Microbiology and management of otitis media.

Otitis media is a complex and multifactorial condition with four defined stages: myringitis, acute otitis media, secretory (serous) otitis media and chronic otitis media. Drugs utilized in its treatment are antihistamines, decongestants, mucolytic agents, non-steroidal anti-inflammatory agents, corticosteroids, vaccine therapy and antibiotics. The rationale for using antibiotics is that inflammation has been associated with the presence of virulent bacteria in all types of otitis media. In acute otitis media the major organisms, present are Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis. In chronic otitis media these organisms, plus Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and anaerobic bacteria are all prevalent. The microbiological flora of the middle ear in secretory otitis media is almost identical with that in acute otitis media. Empirical therapy can be given in most instances of acute and serous otitis media. However, in cases of failure, in the immunocompromised and in instances of chronic otitis media, establishing the individual microbiology of the inflamed middle ear is very helpful. The growing resistance of H. influenzae and M. catarrhalis to amoxycillin, due to beta-lactamase production, increases the risk of treatment failure of acute and serous otitis media. By adding a beta-lactamase inhibitor (clavulanic acid) to amoxycillin, or using second-generation cephalosporins, clearance can be achieved. Management of chronic otitis media requires surgical correction, drainage and coverage of anaerobic bacteria with agents such as amoxycillin plus clavulanic acid, or clindamycin plus antimicrobials against other pathogens such as Pseudomonas spp. where present.