Staohylococcus Infections

Staphylococcus Infections

  • Overview
    • Exploring infections caused by Staphylococcus.
    • Commensal Bacteria:
    • Present in all humans.
    • Neither harms nor benefits the host.
    • Infection Risk Factors:
    • Breaks in the skin or mucous membranes.
    • Immunocompromised individuals.
    • Infection Associations:
    • Skin infections.
    • Central nervous system infections.
    • Gastrointestinal infections.
    • Systemic infections affecting cardiovascular and lymphatic systems.
    • Associated with pneumonia.

Staphylococcus Characteristics

  • Characteristics of Staphylococcus
    • Shape and Arrangement:
    • Cocci: Spherical shape, occurs in clusters.
    • Gram Staining:
    • Gram Positive.
    • Mobility:
    • Non-motile bacterium.
    • Catalase Activity:
    • Positive (can break down hydrogen peroxide).
    • Oxygen Requirement:
    • Facultative anaerobe (can survive with or without oxygen).
    • Oxidase Activity:
    • Negative.
    • Coagulase:
    • Positive (ability to clot blood).
    • Culturing Requirements:
    • Selective via bile salts.
    • Exhibits a hemolytic pattern (specifically, beta hemolysis).

Virulence Factors of Staphylococcus aureus

  • Virulence Factors
    • Coagulase Positive:
    • Clots blood to evade the immune system.
    • Catalase Positive:
    • Breaks down reactive oxygen species, such as hydrogen peroxide.
    • Enzymatic Activity:
    • Staphylocinase: Breaks down blood clots, aids in spreading infection.
    • Specific Toxins:
    • Pyrogenic toxin: Associated with fever.
    • Exfoliative toxin: Linked to scalded skin syndrome.
    • Hyaluronidase: Dismantles extracellular matrix of connective tissues.
    • Hemolysins: Lyse red blood cells, leading to beta hemolytic activity.
    • Lipase: Digests lipids in tissues.

Types of Infections by Staphylococcus aureus

  • Common Infections
    • Folliculitis:
    • Infection of hair follicle, may appear red, swollen, or pus-filled.
    • When occurring on the eyelid, referred to as a stye.
    • May spread to surrounding tissue, termed furuncle (boil).
    • When multiple furuncles coalesce, it is called a carbuncle.
    • Can trigger immune responses, resulting in fever and chills.
    • Staphylococcal Scalded Skin Syndrome:
    • Typically observed in infants.
    • Caused by exfoliative toxin.
    • Characterized by:
      • Skin reddening, blistering (clear fluid).
      • Skin peeling in sheets after 2 days.
    • Risk: Loss of skin as a protective barrier, increasing chance of secondary infections.
    • Impetigo:
    • Primarily affects children aged 2-5.
    • Symptoms include:
      • Itchy, reddened skin with pus-filled vesicles.
      • Lesions typically appear on the face or extremities.
    • Risk of spreading if vesicles rupture or are scratched.
    • Treatment: Penicillin antibiotics.

Conjunctivitis

  • Definition:
    • Refers to inflammation or infection of the conjunctiva (tissue covering the sclera and inner eyelid).
    • Commonly known as pink eye.
    • Causes:
    • Can be caused by bacterial, viral infections, or other pathogens (e.g., streptococci).
    • Symptoms:
    • Bacterial conjunctivitis: Sticky, pus-like discharge; eyelids may stick together.
    • Viral conjunctivitis: More watery discharge.
    • Physiological Response:
    • Eyeball reddens due to inflammation and dilated blood vessels.
  • Ophthalmia Neonatorum:
    • Occurs in newborns exposed to Chlamydia or Gonorrhea during delivery.
    • Risk of permanent eye damage.
    • Standard practice: Prophylactic antibiotic drops in newborns' eyes to prevent infection.