Community-Acquired Pneumonia

Question 1

What are the typical CAP pathogens and their common presentations?

Answer 1

Streptococcus pneumoniae,
Haemophilus influenzae, and
Moraxella catarrhalis

typical CAP classically present with fever, a productive cough with purulent sputum, dyspnea, and pleuritic chest pain

Question 2

What are the atypical CAP pathogens and their common presentations?

Answer 2

Mycoplasma pneumoniae
Chlamydophila ( Chlamydia) pneumoniae
Legionella pneumophila (Legionnaires disease)

atypical CAP may present with more subtle pulmonary findings, nonlobar infiltrates on radiography, and various extrapulmonary manifestations:
Mental confusion
Prominent headaches
Myalgias
Ear pain
Abdominal pain
Diarrhea
Rash (Horder spots in psittacosis; erythema multiforme in Mycoplasma pneumonia)
Nonexudative pharyngitis
Hemoptysis
Splenomegaly
Relative bradycardia

Question 3

Ix of CAP

ERS/ESICM/ESCMID/ALAT guidelines for the management of severe community-acquired pneumonia. Eur Respir J 2023; 61: 2200735 [DOI: 10.1183/13993003.00735-2022].
and Oxford Respi Medical Handbook

Answer 3

1) ABG in SpO2 <92%
2) CXR
- multilobar/ pleural effusion: pneumococcal
- cavitation: Staph aureus
- consider repeating if not improving by 3d
3) CT chest: exclude abscess, pleural disease, Ca etc
4) FBC
- severe infection if WCC >20 or <4
5) RP, LFT
- if deranged, suggested severe infection
6) CRP
- consider repeating if not improving by 3d
7) PCT - to reduce duration of Abx Rx (shortened by 2.4d)
8) Blood C&S
9) Sputum C&S
10) Sputum multiplex PCR testing (viral & bacterial) - allow rapid adjustment of antibiotics for unsuspected antibiotic-resistant pathogens
11) Pleural fluid if with effusion
12) Pneumococcal and Legionella urinary antigen - indicated in severe CAP
13) Bronchoscopy
- useful esp in lobar collapse to suction retained secretions/ exclude endobronch abnorm

Question 4

General Mx and empirical therapy for CAP

ERS/ESICM/ESCMID/ALAT guidelines for the management of severe community-acquired pneumonia. Eur Respir J 2023; 61: 2200735 [DOI: 10.1183/13993003.00735-2022].
and Oxford Respi Medical Handbook

Answer 4

General Mx:
1) O2 supp
2) NIV/ HFNO, kiv IMV
3) IVD
4) Analgesia
5) Nutrition
6) Early mobilization
7) Physio
8) VTE prophylaxis

Empirical Rx:
1) Beta-lactams + macrolides
Macrolides:
e.g. Azithromycin
duration: 3-5d

2) Corticosteroid in pts in shock, EXCLUDING viral CAP (e.g. influenza, SARS, MERS), uncontrolled DM & pt on steroid for other indications)
- dose: Methylpred 0.5mg/kg BD for 5d
- it reduces mortality, shock, septic shock, IMV duration,

Question 5

Severity score assments used in CAP

Reference: Oxford Respi Medical Handbook

Answer 5

1) CURB65
- predicts 30-day mortality
- score: (score 1 for each)
C: confusion
U: urea >7
RR: ≥30
BP: SPB <90 and or DBP ≤60
65: age ≥65

Severity according to score:
3-5: 15-40% mortality → needs ICU
2: 9% mortality → admit
0-1: <3% mortality →outpt Mx

2) Pneumonia Severity Index (PSI)

Question 6

What is the Light’s criteria

Answer 6

Light’s Criteria: Exudative Effusions will have at least one or more of the following:

Pleural fluid protein / Serum protein >0.5
Pleural fluid LDH / Serum LDH >0.6
Pleural fluid LDH > 2/3 * Serum LDH Upper Limit of Normal

Question 7

Causes and Mx of treatment failure in CAP

Answer 7

Failure of CRP to fall by >50% at day 4 suggests Rx failure

Causes:
1) Slow clinical response in elderly
2) Incorrect initial Dx:
- PE
- APO
- Lung Ca
- Acute Eosinophilic Pneumonia
- Alveolar haemorrhage
- OP
- vasculitis
- drug-induced lung injury

3) Secondary complications
- pulm: lung abscess, empyema, ARDS
- extrapulm: thrombophlebitis, HAP, cardiac complications

4) Inappropriate Abx or unexopected pathogen
- e.g. MRSA, pseudomonas, PCP

5) Underlying lung disease: bronchiectasis, aspiration, bronchial obstruction

6) Impaired immunity:
- hypogammaglobuloineamia, HIV, malnutrition

Question 8

Lung abscess
- Ix
- Mx

Answer 8

Ix:
1) Microbiology
- blood C&S
- Sputum/ BAL
- KIV transthoracic percutaneous needle aspirate
2) Imaging
- CXR
- CT scan - help to differentiate empyema/ obstructing endobronchial disease

Mx:
1) Abx that covers both aireobic & anaerobic bacteria
- duration: 1-2w iv, the 2-6w oral
2) Drainage - percutaneous may be considered if failed response to Abx
3) Surgery
- Indications:
a) If failed Abx 6w
b) Abscess >6cm diameter
c) Resistant org
d) Haemorrhage
e) Recurrent disease

Prog:
Cure 85%
Mortality 75% in immunocomp