Moraxella catarrhalis

It is a gram-negative diplococcus present as a commensal of the upper respiratory tract. Was previously called Branhamella catarrhalis. Interestingly its pathogenicity is increased when exposed to cold conditions for a long time. It may cause otitis media, sinusitis (third most common cause) , laryngitis, bronchitis, pneumonia and meningitis.

Diagnosis is by gram stain showing typical morphology and culture on chocolate agar or blood agar. It is oxidase positive, does not ferment glucose, maltose, sucrose and lactose, DNAse positive and reduces nitrate and nitrite. Apart from biochemical features, they can be differentiated from Neisseria by a rapid test based on hydrolysis of tributyrin which is positive in Moraxella and negative in Neisseria. Treatment is with amoxicillin-clavulanic acid, second and third generation cephalosporins and azithromycin/ clarithromycin.