Staphylococcus Staphyle- Bunch of grapes 0.5 to 1 um Non motile Aerobic or Facultative Anaerobic Catalase positive Grow in media containing 10% NaCl at temp 18 to 40 C Present on the skin and mucuos membrane
Structure CAPSULE - loose fitting polysaccharide layer (slime layer) - protects bacteria by inhibiting chemotaxis and phagocytosis - facilitates adherence of bacteria to catheters and synthetic materials PEPTIDOGLYCAN - half of the cell wall - consist of layers of glycan chains with alternating subunits of N –acetylmuramic acid and N- acetylglucosamine - has endotoxin like activity
Structure TEICHOIC ACID- phosphate containing polymers bound to peptidoglycan layer or to cytplasmic membrane - mediates the attachment of staphylococcus to mucosal surfaces S. aureus Ribitol teichoic acid with N-acetylglucosamine ( Polysaccharide A) S. epidermidis glycerol teichoic acid with glucosyl residues (polysaccharide B)-
PROTEIN A- covalentlylinked to peptidoglycan - has affinity to Fc receptor of Ig - blocks opsonization and phagocytosis
Structure CYTOPLASMIC MEMBRANE- osmotic barrier for the cell and provides an anchorage for the biosynthetic and respiratory enzyme COAGULASE and other SURFACE PROTEIN -Clumping factor or Bound coagulase binds fibrinogen convert to insoluble fibrin causing staphylococcus to clump - collagen , elastin and fibronectin binding protein
Cytotoxins Lyse neutrophils release of lysosomal enzymes damage sorrounding tissues Alpha toxin – disrupts the smooth muscle in blood vessels - toxic to erythrocytes, hepatocytes, platelets, cultivated cells - integrates to host cell membrane pores efflux of K and influx of Na,Ca osmotic swelling cell lysis - septic shock
Cytotoxin Beta Toxin - Sphingomyelinase C - specific for sphingomyelin and lysophosphatidylcholine - toxic to RBC, WBC,Macrophage and fibroblast - catalyze hydrolysis of membrane phospholipids in susceptible cells - tissue destruction and abscess formation Delta toxin- disrupts cell membrane - toxic to variety of cells
Induce cytokine release from macrophage and T lymphocytes
Increase sensitivity to endotoxin
Produce leakage of endothelial cells
Penetrate mucosal barrier
Staphylococcal enzymes convert fibrinogen react with globulin plasma factor insoluble fibrin to form staphylothrombin Clumping Cause formation of fibrin layer around abscess protecting staphylococcus from phagocytosis Coagulase Bound Free
Perioral erythema spread body bullous desquamation
Bullous impetigo – localized form of SSSS - localized blister - culture positive
SSSS most commonly in children and neonates. Starts abruptly with perioral (around the mouth) erythema with sunburn-like rash rapidly turning bright red spreading to bullae (large vesicle appearing as a circumscribed area) in 2-3 days and desquamating (peeling) within 5 days.
Folliculitis - superficial folliculitis is essentially a staphylococcal impetigo in which a small area of erythema develops around a hair follicle and subsequently becomes a dome-shaped pustule. Carbuncle - a deep-seated pyogenic infection of the skin and subcutaneous tissues.
Impetigo - a contagious superficial pyoderma, caused by S. aureus and Streptococcus pyogenes, that begins with a superficial flaccid vesicle which ruptures and forms a thick yellowish crust, most commonly occurring in the face.