From the Guidelines
The most likely organism causing otitis media is Streptococcus pneumoniae, which accounts for approximately 30-40% of bacterial cases, as supported by the most recent and highest quality study available 1. Other common bacterial pathogens include Haemophilus influenzae (20-30%), Moraxella catarrhalis (10-15%), and occasionally Streptococcus pyogenes or Staphylococcus aureus. Some key points to consider in the management of otitis media include:
- The pathophysiology typically involves dysfunction of the Eustachian tube, often following an upper respiratory infection, which creates negative pressure in the middle ear and allows pathogens to ascend from the nasopharynx.
- Risk factors include young age (peak incidence between 6-24 months), daycare attendance, bottle feeding while lying down, exposure to secondhand smoke, and anatomical abnormalities like cleft palate.
- Understanding the likely causative organisms helps guide empiric antibiotic therapy, typically amoxicillin as first-line treatment for bacterial cases, with alternatives like amoxicillin-clavulanate for resistant strains, as recommended by principles of judicious antibiotic prescribing for upper respiratory tract infections in pediatrics 1.
- The role of observation (also termed “wait and see” or “delayed prescribing”) instead of immediate antibiotic therapy is an important consideration for children with AOM and acute bacterial sinusitis, as it reduces antibiotic use and is well accepted by families, without resulting in worse clinical outcomes 1. It is essential to note that while multiple studies support these points, the most recent and highest quality study available 1 provides the most reliable evidence for guiding clinical practice.
From the FDA Drug Label
ACUTE BACTERIAL OTITIS MEDIA Caused by Streptococcus pneumoniae, Haemophilus influenzae (including beta-lactamase producing strains) or Moraxella catarrhalis (including beta-lactamase producing strains). Acute otitis media caused by Haemophilus influenzae, Moraxella catarrhalis or Streptococcus pneumoniae. 1.2 Acute Bacterial Otitis Media – caused by beta-lactamase–producing isolates of H. influenzae and M. catarrhalis.
The most likely organisms causing otitis media are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis 2, 3, 4.
From the Research
Causative Organisms of Otitis Media
The most likely organisms causing otitis media are:
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis These organisms are commonly isolated from patients with acute otitis media (AOM) and are responsible for the majority of cases 5, 6, 7, 8, 9.
Prevalence of Causative Organisms
The prevalence of these organisms varies, but Streptococcus pneumoniae is often the most common isolated pathogen, followed by Haemophilus influenzae and Moraxella catarrhalis 7. Other organisms, such as Staphylococcus aureus, Group A beta-hemolytic streptococcus, and Escherichia coli, can also cause otitis media, but are less common 7.
Antibiotic Resistance
The increasing frequency of beta-lactamase-producing strains of Haemophilus influenzae and Moraxella catarrhalis, as well as penicillin-resistant Streptococcus pneumoniae, is a concern for antibiotic treatment of otitis media 6, 9. The use of antibiotics such as amoxicillin-clavulanate and azithromycin can help to address these resistant strains 6, 7.