Virulence Factors of Staphylococcus

A.   Cell Wall Associated

Virulence Factors

Functions

Peptidoglycan – Pyrogenicity

– Complement Activation

– Inhibition of leukocyte migration

Techoic Acid – Adherence to mucosal surfaces
Capsule – Diffusion Barrier

– Prevents Phagocytosis

– Capsular serotypes 5 and 8 are most frequently associated with bacteremia and infections

B.   Cell Surface Associated

Virulence Factors

Functions

Protein A – Basis for Coagglutination Test, used in laboratories for organisms identification (e.g., Gonococci and Streptococci)

– Binds to Fc region of all human IgG subclasses except IgG3

Clumping Factor – Detected by slide test for bound coagulase

C.   Extracellular Enzymes

Virulence Factors

Functions

Coagulase – Clots plasma in the absence of calcium

– Reacts with coagulase-releasing factor (CRF) and the resulting complex (staphylothrombin), converts fibrinogen to fibrin

– Eight Types (most common type is A)

– Detected by tube test for free coagulase

Staphylokinase – Binds to plasminogen and activates it to the fibrinolytic enzyme plasmin
Lipase – Hydrolyzes triglycerides
Thermonuclease – Hydrolyzes RNA and DNA
Urease – Hydrolyzes urea to ammonia

– Plays role in the invasiveness of S. saprophyticus in the urinary tract

Hyaluronate Lyase (Hyaluronidase) – Aids in invasiveness by breakdown of Hyaluronate rich tissue barriers (accounts for persistence of Staphylococcus in tissues)
Proteases – Cleave and Degrade host proteins

D.   Hemolysins

Virulence Factors

Functions

α-Hemolysin – Most important hemolysis

– Lyses RBCs of several animal species

– Leucocidal, cytotoxic, neurotoxic, and dermonecrotic activities

– Leads to β-hemolysis around colonies

β-Hemolysin – Sphingomyelinase activity on RBCs (responsible for CAMP test)

– Displays hot-cold phenomenon

δ-Hemolysin – Surfactant on various cells: erythrocytes, leucocytes, bacterial protoplasts
γ-Hemolysin – γ-Hemolysins composed of two proteins
Leukocidin – Also called Panton-Valentine Toxin

E.   Toxins

Virulence Factors

Functions

Enterotoxin A through E, H, I (the most common type is A) – Pyrogenic toxin Superantigen

– Heat Stable

– Responsible for Staphylococcal food poisoning

– Mechanism of action: Increase intestinal peristalsis by increased vagal stimulation

– Ingestion of preformed exotoxin in food (baked food, custards, potato salad, processed meats, fish, milk products, ice creams)

– Nausea/Vomiting with or without diarrhea in 1 to 6 hours

– Self Limiting. No role of antibiotics

Toxic Shock Syndrome Toxin-1 (TSST-1); formerly known as enterotoxin F or pyrogenic exotoxin C – It is also a Superantigen, leading to a systemic release of a variety of cytokines which is the cause of multisystem involvement in TSS, mostly seen in menstruating women using highly absorbent vaginal tampons

– Resistant to inactivation by heat and proteolytic enzymes

– Pyrogenic, causes erythroderma and endotoxin shock

– Treatment: Clindamycin

Exfoliative TOXIN (epidermolytic toxin) ET A and ET B – Has Superantigen Activity

– ET A: thermostable

– ET B: heat labile

– Dissolve the mucopolysaccharide matrix of epidermis, resulting in intraepithelial splitting of cellular linkages in stratum granulosum and intraepidermal blistering leading to SSSS (Staphylococcal Scalded Skin Syndrome)

– Severe form of the SSSS is known as Ritter’s disease in the new born

– Milder forms are pemphigus neonatorum and bullous impetigo

1 thought on “Virulence Factors of Staphylococcus”

  1. Pleas i want information about pathogenesis of staphylococcus and molecular pathogenic of staphylocococcus aureus and epidermidis

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