Chlamydia

Question 1

Chlamydia

Answer 1

• small
• Gram (-)
• no peptidoglycan/ Murein
• obligate intracellular

Question 2

Where does Chlamydia get its energy

Answer 2

Receives ATP from host

Question 3

What 2 species of Chlamydia pertain to humans?

Answer 3

C. Trachomitis

C. Pneumoniae

Question 4

What is the most common agent of STD infections and the leading cause of preventable blindness?

Answer 4

Chlamydia

Question 5

How is Chlamydia transmitted

Answer 5

Droplet or direct contact

• Mucosal epithelial cells
• localized in eyes, lungs, genitalia
• 4 f’s (fingers, flies, fomites, fornication)

Question 6

What are complications with C. trachomitis

Answer 6

in men: prostititis, epididymis
in women: cervicitis, premature birth
both: urethritis, infertility, proctitis, arthritis
usually asymptomatic in females

Question 7

Does C. trachomitis cause chronic or acute infection

Answer 7

Both

Question 8

What complications can arise during birth

Answer 8

infant can contract pneumonia or conjuctivitis

Question 9

How does Chlamydia enter the cell

Answer 9

Masquerade as nutrients, growth factors, hormones to bind to specific receptors

Question 10

How does the Elementary body (EB) modify the endocytotic vesicle?

Answer 10

Maintain pH above 6.2
Prevents vesicle from fusion with lysosomes

Vesicle is also modified with host components (glycolipids) for camouflage

Question 11

What happens when EB transforms into a larger intracellular active organism RB

Answer 11

Synthesize molecules using host metabolites and energy
Divide by binary fission

Organisms develop slowly
2 – 3 days per cycle
200 – 1,000 organisms
Inclusions observed

Question 12

How does the RB receive nutrients from outside the vaccule?

Answer 12

drinking straws

Question 13

What prevents antimicrobials from reaching the RB

Answer 13

Four membrane layers to penetrate:
Host cell plasma membrane
Inclusion membrane
Chlamydial outer membrane
Chlamydial cytoplasmic membrane

Question 14

Rickettsiae

Answer 14

Small Gram negative rods
Don’t stain well

Obligate intracellular bacteria

Zoonoses - infections transmitted from animals to humans

Question 15

How does Rickettsiae handle energy needs

Answer 15

Can synthesize own ATP. Capable of independent metabolism.

Question 16

R. rickettsii

Answer 16

Rocky Mountain spotted fever.

-Ticks

Question 17

R. prowazekii

Answer 17

Epidemic typhus

• reservoir in humans/flying squirrels
• transmission louse feces

Question 18

R. typhi

Answer 18

Murine typhus

• reservoir fleas/rats
• transmission flea feces

Question 19

R. tsutsugamushi

Answer 19

Scrub typhus

-Reservoir Chiggers

Question 20

How does R. rickettsii spread/multiply

Answer 20

Attach to vascular endothelial cells (small blood vessels)
Induce endocytosis
Once inside, presumably lyse the phagosome (phospholipase) and enter the cytosol

Question 21

spread of the Rickettsia family spread

-differfences

Answer 21

Mode of exit from host cell varies
R. prowazekii exits by cell lysis
R. rickettsii get extruded from the cell through local projections (filopodia)
Actin in the host cell associates with R. rickettsii and the actin helps to “push” the bacteria through the filopodia
R. tsutsugamushi exits by budding through the cell membrane
Remains enveloped in the host cell membrane as it infects other cells

Question 22

How does Rickettsia move through the host cell

Answer 22

It propels itself through actin polymerization resulting in comet tail.

Question 23

How does Rickettsia leave the cell

Answer 23

The F-actin propels it into filopodia at the cell surface.

Question 24

How does R. rickettsia cause injury

Answer 24

Proportional to the number of intracellular bacteria
Lysis of the cells results in leakage of blood (rash)
Hemorrhagic spots
Organism can travel to other vessels including the heart and brain
75% of patients will clear the infection, even before antimicrobial treatment

Question 25

Ehrlichia

Answer 25

Discovered 1987
E. chaffeensis and E. ewingii
Obligate intracellular bacteria
Transmitted by Lone Star tick
Infects mostly monocytes and macrophages
Human granulocytic ehrlichiosis (HGE) and human monocytic ehrlichiosis (HME) 
Fever, malaise, headache and myalgia
Develop within host cell vacuoles first as reticulate cells (RC) and then as dense-core cells (DC)

Question 26

Diagnosis of Rickettsioses

Answer 26

Problematic
During first visit, patients don’t typically have fever or rash, and may not be aware of a tick bite
Requires eukaryotic cell cultures or inoculation of animals
Handling is notoriously hazardous
Clinical diagnostic tests
Antibody titers
Fluorescent antibody assay
Complement fixation
Latex agglutination

Question 27

Mycoplasma

Answer 27

Smallest organisms capable of growth on cell-free media
Requires sterol (cholesterol)
Characteristic “fried egg” appearance
Small colonies
Slow growth

Lack a cell wall (no murein)
Not sensitive to penicillin

Cell membranes contain sterols

Found in other mammals and in birds

Question 28

M. pneumoniae: Encounter and Entry

Answer 28

Humans only reservoir
Unlike pneumococci, prolonged asymptomatic colonization is uncommon

Infections mild and moderately contagious
Spread through close-contact groups
Passed by respiratory droplets

“Walking pneumonia”
Primary atypical pneumonia – not cleared by penicillin

Adhere to respiratory epithelium
Terminal adhesion structures – tip-mediated attachment organelle

Question 29

M. pneumoniae spread/multiplication

Answer 29

Main cells of the inflammatory response are lymphocytes
Unusual
Largely limited to the respiratory mucosa that lines the airways
Doesn’t get into the lung alveoli
Bronchopneumonia
Not highly destructive of tissues, but ciliary function is impaired
Tissue toxic substances, may include H2O2
Inflammatory mediators

Question 30

M. pneumoniae damage

Answer 30

Hemolytic anemia
IgM = cold hemagglutinins
At lower temperatures, these antibodies cause RBCs to stick together
Detectable in 50% of cases
Clinically significant hemolysis is rare

Encephalitis

Erythema multiforme (rash)