Respiratory Infections: Severity, TB, and Antimicrobial Stewardship
Respiratory infections cover community-acquired pneumonia, tuberculosis, hospital-acquired and ventilator-associated pneumonia, and opportunistic fungal disease. The exam tests severity assessment, appropriate investigations, and antimicrobial stewardship.
Core rules
- CAP severity: CURB-65 (confusion, urea >7 mmol/L, respiratory rate ≥30, low BP, age ≥65) supports site of care but does not replace clinical judgement.
- Start antibiotics promptly in severe CAP and obtain cultures before antibiotics when this does not delay treatment.
- Tuberculosis: sputum smear, culture, and NAAT are core; IGRA supports latent TB diagnosis but cannot distinguish active from latent infection.
- HAP/VAP: cover according to local resistance patterns; obtain lower respiratory cultures and review antibiotics at 48–72 hours.
Worked example
A 70-year-old with fever, cough, confusion, urea 9 mmol/L, respiratory rate 32, and BP 95/60 scores CURB-65 4. Admit, take blood and sputum cultures, start broad-spectrum CAP antibiotics according to local guidance, and give oxygen and fluids. Review for complications such as empyema.
Traps
Using procalcitonin alone to withhold antibiotics in severe sepsis; missing TB in a patient with a normal chest radiograph; treating positive sputum Candida as invasive disease; and forgetting infection control.