Moraxella (Branhamella) catarrhalis. Coloured transmission electron micrograph (TEM) of a group of the bacteria Moraxella (Branhamella) catarrhalis. These are aerobic, gram-negative cocci (spherical bacteria) which are commonly found in the mucous membranes of the respiratory tract of mammals, including humans. In immuno- suppressed individuals, or opportunistically, they may cause respiratory tract infections. These include sinusitis, an inflammation of the sinus membranes. This may also lead to otitis media, an infection of the middle ear. Treatment is with antibiotics. Magnification: x28, 000 at 6x7cm size. Magnification: x100,000 at 10x8 size."