URTIs - Sniffles & Sore Throats
| URTI | Pathogen(s) | Key Sx | Complications/Red Flags |
|---|---|---|---|
| Common Cold | Rhinovirus | Coryza, mild sore throat | 2° infection (AOM, sinusitis) |
| Pharyngitis | Viral; GAS (S. pyogenes) | Sore throat, fever; GAS: exudates | Rheumatic fever, PSGN; Peritonsillar abscess |
| Sinusitis (Ac.) | Viral; S. pneumo, H. flu | Facial pain, purulent discharge | Orbital cellulitis, meningitis |
| AOM | S. pneumo, H. flu, M. cat | Otalgia, fever, bulging TM | Mastoiditis, meningitis |
| Epiglottitis | H. flu b (↓); S. pneumo | 3D's: Dysphagia, Drooling, Distress | Airway obstruction! (EMERGENCY) |
⭐ S. pneumoniae: most common bacterial cause of AOM & acute bacterial sinusitis.
Pneumonias - Lung Inflamers Galore
| Pneumonia | Likely Pathogen(s) | Key Clues / Sx | Complications / ⚠️ Red Flags |
|---|---|---|---|
| CAP - Typical | S. pneumoniae; H. flu, M. cat | Sudden fever, rust sputum, lobar CXR shadow | Empyema, sepsis |
| CAP - Atypical | Mycoplasma, Chlamydia, Legionella | Dry cough, low-grade fever, GI / rash signs | Severe hypoxemia, multi-organ failure |
| HAP / VAP | Pseudomonas, Klebsiella, MRSA | ≥48 h in hospital/vent, new infiltrate | Septic shock, MDR bugs |
| Aspiration | Oral anaerobes; mixed GNB | Foul sputum, RLL infiltrate, ↓GCS risk | Lung abscess, bronchopleural fistula |
| Immunocompromised | Pneumocystis (PCP), CMV, Aspergillus | Subacute dyspnea, “bat-wing” CXR (PCP) | Pneumothorax (PCP), invasive aspergillosis |
| 0-1 → out-pt; 2 → ward; ≥3 → ICU. |
⭐ S. pneumoniae remains the #1 cause of community-acquired pneumonia - and post-influenza bacterial pneumonia. ⭐ “Currant-jelly” sputum → think Klebsiella (alcoholics, diabetics).
Tuberculosis - India's Cough Scourge
- Pathogenesis & Types:
- Primary TB: Ghon focus/complex (calcified lung lesion + hilar node). Often subclinical.
- Post-Primary (Secondary) TB: Apical lung lesions, cavitation. Reactivation/reinfection. Symptoms: cough >2 wks, fever, night sweats, weight loss.
- Diagnosis (NTEP):
- Sputum Smear Microscopy (AFB).
- CBNAAT/TrueNat: Initial test for all. Detects TB & Rif-resistance (<2 hrs).
- Culture: LJ medium (4-8 wks), liquid culture (faster). Gold standard.
- Treatment (DOTS - NTEP): 📌 RIPE (Rifampicin, Isoniazid, Pyrazinamide, Ethambutol)
- New PTB: 2(HRZE) + 4(HRE).
- Daily fixed-dose combinations (FDCs). Isoniazid: 5 mg/kg; Rifampicin: 10 mg/kg.
⭐ Cord factor (trehalose-6,6'-dimycolate) is a major virulence factor of M. tuberculosis, inhibiting phagosome-lysosome fusion and promoting granuloma formation.
Other LRTIs & Viruses - Viral Villains & Bronchial Banes
| Feature | Acute Bronchitis | Bronchiolitis | Pertussis (Whooping Cough) | Influenza |
|---|---|---|---|---|
| Etiology | Viral (Influenza, RSV) | RSV (>50%), Adeno, Parainfluenza | Bordetella pertussis | Influenza A, B (Orthomyxovirus) |
| Age Group | Adults | < 2 yrs (peak 3-6 mo) | < 1 yr (unvax), adolescents | All ages |
| Key Clinical | Cough (±sputum), wheeze; no pneumonia | URI → resp distress, wheeze, apnea | 📌 CPC: Catarrhal, Paroxysmal (whoop), Convalescent | Abrupt fever, myalgia, cough, headache |
| Management | Symptomatic; bronchodilators if wheeze | Supportive (O2, fluids); Ribavirin (severe) | Macrolides (Azithro); supportive care | Oseltamivir/Zanamivir (early, high-risk) |
⭐ RSV is the most common cause of bronchiolitis in infants, often leading to hospitalization in this age group globally and in India.
High‑Yield Points - ⚡ Biggest Takeaways
- Streptococcus pneumoniae is the most common cause of Community-Acquired Pneumonia (CAP).
- Atypical pneumonia: think Mycoplasma (cold agglutinins), Legionella (hyponatremia, ↑LFTs, GI symptoms).
- Klebsiella pneumoniae causes currant jelly sputum, especially in alcoholics and diabetics.
- Haemophilus influenzae causes epiglottitis (thumb sign) and pneumonia in COPD patients.
- Pseudomonas aeruginosa is linked to HAP, VAP, and cystic fibrosis exacerbations.
- TB diagnosis: sputum AFB/NAAT (CBNAAT); CXR shows apical lesions/cavitation.
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