Staphylococcus aureus

• staphylococcus spp. family is ?

  staphylococcaceae
• staphylococcus spp. are able to produce enzyme ?

  catalase
• catalase (+) breakdown the hydrogen peroxide into water and oxygen.

  H2O2 = H2O and O2 = bubbles
• staphylococcus spp are coagulase (+) and some are coagulase (-)
• staphylococcus are gram (+) cocci in single, in pairs, and in grape like clusters
• Gram (+) cocci that are occasionally recovered with staphylococcus

  • Rothia mucilaginosa
  • Aerococcus
  • Alliococcus otitis - from external ear fluid
• Resembles the family ? and genus micrococcus

  Micrococcaceae
• Coagulase (-)

  Micrococcus
• Gram (+) cocci in pairs, tetrads, and ultimately, irregular clusters. Found in environment and human skin

  Colonies: Yellow Pigment

  Micrococcus
• Catalase (+)

  • Staphylococcus
  • Micrococcus
• Coagulase (-)

  • Differentiates staphylococcus and micrococcus
• staple meaning bunches of grapes
• Staphylococcus are non motile, non spore forming, and aerobic or facultativr anaerobic except:

  • S. saccharolyticus
  • S. aureus subp. anaerobius

  Obligate anaerobes and may be catalase (-)

  Can't grow in the presence of oxygen
• Staphylococcus is the normal flora of skin and mucous membranes of human and animals
• Colonies: medium size (4 to 8mm) and appear cream-colored, white or rarely light gold, and buttery looking
• Fastidious strains requirements:

  • CO2
  • Hemin
  • Menadione

  with at least 48 hours of incubation
• Virulence factors


  severity of the disease
• Enterotoxin - resistant to hydrolysis bt the gastric and intestia enzymes

  • Groupe A-E & G-J
  • Staphylococcal food poisoning - A,E
  • TSS (Toxic Shock Syndrome) - B,G,C,I
  • Staphylococcal pseudomembranousenterocolitis - B
  • Heat stale exotoxin (100 C for 30mins)
• Toxic Shock Syndrome Toxin - 1

  • TSS - Systemic effect like fever, hypotension that leads to shock or death
  • Previously known as enterotoxin F/ pyrogenic exotoxin C
• Exfoliative toxin

  • Epidermolytic toxin A & B
  • Staphylococcal SSS
  • Ritter disease
  • Bullous impetigo
• Cytolytic toxin/ Cytoxin

  • Extracellular proteins that affect RBC and leukocytes
  • Lysine and Leukocidins
  • S. aureus: a,b,y,g
• a-hemolysin: disrupts the smooth muscle in blood vessels and is toxic to erythrocyte, leukocyte, hepatocytes, and platelets

  hemolysin able to lyse erythrocyte and can also da platelets, macrophages, and can cause severe tissue damage
• b-hemolysin also known as Sphingomyelinase C or Hot-Cold lysin
• b-hemolysin act as sphingomyelin I the plasma membrane of RBCs and act in CAMP test
• Hot and Cold lysin - because they are able to produce an enhanced hemolytic activity on incubation at 37C and subsequent exposure to cold (4C)
• CAMP test - Christie, Atkins, Munch-Peterson is performed if you want to identify the Group B streptococci; test for streptococcus
• h-hemolysin: less toxic than a and b hemolysin- CoNS
• y-hemolysin: functions with PVL or Panton Valentine Leukocidin that exhibit polymorphonuclear leukocyte toxicity and are able to suppress phagocytosis (cell eating)
• Staphylococcal leucocidin

  • PVL
  • exotoxin lethal to PMN
  • suppresses phagocytosis
  • associated with severe cutaneous infections a necrotizing pneumonia
  • often associated with community acquired Staphylococcal infections
• Enzymes

  • Coagulase, protease, hyaluronidase, & lipase
  • STAPHYLOCOAGULASE- responsible for (+) tube coagulation test; produce clot formation
  • HYALURONIDASE - permits the bacteria to spread to connective tissue.
  • hydrolyzes hyaluronic acid present in the intercellular ground substance that makes up connective tissue, permitting the spread of bacteria during infection.
  • LIPASE - degrades lipids on the skin, making it more susceptible to bacterial entry into epidermal layer.
  • by both coagulase (+) and CoNS
  • act on lipids present on the surface of the skin
• PROTEIN A

  • Found in cell wall of the S. aureus
  • Bind the Fc portion of immunoglobulin G (IgG) and complement
  • Block phagocytosis and inhibit action of IgG
• PEPTIDOGLYCAN

  • Provides rigidity of cell wall
  • Activates complement, IL-1, chemotactic to PMNs - Polymorphonuclear leukocytes
  • IL-1 - Interleukin 1 endogenous pyrogen (induces fever)
• TEICHOIC ACID

  • Mediate binding to fibronectin
  • Important in cell wall metabolism
• True or Flase: There is a special procedure in specimen collection

  False
• ideal sample


  aspirates
• Used to identify methicilin resistant- S. aureus

  CHROMagar Staph aureus
• growth of colony


  macroscopic examination
• Characteristics of S. aureus

  • Round
  • Smooth
  • White
  • Creamy
  • Butter looking

  on BAP
• Characteristic of S. epidermidis

  • Small-medium
  • Non hemolytic
  • Gray to white color
• gram staining process is what type of examination

  microscopic