normal microbial flora


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normal microbial flora

  1. 1. Medical Microbiology Department of Microbiology, HMU
  2. 2. Section III Bacteriology Normal Microbial Flora in Human Body Zhao-Hua Zhong, Ph.D., Prof. Department of Microbiology Harbin Medical University
  3. 3. KEY TERMS <ul><li>Pathogen </li></ul><ul><li>Opportunistic infection </li></ul><ul><li>Microdysbiosis </li></ul><ul><li>Translocation </li></ul><ul><li>Medical Microecology </li></ul><ul><li>Nosocomial Infection </li></ul>
  4. 4. Pathogenic Bacteria 少数 细菌总有致病性 许多 细菌具有潜在致病性 大多 细菌不具有致病性
  5. 5. Normal Microbial Flora <ul><li>the population of microorganisms that inhabit the skin and mucous membranes of healthy normal persons </li></ul><ul><li>It is doubtful whether a normal viral flora exists in humans </li></ul>
  6. 6. Normal Microbiota= Normal Flora <ul><li>Normal microbiota </li></ul><ul><li>Normal microflora </li></ul><ul><li>Physiological microbiota </li></ul>
  7. 7. Normal Microbial Flora Groups <ul><li>Resident flora </li></ul><ul><ul><li>consists of relatively fixed types of microorganisms regularly found in a given area at a given age </li></ul></ul><ul><ul><li>If disturbed, it promptly reestablishes itself </li></ul></ul><ul><li>Transient flora </li></ul><ul><ul><li>consists of nonpathogenic or potentially pathogenic microorganisms that inhabit the skin or mucous membranes for hours, or days </li></ul></ul>
  8. 8. Transient Flora <ul><li>It is derived from the environment , does not produce disease, and does not establish itself permanently on the surface </li></ul><ul><li>Members of the transient flora are generally of little significance so long as the normal resident flora remains intact </li></ul><ul><li>If the resident flora is disturbed , transient microorganisms may colonize, proliferate, and produce disease </li></ul>
  9. 9. Classifications of Normal Flora <ul><li>Enviroment </li></ul><ul><ul><li>Autochthony (= aborigines) </li></ul></ul><ul><ul><li>Allochthony (= foreign) </li></ul></ul><ul><li>Relation with host </li></ul><ul><ul><li>Symbiotic flora </li></ul></ul><ul><ul><li>Parasitism flora </li></ul></ul>
  10. 10. Microecosystem - Microecology <ul><li>Skin </li></ul><ul><li>Mouth </li></ul><ul><li>Nasopharynx </li></ul><ul><li>Ear </li></ul><ul><li>Eye </li></ul><ul><li>Gastrointestine </li></ul><ul><li>Urinary truct </li></ul><ul><li>Reproductive tract </li></ul><ul><li>Staphy </li></ul><ul><li>E. coli </li></ul><ul><li>Pseudomonas </li></ul><ul><li>Strepto </li></ul><ul><li>Nesseria </li></ul><ul><li>Corynebacteria </li></ul><ul><li>… . </li></ul><ul><li>… . </li></ul>
  11. 12. Skin Flora <ul><li>The surface of the skin itself comprises several distinct environments </li></ul><ul><ul><li>the axilla (armpit) </li></ul></ul><ul><ul><li>the perineum (groin) </li></ul></ul><ul><ul><li>the toe webs </li></ul></ul><ul><ul><ul><li>provide typically moister regions for bacterial growth. These &quot;tropical forest&quot; environments often harbor the largest diversity amongst the skin flora </li></ul></ul></ul><ul><li>Typical organisms include Staphylococcus aureus, Corynebacterium and some Gram-negative bacteria </li></ul><ul><ul><li>predominantly inhabited by Staphylococcus epidermidis and Propionobacterium </li></ul></ul>
  12. 13. Oral Cavity and Nasopharyngeal Flora <ul><li>Streptococci predominate in the oral cavity and nasopharyngeal regions </li></ul><ul><ul><li>Other anaerobes and species of Neisseria </li></ul></ul><ul><li>Many potential pathogens may also be found in the nasopharynx of a healthy individual, providing a reservoir for infection of others </li></ul><ul><ul><li>These pathogens include Streptococcus pneumoniae , Neisseria meningitidis and Haemophilus influenzae </li></ul></ul>
  13. 14. Intestinal Flora <ul><li>The intestinal tract is a rather hostile environment for microorganisms </li></ul><ul><ul><li>the colon may contain 10 9 to 10 11 bacteria per gram of material </li></ul></ul><ul><li>Most (95 - 99.9%) of these are anaerobes, represented by Bacteroides , Bifidobacterium, anaerobic streptococci and Clostridium </li></ul><ul><li>These organisms inhibit the growth of other pathogens </li></ul><ul><ul><li>but some can be opportunistic (e.g. C. difficile can produce pseudomembranous colitis ) </li></ul></ul>
  14. 15. Urogenital Flora <ul><li>The urogenital tract is normally sterile with the exception of the vagina and the distal 1 cm of the urethra </li></ul><ul><li>Vagina </li></ul><ul><ul><li>the genus Lactobacillus predominate in the vagina </li></ul></ul><ul><ul><li>Lactobacillus generally lower the pH to around 4-5, which is optimal for the lactobacilli but inhibitory for the growth of many other bacteria </li></ul></ul><ul><ul><li>Loss of this protective effect by antibiotic therapy can lead to infection by Candida (&quot;yeast infection&quot;) </li></ul></ul><ul><li>Urethra </li></ul><ul><ul><li>may contain predominantly skin microorganisms including staphylococci, streptococci and diphtheroids </li></ul></ul>
  15. 16. Normal Flora <ul><li>Skin </li></ul><ul><ul><li>Staphylococcus aureus , </li></ul></ul><ul><ul><li>S. epidermidis </li></ul></ul><ul><ul><li>Propionibacterium acnes </li></ul></ul><ul><li>Intestine </li></ul><ul><ul><li>Bacteroides </li></ul></ul><ul><ul><ul><li>high numbers </li></ul></ul></ul><ul><ul><li>Enterobacteriaceae </li></ul></ul><ul><ul><ul><li>low number </li></ul></ul></ul>
  16. 17. Biological Outcomes <ul><li>Help us by competing with pathogens such as Salmonella </li></ul><ul><li>Help us by providing vitamins or eliminating toxins (e.g. Bacteroides) </li></ul><ul><li>Harm us by promoting disease (e.g. dental caries) </li></ul><ul><li>Cause neither help nor harm (e.g. &quot;commensals&quot;) </li></ul>
  17. 18. Physiological Benefits <ul><li>Antagonism </li></ul><ul><ul><li>Bio-barrier: microcolony </li></ul></ul><ul><ul><li>Chemical barrier </li></ul></ul><ul><ul><li>Nutrient competition </li></ul></ul><ul><li>Provide nutrients </li></ul><ul><li>Stimulate immune system </li></ul><ul><ul><li>Anti-tumor </li></ul></ul>
  18. 19. 占位性生物屏障作用
  19. 20. Opportunistic Infections <ul><li>Compromised people </li></ul><ul><ul><li>normal flora </li></ul></ul><ul><ul><li>Environment </li></ul></ul>
  20. 21. Microeubiosis / Microdysbiosis <ul><li>Microeubiosis </li></ul><ul><ul><li>Normal flora </li></ul></ul><ul><ul><ul><li>Location </li></ul></ul></ul><ul><ul><ul><li>Quality </li></ul></ul></ul><ul><ul><ul><li>Quantity </li></ul></ul></ul><ul><ul><li>Host </li></ul></ul><ul><ul><li>Environment </li></ul></ul><ul><li>Microdysbiosis </li></ul><ul><ul><li>Flora disequilibrium </li></ul></ul><ul><ul><ul><li>Dysbacteriosis </li></ul></ul></ul><ul><ul><li>Translocation </li></ul></ul><ul><ul><ul><li>Horizontal </li></ul></ul></ul><ul><ul><ul><li>Vertical </li></ul></ul></ul><ul><ul><ul><li>Blood </li></ul></ul></ul>
  21. 22. Causes of Microdysbiosis <ul><li>Abuses of Antibiotics </li></ul><ul><li>Radiation </li></ul><ul><li>Surgery </li></ul><ul><li>Use of immune suppressors </li></ul><ul><li>Use of hormones </li></ul><ul><li>Acquired immune deficiency </li></ul>
  22. 23. Opportunistic pathogen <ul><li>E. coli </li></ul><ul><li>Klebsiella </li></ul><ul><li>Pseudomonas </li></ul><ul><li>Enterbacteria </li></ul><ul><li>Staphy </li></ul><ul><li>Opportunities </li></ul><ul><ul><li>Translocation </li></ul></ul><ul><ul><li>Dysbacteriosis </li></ul></ul><ul><ul><li>Immune suppression </li></ul></ul>
  23. 24. Hospital Infection <ul><li>Nosocomial infection </li></ul><ul><li>Hospital-acquired infection </li></ul>