Staphylococcus Infection (Staph Infection)
What Is Staphylococcus?
Staphylococcus bacteria (also termed staph) are responsible for a number of common infections. Staphylococcus is a genus of bacteria that is characterized by a round shape (coccus or spheroid shaped), Gram-stain positive, and found as either single cells, in pairs, or more frequently, in clusters that resemble a bunch of grapes. The genus name Staphylococcus is derived from Greek terms (staphyle and kokkos) that mean "a bunch of grapes," which is how the bacteria often appear microscopically after Gram-staining. In 1884, Rosenbach first described and named the bacteria. Two major divisions of the genus Staphylococcus are separated by the ability to produce coagulase, an enzyme that can clot blood. Most, but not all, human bacterial infections are caused by coagulase-positive Staphylococcus aureus strains. Staphylococcus epidermidis strains and other Staphylococcus species that are coagulase-negative produce slime that interferes with immune defenses. S. epidermidis are often associated with implanted devices (for example, catheters or prosthetic devices).
What Is a Staph Infection? How Does Someone Get a Staph Infection?
Almost any organ system can be infected by S. aureus. Most frequently, S. aureus strains first infect the skin and its structures (for example, sebaceous glands, hair follicles) or invade damaged skin (cuts, abrasions). Sometimes the infections are relatively limited (such as a sty, boil, furuncle, or carbuncle), but other times they may spread to other skin areas (causing cellulitis, folliculitis, or impetigo). Unfortunately, these bacteria can reach the bloodstream (bacteremia) and end up in many different body sites, causing infections (wound infections, abscesses, osteomyelitis, endocarditis, pneumonia) that may cause severe harm or even be fatal.
What Does a Staph Infection Look Like?
What Are Some Types of Staph Infections? How Do Staphylococcus aureus Infections Differ From Staphylococcus epidermidis Infections?
S. aureus strains also produce enzymes and toxins that likely cause or increase the severity of certain diseases. Such diseases include food poisoning, septic shock, toxic shock syndrome, and scalded skin syndrome. S. epidermidis strains, which usually do not cause infections, can cause infections in people whose immune system is suppressed. Patients who have any type of indwelling catheter or implanted device are also known to get S. epidermidis infections.
Medically Reviewed by a Doctor on 7/27/2015
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