Staphylococci

Rosenbach, 1884

Staphylococci are roundish, non-mobile, grape-like arranged, gram-positive, non-sporeforming, catalase-positive, optionally anaerobic spherical bacteria with a diameter of 0.5-1.5 µm. They are immobile and are thus arranged in pairs or in irregular (grape-like) clusters. Optimum temperature for growth and multiplication is 30-37 °C. Extensive pH tolerance and resistance to dehydration make them comparatively insensitive.

Many species have a high proportion of branched fatty acid chains in their membrane lipids. Staphylococci play a major role as infectious agents as colonizers of the skin and the mucous membranes of the oropharynx in humans and warm-blooded vertebrates. They are facultative pathogens. Staphylococcus (S.) aureus has the greatest medical significance of the known Staphylococcus species. Furthermore, they also occur in the environment (water, air, food; medical devices such as plastic cannulas, plastic joint materials).

The genus Staphylococcus contains almost 50 species. Numerous species are still divided into subspecies (see also List of Prokaryotic names with Standing in Nomenclature). In medicine, staphylococci are classified according to the coagulase reaction into:

• coagulase-positive staphylococci(Staphylococcus aureus)
• and
• coagulase-negative staphylococci (for example: Staphylococcus epidermidis).

By means of differentiated detection methods (e.g. MALDI-TOF mass spectrometry), numerous species can now be precisely distinguished from one another.

Coagulase-positive staphylococci: The staphylococcal species with the highest pathogenic potency and generally one of the most important pathogens in humans is the coagulase-positive species. In human medicine, coagulase-positive staphylococci are usually equated with Staphylococcus aureus. Multi-resistant strains (MRSA) in particular are a problem because of their poor treatability with antibiotics.

• Staphylococcus aureus (complete: Staphylococcus aureus subsp. aureus)
• (S. intermedius)

So far found exclusively in animals or very rarely in association with infections in humans:

• Staphylococcus agnetis (coagulase variable)
• Staphylococcus aureus subsp. anaerobius
• Staphylococcus delphini
• Staphylococcus hyicus (coagulase variable)
• Staphylococcus intermedius (rarely - especially after dog bites - also in human wound infections)
• Staphylococcus lutrae
• Staphylococcus pseudintermedius
• Staphylococcus schleiferi subsp. coagulans

Coagulase-negative staphylococci: The coagulase-negative staphylococci are usually colonizers of the skin and mucous membranes without disease significance. However, they have medical significance in immunosuppressed patients. Furthermore, they cause therapeutic problems in connection with so-called polymer-associated infections (plastic infections), i.e. colonisation of plastic surfaces (e.g. catheters, artificial heart valves, artificial joints; problem of biofilm formation). In humans, the following species in particular may be involved:

• Staphylococcus epidermidis
• Staphylococcus saprophyticus (causative agent of honey-moon cystitis)
• Staphylococcus haemolyticus
• Staphylococcus lugdunensis
• Staphylococcus hominis
• Staphylococcus warneri

Another 45 species, although rarely found in humans.

Virulence factors of S. aureus, modified from Horn (2019).

• Protein A: Cell wall associated protein
• Catalase: Oxygen radical secretory protein Limiting the effect of oxygen radicals.
• DNAse secretory protein nucleic acids hereditary damage.
• α-Toxin: secretory protein, damage to endothelial cells; intravascular coagulation
• β-toxin: secretory protein, damage to erythrocytes; monocytes
• Sphingomyelinase: hemolysis; scleral edema; hemorrhagic organ changes
• TSST-1 and enterotoxins: secretory proteins: superantigenic effect; food intoxication.
• Exfoliative toxins: secretory protein; binding to keratohyaline granules in stratum granulosum.
• PVL: Secretory protein; stimulates and destroys polymorphonuclear leukocytes.
• Coagulase: surface associated protein
• Prothrombin: surface adhesion; fibrinogen activation
• Elastin-binding protein: surface exotoxin components of extracellular matrix (elastin)
• Fibrinogen-binding protein(clumping factor A and B): Cell wall-associated proteinBinding and activation of fibrinogen, activation of the coagulation cascade; activation of platelets
• Collagen-binding protein: Cell wall-associated protein, direct binding to collagen.
• Staphylokinase: Extracellular protein Serine protease Fibrinolysis
• Fibronectin-binding protein: Cell wall-associated, protein Multi-adhesion proteins in the extracellular matrix Adhesion/colonization

Staphylococcus (Singular Staphylococcus) is a term introduced by Alexander Ogston in reference to the term streptococcus, which was coined by Billroth in 1874 and is composed of the components staphyle (Greek) = grape and kokkos (Greek) = core.