Antimicrobial Chemotherapy 3

Question 1

Which species of bacteria are resistant to polymyxins?

Answer 1

Proteus spp.
Providencia spp.
Morganella morganii
Hafnia alvei
Serratia marcescens
Enterobacter cloacae complex (some clusters)

Question 2

Which antibiotics can be used unrestricted?

Answer 2

Amoxicillin (oral/parenteral)
Benzylpenicillin (oral/parenteral)
Cefalexin (oral)
Penicillin V
Phenoxymethylpenicillin (oral)

Question 3

Give examples of an antibiotic which works intracellularly

Answer 3

Cycloserine
Bacitracin

Question 4

Give an example of a glycopeptide antibiotic

Answer 4

Vancomycin

Question 5

Give examples of antibiotics which are beta-lactams (penicillin binding protein inhibitors)

Answer 5

Penicillins
Cephalosporins
Monobactams
Penems
Carbapenems
Beta-lactamase inhibitors

Question 6

Give examples of extended spectrum penicillins which target gram positive and gram negative bacteria

Answer 6

Amoxicillin
Ampicillin
Carbenicillin
Piperacillin

Question 7

Give examples of first generation cephalosporins

Answer 7

Cefalexin
Cefradine

Question 8

Give examples of beta-lactamase inhibitors

Answer 8

Clavulanic acid
Penam (sulbactam)

Question 9

What is the peptidoglycan layer?

Answer 9

Essential wall polymer
- responsible for shape and integrity
- unique in prokaryotes

Question 10

What does interference with the peptidoglycan cause?

Answer 10

Leads to a loss of cell shape and integrity followed by bacterial death

Question 11

What is the structure of the peptidoglycan?

Answer 11

Chains of alternating N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) residues, cross-linked through pentapeptide side chains attached to MurNAc

Question 12

What are the stages in peptidoglycan synthesis in bacterial cells?

Answer 12

Stage 1 - synthesis of precursors in the cytoplasm or at the inner surface of the cytoplasmic membrane
- sugars
- amino acids
Stage 2 - transfer across the cytoplasmic membrane
Stage 3 - polymerisation on the outer surface

Question 13

What is stage 1 of peptidoglycan synthesis?

Answer 13

Assembly of the disaccharide-peptide monomer unit by enzymes located in the cytoplasm, or at the inner surface of the cytoplasmic membrane

Synthesis of the cytoplasmic cell wall precursors

Question 14

What is stage 2 of peptidoglycan synthesis?

Answer 14

Synthesis of wall subunit attached to lipid carriers

Transfer of the monomer unit across the cytoplasmic membrane

Question 15

What is stage 3 of peptidoglycan synthesis?

Answer 15

Polymerisation of the monomer unit on the outer surface of the membrane and concomitant binding of the nascent peptidoglycan to the pre-existing cell wall

Polymerisation of glycan and attachment to wall by transpeptidation

Question 16

What is the function of Penicillin Binding Protein (PGP) 1A, 1B, alpha, beta and gamma?

Answer 16

Transglycosylase and transpeptidase activities
- synthesis of peptidoglycan at the growing side wall

Question 17

Give examples of antibiotics which target PBP 1A, 1B, alpha, beta and gamma?

Answer 17

Benzylpenicillin
Most cephalosporins