and the initiation of antibiotic therapy should the child worsen or if symptoms persist beyond 48 to 72 hours (See CHOP Clinical Pathway for Evaluation/Treatment of Acute Otitis Media in Children Months to 12 Years Old; https://www.chop.edu/clinical-pathway/otitis-media-acute-clinical-pathway ) Most cases of AOM involve coinfection of a viral respiratory pathogen and bacteria The Eustachian tube dysfunction caused by the viral URI leads to negative middle ear pressure, aspiration of contaminated upper airway secretions into the middle ear cavity, and subsequent development of acute bacterial infection A viral prodrome followed by clinical worsening signals the onset of AOM AOM may also develop secondary infection of ongoing middle ear fluid (OME) Bacteria or bacterial DNA are found in middle ear fluid from almost all patients with properly diagnosed AOM The predominant bacterial pathogens are nontypeable Haemophilus influenzae , Streptococcus pneumoniae , Moraxella catarrhalis , and occasionally Streptococcus pyogenes Since the advent of immunization against S pneumonia , H influenza has become the most prevalent bacterial pathogen recovered from middle ear aspirates While some H influenza produce β-lactamase, the number of β-lactam–resistant strains is lower than previously reported High-dose amoxicillin (80 to 90 mg/kg/day) achieves middle ear fluid concentrations that are greater than the minimum inhibitory concentrations of all penicillin-sensitive and intermediately resistant S pneumonia serotypes, and many highly penicillin-resistant strains Although all M catarrhalis produce β-lactamase, most experts believe AOM from M catarrhalis is mild, has a high spontaneous resolution rate, and is without significant invasive potential, making coverage with a β-lactamase–resistant antibiotic unnecessary in the majority of cases