Staphylococci are gram-positive, spherical-shaped bacteria that form clusters and are commonly found on the skin and mucous membranes. Clinically, the most important species include Staphylococcus aureus and Staphylococcus epidermidis, which are categorized according to their coagulase activity. S. aureus is coagulase positive and expresses several virulence factors which support evasion of the host immune response. S. epidermidis is coagulase negative and is usually less virulent, although it can evade the host immune system by forming and subsequently hiding in a biofilm. S. aureus is commonly responsible for many localized infections (e.g., , cervical ) and also severe organ infections in the setting of bacteremia (e.g., , ). As a toxin producer, S. aureus can cause food poisoning (see ) and, in severe cases, life-threatening diseases such as (SSSS) or (TSS). Methicillin-resistant S. aureus ( ), in particular, poses a major threat to both immunocompromised and multimorbid patients and is a considerable challenge to hospital hygiene. S. epidermidis is mostly responsible for foreign body infections caused by, for example, contaminated peripheral lines or prosthetic joints. The treatment of choice is anti-staphylococcal penicillins (e.g., oxacillin, flucloxacillin) or first and second-generation cephalosporins.
Staphylococci are immotile, gram-positive bacteria that have a round shape and are found in clusters.
Approx. 30% of the general human population are long-term carriers of S. aureus. 
- Three patterns of carriage have been observed: 20% are permanent carriers, 60% are intermittent carriers, 20% are noncarriers
- MRSA carrier rates and invasive infections have increased during the last decades.
Epidemiological data refers to the US, unless otherwise specified.
For more information, see and “Gram-positive cocci” section in the .
- Clumping factor A: binds to fibrinogen → platelet activation, aggregation, and blood clumping
- Protein A: inhibits phagocytosis and complement fixation by binding to the Fc region of IgG
- Modified penicillin-binding protein (PBP) in MRSA
- Microbial surface components recognizing adhesive matrix molecules (MSCRAMMs): facilitate the adherence of S. aureus to the extracellular matrix of host tissue 
- Capsular polysaccharides: promote colonization and persistence in host tissues
- Anti-staphylococcal penicillins: oxacillin, flucloxacillin
- First and second generation cephalosporins
- In case of penicillin allergy: clindamycin
- vancomycin and linezolid: drugs of last resort such as
Coagulase-negative staphylococcus (particularly S. epidermidis)
Subtypes and variants
Ear, nose, and throat
Foreign body infections
- Infections associated with catheters and shunts
- Treatment: treatment with antibiotics and foreign body removal
Toxic shock syndrome (TSS)
Staphylococcal toxic shock syndrome
- ∼ 50% of cases: caused by prolonged placement of tampon
- Prolonged placement of nasal packing
- Postsurgical or after wound infections
- Clinical findings: If tampon-associated, symptoms usually appear within 5 days after menstruation.
- Laboratory tests
- Differential diagnosis: Streptococcus pyogenes toxic shock syndrome
Streptococcal toxic shock syndrome
- Etiology: : group A streptococcus (particularly Streptococcus pyogenes)
- Pathophysiology: Exotoxins A, B, and C act as superantigens and can activate large numbers of T cells, resulting in the massive release of cytokines.
- Clinical findings
- Laboratory findings