Characteristics, pathogenesis, and microbiology

Acute otitis media (AOM) is defined by inflammation and fluid in the middle ear. Otalgia (ear pain) is characteristic, often causing the child to tug at the ear or just hold it. Other symptoms include fever, vomiting, irritability, impaired hearing, sleeplessness, and otorrhea (discharge from the ear, usually purulent [pus containing]).

AOM may be bacterial, viral, or both. In children with full-blown bacterial AOM, the inner ear is filled with purulent fluid, which can cause the tympanic membrane to bulge outward. If the membrane is perforated, otorrhea results. In children with nonbacterial AOM or with mild bacterial AOM, the tympanic membrane does not bulge. Of the two presentations—bulging or nonbulging eardrum—nonbulging is the more common.

How does AOM develop? As a rule, the process begins with a viral infection of the nasopharynx, which can cause blockage of the eustachian tube, which in turn can cause negative pressure in the middle ear. When the eustachian tube opens, causing pressure equalization, bacteria and viruses can be sucked in. If the mucociliary system is sufficiently impaired, it will be unable to transport these pathogens back to the nasopharynx. Otitis media results when bacteria colonize the fluid of the middle ear and/or when viruses colonize cells of the middle-ear mucosa. As indicated in Table 106–1, bacteria are present in 70% to 90% of fluid samples taken from the middle ear of children with AOM, and viruses are present in nearly 50%. The most common bacterial pathogens are Streptococcus pneumoniae (40% to 50%), Haemophilus influenzae (20% to 25%), and Moraxella catarrhalis (10% to 15%).

Diagnosis

To diagnose AOM, three elements must be present: (1) acute onset of signs and symptoms, (2) middle-ear effusion (MEE), and (3) middle-ear inflammation. The patient history will reveal whether onset of signs and symptoms has been both recent and rapid. The presence of MEE is indicated by any of the following: bulging tympanic membrane (the best predictor of MEE), limited mobility of the tympanic membrane, and otorrhea (fluid in the EAC following perforation of the tympanic membrane). Middle-ear inflammation is indicated by either (1) distinct erythema of the tympanic membrane or (2) distinct otalgia (discomfort, clearly referable to the ear, that disrupts normal activity or sleep).

Frequently, the diagnosis of AOM is somewhat uncertain. Why? Because in many cases, MEE can’t be confirmed. When the presence of MEE is questionable, a diagnosis of AOM may be considered, but cannot be deemed certain.

It is important to distinguish between AOM and otitis media with effusion (OME). As discussed below, children with OME have fluid in the middle ear but no signs of local or systemic illness. Prolonged OME is common following resolution of AOM.

Standard treatment

All children with AOM should receive required pain medication (eg, acetaminophen, ibuprofen, codeine), and some should receive antibiotics. Prescribing antibiotics for all children should be discouraged. Why? Because the vast majority (over 80%) of AOM episodes resolve spontaneously within a week. Hence, if antibiotics are prescribed routinely, most recipients will be taking drugs they don’t really need. Not only does this generate unnecessary expense, worse yet, it puts children at needless risk of adverse drug effects, increases their risk of recurrent AOM, and accelerates the emergence of antibiotic-resistant bacteria.

In 2004, two organizations—the American Academy of Pediatrics and the American Academy of Family Physicians—released guidelines for treating AOM in children. The guidelines stress the need for an accurate diagnosis, and they recommend basing treatment on three factors: age, illness severity, and the degree of diagnostic certainty.

For some patients, the guidelines include an important option—observation—rather than immediate treatment with antibacterial drugs. Observation is defined as management by symptomatic relief alone for 48 to 72 hours, thereby allowing time for AOM to resolve on its own. If symptoms persist or worsen, antibacterial therapy is then started. As part of this strategy, parents are informed about (1) the high probability of spontaneous AOM resolution, and (2) the drawbacks of giving antibiotics when they are not needed. Observation is considered appropriate only when follow-up can be ensured. The recommendation for observation is based on studies showing that:

Criteria for choosing between observation and initial antibacterial therapy are summarized in Table 106–2. The choice is based on patient age, how certain the diagnosis is, and severity of symptoms. As indicated, all children less than 6 months old should receive antibiotics, regardless of diagnostic certainty or symptom severity. Among children 6 months to 2 years old, antibiotics are indicated whenever the diagnosis is certain. If the diagnosis is uncertain, antibiotics are indicated only if symptoms are severe. For children age 2 years and older, antibacterial therapy is indicated only if the diagnosis is certain, and then only if symptoms are severe. In all other cases, observation is the preferred strategy.