Introduction of Staphylococcus and Micrococcus
Table of Contents
Staphylococci are Gram-positive bacteria, with diameters of 0.5 – 1.5 µm and non-motile, non-spore-forming facultative anaerobes that grow by aerobic respiration or by fermentation, and they are characterized by individual cocci, which divide in more than one plane to form grape-like
clusters. Most species and sub-species in the genus Staphylococcus are responsible to colonise the human body. Staphylococcus aureus and Staphylococcus epidermidis are the two most characterized and studied strains in this genus. Staphylococcus aureus is a clinically important species that is responsible for abscesses, conjunctivitis, corneal ulcer, septicemia, endocarditis, pneumonia, mastitis (an inflammation of the breast), empyema (an accumulation of pus in the body cavity), food poisoning, staphylococcal scalded syndrome, toxic shock syndrome (TSS)-enterotoxin F, septic arthritis meningitis and osteomyelitis.
Micrococcus are Gram-positive cocci occurring in tetrads (special feature) and in irregular clusters that are usually nonmotile and non-spore-forming. They are catalase and modified oxidase tests positive and are usually aerobic with strictly respiratory metabolism. Most species form carotenoid pigments. This genus is not considered to be pathogenic. However, strains of this genus, Micrococcus have been reported to cause numerous types of infections, normally as opportunistic pathogens. Micrococcus luteus strains were associated with clinical conditions like septic arthritis, prosthetic valve endocarditis, and recurrent bacteremia.
The differences between Staphylococcus and Micrococcus are as follows- on the basis of the following properties-
- Anaerobic growth
- Arrangement of cells (predominant)
- Mol % G+C of DNA
- Carbohydrate utilization
- Oxidase (modified )
- 0.04U bacitracin
- Teichoic acid in the cell wall
|Arrangement of cells (predominant)||Clusters||Clusters, tetrads|
|Mol % G+C of DNA||30-39||64-75|
|Carbohydrate utilization||Fermentative||Oxidative or nil|
|Oxidase (modified oxidase test)||Negative|
|Teichoic acid in the cell wall||Present||Absent|
- Other than Staphylococcus cluster-forming cocci are Micrococcus, Gafkey, Sarcina, Peptococcus, and Aerococcus.
- Some strains of S. aureus are encapsulated. The capsule is of two types. Microcapsule is less than 200 nm whereas macro capsule is larger than 200 nm and which is responsible for the slime layer.
- Common genera found in the human skin microbiome are Staphylococcus and Micrococcus.