chapter 4 normal flora host parasite relationship n.
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Chapter 4 – NORMAL FLORA & HOST PARASITE RELATIONSHIP. Miss Rashidah Hj Iberahim. Types of Pathogens. Primary Pathogens Cause disease upon infection, not normally associated with host Plague ( Yersinia pestis ), influenza virus Opportunistic Pathogens

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chapter 4 normal flora host parasite relationship


Miss RashidahHjIberahim

MIC342 - Miss Rashidah Hj Iberahim

types of pathogens
Types of Pathogens
  • Primary Pathogens
    • Cause disease upon infection, not normally associated with host
      • Plague (Yersiniapestis),
      • influenza virus
  • Opportunistic Pathogens
    • Cause disease under some circumstances, sometime members of normal flora
      • Pseudomonas,
      • Candida albicans
progression of disease
Progression of Disease
  • Transmission: infectious dose from 10-106 organisms
  • Incubation period: few days (common cold)-weeks (hepatitis A)-months (rabies)
  • Convalescence:
    • Clearing (Strep throat, S. pyogenes)
    • Latency (Chicken pox, tuberculosis, cold sores)
koch s postulates
Koch’s Postulates
  • Proposed by Robert Koch
  • Conclude that a microbe causes a particular disease
  • Must fulfill four postulates
    • Microorganism must be present in every case of the disease
    • Organism must be grown in pure culture from disease hosts
    • Produce the same disease from the pure culture
    • Organism recovered from experimentally infected hosts
molecular postulates
Molecular Postulates
  • Describe virulence factors
  • Four postulates
  • 1. Virulence gene or its product must be present
  • 2. Virulence gene must transform a non-pathogen into a pathogen
  • 3. Virulence gene must be expressed during disease process
  • 4. Antibodies against gene products are protective
establishing an infection
Establishing an Infection
  • 1. Encounter:
    • fecal-oral (cholera)
    • human-human (tuberculosis)
    • animal-human (rabies)
    • vector-borne (plague, lyme disease)
    • environmental contact (anthrax)
establishing an infection1
Establishing an Infection
  • 2. Adherence
    • Prevents early clearance
    • Often bind host tissues via pili
    • Specificity can determine host range of pathogen
establishing an infection2
Establishing an Infection
  • 3. Colonization: multiplication and maintainance
    • Competition with normal flora
    • Resist:
      • bile
      • stomach acid
      • peristalsis
      • skin secretions
      • IgA (mucosal antibodies)
      • compete with host for iron
establishing an infection3
Establishing an Infection

4. Molecule Delivery

  • Affects target cell structure and host response
invasion breaching anatomical barriers
Invasion:Breaching Anatomical Barriers
  • Find new niche with few competitors
  • Gain access to rich nutrient supply

1. Skin: tough barrier, rely on wounds or insect vectors

2. Crossing mucous membrane (e.g. intestinal epithelial cells)

definition of normal flora
Definition of normal flora
  • m/org that normally found in particular area that do not cause harm to host cell and body system
  • Also known as microflora
  • *microorganism in perianal area enter the urinary tract (UT) causing infection in internal UT

Can prevent infection by:

      • Medical asepsis – personnel and hospital environment should be clean from pathogens
      • Surgical asepsis – instrument used should be sterile and including the surgical room
      • What did you implement in daily life?

MIC341 - Miss Rashidah Hj Iberahim

normal flora
Normal Flora
  • More bacterial than human cells in the body
    • provide some nutrients (vitamin K)
    • stimulate immune system, immunity can be cross-reactive against certain pathogens
    • Prevent colonization by potential pathogens

(antibiotic-associated colitis, Clostridium difficile)

normal flora of body system
Normal flora of body system


Gram positive org:

  • Staphylococcus sp,
  • Micrococcus,
  • Coryneform bacteria/Demodexfolliculorum (opening glands – eyebrows)


  • M. smegmatis,
  • Lactobacili,
  • Streptococci,
  • Staphylococcus,
  • E.coli
body system w out normal flora
Body system w/out normal flora
  • Lower respiratory tract
  • Systemic and cardiovascular
  • Nervous system
skin flora
Skin Flora

MIC342 - Miss Rashidah Hj Iberahim

oils production
Oils production
  • Different area consist of different microflora. Example armpits vs forehead.
  • Moisture area will support larger populations; nutrients from oils and sweat
  • Those normal flora might have capability to produce oils that known as fatty acid providing an acidic condition of particular area
  • Initiating host defense against infection in the 1st line stage
  • But, excess of oils production might resulting an odour of unpleasant smell to the body

MIC341 - Miss Rashidah Hj Iberahim

  • Beside oils, the 2nd line of host defends is the sweat that are salty
  • However, in opposite situation, there are bacteria that able to live in salty area such as Staphylococcus sp.
  • Majority of the skin flora – Gram +ve : Staphylococcus, Micrococcus and Corynebacterium
  • Hair follicles inhabitants – mite Demodexfolliculorum

MIC341 - Miss Rashidah Hj Iberahim

skin shedding
Skin shedding
  • 3rd line defends is regarding the keratin-degrading fungi
  • It helps in rapid and continuous shedding of skin cells replacing layer by layer
  • Removing of skin cell together with group of m/org on the skin

MIC341 - Miss Rashidah Hj Iberahim

normal flora1
Normal flora

Gram positive org.

    • Staphylococcus sp
    • Micrococcus
    • Coryneform bacteria
  • Demodexfolliculorum (opening glands – eyebrows)

MIC341 - Miss Rashidah Hj Iberahim

urogenital flora
Urogenital Flora

MIC342 - Miss Rashidah Hj Iberahim

  • Al parts are sterile except urogenital opening
  • Urine collection should have ‘clean catch’ technique
  • E.coli and Lactobacillus are common flora = 100,000 bact/ml of urine
  • Collection during direct puncture (suprapubic) = sterile sample
  • Acid pH, high salt and urea concentration leads to high m/org growth
  • Urine sample should be refrigerated during transportation if delay – high multiplication if stir in RT

MIC341 - Miss Rashidah Hj Iberahim

  • Mycobacterium smegmatis (acid fast staining bacili) live in external genitalia of female and male
  • Esp under penis of uncircumsized male – smegma
  • If included in the sample, might leads to confusion wt the tuberculosis patient which actually having M. tuberculosis
  • In male, 1/3 of deep are for genital area don’t have normal flora

MIC341 - Miss Rashidah Hj Iberahim

in female
In female..

Due to hormonal changes..

  • Child-bearing – lactobacili numerous in vagina (eating glycogen)
  • Glycogen in vaginal cell will be fermented become lactic acid and pH decrease to 4.7
  • Childhood and after menopause, lactobacili absent coz no glycogen –replaced by streptococci and staphylococci due to alkaline pH in vagina

MIC341 - Miss Rashidah Hj Iberahim