Staphylococcus

Staphylococcus is a genus of Gram-positive bacteria that commonly inhabit human skin and mucous membranes. Its species range from harmless commensals to pathogens that cause infections and toxin-mediated illness.

Gram-positive bacteria: Bacteria whose thick peptidoglycan cell walls retain the crystal violet stain in Gram staining. Staphylococci share this cell-wall architecture, which shapes their staining and antibiotic susceptibility.
Staphylococcal protein A: A surface protein of Staphylococcus aureus that binds the Fc region of immunoglobulin G. This binding disrupts antibody orientation and helps the bacterium evade immune recognition.
Staphylococcal infection: An infection caused by bacteria belonging to the genus Staphylococcus. This broad clinical category includes localized skin disease and life-threatening invasive infections.
Staphylococcus saprophyticus: A coagulase-negative staphylococcal species that can cause urinary tract infections, especially in young women. It is a species-specific cause of cystitis distinct from the more familiar S. aureus.
Bacterial biofilm: A community of microorganisms attached to a surface and embedded in a self-produced matrix. Biofilms help some staphylococci persist on tissues and implanted medical devices.
Staphylococcal enterotoxin: A heat-stable toxin produced by some Staphylococcus aureus strains that can cause food poisoning. Preformed enterotoxins explain rapid vomiting after contaminated food is eaten.
Methicillin-resistant Staphylococcus aureus: Staphylococcus aureus strains resistant to methicillin and most other beta-lactam antibiotics. MRSA is a major example of resistance shaping treatment and infection-control decisions.
Staphylococcus lugdunensis: A coagulase-negative staphylococcal species capable of causing aggressive infections, including endocarditis. Its virulence shows that coagulase-negative status does not guarantee harmlessness.
Coagulase: An enzyme that promotes blood clotting by converting fibrinogen to fibrin. Coagulase production distinguishes Staphylococcus aureus from most other staphylococcal species.
Toxic shock syndrome toxin-1: A Staphylococcus aureus superantigen that can trigger widespread immune activation and toxic shock syndrome. It illustrates how a secreted staphylococcal toxin can cause systemic illness without tissue invasion.

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