coccous

a spherical bacterium, usually slightly less than 1 μ in diameter, belonging to the Micrococcaceae family. It is one of the three basic forms of bacteria, the other two being bacillus (rod-shaped) and spirillum (spiral-shaped). A pathogenic coccus can almost always be classified as either a staphylococcus (occurring in clusters), or a streptococcus (occurring in short or long chains). Both staphylococci and streptococci are gram-positive and do not form spores.

The staphylococci are responsible for many serious infections, especially Staphylococcus aureus, which is the causative agent in boils, abscesses, osteomyelitis, and a large variety of other infections. Staphylococci have received much attention in recent years because of the ability of most strains to develop a resistance to antibiotics.

The most dangerous streptococci are those of the beta-hemolytic type. Various species of streptococci cause sore throat, scarlet fever, mastoiditis, and septicemia.