Staphylococcus capitis- An Overview


Staphylococcus capitis is a bacterium that belongs to the genus Staphylococcus, which comprises Gram-positive, spherical cells that usually form clusters resembling grapes. Staphylococcus capitis is one of the coagulase-negative staphylococci (CoNS), meaning it does not produce the enzyme coagulase that can clot plasma. Coagulase-negative staphylococci are generally less virulent than coagulase-positive species, such as Staphylococcus aureus. However, they can still cause human infections, especially in immunocompromised patients or those with implanted medical devices.

Staphylococcus capitis was first isolated from human skin in 1975 by Kloos and Schleifer, who named it after the Latin word for head, "caput," because it was found to be more prevalent on the scalp and face than other body sites. Later, it was divided into two subspecies based on their urease activity, acid production from maltose, fatty acid profile, colony size, and DNA sequence: S. capitis subsp. capitis and S. capitis subsp. ureolyticus. The former is more common on human skin, while the latter is more frequently isolated from primates and the external auditory meatus of adults.

Staphylococcus capital is part of the normal flora of the skin and mucous membranes of humans and other warm-blooded animals, where it usually does not cause any harm. However, it can also be an opportunistic pathogen that can cause infections in various sites, such as the bloodstream, heart valves, joints, bones, and central nervous system. These infections are often associated with foreign bodies, such as prosthetic valves, catheters, shunts, or prosthetic joints, which provide a surface for the bacteria to adhere to and form biofilms. Biofilms are complex communities of bacteria embedded in a matrix of extracellular substances that protect them from host defenses and antibiotics. Staphylococcus capitis can also produce various virulence factors, such as exopolysaccharides, endopeptidases, phenol-soluble modules, and exoproteins, that contribute to its pathogenicity by facilitating adhesion, immune evasion, tissue damage, and antimicrobial resistance.

Staphylococcus capitis infections are usually diagnosed by culturing the bacteria from clinical specimens, such as blood, pus, or joint fluid, and performing biochemical tests or molecular methods to identify the species and subspecies level. The treatment of S. capitis infections depends on the site and severity of infection, as well as the susceptibility of the bacteria to different antibiotics. In some cases, removal or replacement of the infected device may be necessary to eradicate the infection. Preventing S. capitis infections involves:

Maintaining a clean hospital environment.

Practicing good hygiene and infection control measures.

Coating medical devices with antimicrobial agents to prevent bacterial colonization.

In summary, Staphylococcus capitis is a Gram-positive, coagulase-negative coccus that is part of the normal flora of human skin but can also cause opportunistic infections in certain conditions. It is a biofilm-forming bacterium that can adhere to medical devices and produce various virulence factors that enhance its pathogenicity. It can be diagnosed by culture and identification methods and treated with antibiotics or device removal. Prevention strategies include hygiene and infection control measures and antimicrobial coating of devices.

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