettsia
- ehrlichia
- anaplasma
- bartonella
- most of these organisms are obligate intracellular pathogens (except Bartonella)
- cannot be grown in the lab except in tissue culture, or in other eukaryotic cells such as embryonated hens’ eggs (except Bartonella & Coxiella CAN be cultured)
- many produce rashes and many have arthropod vectors
chlamydia trachomatis:
4 major clinical symptoms
-
genital infection: nongonoccocal urethritis
- Serovars D-K
- inclusion conjunctivitis in infants (Serovars, D-K)
- Trachoma: chronic follicular conjunctivitis leading to blindness
- Serivars A, B, Ba, C
- lymphogranulumoa nevereum: STD-swelling in inguinal lymph nodes leading to bubos; serovars L1, L2, L3 (uncommon in US)
*Chlamydia infections ONLY have a human reservoir
Chlamydia trachomatis:
genital infections (serovars D-K)
- this organism causes urethritis, characterized in male by a thin urethral discharge, and sometimes dysuria
- *the absence of purulent discharge distinguishes Chlamydia from gonococcal infxn in men
- women may have dysuria and a discharge or be asymptomatic
what is often co-infected w/ chlamydia trachomatis?
- *Co-infection w/ Neisseria gonorrhoeae is common; sometimes called “nongonococcal urethritis” or “post-gonococcal urethritis”
- male: epididymitis over 50% can be asymptomatic
- female: cervicitis, salpingitis, pelvic inflammatory disease (PID), ectopic pregnancy, sterility
- 2/3 of females are asymptomatic
- 2016 US > 1,598,354 cases reported to CDC; most common notifiable disease in the US
Serovars can cause genital infections, and can cause what else?
- extragenital infxns: rectal and pharyngeal infections in men/women
- highest rates: men who have sex with men
In what 2 ways do infants manifest the Chlamydia trachomatis?
Infants may acquire the organism when passing thru the vaginal tract of an infected mother; transmission rate is over a 1/3. Infants manifest by:
- Inclusion conjunctivitis: watery progressing to mucopurulent discharge 5-12 days after birth
- Interstitial pneumonia: 6 wks- 6 months
What is the leading cause of blindness in the world?
Causing 41 million infected, 10 million bind
Chlamydia trachomatis causes trachoma;
- a bacterial infection of the eye causing follicular conjunctivitis
- cobblestone inflammation
- late trachoma
Chlamydia trachomatis: Trachoma
- serovars
- mechanism
- transmission
- serovars: A, B, Ba, C
- mechanism:
- scarring on the inside of the eyelid, which becomes rough –> corneal scarring and damage
- blindness due to chronic infxn and reinfxn in endemic areas
- transmission
- transmitted person-to-person by fingers, fomites (towels & wash cloths), and flies
Chlamydial microbiology:
- type of pathogens
- structure & staining
- morphological forms
- actions
- type of pathogens: all organisms are obligate intracellular pathogens
- structure & staining:
- gram negative: no peptidoglycan
- small 0.3-1 micrometer
- morphological forms
- elementary body: infectious form
- reticulate body: intracellular replicative form; replication is in an “inclusion”, which is a membrane bound vacuole
- actions:
- no phagolysosomal fusion: organisms stay in the vesicle
- infect columnar or transitional epithelial cells
chlamydia life cycle:
elementary body and reticulate body
-
Elementary body
- size about 0.3 micrometers
- rigid cell wall
- RNA:DNA content #1:1
- Isolated organisms infectious
- adapted for extracellular survival
-
Reticulate body
- size 0.5-1 micrometer
- fragile cell wall
- RNA:DNA content #3:1
- Isolated organisms not infectious
- adapted for intracellular survival
which is the phase of the Chlamydia lifecycle is:
- adapted for extracellular survival
- adapted for intracellular survival
-
Extracellular survival: Elementary body
- smaller, rigid cell wall
-
Intracellular survival: Reticulate body
- larger, fragile cell wall
Chlamydia trachomatis:
diagnosis and treatment
- Diagnosis: nucleic acid amplification (NAATs) for genital serovars, both for genital and extragenital infxns
- samples
- women: vaginal swab, or cervical
- male: clean catch urine or urethral swab
- specimens do not have to have living organisms
- Chlamydia are obligate intracellular pathogens and cannot be cultured on bacteriologic media
- samples
- Treatment: Azithromycin or Doxycycline or topical tetracycline
Chlamydophila (Chlamydia) pneumoniae infections:
- transmission
- symptoms
- transmission: human to human
- sxs:
- pneumonia (walking pneumoniae or atypical pneumoniae)
- bronchitis
- sinusitis, laryngitis, pharyngitis less common
- atherosclerosis, asthma, alzheimer’s disease, lung cancer, COPD, multiple sclerosis
Chlamydophila (Chlamydia) pneumoniae
diagnosis and treatment
- These organisms are obligate intracellular pathogens; they have elementary bodies and reticulate bodies like other Chlamydia
- Diagnosis
- cell culture of oropharyngeal swabs
- 4x rise in IgG antibody detected by indirect immunofluorescence against formalin fixed in elementary bodies of reagent strains grown in tissue culture
- Treatment: macrolides: (Azithromycin or tetracycline in adults)
Rickettsia can cause what types of fevers?
how many organisms cause spotted fevers?
- Spotted fevers
- Typhus fevers
18 diff’t species can cause just spotted fevers; most countries have their own endemic organisms
Rickettsia rickettsii:
- transmission
- incubation period
- sxs
- rash
- transmission:
- rodent reservoirs (mice, voles, squirrels, chipmunks)
- transmitted by ticks; infected tick bite transmits disease
- incubation period of 5-14 days
- sxs: fever, headache, maculopapular rash, myalgia, confusion
- rash: rash starts on extremities: wrists and ankles and spreads to the trunk;
- appearance of rash on palms and soles is diagnostic;
- only syphilis also has a rash on palms and soles
Which tick causes the Rocky Mountain Spotted Fever?
Rocky Mountain Wood Tick;
aka Dermacentor andersoni
Rickettsia rickettsii:
- structure
- type of pathogen
- sxs
- 2nd week of disease?
- structure:
- small coccobacilli (0.3-0.5 um)
- stains poorly w/ gram stain,
- structurally similar to Gram negative bacteria
- type of pathogen: obligate intracellular pathogen; infects vascular endothelium. Escapes endocytic vacuole and replicates in the cytoplasm
- sxs: vascular vessel damage, rash
- 2nd week of disease can get shock syndrome and disseminated intravascular coagulation
Rickettsia rickettsii:
- diagnosis
- treatment
- Diagnosis
- hx of tick on patient; –> highest incidence April to September
- direct fluorescence of skin lesion biopsy
- growth in embryonated hens’ eggs
- does not stain w/ standard stains so cannot be seen on smears of blood or tissue
- Treatment
- doxycycline in first week
- prior to Abx era: 28% mortality; w/ Abx tx: 1% mortality
Rickettsia prowazekii:
- reservoir
- mechanism
- sxs
- diagnosis
- treatment
- reservoir: body louse reservoir
- mechanism:
- infected louse bites human and defecates infected feces
- human scratches adn rickettsia enters the body
- sxs: fever, headache, rash, myalgia begin 1-2 wks after bite
- diagnosis: serology by indirect fluorescence
- treatment: doxycycline
Hx of Rickettsia prowazekii
an ancient scourge;
Napoleon’s defeat in Russia has been attributed to the weather; but RT-PCR evidence from body segments of lice in graves of soldiers;
extracts of dental pulp of skeletons, shows that lice and soldiers were infected w/ R. prowazekii
Where do R. rickettsi and R. prowasekii replicate?
these replicate in cytoplasm
Ehrlichia & Anaplasma:
similarities and differences
Both are both tickborne diseases
-
Ehrlichia chaffeensis: human monocytic Ehrlichiosis
- Lone star ticks
-
Anaplasma phagocytophilium: human granulocytic anaplasmosis (formerly human granulocyte ehrlichiosis)
- Ixodes ticks
~10% of people bitten by ticks are co-infected w/ lyme disease
Which type of tick causes Anaplasmosis & Lyme disease?
What about Ehrlichiosis?
- Blacklegged tick (Ixodes scapularis) –> Anaplasmosis
- Lone star tick (Amblyomma americanum) –> Ehrlichiosis
How do HME and HGA present histologically?
(Human monocytic ehrlichiosis - HME)
(Human granulocytic anaplasmosis - HGA)
Inclusions or morulae
Ehrlichiosis and Anaplasmosis:
- symptoms
- diagnosis
- therapy
- sxs: fever, severe headache, myalgias, chills, fatigue
- sxs occur 1-2 weeks following tick bite
- diagnosis: PCR and/or 4x rise in IgG antibody in acute and convalescent serum as detected by indirect fluorescence
- therapy: doxycycline
Life cycles of Ixodes ticks
-
Primary route:
- 1st blood metal –> Infected nymph –> infected human
-
Secondary route:
- 2nd blood metal –> Infected adult –> infected human
Mechanism of action: Ehrlichia Infection
- Ehrlichia replicate in the phagosome of monocytes which results in “Incusion Bodies” or morulae visible in the light microscope
- Ehrlichia in morula then exit the host cell following rupture of the morula –> can then spread the infection
Bartonella henselae (cat scratch disease):
- sxs
- transmission
- how was etiologic agent discovered?
- type of pathogen
- sxs: febrile lymphadenitis (enlarged lymph nodes), rash, conjunctivitis, fever, rarely encephalitis, usually self-limiting (many are asymptomatic)
- transmission: cat fleas may transmit b/w cats: cats transmit to humans, possibly via fleas. No human-human transmission
- how was etiologic agent discovered?
- discovered in 1983 w/ silver stain
- type of pathogen: not an obligate intracellular pathogen; will grow on laboratory medium, but difficult to culture
- PCR was best for diagnosis
Which bacteria can cause bacillary angiomatosis?
Define bacillary angiomatosis.
Patients and symptoms.
- Bartonella henselae and Bartonella quintana
- Bacillary angiomatosis: a disease characterized by unique vascular lesions caused by infection with small, gram-negative organisms
- Affects AIDS patients; proliferation of small blood vessels of skin and viscera
Compare chlamydia trachomatis, and pneumoniae?
-
C. trachomatis: human to human
- multi. serogroups each causing diff’t diseases; urogenital, incl. conjunctivitis, trachoma
- C. pneumoniae: human to human
Compare Rickettsia rickettsii and prowazekii
Rickettsia rickettsii:
- caused by tick vector –> Rocky Mt. Spotted Fever
Rickettsia prowazekii:
- caused by louse vector –> Epidemic Typhus
Compare Ehrlichia chaffeensis and Anaplasma phagocytophilia
-
Ehrlichia chaffeensis:
- human monocytic Ehrlichiosis: tick vector
-
Anaplasma phagocytophilia:
- human granulocytic anaplasmosis
- tick vector same as lyme disease
Compare Bartonella henselae and quintana
Bartonella: can be cultured on media but fragile and fastidious. Not an obligate intracellular pathogen
-
henselae: cat scratch fever
- fleas transmit between cats –>
- cats can transmit to humans, so it is a zoonosis
-
quintana: trench fever and bacillary angiomatosis
- body louse transmits
Chlamydia trachomatis: lymphogranuloma venereum
- sxs in males
- sxs in females
A sexually transmitted disease:
-
Males: initial small painless ulcer or papule that heals; MSM get proctitis
- progression to infxn of the inguinal lymph nodes which enlarge, becoming bubos
- MSM may not get inguinal sxs; generalized sxs may occur
- late sxs: urethral and rectal strictures, perirectal abscesses, and fissures
-
Females: ulcers may go unnoticed; inguinal sxs do not alwasy occur
- Get cervicitis and salpingitis
