AB Resistance Genes

Question 1

What are 3 types of mechanisms bacteria use to be resistant to antibiotics?

Answer 1

1. Exclusion from within the bacteria (efflux pumps)
2. Inactivation of the antibiotic (enzymes)
3. Alteration of antibiotic binding site

Question 2

Give 3 examples of genes and their corresponding antibiotic that lead to exclusion of the antibiotic from within the bacteria?

Answer 2

Efflux pumps

1. Tet K and tet L - tetracyclines
2. Msr(A)- MLSB
3. NorA- quinolones

Question 3

Give 3 examples of genes and their corresponding antibiotic that lead to inactivation of the antibiotic?

Answer 3

1. blaZ - encodes for B-lactamase in B-lactam antibiotics
2. aac(6)/aph(2) - encodes for enzymes that deactivate aminoglycosides
3. CAT - enzymes that attach acetyl to chloramphenicol which then prevents binding

Question 4

Give 3 examples of genes and their corresponding antibiotic that lead to a change/ alteration in antibiotic binding site?

Answer 4

1. MecA - PBP2a in BLactam (penicillin/cephalosporins)
2. Tet O / tet M - tetracycline- chromosomal mutation - protects 30s ribosome
3. Erm - MLsB - blocks binding to 50s 23s subunit
4. GyrA/ GyrB: GrlA/GrlB both fluroquinolone chromosomal- leads to decreased affinity to binding to DNA gyrase (Gyr) and Topoisomerase IV (Grl)
5. rpoB - rifampin - encodes for B-subunit of RNA polymerase

Question 5

Gene for vancomycin resistance?

Answer 5

VanA

Question 6

Gene for rifampin resistance?

Answer 6

rpoB

Question 7

Gene for gentamicin resistance?

Answer 7

aac(A)/aph(D)

Question 8

Gene for macrolide resistance?

Answer 8

Mph(c) -inactivates antibiotic

Msr(A) - efflux pumps for MLSB

Erm- blocks 50s binding site for MLSB

MLSB= Macrolide, lincosamide, streptogramin B

Question 9

Gene for aminoglycoside resistance?

Answer 9

str

aac(6)/aph(2) - enzymes inactivation

Question 10

Gene for trimethoprim resistance?

Answer 10

dfrA+dfrD