Pathogenesis of s aureus Stage iv, continued Development--involves both host and bacterial factors Acute inflammatory reaction Proportion of bacteria survive and are capable of lysing neutrophils that engulfed them >>Outpouring of lysosomal enzymes that damage surrounding tissues Inflammatory area surrounded by fibrin clot BIOL 533 Lecture 10
BIOL 533 12 Lecture 10 Pathogenesis of S. aureus • Stage IV, continued – Development—involves both host and bacterial factors • Acute inflammatory reaction – Proportion of bacteria survive and are capable of lysing neutrophils that engulfed them » Outpouring of lysosomal enzymes that damage surrounding tissues – Inflammatory area surrounded by fibrin clot
Virulence factors of s. aureu Stage iv, continued Virulence factors-most designed to avoid phagocytosis or survive once ingested Wall components Surrounded by capsule: not as effective as pneumococcus or menIngococcus Cell wall murein activates complement by alternative pathway Teichoic acid also activates and involved in adherence Protein a interferes with opsonization by binding with Fc region of Ab--complement activated primary pathway BIOL 533 13 Lecture 10
BIOL 533 13 Lecture 10 Virulence Factors of S. aureus • Stage IV, continued – Virulence factors—most designed to avoid phagocytosis or survive once ingested • Wall components – Surrounded by capsule: not as effective as pneumococcus or meningococcus – Cell wall murein activates complement by alternative pathway – Teichoic acid also activates and involved in adherence – Protein A interferes with opsonization by binding with Fc region of Ab—complement activated primary pathway
Virulence factors of s. aureu Stage iv, continued Secretion of enzymes Catalase--hydrogen peroxide to water and oxygen (all staphylococci produce) Coagulase--makes fibrin clot(wbc penetrate badly; only S aureus) Hylauronidase--degrades connective tissues (facilitates spread; 90% of S, aureus strains Fibrinolysin(staphylokinase)dissolve fibrin clots (virtually all S. aureus) BIOL 533 Lecture 10
BIOL 533 14 Lecture 10 Virulence Factors of S. aureus • Stage IV, continued – Secretion of enzymes • Catalase—hydrogen peroxide to water and oxygen (all staphylococci produce) • Coagulase—makes fibrin clot (wbc penetrate badly; only S. aureus) • Hylauronidase—degrades connective tissues (facilitates spread; 90% of S. aureus strains) • Fibrinolysin (staphylokinase)—dissolve fibrin clots (virtually all S. aureus)
Virulence factors of s. aureu Stage iv, continued Secretion of enzymes Lipasesrequired for invasion into cutaneous and subcutaneous tissues (found in all s. aureus and 30% of others) Nuclease--heat stable(role is uncertain; S.au∥reus) ● Penicillinase BIOL 533 Lecture 10
BIOL 533 15 Lecture 10 Virulence Factors of S. aureus • Stage IV, continued – Secretion of enzymes • Lipases—required for invasion into cutaneous and subcutaneous tissues (found in all S. aureus and 30% of others) • Nuclease—heat stable (role is uncertain; S. aureus) • Penicillinase
Virulence factors of s. aureu Stage iv, continued Secretion of toxins Cytolytic(membrane-damaging by pores) Alpha, beta, (sphingomyelinase C), delta, gamma, leukocidin(cannot lyse red blood cells Others lyse rbc and leukocytes (referred to previously as hemolysins) Cause lysis of neutrophils leading to massive lysosomal enzyme secretion BIOL 533 Lecture 10
BIOL 533 16 Lecture 10 Virulence Factors of S. aureus • Stage IV, continued – Secretion of toxins • Cytolytic (membrane-damaging by pores) – Alpha, beta, (sphingomyelinase C), delta, gamma, leukocidin (cannot lyse red blood cells) – Others lyse rbc and leukocytes (referred to previously as hemolysins) – Cause lysis of neutrophils leading to massive lysosomal enzyme secretion