What organism is the most common cause of acute otitis media in children?

• A. Haemophilus influenzae
• B. Streptococcus pneumoniae
• C. Moraxella catarrhalis
• D. Staphylococcus aureus

Answer: (B)

The main idea here is understanding which bacteria most often trigger middle-ear infection in kids. Streptococcus pneumoniae is the leading cause of acute otitis media in children. This is because many children carry S. pneumoniae in the nasopharynx, and after a viral upper respiratory infection the bacteria can ascend the Eustachian tube into the middle ear, causing inflammation and pus. While non-typeable Haemophilus influenzae and Moraxella catarrhalis are also common culprits, S. pneumoniae occurs most frequently as a single pathogen in pediatric AOM. Vaccination against pneumococcus has reduced its share, but it remains the top culprit among bacterial causes. Staphylococcus aureus is much less typical for AOM in children.