(incomplete) Chlamydia and Rickettsia

Question 1

List some common characteristics of intracellular pathogens.

Answer 1

Gm- by phylogeny, but not analyzed by Gm stain (OBLIGATE intracellular pathogens)
Small size (~300nm)
Bacteria-like cell walls

Question 2

Why is Chlamydia an obligate intracellular pathogen? Describe the two stages in its developmental cycle.

Answer 2

Cannot make ATP - depends on host cell ATP

1. Elementary bodies: small, non-multiplying, with rigid bacterial-like cell wall; this form transmits infection
2. Initial bodies (aka reticulate bodies): larger, actively multiplying, lack rigid cell wall, noninfectious

Question 3

List the steps in the intracellular growth cycle of Chlamydia.

Answer 3

1. Elementary bodies induce phagocytosis by host cell (can enter non-phagocytic cells this way)
2. Elementary bodies -> initial bodies via loss of cell wall, increase in size, and RNA synthesis
3. Initial bodies divide by binary fission
4. Some progeny converted back to elementary bodies -> further spread

Question 4

What organisms are affected by Chlamydia?

Answer 4

Humans, other mammals, birds

Question 5

List the three known human pathogens in Chlamydiaciae, how many serotypes, and what they cause (briefly).

Answer 5

Chlamydophilia psittaci: one serotype, causes psittacosis
Chlamydophilia pneumoniae: one serotype, pneumonia in adults
Chlamydia trachomatis: different serotypes cause a variety of things

Question 6

Chlamydophilia psittaci: reservoir, transmission, pathogenesis, detection

Answer 6

AKA “parrot fever”
Zoonosis - infects birds, -> constant fecal excretion
–Mostly subclinical in birds, but can increase in malnutrition and crowding

Transmission: inhaling fresh bird feces

Pathogenesis: generalized infection, -> fever, headache
–Severe -> extensive INTERSTITIAL PNEUMONIA

Detection: isolatable from blood or sputum

Question 7

Chlamydophilia pneumoniae: disease caused, transmission

Answer 7

Causes 10% of pneumonia (atypical pneumonia)

Transmission: person to person via respiratory aerosols (no birds)

Question 8

Chlamydophilia trachomatis serotypes D-K in adults: disease caused, transmission, symptoms, diagnosis, treatment

Answer 8

Nongonococcal urethritis - common venereal disease (non-gonococcal = no N. gonorrhea)

Mostly asymptomatic in males, frequently asymptomatic in females

• -Symptom: purulent urethral discharge
• -Increases likelihood of HIV transmission
• -Can -> severe disease/scarring of epididymus or Fallopian tubes -> infertility

Diagnosis: rapid PCR of urine specimens

Treatment: single high dose of azithromycin for both sexual partners

Question 9

Chlamydophilia trachomatis serotypes A-C: disease caused, transmission, symptoms, treatment

Answer 9

Trachoma

Transmission: mechanical (finger to eye) and by flies under conditions of poor hygiene

Symptoms: chronic reinfection of conjunctiva -> infolding of eyelashes -> corneal scarring and blindness

Treatment: annual treatment with azithromycin, surgery

Question 10

Chlamydophilia trachomatis serotypes L1-L3:

Answer 10

Lymphogranuloma venereum: venereal disease, more invasive than serotypes D-K

FINISH

Question 11

Treatment of Chlamydia

Answer 11

MUST ENTER CELLS
Tetracyclines work well
Azithromycin preferred

Question 12

Diagnosis of Chlamydia

Answer 12

NO CULTURE

Check for group antigen shared by all ChlamydiaFINISH

Question 13

Chlamydophilia trachomatis serotypes D-K in neonates: disease caused, transmission, symptoms, diagnosis, treatment

Answer 13

Inclusion conjunctivitis and infant pneumonia

Transmission: from infected mother to neonate at birth or environmental contamination

Symptoms:
Inclusion conjunctivitis:
FINISH

Question 14

Basic properties of Rickettsia

Answer 14

Mostly arthropod-transmitted

Intracellular growth cycle, but CAN make their own ATP

Question 15

Rickettsia prowazekii:

Answer 15

Epidemic typhoid fever

First multiplies in capillary endothelial cells

Incubation period: 10 days

Symptoms: fever, severe intractable headache, rash 4-7 days later
–Frequently fatal in children

Transmitted by body lice: human -> louse -> human -> louse

• -Scratching increases transmission
• -Aggravating factors: poor hygiene, famine, war
• -Also maintained in flying squirrels

Treatment: tetracyclines

Diagnosis: PCR detection, serological tests for specific antigens, LFTs

Prevention: louse control

Question 16

What is Brill-Zinsser disease?

Answer 16

A recrudescent disease that occurs due to R. prowazekii FINISH

Question 17

Rickettsia typhi:

Answer 17

Endemic murine typhus

Hosts: rats, ground squirrels

FINISH

Question 18

Rickettsia rickettsii:

Answer 18

Rocky Mountain spotted fever

Symptoms: fever, headache, arthritic pains, abdominal pain, N/V

Incubation period: < 1 week

Transmission:

Treatment:

Diagnosis: fluorescent Ab tests on skin biopsy -> immediate diagnosis

Prevention: suitable clothing to avoid ticks

FINISH

Question 19

Rickettsia akari:

Answer 19

Rickettsial pox

Incubation period: primary skin lesion + incubation period of 1 week

Symptoms: fever, chills, headache, rash

Transmission: mouse mite -> mouse -> mouse mite -> humans
–Often in urban setting combined to large apartment complexes

Question 20

Coxiella burnetii:

Answer 20

Q fever

Transmission: inhalation of pathogen associated with carcasses of farm animals
-> sheep/goat/cow/cat -> tick -> sheep/goat/cow/cat -> placental tissue with spores -> humans

Symptoms: interstitial pneumonia, fever, headache, elevated LFTs, sometimes rash (FINISH)

Question 21

Ehrlichioses: what are they, two types and what each infects, symptoms, treatment

Answer 21

Newly emerging tick-borne diseases

• -Monocytic ehrlichiosis: infects monocytes
• -Granulocytic ehrlichiosis: infects granulocytes

Symptoms: fever, lymphocytopenia, elevated LFTs

Treatment: tetracycline