Microbiology 3 -The Prokaryotes Strike Back (Antibiotic resistance)

Question 1

State the mechanism of action of b-lactams

Answer 1

Inactivates PBP’s (crossliking step of peptidoglycan synthesis)

Question 2

State the mechanism of action of Glycopeptides

Answer 2

Binds to precursor of peptidoglycan

Question 3

State the mechanism of action of Aminoglycosides

Answer 3

Inhibits protein synthesis (binds to 30s subunit)

Question 4

State the mechanism of action of Microlides

Answer 4

Inhibits protein synthesis (binds to 50s subunit)

Question 5

State the mechanism of action of Quinolones

Answer 5

Inhibits Topiosomerases (DNA synthesis)

Question 6

State 2 things that determine Acquired resistance

Answer 6

1) Acquisition of plasmids or transposons

2) Mutation in chromosomal genes

Question 7

What is Intrinsic resistance determined by ?

Answer 7

• Genetic material in chromosome

Question 8

What is Horizontal gene transfer ?

Answer 8

The process of swapping genetic material between neighbouring bacteria -a means by which antibiotic resistance can be acquired.

Question 9

Horizontal gene transfer may occur via three main mechanisms. Name them

Answer 9

1) Transformation
2) Transduction
3) Conjugation

Question 10

What are Transposons ?

Answer 10

Discrete genetic elements capable of moving (transposing) within the bacterial genome

Question 11

Transposons are found in all organisms. TRUE or FALSE

Answer 11

TRUE

Question 12

Transposons are capable of independent replication. TRUE or FALSE

Answer 12

FALSE. Transposons aren’t capable of independent replication

Question 13

Transposition provides multiple copies. TRUE or FALSE

Answer 13

TRUE

Question 14

Describe composite transposons

Answer 14

Consists of 2 copies of insertion sequence (IS) flanked by inverted repeats

Question 15

Composite transposons display Replicative transposition. TRUE or FALSE

Answer 15

FALSE. They display conservative transposition; DNA replication doesn’t occur

Question 16

Name 2 types of Transposons

Answer 16

1) Simple transposons

2) Composite transposons

Question 17

What type of transposition does Simple transposons express ?

Answer 17

Replicative transposition

Question 18

What is the role of Resolvase

Answer 18

Responsible for resolution of the transfer

Question 19

What is the role of Transposase

Answer 19

Responsible for excision and transfer of transposon

Question 20

State 4 types of b-Lactam antibiotics

Answer 20

1) Penicillins
2) Cephalosporins
3) Carbapenems
4) Monobactams

Question 21

What are PBP’s ?

Answer 21

Penicillin binding proteins

Question 22

PBP’s catalyse final steps of peptidoglycan synthesis. TRUE or FALSE

Answer 22

TRUE

Question 23

State 3 things the activity of b-lactams is determined by

Answer 23

1) Affinity for PBP’s
2) Stability of b-lactamases
3) Membrane permeabilty

Question 24

Most MRSA are multi-drug resistant but susceptible to Vancomycin. TRUE or FALSE

Answer 24

TRUE

Question 25

MRSA contains novel PBP1a. TRUE or FALSE

Answer 25

FALSE. MRSA contains novel PBP2a

Question 26

MRSA chromosome contain around 50kb mec region. TRUE or FALSE

Answer 26

TRUE

Question 27

What is PBP2a encoded and controlled by

Answer 27

Encoded by mecA gene and controlled by mecl, mecR1 and other factors

Question 28

What family of antibiotics does Vancomycin belong to

Answer 28

Glycopeptide

Question 29

Name 2 processes inhibited by Vancomycin

Answer 29

1) Transglycosylation

2) Transpeptidation

Question 30

Vancomycin is only active against Gram negative bacteria. TRUE or FALSE

Answer 30

FALSE, it cannot cross outer-membrane of gram negative bacteria so only active against gram positive bacteria

Question 31

What is Vancomycin primarily used for

Answer 31

Primarily for multi drug resistant (MDR) Staphylococci infections,
patients with penicillin allergy or C. difficile infections

Question 32

Name the antibiotic used as a last resort

Answer 32

Cabapenem