Mycoplasma/Legionella

Question 1

Mycoplasma is said to have a ____________ shape.

Answer 1

pleiomorphic (meaning it is not coccoid or bacillary –it can change shape)

Question 2

Most Mycoplasma have a fried-egg appearance, but ___________ does not.

Answer 2

M. pneumoniae

Question 3

What kind of URIs does Mycoplasma usually cause?

Answer 3

Pharyngitis
Tracheobronchitis
Rhinitis

Question 4

How is M. pneumoniae transmitted?

Answer 4

Via respiratory droplets

Question 5

How does M. pneumoniae establish infection?

Answer 5

It attaches to the base of respiratory cilia (via terminal cytoadherence organelle) and secretes H2O2 and CARDS toxin (which causes the cilia to stop beating).

Question 6

Uniquely, the ______________ duplicates first in mitosis of the M. pneumoniae bacterium.

Answer 6

cytoadherence organelle

Question 7

What does CARDS stand for?

Answer 7

Community Acquired Respiratory Distress Syndrome toxin

Question 8

The diagnostic PCR for M. pneumoniae targets ____________.

Answer 8

P1 on the cytoadherence organelle and the CARDS toxin

Question 9

How does the CARDS toxin work?

Answer 9

Like pertussis toxin, it is an ADP-ribosylator

Question 10

How long after colonization does M. pneumoniae cause symptoms?

Answer 10

Typically 4 weeks

Question 11

Although M. pneumoniae is usually self-limited, treating with macrolides or fluoroquinolones shortens symptoms by about ___________.

Answer 11

3-4 days

Question 12

What are the four leading causes of community-acquired pneumonia?

Answer 12

1) S. pneumoniae
2) H. influenzae
3) C. pneumoniae
4) L. pneumophila

Question 13

Although Legionella stains poorly, it is __________.

Answer 13

Gram-negative

Question 14

What does Legionella need to grow?

Answer 14

Charcoal yeast
Cysteine
Iron

Question 15

What will you see on histologic examination of someone with L. pneumophila?

Answer 15

Macrophages and neutrophils

Question 16

List some things that might make you consider a diagnosis of Legionnaire’s disease?

Answer 16

• Hyponatremia
• High fever (greater than 104º)
• Diarrhea
• Failure to respond to beta-lactams
• Confusion
• Onset of symptoms 10 days or more after contact with sick people

Question 17

Two tests can detect Legionella: ______________.

Answer 17

urine ELIZA for Legionella LPS; FISH

Question 18

How is Legionnaire’s disease different from Pontiac fever?

Answer 18

Pontiac fever does not cause pneumonia –only pleuritis –and the incubation period is shorter.

Question 19

How does Legionella survive inside macrophages?

Answer 19

It causes fusion of the endosome that is containing it with mitochondrial membrane and form a unique Legionella-containing vacuole that does not undergo phagolysosome maturation.

(Think of the submarine in the Sketchy scene –it’s a floating powerhouse, just like mitochondria!)

Question 20

Consolidation (as seen on x-ray) persists for much longer in ______________.

Answer 20

Legionella pneumonia (as compared to Streptococcus pneumoniae)

Consolidation can persist for months.

Question 21

Where does Legionella live in the environment?

Answer 21

Water

There have been cases where Legionella has colonized water towers and shower heads.

(Think of the Sketchy scene set in the navy pier.)

Question 22

What epidemiologic pattern does M. pneumoniae follow?

Answer 22

It is transmitted by close contact with infected people, but other than that there is no seasonal or age preference.

Question 23

Three drugs can treat M. pneumoniae: ______________.

Answer 23

tetracyclines, macrolides, and fluoroquinolones

Question 24

Legionella is resistant to ________________.

Answer 24

penicillins because it produces a beta-lactamase

Question 25

_____________ staining can reveal Legionella, but it is not specific to Legionella.

Answer 25

Silver