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Microbiology includes

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									Medical Microbiology
   Department of Microbiology, HMU
 Section III Bacteriology


Normal Microbial Flora
   in Human Body
  Zhao-Hua Zhong, Ph.D., Prof.
  Department of Microbiology
   Harbin Medical University


                      Department of Microbiology, Harbin Medical University
                 KEY TERMS
   Pathogen
   Opportunistic infection
   Microdysbiosis
   Translocation
   Medical Microecology
   Nosocomial Infection




                              Department of Microbiology, Harbin Medical University
       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
                  Department of Microbiology, Harbin Medical University
Normal Microbial Flora
   the population of microorganisms that
    inhabit the skin and mucous membranes of
    healthy normal persons

   It is doubtful whether a normal viral flora
    exists in humans



                             Department of Microbiology, Harbin Medical University
 Normal Microbiota= Normal Flora

 Normal microbiota
 Normal microflora
 Physiological microbiota




                             Department of Microbiology, Harbin Medical University
Normal Microbial Flora Groups
   Resident flora
     consists of relatively fixed types of
      microorganisms regularly found in a given area
      at a given age
     If disturbed, it promptly reestablishes itself

   Transient flora
     consists of nonpathogenic or potentially
      pathogenic microorganisms that inhabit the
      skin or mucous membranes for hours, or days
                               Department of Microbiology, Harbin Medical University
                Transient Flora
   It is derived from the environment, does not
    produce disease, and does not establish itself
    permanently on the surface
   Members of the transient flora are generally of
    little significance so long as the normal resident
    flora remains intact
   If the resident flora is disturbed, transient
    microorganisms may colonize, proliferate, and
    produce disease


                                  Department of Microbiology, Harbin Medical University
Classifications of Normal Flora
   Enviroment
     Autochthony  (= aborigines)
     Allochthony (= foreign)

   Relation with host
     Symbiotic  flora
     Parasitism flora




                               Department of Microbiology, Harbin Medical University
      Microecosystem - Microecology
   Skin                    Staphy
   Mouth                   E. coli
   Nasopharynx
                            Pseudomonas
   Ear
   Eye
                            Strepto
   Gastrointestine         Nesseria
   Urinary truct           Corynebacteria
   Reproductive tract      ….
                            ….

                               Department of Microbiology, Harbin Medical University
Department of Microbiology, Harbin Medical University
                    Skin Flora
   The surface of the skin itself comprises several distinct
    environments
       the axilla (armpit)
       the perineum (groin)
       the toe webs
            provide typically moister regions for bacterial growth. These
             "tropical forest" environments often harbor the largest diversity
             amongst the skin flora
   Typical organisms include Staphylococcus aureus,
    Corynebacterium and some Gram-negative bacteria
       predominantly inhabited by Staphylococcus epidermidis and
        Propionobacterium


                                                   Department of Microbiology, Harbin Medical University
    Oral Cavity and Nasopharyngeal
                 Flora
   Streptococci predominate in the oral cavity and
    nasopharyngeal regions
     Other   anaerobes and species of Neisseria
   Many potential pathogens may also be found in
    the nasopharynx of a healthy individual,
    providing a reservoir for infection of others
     These pathogens include Streptococcus pneumoniae,
      Neisseria meningitidis and Haemophilus influenzae



                                      Department of Microbiology, Harbin Medical University
                Intestinal Flora
   The intestinal tract is a rather hostile environment
    for microorganisms
     thecolon may contain 109 to 1011 bacteria per gram of
      material
   Most (95 - 99.9%) of these are anaerobes,
    represented by Bacteroides, Bifidobacterium,
    anaerobic streptococci and Clostridium
   These organisms inhibit the growth of other
    pathogens
     butsome can be opportunistic (e.g. C. difficile can
      produce pseudomembranous colitis)


                                    Department of Microbiology, Harbin Medical University
                      Urogenital Flora
   The urogenital tract is normally sterile with the exception of
    the vagina and the distal 1 cm of the urethra
   Vagina
       the genus Lactobacillus predominate in the vagina
       Lactobacillus generally lower the pH to around 4-5, which is optimal
        for the lactobacilli but inhibitory for the growth of many other bacteria
       Loss of this protective effect by antibiotic therapy can lead to infection
        by Candida ("yeast infection")
   Urethra
       may contain predominantly skin microorganisms including
        staphylococci, streptococci and diphtheroids



                                                 Department of Microbiology, Harbin Medical University
                      Normal Flora
•   Skin
    –   Staphylococcus aureus,
    –   S. epidermidis
    –   Propionibacterium acnes
•   Intestine
    –   Bacteroides
         *   high numbers
    –   Enterobacteriaceae
         *   low number


                                  Department of Microbiology, Harbin Medical University
           Biological Outcomes
   Help us by competing with pathogens such as
    Salmonella
   Help us by providing vitamins or eliminating
    toxins (e.g. Bacteroides)

   Harm us by promoting disease (e.g. dental caries)

   Cause neither help nor harm (e.g. "commensals")

                                 Department of Microbiology, Harbin Medical University
         Physiological Benefits
   Antagonism
     Bio-barrier:microcolony
     Chemical barrier
     Nutrient competition

 Provide nutrients
 Stimulate immune system
     Anti-tumor



                                Department of Microbiology, Harbin Medical University
占位性生物屏障作用
      Department of Microbiology, Harbin Medical University
     Opportunistic Infections
 Compromised     people
  normal flora
  Environment




                           Department of Microbiology, Harbin Medical University
Microeubiosis / Microdysbiosis
   Microeubiosis         Microdysbiosis
     Normal   flora        Flora      disequilibrium
        Location               Dysbacteriosis

        Quality

        Quantity           Translocation
     Host                      Horizontal

     Environment               Vertical

                                Blood




                             Department of Microbiology, Harbin Medical University
    Causes of Microdysbiosis
 Abuses of Antibiotics
 Radiation
 Surgery
 Use of immune suppressors
 Use of hormones
 Acquired immune deficiency



                         Department of Microbiology, Harbin Medical University
          Opportunistic pathogen
   E. coli             Opportunities
   Klebsiella            Translocation
   Pseudomonas           Dysbacteriosis
   Enterbacteria         Immune            suppression
   Staphy




                           Department of Microbiology, Harbin Medical University
          Hospital Infection
 Nosocomial infection
 Hospital-acquired infection




                           Department of Microbiology, Harbin Medical University

								
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