Lecture Set 7 : Part 2 Flashcards
what is intrinsic resistance?
-some bacteria are naturally resistant to one or more antibiotics
-ex: mycoplasmas are naturally resistant to cell wall synthesis inhibitors because they dont have cell walls
-ex: gram negatives are often resistant to large hydrophilic antibiotics because of their outer membrane
what is acquired resistance?
-the ability of a microorganism to resist the effects of an agent to which it is normally sensitive to
-genetically coded characteristic (resistance genes)
-can be carried on a chromosome or plasmid
-frequently moved from one bacteria to another by horizontal gene transfer
what are 5 mechanisms of antibiotic resistance?
-inactivation of the drug
-metabolic bypass
-efflux pumps
-modification of the drug target
-decreased uptake
what is the inactivation of the drug mechanism?
-resistance genes encode an enzyme that inactivates the antibiotic
-ex: b-lactamase
what is an example of the metabolic bypass mechanism?
-some sulfonamide resistant bacteria have acquired the folate uptake system (uptake folate from the environment)
-reduces their dependence on folate synthesis (metabolic process)
what is the modification of the drug target mechanism?
-several antibiotics work by binding to the ribosome
-resistant bacteria have modified ribosomal proteins so that the antibiotic does not bind
what is the decreased uptake mechanism?
-some gram negative bacteria have modified their porin proteins by making them smaller to allow less through
-ex: mutation in the porin gene results in a smaller channel and resistance to several penicillins and cephalosporins
what are efflux pumps?
-present in gram negative bacteria
-transport metabolic wastes, toxins, and antibiotics out of the cell
-some use ATP but most are powered by the PMF
-ex: E.coli’s multidrug efflux pump can pump out aminoglycosides and tetracyclines
-with additional mutations it can pump out others as well
how do antibiotic resistant strains develop?
-widespread use of antibiotics selects for resistance
-antibiotic sensitive bacteria are kileld
-antibiotic resistant mutants are able to thrive
what are antibiotics used for?
-extensively in medicine
-greater than 50% produced are used for agriculture
what are the gram positive antibiotic resistant pathogens?
-methicillin resistant staphylococcus aureus (MRSA) (treated frequently with vancomycin)
-vancomycin resistant enterococci (VRE) (resistant to all known antibiotics)
-multidrug resistant mycobacterium tuberculosis
what are the gram negative antibiotic resistant pathogens?
neisseria gonorrhoeae (increasinly difficult to treat, STI cause)
-pseudomonas aeruginosa (opportunistic because of nosocomial infections, including septic shock) (impossible to treat, resistant to all know)
what are ways we can prevent antibiotic resistance?
-infection prevention
-rapid and conclusive diagnosis
-appropriate/prudent use of antibiotics
-prevention of transmission
