Respiratory Infections

Question 1

Define ‘community-acquired’ CAP:

Answer 1

In someone who has not been a hospital inpatient in the last 10-14 days

Question 2

Most common organism in CAP:

Answer 2

Strep pneumoniae (pneumococcus)

30%

Question 3

List 5 CAP organisms, and their general demographic/ features:

Answer 3

Strep pneumoniae (pneumococcus) - 30%
- Overall most common
- Unwell
- Rust-colour sputum, pleurisy
- Vaccine available

Mycoplasma pneumoniae- 15% + Chlamydia pneumoniae - 8%
- Young (<40), otherwise healthy
- Ambulant, not too sick
- WON’T CULTURE: serology/ PCR (intracellular)

Legionella (Legionairre’s Disease)- 10%
- Water (AC towers), soil, travel
- PUBLIC HEALTH ISSUE often
- Severe CAP, multisystem disease
–> Diarrhoea, LFT derangement, CK up, confusion

Staph aureus
- Severe, high mortality
- Often context of INFLUENZA or IVDU
- Often haematog (or asp)

Viruses
SARScov2
Influenza A and B
Parainfluenza
RSV
Adenovirus
EBV, CMV, VZV, HSV

__________________________

OTHER:
COPD- H. influenzae, M. catarrhalis
Alcoholic (asp): Gram neg rods: Klebsiella, E.Coli
Abbatoir- Coxiella Burnetti (Q fever)
Birds- Chlamydia psittaci
Bad teeth: anaerobes
Immunosupp: PJP, TB

Question 4

What organisms common in aspiration pneumonia?

Answer 4

S. aureus

Gram neg rods
Klebsiella
E.Coli
Anaerobes

Question 5

Organisms of concern in HAP:

Answer 5

Inpatients >48 hours

More drug resistant

Usual pathogens
+
GRAM NEGATIVES:
Klebsiella
E.Coli
Pseudomonas
ESCAPPM
+
MRSA

Question 6

Organisms of concern in VAP:

Answer 6

Same as HAP.

Question 7

SMART COP Score:

Answer 7

Australian
Predicts risk for INTENSIVE RESPIRATORY OR VASOPRESSOR SUPPORT. ie. need for ICU
Scoring is different if age <50 vs >50

Very sensitive (92%)

Not valid in immunosuppression
Less accurate in viral
Tends to overpredict severity. (62% specific)

———————

>5 = severe, high/very high risk of IRVS

Question 8

CORB score:

Answer 8

Australian
Also about IRVS
2 or more = severe/ risk IRVS

Easy to remember
Doesn’t reply on lab tests

Single centre- ?external validity
Less sensitive and specific than SMARTCOP (80 vs 90% sensitive)

Question 9

CURB65 score:

Answer 9

Looks as inpatient vs outpatient disposition

Easy to remember
Less sensitive than SMARTCOP

Question 10

CXR appearances in pneumonia (and aetiologies clues):

Answer 10

BRONCHOPNEUMONIA
- Patchy consolidation
- Often bilateral
- Most organisms incl viral and atypicals

LOBAR PNEUMONIA
- Single or multi
- Air bronchograms
- Pneumococcus

INTERSTITIAL
- Volume loss, honeycombing
- Mycoplasma, PJP
- Viruses

APICAL
- TB
Always consider TB in apical pneumonia

MILIARY
- TB
- Fungal

BILATERAL LOWER LOBE
- Aspiration
Eg. Klebsiella, E.coli

PERIPHERIES
- Haematogenous
Eg. S. Aureus

CAVITATIONS
- TB
- S. Aureus
- Anaerobes
- Gram negs: pseudomonas, klebsiella
- Fungal
But can be most things. Rare.

Question 11

What is ‘round’ pneumonia?

Answer 11

Can occur in children

Connections between alveoli (pores of Kohns) aren’t developed yet- so pneumonia contained.

Can be mistaken for mass

Question 12

First-line antibiotics and rationale in (non tropical) CAP:

Answer 12

Standard regime covers pneumococcus and atypicals.
- Blactam for pneumococcus
- Macrolide for atypicals (doxy —> azithro)
With increasing severity, add cover for gram negatives, pseudomonas, staph aureus.
If super sick, broaden cover (NOTE: still doesn’t cover for MRSA)

In aspiration, don’t need atypical cover. Do need anaerobe cover (metro)

Atypicals in kids very self-limiting.

———————-

MILD:
Amoxicillin 1g (30mg/kg) TDS PO
Or
Doxycycline 100mg BD
both if no improvement at 48hrs

MODERATE
Benzylpenicillin (60mg/kg) 1.2g QID IV
AND
Doxycycline 100mg BD (no need in kids)
Metro instead of doxy for aspiration

SEVERE (CURB65 5+, CURB 2+)
Ceftriaxone 1 or 2g (50mg/kg) daily IV
AND
Azithromycin 500mg daily IV
Metro instead of doxy for aspiration

Question 13

How does treatment of tropical CAP differ:

Answer 13

Atypicals are uncommon.
Acitenobacter and Burkholdia more common.
—> Need aminoglycoside

MILD
Amoxy only

MODERATE
Ceftriaxone 2g AND Gentamicin

SEVERE
Meropenem 1g TDS AND Gentamicin

Question 14

CAP antis in penicillin allergy:

Answer 14

….

Question 15

Antibiotics and rationale in HAP:

Answer 15

Concern is multi-drug-resistant organisms
Gram negs like E.Coli, Klebsiella, pseudomonas more common
Antibiotic choice largely based on MDR risk
—> HDU/ICU for >5days

MILD HAP and low risk MDR:
Augmentin

MODERATE and low risk MDR:
Ceftriaxone

SEVERE or HIGH RISK of MDR:
Tazocin

Question 16

Empyema:

Answer 16

Up to 50% hospitalised CAP

Indistinguishable from effusion on CXR

Any non-minor effusion should be tapped for diagnosis:
- Cloudy/ Frank pus
- WCC > 100 (mm3)
- Low glucose <2.2
- Organisms on stain
+- CT chest contrast

Drain via pigtail catheter (eg. 12F)
—> Noninferior to larger bore

Antibiotics as per CAP/ gram stain

Question 17

What lab test/a diagnose an atypical pneumonia?

Answer 17

PCR
- NP swab
- Sputum
- Blood

or

SEROLOGY to look for antibodies
- requires sick and convalescent serum