infection and immunity

  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
Card Set
infection and immunity
semester 3