CP 2 - Mechanisms of Antibiotic Resistance

Question 1

what are some of the resistance mechanism for antibiotic resistance

Answer 1

No target – no effect

Altered target – no effect

Over-expression of target – effect diluted

Reduced permeability – drug can’t get in

Enzymatic degradation – drug destroyed

Efflux pump – drug expelled

Question 2

what is the possible explanation for absent target

Answer 2

using anti-bacterial agents on fungi etc

Question 3

what are some examples target alteration?

Answer 3

• flucloxacilin - MRSA (altered penicillin-binding protein ie no binding of beta-lactam
• vacnomycin - VRE (altered peptide sequence in gram +ve peptideoglycan DADA - DADL)
• Trimethoprim - Gram -ve bacilli (mutation in dihydrofolate reductase gene)

Question 4

what are some of the example for reduced permeability?

Answer 4

• vancomycin - gram -ve bacilli (gram -ve have an outer memebrane that is impermeable to vancomycin)
• gentamicin - anaerobic organisms (uptake of aminoglycosides requires O2 dependent active transport mechanism)

Question 5

what are some of the example for enzymatic degradation as a way to resistance antibiotic

Answer 5

penicillin & cephalosporins - beta-lactamases

gnetamicin - aminoglycoside modifying enzmyes

Question 6

what are some of the example for drug efflux as a way to resistance antibiotic

Answer 6

specially in gram -ve organism

antifungal triazole & candida spp

Question 7

what is an example for development of resistance

Answer 7

developing resistance genes through horizontal and vertical transfer

Question 8

what are some of the single genes antibiotic resistance genes

Answer 8

• antibiotic modifying enzymes - beta-lactamases, aminoglycoside-modifying enzymes
• altered antibiotic targets - PBP in MRSA, peptide sequence in VRE peptidoglycan
• resistance genes encoded in plasmids (between species via conjugation) and then transfer through horizontal and vertical transfer of resistance

Question 9

what in conjugation

Answer 9

it is the transfer of DNA sequences transmitted within species and between species