3.13 Moraxella Catarrhalis

Microbiology review for the USMLE Step 1 exam

• Moraxella Catarrhalis is a gram negative diplococcus that is part of normal upper respiratory tract flora
• Mainly causes three different types of infections: otitis media in children, lower respiratory tract infections in COPD patients, and pneumonia in elderly patients
• Otitis media is the most common bacterial infectious disease in childhood and the most common reason for which children receive antibiotics. M. catarrhalis causes about 15-20% of otitis media cases.
• Symptoms of otitis media in children include pulling or tugging at the ears, irritability, headache, disturbed or restless sleep, poor feeding, anorexia, vomiting, or diarrhea.
• In COPD patients, exacerbations are often due to bacterial and viral infections. M. catarrhalis is a bug to keep in mind and symptoms of a COPD exacerbation caused by this bug are very similar to those caused by other bacteria, including increased sputum production, sputum purulence, and dyspnea.
• Pneumonia due to M. catarrhalis is a cause of pneumonia in elderly patients, especially in elderly patients with an underlying cardiopulmonary disease like COPD.
• These infections are usually treated empirically with broad spectrum antibiotics such as 3rd generation cephalosporins and amoxicillin-clavulonic acid.