Acute Otitis Media

Explanation

Acute otitis media is usually preceded by a viral upper respiratory infection that causes eustachian tube dysfunction and negative middle ear pressure, allowing nasopharyngeal bacteria to ascend into the middle ear. Respiratory syncytial virus is the virus classically and most frequently recovered from middle ear fluid at tympanocentesis, and it also has the highest rate of middle ear invasion of any respiratory virus, being detected in roughly three-quarters of children who develop otitis media during an RSV infection, compared with about half for parainfluenza viruses, around 40 in 100 for influenza, and a very small minority for adenovirus. This is why bronchiolitis season is also the peak season for acute otitis media, and why influenza and pneumococcal conjugate vaccination reduce the number of episodes. Series that use highly sensitive reverse transcriptase PCR, particularly in northern Europe, recover rhinovirus and enterovirus even more often than RSV, so the reported ranking depends on the detection method, but of the viruses listed here RSV is the only one that heads any published series. Despite the viral trigger, the pathogens cultured from middle ear fluid remain predominantly bacterial: Streptococcus pneumoniae, non-typeable Haemophilus influenzae, and Moraxella catarrhalis, with Haemophilus relatively more prominent since pneumococcal conjugate vaccine introduction. Diagnosis requires a bulging tympanic membrane or new otorrhoea with signs of middle ear inflammation, and pneumatic otoscopy showing reduced mobility supports an effusion. First-line therapy when antibiotics are indicated is high-dose amoxicillin at 80 to 90 mg/kg per day, escalating to amoxicillin-clavulanate after recent amoxicillin use, with concurrent purulent conjunctivitis, or after treatment failure. Antibiotics are given without delay for children under 6 months, for severe disease with a temperature of 39 °C or higher or significant otalgia, and for bilateral disease under 24 months, whereas watchful waiting for 48 to 72 hours is an option for older, mildly affected children with reliable follow-up.

Why each option

A.

Influenza A commonly triggers otitis media but invades the middle ear less often than respiratory syncytial virus.

B.

Adenovirus is recovered from only a small minority of middle ear effusions.

C.

Correct. Respiratory syncytial virus is the virus most often recovered from middle ear fluid in acute otitis media and has the highest rate of middle ear invasion.

D.

Parainfluenza viruses invade the middle ear frequently but still rank below respiratory syncytial virus.

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