BIOL0131_L2 handout_2009

BIOL0131_L2 handout_2009 - 1 Basic Medical Microbiology...

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Unformatted text preview: 1 Basic Medical Microbiology BIOL0131 Lecture 2: The normal human microbial fora E.coli- did you know there is more bacterial DNA in the human body than human DNA ! Lecture titles 1. A review oF signi¡cant advances during the history oF medical microbiology 2. The ‘normal’ human microbial fora 3. Immune responses to inFection 4. Host-parasite interactions 5. Spread and control oF inFection: sterilization and disinFection 6. Spread and control oF inFection: epidemiology oF inFectious diseases 7. Antibacterial and antiviral agents, microbial resistance 8. Case studies in disease I: Bird fu and SARS 9. Case studies in disease II: ¢orensic microbiology and bio- weapons 10. Case studies in disease III: HIV and sexually transmitted disease 11. Case studies in disease IV: Malaria 12. Principles oF laboratory diagnosis oF inFectious diseases Some de¡nitions • The term ‘normal fora’ is used to describe microorganisms that are Frequently Found in various body sites oF a normal healthy individual • The fora may vary with: – Physiological state – Age • These microorganisms have morphological, physiological and genetic Features that allow them to: –colonize and multiply at a particular site in the body –Inhibit competing intruders (e.g. other bacteria) 2 • Each accessible part of the body therefore represents a speciFc Ecological Niche • Each niche demands a different set of qualities from a microbe capable of colonization • Interesting fact: The number of microbial cells in the human body outnumbers the number of human cells by ten to one ! 10 : 1 • The normal microbial ¡ora comprises both: • Symbiotic microorganisms – Those that beneFt the host • Commensal microorganisms – Those that have a neutral relationship with the host (neither harmful nor beneFcial) • BUT in many cases not enough is known about the microorganism to make this distinction • ¢lora may stay in the body for short or extended periods: • Residents – Microbial strains that have an established niche at one of the body sites • Transients – Acquired from the environment and establish themselves brie¡y – But tend to eventually be excluded by the human immune system or microbial competition 3 • If a potentially pathogenic microbe is present in the body (without disease symptoms) this is called the Carrier State • BUT the implication of risk is not always justiFed – ¡or example Neisseria meningitidis , a cause of meningitis, can be isolated from the throat of 5-40% of healthy people So where does the normal...
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This note was uploaded on 10/28/2010 for the course BIO microbiolo taught by Professor Point during the Spring '09 term at HKU.

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BIOL0131_L2 handout_2009 - 1 Basic Medical Microbiology...

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