A 4-year-old child presents with acute onset ear pain, fever, and conductive hearing loss. Otoscopy reveals a bulging, hyperemic tympanic membrane with pus behind it. What is the most common bacterial organism responsible for acute suppurative otitis media in this age group?

Question

Accepted Answer

B. Streptococcus pneumoniae. ## Most Common Pathogen in Acute Suppurative Otitis Media

**Key Point:** Streptococcus pneumoniae remains the most common bacterial cause of acute suppurative otitis media (ASOM) in children and adults, despite the introduction of pneumococcal vaccines.

### Epidemiology of ASOM Pathogens

| Organism | Frequency | Age Group | Notes |
|----------|-----------|-----------|-------|
| *Streptococcus pneumoniae* | 25–40% | All ages | Most common; encapsulated gram-positive diplococcus |
| *Haemophilus influenzae* (non-typeable) | 20–30% | Children < 5 yrs | Second most common; gram-negative coccobacillus |
| *Moraxella catarrhalis* | 10–15% | Children < 2 yrs | Third most common; gram-negative diplococcus |
| *Group A Streptococcus* | < 5% | Rare in ASOM | More common in acute mastoiditis |

**High-Yield:** The "Big Three" pathogens account for ~85% of bacterial ASOM cases. *S. pneumoniae* leads in virtually all age groups and geographic regions.

### Pathogenesis

1. Viral upper respiratory tract infection → Eustachian tube dysfunction
2. Bacterial colonization of nasopharynx (often preceded by viral URI)
3. Retrograde ascent via Eustachian tube into middle ear
4. Suppuration → pus accumulation → tympanic membrane bulging
5. Spontaneous perforation or myringotomy drainage

**Clinical Pearl:** While *Haemophilus influenzae* type b (Hib) incidence has declined post-vaccination, non-typeable *H. influenzae* (NTHi) remains a significant pathogen. However, *S. pneumoniae* still dominates in frequency.

**Mnemonic:** **SPHiM** = *S. pneumoniae*, *Pseudomonas* (chronic suppurative), *H. influenzae*, *Moraxella*, *Mycobacterium* (TB otitis) — though for acute suppurative, focus on the first three.

### Clinical Significance

- **Antibiotic selection:** First-line agents (amoxicillin-clavulanate, cephalosporins) cover *S. pneumoniae* and *H. influenzae*
- **Resistance patterns:** Penicillin-resistant *S. pneumoniae* (PRSP) is geographically variable; in India, prevalence is moderate
- **Vaccination impact:** PCV13 has reduced *S. pneumoniae* ASOM incidence but has not eliminated it as the leading cause

[cite:Scott-Brown's Otorhinolaryngology Ch 28]

Answer

A. Moraxella catarrhalis

Answer

C. Haemophilus influenzae type b

Answer

D. Group A Streptococcus

A 4-year-old child presents with acute onset ear pain, fever, and conductive hearing loss. Otoscopy reveals a bulging, hyperemic tympanic membrane with pus behind it. What is the most common bacterial organism responsible for acute suppurative otitis media in this age group?

Explanation

Most Common Pathogen in Acute Suppurative Otitis Media

Epidemiology of ASOM Pathogens

Pathogenesis

Clinical Significance

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Organism	Frequency	Age Group	Notes
Streptococcus pneumoniae	25–40%	All ages	Most common; encapsulated gram-positive diplococcus
Haemophilus influenzae (non-typeable)	20–30%	Children < 5 yrs	Second most common; gram-negative coccobacillus
Moraxella catarrhalis	10–15%	Children < 2 yrs	Third most common; gram-negative diplococcus
Group A Streptococcus	< 5%	Rare in ASOM	More common in acute mastoiditis