Branhamella catarrhalis (previously named Moraxella catarrhalis )


Gram Stains: Gram-negative cocci (subgenus Branhamella ). May resist decolorization and appear gram-positive.
Morphology: Absence of flagella, both rod-shaped and coccal species may be fimbriated.
Size: 1.0-1.5 micrometers by 1.5-2.5 micrometers.
Motility: Swimming motility is absent, but some surface-bound "twitching" has occurred in pairs and short chains, with adjacent sides flattened.
Capsules: Cells may be capsulated.
Spores: No.


Branhamella catarrhalis has a pinkish-brown pigmentation on Chocolate Agar. Colonies at 48 hours are approximately 2-2.5mm in diameter, hemispherical, becoming larger and flat or convex with prolonged incubation. The colonies have a "hockey puck" consistency and may be moved intact over the surface of the medium using an inoculating loop. The colonies will disintegrate in chunks when broken with a loop.


Obligately aerobic. Most species are nutritionally fastidious. Chemoorganotrophic.



An opportunistic pathogen of the upper and lower respiratory tract.


Branhamella catarrhalis causes infections ranging from acute, localized infections such as otitis media, sinusitis, and bronchopneumonia to life threatening, systemic diseases including endocarditis and meningitis. B. catarrhalis causes 10-15% of cases of otitis media and a similar proportion of sinusitis. In addition, this organism causes a large proportion of cases of lower respiratory tract infections in elderly patients with chronic obstructive pulmonary disease. B. catarrhalis is exceeded only by Haemophilus influenzae and Streptococcus pneumoniae as a causative agent of acute purulent exacerbations of chronic bronchitis. (2) Infections of the maxillary sinuses, middle ears, or bronchi may occur through contiguous spread of organisms from their normal habitat. Branhamella catarrhalis is also associated with frank pneumonia.


For culture: Chocolate Agar, Blood Agar, Columbia Agar, Tryptic Soy Agar (TSA), Brain Heart Infusion Agar (BHIA) and BHI Broth.
For selective isolation: Modified Thayer Martin (MTM), Thayer Martin Agar, New York City (NYC) Medium.
For maintenance: Chocolate Agar, Blood Agar, Columbia Agar.


Temperature: 35 degrees C.
Time: 16-24 hours.
Atmosphere: Aerobic with increased CO 2 .


1. Holt, J.G., et al. 1994. Bergey's Manual of Determinative Bacteriology , 9th ed. Williams & Wilkins, Baltimore, MD.

2. Holt, J.G., et al. 1986. Bergey's Manual of Systemic Bacteriology , Vol. I & II. Williams & Wilkins, Baltimore, MD.

3. The Oxoid Vade-Mecum of Microbiology . 1993. Unipath Ltd., Basingstoke, UK.

4. Murray, P.R., et al. 1995. Manual of Clinical Microbiology , 6th ed. American Society for Microbiology, Washington, D.C.