Chlamydia, Rickettsia

Question 0

Chlamydia life cycle

Answer 0

Both Chlamydia and Chlamydiophilia

Elementary body - rigid cell wall, not dividing, infective, small
-> phagocytosis -> lose cell wall -> make RNA ->
Reticulate/initial body - actively dividing, not infectious, large, no cell wall
-> replicate -> produce elementary bodies -> lysis/extrusion

Prompts phagocytosis, manipulates trafficking machinery
-> cell death from lysis

Question 1

Obligate intracellular

Answer 1

MUST grow within host cell
- can’t make ATP -> induce host machinery
Chlamydia/Chlamydophilia
Rickettsia
Mycobacterium leprae
Small
Cell wall - similar to Gram (-) bacteria but not identical

vs facultative intracellular: Salmonella, Shigella, Legionella

Question 2

Chlamydophilia psittaci

Answer 2

Zoonosis: birds (parrots, pigeons, poultry)
- chronic/subclinical -> fecal excretion
- acute stress (overcrowding, malnutrition) -> more elementary bodies released
Inhalation of bird feces (birdcage, occupational)
Psittacosis = generalized -> epithelial, endothelial, macrophages
- +blood, +sputum
- fever, H/A -> interstitial/diffuse pneumonia

Rare, reportable

Question 3

Chlamydophilia pneumoniae

Answer 3

Up to 10% of adult pneumonia (can’t be cultured -> underdx?)

Person-person aerosol transmission (NOT birds)

• > gradual onset of cough, no fever
• > atypical pneumonia (vs lobar) - similar to Mycoplasma, Legionella

Serologic correlation with CAD?

Question 4

Chlamydia trachomatis

Answer 4

Multiple serotypes

• D-K - urethritis, conjunctivitis, pneumonia
• A-C - trachoma
• L1-L3 - lymphogranuloma venereum

Inflammation key in pathology

Question 5

Non-gonococcal urethritis

Answer 5

aka Chlamydia trachomatis (serotypes D-K)

Most common venereal disease worldwide (4-5% young adults in US)
Frequently asymptomatic or purulent urethritis
-> increased HIV transmission
-> epididymitis
-> inflammation -> scarring -> ectopic or sterility
-> Reiter’s syndrome

Dx: negative Gonococcal culture, urine PCR
(yearly screening for at-risk women)
Tx: single high dose azithromycin (both partners!)

Question 6

Infant chlamydia

Answer 6

C. trachomatis - perinatal transmission

Inclusion conjunctivitis (intracellular inclusion bodies)

• sticky discharge, large lymphoid follicles
• not prevented by erythromycin, sulfonamides
• can see from env’t, swimming pools, STI
• can progress to chlamydial pneumonia

Question 7

Trachoma

Answer 7

aka C. trachomatis (serotypes A-C)

Mechanical transmission (finger, fly -> eye)

Cloudy cornea, discharge
Swelling of lymph nodes, eyelids
Eyelashes turn in -> scratching of cornea -> blind
- leading cause of preventable blindness

Tx: azithromycin, surgery for advanced blindness

Question 8

Lymphogranuloma venereum (LGV)

Answer 8

caused by C trachomatis (serotypes L1-L3)

Venereal
Painless papule -> vesicle -> ulcer
 -> lymph nodes
 - often resolves but better to tx early
Frei test: heat-killed LGV -> delayed hypersensitivity (sim to PPD)
 - indicates current or past exposure

Tx azithromycin

Question 9

Dx and tx of Chlamydia

Answer 9

Intracellular - can’t simply culture
- can innoculate cultured cells -> slow growth -> fluorescent antibodies of staining of inclusion bodies
Antigens - shared group antigen, specific to distinguish
- compare acute vs convalescent titers
Trachomatis - smear -> immunofluor, enzyme immunoassay, DNA probe, PCR
Psittaci, Pneumoniae - specific antibody tests

Tx: must penetrate cells

• tetracyclines
• azythromycin prefered

Question 10

Rickettsia

Answer 10

Obligate intracellular (related to mitochondria)
- why? they can make ATP
Arthropods are normal host, vector
Phagocytosis (induced, expends energy) -> slow growth (1 day) -> lysis

Dx: PCR, immunohistology
Tx: tetracyclines

Question 11

Rickettsia prowazeckii

Answer 11

Primary endemic typhus
- capillary endothelium -10 d> fever, intractable H/A -4-7 d> rash
- frequently fatal
- latent -> recrudescence aka Brill-Zinser (Russia, immunocompromised)
Transmission via body lice (live in seams of clothing)
- punctures skin -> defecates -> scratching pushes into body
- prevent with DDT, hygeine
- reservoirs - flying squirrel, latent cases (Brill-Zinser)
Dx: specific antigens, LFTs
- Weil-Felix rx - cross-reacts with Proteus -> hemagglutination
Tx: tetracyclines

Question 12

Rickettsia typhi

Answer 12

Endemic murine typhus
 - related to prowazeckii but milder (sudden fever, H/A -> rash)
Transmission:
 - rats, ground squirrels -> fleas
 - endemic in Atlantic, Gulf of Mexico
Dx: serum antigen, antibodies
Tx: tetracyclines

Question 13

Rickettsia rickettsii

Answer 13

-> Rocky Mtn Spotted Fever
One week incubation -> fever, h/a, arthritis, abdominal n/v ->
Rash (lesions on hands, feet -> trunk)
Mortality 20% if untreated

Transmission: ticks (including transovarian to tick eggs, larvae)

• mammal reservoirs
• Western - forest tick
• Eastern = most cases! - dog tick

Dx: skin biopsy -> fluorescent antibody

Question 14

Rickettsia akari

Answer 14

aka Rickettsial pox
Primary skin lesion -1 week> fever, h/a, rash (resembles chicken pox)
- benign, not life-threatening
Transmission: mouse -> mouse mite
- common in apartment buildings, urban (vs forest)

Question 15

Coxiella burneti

Answer 15

aka Q fever
Related to Legionella (not Rickettsia)
Interstitial pneumonia, fever, h/a, LFT’s, sometimes rash
Can have chronic vasculitis, endocarditis

Transmission:
- farm animals (sheep, cow) -> tick -> animal
-> placenta, carcasses contains spore-stage -> inhalation
NO vector for transmission to humans!!
Present in Southern US

Dx: serologic antigen, immunofluorescence, immunohistology
Tx: doxycycline, quinolone
Prevention: vaccine, hygiene

Question 16

Ehrlichioses

Answer 16

Emerging tick-borne diseases
Obligate intracellular

Monocytic -
Granulocytic - via same tick as Lyme’s disease

-> fever, lymphocytopenia (lysis), LFT’s
Tx: tetracycline, doxycycline