antimicrobials and resistance Flashcards
What is the difference between endotoxins and exotoxins?
Endotoxins - Inflammatory response to bacterial products
Exotoxins - Response to bacterial secretions
what is a bacterial endotoxin
-released when organism dies
-triggers immune system
-heat stable, intrinsically poorly antigenic
-overactivates complement cascade to generate effects
what are the effects of bacterial endotoxin activating the complement cascade
-high fever
-severe fluid from blood system–> vascular collapse
-IV coagulation then organ haemorrhaging
-septicaemia/endotoxic shock–> death
what are the factors facilitating entry/invasion/survival of bacterial exotoxins
-mucinase, collagenase, urease, leukocidins etc
what are antimicrobial agents
-inhibit/kill microorganisms
-99% unsuitable for treatment of infectious diseases- e.g. disinfectants, antiseptics
-<1% suitable for treatment= chemotherapeutic agents
what is the mark of a successful CTA
-its selective toxicity i.e. toxicity to prokaryotes»>toxicity to eukaryotes
what is a therapeutic dose
-level of CTA needed for clinical treatment of an infection in a specific host
what is a toxic dose
level of same CTA which is too toxic for use in that host
therapeutic index=
toxic dose/therapeutic dose
High- selectively toxic, useful
Low - toxic to host, side effects
what do bacteriostatic CTAs do
-inhibit bacterial growth/multiplication but then reply on the hosts immune system to remove the bugs
-it is therefore essential to give full course of such agents to allow sufficient time for immune system to complete its job whilst preventing regrowth of the bacterial population
what are bactericidal CTAs
rapidly lethal to the bacteria in their own right
depending on bug and conditions, some agents may be…
bactericidal and bacteriostatic e.g. chloramphenicol kills H.influenzae but only inhibits E.coli
what are the mechanisms of action of antibiotics
- Inhibition of cell wall synthesis
- inhibition of protein synthesis
- Inhibition of nucleic acid
- impair membrane functions
- metabolic antagonism
what are the antibiotics that inhibit cell wall synthesis
cycloserine
glycopeptides- bacitracin
beta-lactams e.g. penicillins and cephalosporins
what are the antibiotics involved in inhibition of protein synthesis
aminoglycosides
tetracyclines
chloramphenicol
