Bacterial Skin Infections Part 2

• Staphylococcal Infections

  Staph aureus – gram (+) cocci in grape-like cluster

  Endotoxin forming

  Commonly localized infections ; can complicate to pneumonia,

  lung abscess, osteomyelitis, sepsis, septic arthritis, endocarditis,

  and toxic shock syndrome
• Common types of Staphylococcal Infections

  Furuncles (Boils)

  Carbuncles

  Impetigo

  Cellulitis

  Staphylococcal Scalded Skin Syndrome (SSSS)
• Furuncles – Boils, pus-filled bump under the skin, usually of the hair follicle
• Carbuncles – cluster of 2 or more sub-cutaneously connected furuncles
• Impetigo – occurs in children ; pus-filled blisters/pustules

  There is impetigo of the newborn or impetigo neonatorum
• Cellulitis – non-necrotizing inflammation of the skin and subcutaneous tissues; its hyaluronidase breaks down hyaluronic acid of the connective tissue and can easily spread through out the body
• Staphylococcal Scalded Skin Syndrome (SSSS)

  The toxins:

  cause the epidermis to separate from the dermis, causing the exfoliation (peeling) of the skin.

  Targets the protein that holds skin cells together

  Primarily affects the children and infants with immature immune system
• Drug_Resistant Infections : Methicillin – resistant Staphylococcus aureus (MRSA)

  Commonly a nosocomial infection, however, there are community-associated MRSA

  Cause: Overuse and misuse of antibiotics

  Methicillin

  Beta-lactam antibiotic that acts by inhibiting penicillin-binding proteins (PBP) that are involved in the synthesis of peptidoglycan layer
• TOXIC SHOCK SYNDROME (TSS)

  A rare and fatal disease

  Caused by Staphylococcus (also, by

  Streptococcus, and Clostridium)

  Initial symptoms are fever and rash, but with

  hypotension, tachycardia, dyspnea, seizures

  Often associated with tampon use

  Immune system overreacts because of the

  response to the release of toxin
• Streptococcal Skin Infections

  Gram (+) cocci in chain and in pair

  Classification of Strep. According to Lancefield Groups (presence of specific carbohydrate antigen in the cell wall).

  Classification according to hemolytic pattern on Blood Agar Plate (BAP) medium
• S. pyogenes


  Mostly skin infections, scarlet fever, rheumatic fever, strep throat/pharyngitis
• S. pyogenes


  • Group A
  • Beta hemolytic
• S. agalactiae


  Commonly colonizes GIT and genitourinary tract to cause sepsis, pneumonia, meningitis to those with weak immune systems (esp. newborns)
• S. dysgalactiae subsp. equisimilis


  Pharyngitis, cellulitis, abscesses, respiratory tract infections, rheumatic fever (less common)
• Strep viridans


  NF of the mouth and GIT but can cause opportunistic infections for the immune compromised
• Strep mutans


  Dental caries or demineralize the tooth enamel by metabolizing sugar