Lecture 20 - Antimicrobial Drug Resistance Flashcards
When was the first case of penicillin resistant S aureus?
1947
When was the first case of MRSA in the UK?
1960
What are the two types of resistance?
intrinsic and acquired
What is intrinsic resistance?
if we give a antibiotic used for gram positives to treat gram negatives
e.g. gram negatives are intrinsically resistant to vancomycin
How is acquired resistance acquired?
either by vertical or horizontal transfer
What is vertical transfer?
if a mother cell is in the presence of a drug, it is possible that some spontaneous mutations occur leading to this sensitive cell producing some drug resistance
What can drug resistant bacteria do?
survive and multiply and form many colonies of bacterial cells carrying DNA that will code for drug resistance
What are the steps of vertical transfer?
non resistant bacteria exist
bacteria multiply by the millions
some mutations make the bacterium drug resistant, in the present of drugs only the resistant bacteria survive
drug resistant bacteria multiply and thrive
What are the types of horizontal transfer?
transformation
conjugation
transduction
What is transformation?
if a drug resistant cell is killed by another antibiotic, the bit of the plasmic with genes conferring drug resistance can be transferred to another cell
bacterial cell transferring info to another bacterial cell
What is conjugation?
when bacteria are in close proximity and can transfer genes coding for drug resistance from a resistant bacterial cell by producing a bridge/link between the two cells
What is transduction?
happens when a bacterium becomes infected with a virus
viruses replicate inside the bacterial cell and if they do this within a drug resistant bacteria then once they leave they take some DNA coding for drug resistance
they continue to reinfect sensitive bacterial cells and bring these bits of info coding for resistant into these cells
What are bacterialphages?
viruses that infect bacteria
Examples of antimicrobial resistance?
reducing drug accumulation
inactivating/altering drugs
altering target sites
Reducing drug accumulation?
production of efflux pumps which remove any antibiotics that enter the cell
changes the structure of the porins
What does changing the structure of the porins do?
they no longer act as a way for small hydrophilic drug molecules to get into the gram negative - stops the drug working
Inactivating/altering drugs?
beta lactamases
degrade beta lactam antibiotics
What can the resistance genes of beta lactamases code for?
new penicillin binding proteins that work in the presence of beta lactams
Altering target sites?
changes in ribosomes (macrolides)
changes in PBPs (MRSA)
What is there correlation between with AMR?
antimicrobial resistance/overuse and high levels of AMR
What do resistant microbes do?
increase the severity and duration of an illness (high costs)
Why is rapid emergence of AMR a problem?
ease of transfer between species
bacteria multiply very rapidly and are able to transfer the genes coding for drug resistance very easily
What is a reason AMR is such a problem?
dramatic decline in antibiotic research and discovery
What are the ESKAPE pathogens?
Enterococcus faecium
S. aureus
Klebsiella (-ve)
Acinetobacter (-ve)
Ps. aeruginosa (-ve)
Enterobacter
