Microbial etiologies of acute otitis media

The bacterial etiology of acute otitis media (AOM) in children is well known; Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis account for up to 80% of the cases. Negative cultures are obtained from 15 to 34% of the middle ear effusions obtained from patients with AOM and could represent non-viable bacterial organisms, Chlamydia, Mycoplasma, anaerobes and, perhaps, new and unknown organisms. Viruses are rarely involved as a cause of AOM but upper respiratory tract infections by respiratory syncitial virus, adenovirus, enterovirus, influenza virus and rhinovirus usually precede AOM episodes. Other organisms isolated from middle ear effusions are identified as coagulase-negative staphylococci, alpha---haemolytic streptococci and diphtheroids and could be responsible for AOM; thus these organisms should not always be disregarded and considered as contaminants.