Resistance

Question 1

Conjugation

Answer 1

1) donor cell attached to a recipient cell with its pilus, pili allows contact between host and recipient
2) one strand of plasmid DNA transfers to recipient
3) recipeint synthesises a complimentary strand to become a F+ cell
4) donor synthesis a complimentry strand restoring its complete plasmid

Question 2

Transposition

Answer 2

Transposon is a self replicating unit that can move from one location to another on a bacterial chromosome.
Can insert mutation by physically disurpting the sequence encoding for a specific gene
Can create polar mutations by insertion into an operon
Block gene expression downstrsm from site of insertion

Question 3

Transformation

Answer 3

Bacteria can take up free DNA from its environment and express it
Competent bacteria can take up any type from even different species (not different gram)
Competence can be artificial by taking up recombinant DNA via heat shock and electroporation

Question 4

Transduction

Answer 4

Bacteriophage mediated gene transfer
During viral replication, small pieces of host chromosome can be incorporated into phage capsids
Phage is released infecting the new host and injecting genetic material
Phage DNA(including host cell DNA) can be integrated into the recipient chromosome

Question 5

transposable elements

Answer 5

Specific dna segments that can be repeatedly inserted into one or more sites in one or more genomes

Question 6

Decreased cell wall/membrane permeability - antibiotic resistance mechanism

Answer 6

Decreases amount of antibiotic entering cell
Porins are beta barrel proteins that allows antibiotics to get through
Bacteria can alter its composition
Beta lactams: production of new PBP which it cannot bind to (mediated by MecA)
Quinolones: decrease porin and altered LPS

Question 7

Enzymatic inactivation - antibiotic resistance mechanism

Answer 7

beta-lactamases hydrolyse beta lactam ring
Possible cross resistance between beta-lactams
Macrolides: hydrolysis of lactone ring by plasmid encoded esterase (ereA,ereB

Question 8

modification of target site - antibiotic resistance mechanism

Answer 8

Beta lactams: production of new PBP
Aminoglycosides: biosynthesis of peptidoglycan with altered aminoglycosides binding regions
Tetracycline dislodged from ribosomes by ribosomal protection factors
Translocation factors with altered affinity for fusidic acid
Single amino acid substitution on DHPS - sulphonamides/trimethoprim
Point mutation on gyrA causing conformational changes and decreased binding to quinolones

Question 9

increased efflux - antibiotic resistance mechanism

Answer 9

Increased Efflux = more drugs can be removed
Tetracyclines: overexpression of norA in S.aureus
Macrolide: overexpression of MefA in strep, mrsA in s.aerus
Quino: overexpression of qepA and ogxAB

Question 10

Multiplication of target site - antibiotic resistance mechanism

Answer 10

Increased PABA - sulphonamides
Overproduction of dihydrofolate reductase - trimethoprim