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A 2-year-old child presents to the physician's office with her mother. The mother states that for the past few days the child has had a low-grade fever, upper respiratory tract symptoms, and has been tugging at her right ear. An examination of the right ear with the pneumatic otoscope reveals a hyperemic, opaque, bulging, tympanic membrane with poor mobility. The patient attends daycare three times a week. There has been no recent travel, and no one else is ill in the household. Which of the following organisms is the most likely causative pathogen?
A: Haemophilus influenzae
B: Staphylococcus aureus
C: Moraxella catarrhalis
D: Streptococcus pneumoniae
E: Respiratory syncytial virus
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The presentation of this patient is most consistent with the diagnosis of acute otitis media. The most common causes of acute otitis media are Streptococcus pneumoniae (choice D), found in approximately 40% of cases; Haemophilus influenzae (choice A) was found in approximately 25“30% prior to the advent of a vaccine; and Moraxella catarrhalis (choice C), in approximately 15%; while Staphylococcus aureus (choice B), group A Streptococcus, and Gram-negative organisms (e.g., Pseudomonas aeruginosa) are less common causes of acute otitis media, and together account for approximately 5% of cases. Respiratory syncytial virus (RSV) (choice E) and other respiratory viruses are also associated with acute otitis media. However, even though otitis media can be a sequela of bronchiolitis caused by RSV, rarely, if ever, is the aspirate from the middle ear solely positive for RSV. These children usually have a bacterial pathogen isolated in their aspirate. It remains to be discovered whether viruses alone can cause acute otitis media or if their presence only enhances the chances for bacterial invasion.
