Community Acquired Pneumonia

This week is another busy week since the third block of undergraduate medical students are starting their new session this coming Monday. I have to ensure the course guideline, log books and rosters are ready by then. I am just helping the department, yes the department (not MY department). I am having problem with someone, let me correct it not just me..at least there are two more members feel the same way......"Please" costs nothing, "Sorry" costs your pride, "I forgive you" liberates you from the shackles of prejudice.

The mortality of CAP patients admitted to ICU is about 35%. About 20% of patients admitted to ICU with CAP are in septic shock, with mortality as high as 60%.
The presence of comorbidities below contribute significantly to mortality and also alter the etiologic organisms underlying the infection.

1. COPD
2. asthma
3. diabetes mellitus
4. renal insufficiency
5. congestive heart failure
6. coronary artery disease
7. malignancy
8. alcoholism
9. age>70years
10. chronic nerological disease
11. chronic liver disease

The most common pathogens are:

1. Strep pneumonia
2. Legionella species
3. Staphylococcus aureus
4. Haemophillus Influenza
5. Gram negative bacilli

Pathogens associated with underlying comorbid condition:
1. S.pneumonia

• Dementia
• congestive heart failure
• COPD
• Cerebrovascular disease
• Institutional crowding
• seizures

2. Penicillin resistant and drug resistant pneumococcus

• age>65
• alcoholism
• immunomodulating illness or therapy (including steroids)
• Previous B lactam therapy within 3 months
• Multiple medical comorbidities
• exposure to child in day care centre

3. Enteric gram negatives

• residence in long term facility
• underlying cardiopulmonary disease
• recent antibiotic therapy
• multiple medical comorbidities

4. Pseudomonas aeruginosa

• broad spectrum antibiotics for > 7 days in the past month
• structural lung disease (bronchiectasis)
• corticosteroid therapy
• malnutrition
• undiagnosed HIV infection
• netropenia

5. Legionnaires' disease

• AIDS
• haematologic malignancy
• end stage renal disease

Non infectious diseaseas masquerading as CAP should be excluded:

1. Cryptogenic organizing pneumonia (COP)
2. Eosinophilic pneumonia
3. Hypersensitivity pneumonia
4. Drug induced pneumonitis: methotrexate, nitrofurantoin, gold, amiodarone etc
5. Pulmonary vasculitis
6. PE/ infarction
7. Pulmonary malignancy
8. Radiation pneumonitis
9. TB

The following are the major reasons for a failure to respond to anti microbial agents:

1. Wrong antibiotic: wrong spectrum or drug resistance. Wrong dosage
2. Viral, fungal, or opportunistic pathogen.
3. Unusual pathogens
4. Superadded complication
5. Complicated pleural effusion/ empyema
6. endocarditis
7. Purulent pericarditis
8. Septic arthritis
9. Meningitis
10. Exclude masquerader
11. Consider CA-MRSA in toxic patients and those with severe disease.

Unusual pathogens

1. Coxiella burnetii - cats, goats, sheep, cattle
2. Tularemia - rabbits, ticks
3. Leptospirosis -rats
4. Hantavirus - rats
5. SARS
6. Psittacosis - birds
7. Nocardia - steroids
8. Aspergillus -steroids
9. Pneumocystis jiroveci -immunosuppression
10. Dimorphic fungi -recent travel
11. Burkhodelria pseudomallei -recent travel
12. TB

Complicated Pleural effusions -
drainage is necessary if the pleural fluid is grossly purulent or if pleural fluid show the following

• pH less than 7.2
• Glucose less than 2.2mmol/l
• WCC > 10,000/ml