chap 10

• Indigenous microflora


  All the microbes (bacteria, fungi, protozoa and viruses) that reside on and within a person
• Blood, lymph, spinal fluid, and most internal tissues and organs are normally free of microorganisms (i.e., they are sterile)
• Transient microflora


  Microbes that take up temporary residence on and within humans
• Destruction of resident microflora disturbs the delicate balance between host and microorganisms
• Microflora of the skin

  • Primarily bacteria and fungi - about 30 different types; most common = Staphylococcus spp.
  • Number and variety depend on: amount of moisture, pH, temperature, salinity, presence of chemical wastes and other microbes
• Microflora of the ears and eyes


  • Middle ear and inner ear are usually sterile; outer ear and auditory canal contain the same microorganisms as on the skin
  • Eye is lubricated and cleansed by tears, mucus and sebum - few microorganisms present
• Microflora of the respiratory tract

  • Upper respiratory tract (nasal passages and throat) has an abundance of microorganisms; many are harmless, some are opportunistic pathogens
  • Carriers harbor virulent pathogens in their nasal passages or throats, but do not have the diseases usually caused by these pathogens
  • Lower respiratory tract is usually free of microbes
• Microflora of the oral cavity


  • A shelter for numerous anaerobic and aerobic bacteria; remaining food particles provide a rich nutrient medium for bacteria
  • Careless dental hygiene may cause dental caries, gingivitis, and periodontitis
  • The most common organisms are various species of alpha-hemolytic streptococci and Peptostreptococcus
• Microflora of the gastrointestinal tract


  • The colon (large intestine) contains the largest number and variety of microorganisms of any colonized area of the body; an estimated 500-600 different species - primarily bacteria
  • Colon is anaerobic; bacteria in colon are mostly obligate-, aerotolerant-, and facultative anaerobes
  • Many of the microflora of the colon are opportunists
• Microflora of the genitourinary tract


  • Kidney, ureters and urinary bladder are usually sterile; the distal urethra and its external opening harbor many microbes including bacteria, yeasts and viruses
  • Most frequent causes of urethral infections include Chlamydia trachomatis, Neisseria gonorrhoeae, and mycoplasmas
  • The male and female reproductive systems are usually sterile, with the exception of the vagina
• Microbial antagonism


  Microbes versus microbes - many members of our indigenous microflora are beneficial in that they prevent other microbes from becoming established
• Microbial antagonism


  • Production of antibiotics and bacteriocins (antibacterial proteins); an example is colicin, produced by E. coli
• Opportunistic pathogens


  Microorganisms that "hang around", waiting for the opportunity to cause infection
• Opportunistic pathogens


  • E. coli, other members of the family Enterobacteriaceae, S. aureus, and Enterococcus spp.

  
• Biotherapeutic agents or probiotics

  Bacteria and yeasts used to stabilize the microbial balance
• Biofilms


  • Complex communities of assorted microorganisms, consisting of a variety of different species of bacteria plus a gooey polysaccharide that the bacteria secrete
  • Bacteria grow in tiny clusters called microcolonies, separated by water channels
  • Biofilms are very resistant to antibiotics and disinfectants

  
• Microbes commonly associated with biofilms on medical devices

  • Candida albicans, Staphylococcus aureus, Enterococcus spp., Klebsiella pneumoniae, and Pseudomonas aeruginosa

  
• Synergistic infections, polymicrobial infections, or mixed infections


  When 2 or more organisms "team up" to produce a disease that neither could cause by itself
• Synergistic infections


  • Acute necrotizing ulcerative gingivitis (ANUG, trench mouth, or Vincent's disease)
  • Bacterial vaginosis (BV)
• Role of microbes in elemental cycles


  • Microorganisms play an important role in the cycling of nutrients and elements like nitrogen, carbon, oxygen, sulfur, and phosphorus
  • N2 is converted by nitrogen-fixing bacteria and cyanobacteria into ammonia (NH3) and ammonium ion (NH4)
• Other soil microorganisms


  • Bacteria, fungi, algae, protozoa, viruses, and viroids; many are decomposers
  • Human pathogens like Clostridium spp. (such as C. tetani and C. botulinum) and the spores of Bacillus anthracis
• Biotechnology


  Any technological application that uses biological systems, living organisms, or derivatives thereof, to make or modify products or processes for specific use
• Uses of microbes in biotechnology


  • Production of certain foods and beverages, food additives, vaccines, and antibiotics
  • Production of foods like bread, cheeses, olives, pickles, vinegar and yogurt, as well as in the production of alcoholic beverages like beer and wine
  • Production of many antibiotics and drugs by fungi and bacteria (e.g. penicillin)