Moraxella catarrhalis

Gram Stain

• Gram negative coccobacilli (plump) in pairs and short chains - nonfermenter

Clinical Significance

This organism is a potential pathogen in acute exacerbation of chronic bronchitis, sinusitis, otitis media, pneumonia, and conjunctivitis.  Rare cases of meningitis, endocarditis, septicemia, and peritonitis have been reported, usually in immunocompromised patients.

This organism can also cause urethritis/urethral syndrome.

Usual Susceptibility Pattern

M. catarrhalis is resistant to amoxicillin and 1st generation cephalosporins.  Activity of 2nd generation cephalosporins is variable and may be more bacteriostatic than cidal.

Resistance to TMP/SMX increasing.

It is generally susceptible to amoxicillin-clavulanate, cefixime, ceftriaxone, tetracyclines, macrolides, and quinolones.