What is the most common cause of acute suppurative otitis media (ASOM) in children?

Most Common Cause of Acute Suppurative Otitis Media in Children

The most common cause of acute suppurative otitis media (ASOM) in children is mostly bacterial infection (option C). According to comprehensive evidence, the vast majority of cases of acute otitis media involve pathogenic bacteria either alone or in combination with viral pathogens 1.

Microbiology of ASOM

Bacterial Pathogens

The three most common bacterial pathogens in acute otitis media are:

1. Streptococcus pneumoniae
2. Non-typeable Haemophilus influenzae
3. Moraxella catarrhalis

When using appropriate diagnostic criteria and sensitive microbiologic techniques, bacteria can be detected in the middle ear fluid in up to:

• 66% of cases with bacteria and viruses together
• 27% of cases with bacteria alone
• 4% of cases with virus alone 1

This means that bacterial pathogens are isolated from middle ear fluids in approximately 69-84% of cases 1.

Changing Patterns in Bacterial Prevalence

The prevalence of specific bacteria has evolved over time, particularly since the introduction of pneumococcal conjugate vaccines:

• Before PCV7 introduction: S. pneumoniae was the most frequently cultured pathogen
• After PCV7 introduction: H. influenzae temporarily became the most frequently isolated pathogen
• Later (6-8 years after PCV7): S. pneumoniae (non-vaccine serotypes) and H. influenzae became nearly equal in frequency 1

Role of Viruses

While viruses play an important role in ASOM, they typically act as initiators rather than primary causative agents. AOM occurs most frequently as a consequence of viral upper respiratory tract infection, which leads to:

• Eustachian tube inflammation
• Negative middle ear pressure
• Movement of secretions containing both the causative virus and pathogenic bacteria from the nasopharynx into the middle ear 1

Clinical Implications

The bacterial etiology of ASOM has important treatment implications:

• Amoxicillin remains the first-line treatment for most cases of ASOM
• For children who have received amoxicillin in the past 30 days, have concurrent purulent conjunctivitis, or have a history of recurrent AOM unresponsive to amoxicillin, antibiotics with additional β-lactamase coverage are recommended 1

Common Pitfalls and Caveats

1. Diagnostic challenges: Proper specimen collection is critical. Swabs are not recommended for otitis media; middle ear fluid obtained by tympanocentesis is the only representative specimen 1.

2. Changing resistance patterns: The emergence of penicillin-resistant S. pneumoniae and increasing frequency of β-lactamase-producing strains of M. catarrhalis and H. influenzae must be considered when selecting antibiotics 2.

3. Viral vs. bacterial confusion: While viral upper respiratory infections often precede ASOM, the suppurative (pus-forming) nature of ASOM is characteristic of bacterial infection.

4. Vaccine impact: Pneumococcal conjugate vaccines have significantly altered the microbiology of ASOM, with shifts in the predominant serotypes and bacterial species 1.

In conclusion, while viral infections often precede and contribute to ASOM development, bacterial pathogens are the predominant cause of the suppurative process, making option C (mostly bacterial infection) the correct answer.