microbes 2

• Microbes


  Present all over the skin, but especially in the moist regions, which include nose, mouth, urethra
• Skin biota


  • Primarily commensals and keeps the skin healthy by excluding pathogens
• Biota present on the skin

  • Staphylococcus aureus
  • Staphylococcus epidermidis
  • Pityrosporum sp.
• Biota present in conjuctiva

  • Staphylococcus spp,staphylococcus aureus, Staphylococcus epidermidis,
• Staphylococcus spp. in conjuctiva

  May become opportunistic if normal flow of tears is reduced or stopped
• Biota present in Nasal cavity & Nasopharynx


  • S. epidermidis
  • S. aureus
  • Moraxella catarrhalis
• S. epidermidis, S. aureus, Moraxella catarrhalis in Nasal cavity & Nasopharynx


  May become opportunistic if airways are compromised
• Biota present in Mouth

  • Streptococci predominates
• Streptococcus mutans


  Causes tooth decay
• Lower intestine


  • Slower peristaltic movements in this region, as well as little bile, thus supports wide variety of microbes as compared to upper digestive tract
• Biota of lower intestine

  • Bacteroides
  • Bifidobacterium
  • Clostridium
  • E. coli
• Vagina

  • Warm, moist area with a scarcity of nutrients and low pH that limit microbial growth
• Biota of vagina

  • Candida albican
• Urethra


  • Upper part, which joins bladder, is usually free of microorganisms. Flow of urine tends to flush away microorganisms
• Biota of urethra

  • Scant, some S. epidermidis, Enterococci
• Loss of normal biota

  Changes in normal biota may have undesirable effects, Pathogens may be able to colonize and establish an infection and Opportunists may proliferate and then go on to establish an infection (as is sometimes the case in Candida overgrowth after treatment with antibiotics)
• What is the conjunctiva protected by?

  mechanically and biochemically by lysozyme found in the tears
• What is the nasal cavity and Nasopharynx protected by?

  mucociliary system.
• Benefits of normal biota

  • Produce antimicrobial compounds
  • Compete for receptors on epithelial cells
  • Alter environmental pH to limit colonization potential of pathogens
• Benefits of normal biota

  • Stimulates the immune system
  • Does not provide immunity against any particular disease, but acts to improve the entire defense system
• Benefits of normal biota


  • Intestinal microbiota provide a supplemental source of certain vitamins
  • Eg. Vitamin K, important in blood clotting
  • Vitamin B12 which is important in the production of red blood cells and nervous system function