Community-Acquired Pneumonia

Question 1

Which is true about PNA?

a. It’s incidence has declined since ABx.
b. ID’ing the causative organism is key to diagnosis.
c. It can occur in a healthy person w/o other risk factors.
d. The clinical picture (history, physical exam) for community-acquired PNA is very sensitive and specific.`

Answer 1

c. It can indeed occur in healthy people without risk factors.

Question 2

Which is more useful in determining how to treat PNA?

a. A procedure that will reliably ID the organism.
b. A thorough history, physical exam, and plain CXR.

Answer 2

b.

Really you only need to do a procedure like bronchoscopy/lavage if the patient is very very sick.
(This is not to say that culture and sensitivity testing aren’t important, but the ABx that you would start based on the clinical picture usually tend to work well.)

Question 3

Lungs are usually sterile.

Answer 3

But mouths are not. Which is pretty remarkable.

Question 4

If you know the kind of deficit in someone’s defense mechanism, it suggests potential organism that could be causing the infection.

Answer 4

Yes. For example neutropenia predisposes to invasive aspergillosis.

Question 5

Interestingly, Strep. pneumo doesn’t have many virulence factors. What is its superpower?

Answer 5

Its capsule, which enables it to avoid phagocytosis.
Interestingly… it promotes complement fixation, so there’s lots of inflammation and damage, but not much clearance of the bug.

Question 6

Definition of community acquired PNA (CAP)?

Answer 6

It’s not… hospital-acquired, healthcare-associated, or chronic.

Question 7

Common clinical presentation of PNA?

Answer 7

Fever, cough, dyspnea, pleuritic chest pain, with a sudden onset.

(though elderly can present with fever and altered mental status alone)

Question 8

Does sputum production give you a clue about the location of the inflammation?

Answer 8

Yes…
Clear or non-productive: Interstitial.
Productive: lobar or bronchopneumonia.
(within the latter category, sputum color really doesn’t tell you that much)

Question 9

Physical exam findings typical of PNA?

Answer 9

Tachypnea.
Tachycardia.
Dullness to percussion.
Rales.
Eegophony.
Splinting (trying not to move side of ribcage with PNA)

Question 10

If the clinical picture looks like PNA, but the CXR doesn’t show infiltrates, what do you call it? (usually)

Answer 10

Bronchitis.

sometimes, though, the infiltrates don’t show up if the patient is dehydrated

Question 11

Should bronchitis be treated with ABx?

Answer 11

Not usually.

Exceptions = pertussis, to reduce transmission. COPD? Influenza.

Question 12

What’s the yield of ID’ing a specific organism in PNA?

Answer 12

Low - 20-50% from sputum culture, 10-20% from blood culture.

Question 13

What characteristic of a sputum sample makes you think it’s from the lungs, and not the nose/mouth?

Answer 13

If from lungs, will have many PMNs and few epithelial cells.

Question 14

8 common organisms causative of acute CAP?

Answer 14

Strep. pneumo
Legionella
Mycoplasma
Chlamydia pneumoniae (not trachomatis, fyi)

Drug resistant S. pneumo
Enterobacteriaceae
Staph. aureus
Pseudomonas

Question 15

Severity gives you a big clue about the etiology of the CAP. What are 3 categories of severity?

Answer 15

Ambulatory
Hospitalized, non-ICU
ICU

Question 16

Most common organism causing CAP in an ambulatory setting?

Answer 16

Mycoplasma (and viruses)

and just never determined

Question 17

Most common organism causing CAP in a hospitalized, non-ICU setting?

Answer 17

S. pneumo

Question 18

What organism becomes much more prevalent when you look at in CAP patients in an ICU?

Answer 18

Legionella jumps up to 2nd most common (still behind S. pneumo)

Question 19

What in particular should you ask about when taking the history of a patient with CAP (or really, any PNA)?

Answer 19

Exposures to unusual stuff.

Like spelunking or inhaling rabbit shit.

Question 20

Does culturing a pathogen mean the patient has PNA?

Answer 20

Nope. Many pathogens colonize the mouth, oropharynx etc. without causing disease.

Question 21

Which 3 organisms causing CAP are called “the atypicals”? Why?

Answer 21

Legionella, mycoplasma, and clamydia.
The distinction is based on the ABx used - macrollides/quinalones are more effective. (as compared to penicllins and cephalosporins for “typical” PNAs)