Antibiotic resistance Flashcards
Define Antibiotic Resistance
The ability of an organism to survive treatment with an antibiotic (evade antibiotics)
How does Penicillin work?
Penicillin binds to the PBP (preventing the PBP from cross linking the amino acid strands in the cell wall)
When PBP is unable to cross link the amino acids in the cell wall …the cell wall is weakened and eventually leads to rupture of the bacteria (due to osmotic pressure)
what is the function of PBP?
PBP (penicillin binding protein) cross link the amino acid strands (in the cell wall of bacteria) to strengthen the cell wall.
What is the mechanism PRSP (?) uses for resistance and how did it probably acquire resistance?
Penicillin resistant S. pneumonia
Alterations in one or more penicillin binding proteins
Originated through the acquisition of foreign DNA leading to altered PBP’s that spread as a result of selective pressure and clonal dissemination
Probably from viridian strep
Define antibiotic selective pressure
Refers to impact of antimicrobial use on a population of organisms, in which organisms that are resistant to the antibiotic gain a survival advantage over those susceptible to an antibiotic
In DEVELOPING countries what is thought to have led to an increase in non-typhoidal floroquinolone resistant salmonella?
Unregulated antimicrobial dispensing for human use
In DEVELOPED countries what is thought to have led to the increase in non-typhoidal fluoroquinolone resistant Salmonella?
Extensive use of antimicrobials in food, animals to improve growth rate
Define MRSA
HA-MRSA
CA-MRSA
MRSA-methicillin resistant S.
HA-MRSA- hospital/healthcare acquired MRSA
CA-MRSA- Community acquired MRSA
Explain the differences between HA-MRSA and CA-MRSA
HA-MRSA. - more frequently carries and SCC mec element from groups I-III
Limited number of clones
Only five clones associated with HA-MRSA
These tend to be resistant to other antibiotics in addition to methicillin
tend to be associated with wound infection, surgical incision, opportunistic infection
CA-MRSA- more skin manifestation, distinguished by mobile chromosomal cassette SCC which carries the methicillin resistant gene mec contains a novel SCC mec type known as SCC mec type IV
SCC mec IV- Smaller in size and more mobile
Usually sensitive to antibiotics
Define clonal dissemination
Spread of specific clones of an organism throughout the community.
These clones are thought to be more transmissible than other clones
Why might a reduction in the use of antibiotics not lead to a reduction in infections that are caused by resistant organisms
If the expression of the resistant gene already exist -and there is no fitness cost component-then if you remove selection pressure (drug) –there is no incentive for the organism to remove the resistant gene
define protection of the target
when bacteria produce a different molecule (usually a protein) that protects the target
example: bacteria will produce a protein that alters the binding sites on its ribosome —this renders tetracycline ineffective because tetracyclines target is the ribosome.
explain altered target
some bacteria can express proteins with decreased affinity for an antibiotic
example : altered PBP –decreases the ability for penicillin to bind—rendering penicillin ineffective
explain efflux
proteins that pump drugs out of the cell
Expressed protiens that pump drugs out of the cell
this doesn’t allow drug to build up in the cell and renders drug ineffective
describe decreased cell permeability
porins particularly in gram neg cells
decreased porin expression- which decrease the amount of antibiotic that can ENTER the cell
