The family
Micrococcaceae is composed of three genera : Micrococcus, Planococcus
and Staphylococcus. They are catalase positive, gram positive, spherical
cocci which divide incompletely in three perpendicular planes to form pairs,
tetrads, short chains. Micrococci are coagulase negative and usually oxidase
positive, are rarely associated with infections. They have a tendency to
produce a yellow pigmented colony. Planococci are capable of withstanding
saline concentrations of upto12%, arranged in tetrads, produce a yellow – brown
pigment on nutrient agar. Staphylococci are associated with colonisation and/or
infection of man. Some are coagulase negative while some are positive. They are
ubiquitous, cause localized lesions. Snce they develop resistance to penicillin
and other antibiotics they are important as human pathogen, especially in the
hospital environment.
Staphylococci
were first seen in pus by Koch in 1878, first cultivated in the medium by
Pasteur in 1880 and named by Alexander Ogston in 1881.
Important species are:
S.
aureus
