Intracellular Bacterial Infection

Question 1

Listeria’s ability to enter cells allows it to infect _______________.

Answer 1

the CNS and the placenta (and subsequently fetuses)

Question 2

Listeria monocytogenes is __________-positive.

Answer 2

catalase (remember the cat –who kind of looks like Walter –playing with the Christmas tree ornaments beneath the table holding Santa’s cheese)

Question 3

Obligate intracellular pathogens often have mutations in _______________.

Answer 3

nutritional enzymes (indicating that they are entirely reliant on host enzymes)

Question 4

List the facultative intracellular bacteria.

Answer 4

Salmonella (birds walking in and out of cages) 
Shigella (gorilla being shot out of actin cannon) 
Listeria (rocket toys beneath the tree) 
Bartonella
Brucella 
Francisella
Legionella
Mycobacterium tuberculosis 
Nocardia

Question 5

List the obligate intracellular bacteria.

Answer 5

CREM E: 
Chlamydia
M. leprae
Coxiella
Rickettisa
Ehrlichia

Question 6

There are two kinds of Salmonella typhi: _________________.

Answer 6

• Salmonella typhimurium (generalist)

- Salmonella typhi (human-specific)

Question 7

What are the two mechanisms by which bacteria can enter cells?

Answer 7

• Zipper: close contact with host membrane

- Trigger: forced entry, usually by T3SS (such as that in Shigella or Salmonella)

Question 8

Intracellular infection allows for very fast _______________.

Answer 8

systemic infection; Salmonella can be found inside bloodstream macrophages only five minutes after inoculation in the stomach

Question 9

What makes Salmonella appear black on Hektoen agar?

Answer 9

Production of H2S

Question 10

NADPH oxidase produces ____________.

Answer 10

superoxide radicals (O2–•)

Question 11

How can pathogens deal with O2–•?

Answer 11

Superoxide dismutase, which produces H2O2

Question 12

Catalase breaks down __________.

Answer 12

H2O2 to water

Question 13

If a bacterium does not have enzymes to eliminate O2–• and H2O2, what other ways could it escape oxidative bursts?

Answer 13

By escaping the phagolysosome (such as Shigella and Listeria)

Question 14

What are some oxygen-independent mechanisms of killing intracellular pathogens?

Answer 14

Defensins
Phospholipase
Lysozyme

Question 15

What is the difference between a phagosome and phagolysosome?

Answer 15

Phagosomes are vacuoles that contain bacteria, while phagolysosomes are mature phagosomes that have created an acidic interior environment.

Question 16

How does Legionella escape phagocytic destruction inside cells?

Answer 16

It grows in the endoplasmic reticulum!

Question 17

How does Mycobacterium escape intracellular destruction?

Answer 17

It stays in early endosomes, which don’t acidify.

Question 18

Which bacterium escapes intracellular destruction by intercepting Golgi traffic?

Answer 18

Chlamydia

Question 19

Coxiella survives by _________________.

Answer 19

residing in phagolysosomes (the only organism to do so!); as such, it is said to be fusogenic

Question 20

Bartonella survives inside _______________.

Answer 20

erythrocytes; this is why it causes bacillary angiomatosis

Question 21

In general, the best antibiotic for intracellular bacteria is ______________.

Answer 21

tetracycline

Question 22

Which antibiotics reside in lysosomes?

Answer 22

Macrolides and aminoglycosides; this happens because these two are weak bases and get trapped in the acidic environment of the lysosome

Question 23

Which method of entry is also called macropinocytosis?

Answer 23

Trigger

Question 24

Which two human-cell-made products can inactivate aminoglycosides and beta-lactams?

Answer 24

Nitric oxide and IFN-gamma