infection and immunity

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infection and immunity
2010-12-13 09:22:03
infection immunity

semester 3
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  1. what are the advantages of normal flora?
    protect by preventing colonisation from other (potentially) pathogenic bacteria
  2. how does our normal flora (commensals) protect against other organisms?
    • - compete for colonisation sites
    • - produces bacteriocins
    • - (anaerobic) - produce toxic metabolites
    • - (in female genital tract) - lactobacilli produce lactic acid lowering the pH
  3. what is the innate immune system?
    • bodies defense against infection
    • consists of physical and chemical barriers, normal flora, antibacterial proteins, phagocytic cells
  4. list some of trhe physical and chemical barriers of the innate immune system
    • - skin + sebum + secreted FAs
    • - gastric acid
    • - mucus containing similar polysaccharides to underlying epithelium
    • - mucociliary clearance
    • - urinary flushing
    • - lysozyme in tears
    • - lactoferin in breast milk
  5. define pathogen
    organism capable of causing infection
  6. define pathogenicity
    capacity to cause disease
  7. define virulence
    capacity to cause serious disease
  8. what is a parasite?
    often used to describe protozoan and metazoan can be either pathogen or commensals
  9. HIV and treponema pallidium are ...
    obligate pathogens
  10. what are conditional pathogens
    give an example
    • these are commensal organisms that can lead to disease if conditions are met
    • eg. stap aureus is a commensla in the anterior nares but can cause an abscess in a wound
  11. who do opertunistic pathogens effect?
    give an example
    • the immunocompromised
    • eg. pneumocystis jiroveci in patients with HIV/AIDS
  12. how do organisms cause disease?
    (6 stages)
    • 1. access vunerable host - transmission
    • 2. attach to host
    • 3. invasion
    • 4. motility
    • 5. immune evasion
    • 6. damage the host - endo/exotoxins
  13. what is resistance?
    when a previously suseptible organism is no longer inhited by an antibiotic that is given at a safe clinical level
  14. how does resistance occur?
    • bacteria gene pool changes rapidly - facillitated by rapid division and haploid genome
    • organisms can also tranfer genetic material within and between species
    • antiobiotic use allows the survival and replication of resistant organisms
  15. how do bacteria transfer resistance between themselves?
    • transformation - bacteria pick up naked DNA and incorparate it into their own genome
    • conjugation - moving plasmids between bacteria
    • transposons - jumping genes
  16. list 6 mechanisms of resitance and give an example of each
    • 1. enzyme inactivation - staph aureus produces a betalactamase that breaks down the penicillin ring
    • 2. enzyme addition - bacteria adda chemical group to the antibiotic this is how staph aureus and pseudomonas became aminoglycoside resistant
    • 3. impermeability - some bacterial are naturally resistant to some antibiotics eg. aminoglycosides taken up by an O2 dependant pathway and are therefore ineffective against anaerobes
    • 4. efflux mechanism - acquasition of membrane protein that pumps antibiotic back out of the call eg. E. coli and tetracyclines
    • 5. alternative pathway - avoid metabolic block cause by antibiotic eg. staph aureus and mecA gene = MRSA
    • 6. alteration of target site- eg. change in RNA polymerase gene = rifampicin resitant
  17. what are the two catergeries of sources of infection
    • endogenous - organisms of normal flora invade
    • endogenous - animal/environmental pathogens