Bacteria II

Question 1

How does mupirocin work?

Answer 1

Analogue of isoleucyl tRNA and so inhibits isoleucyl tRNA synthetase - the role is to tether amino acids to their tRNA adapters
Selectivity - binds bacterial synthetase
Narrow spectrum

Question 2

What is mupirocin specific for?

Answer 2

Gram positive

Outer membrane on gram negative restricts access

Question 3

What does mupirocin treat?

Answer 3

Topical treatment of staphylococcus and streptococcal skin infections & eliminate nasal carriage of MRSA in hospital patients and staff

Question 4

Why is mupirocin not applied systemically?

Answer 4

Broken down in the body

Normal - rapidly broken down in kidney and liver producing metabolites which are not antibacterial action

Question 5

Why is linezolid activity restricted to gram positives?

Answer 5

Removed by efflux pump in gram negatives

Question 6

What does linezolid bind to?

Answer 6

50S ribosome - interferes with binding or correct positioning of aminoacyl-tRNA in the ribosomal A site

Question 7

What does linezolid treat?

Answer 7

Skin/soft tissue infections and pneumonia

Question 8

What are the adverse side effects of linezolid?

Answer 8

Mild/moderate

Skin reactions, GI disturbances, mild and transient abnormalities of liver function

Question 9

Are tetracyclines broad or narrow spectrum?

Answer 9

Broad

Question 10

What do tetracycline bind to?

Answer 10

30S subunit and prevent association of aminoacyl-tRNA with the ribosome

Question 11

What is the purpose of tigecycline?

Answer 11

Solves resistance problems to earlier tetracyclines

IV only - skin, soft tissue and intra-abdominal infections

Question 12

What are the clinical uses of tetracyclines?

Answer 12

Chlamydia, Lyme disease, cholera, mycoplasma pneumonia

Question 13

What are the adverse side effects of tetracyclines?

Answer 13

Deposition in bones
CNS effects
Photo sensitivity
GI disturbances for oral products

Question 14

Are aminoglycosides bactericidal?

Answer 14

Yes

Question 15

Which aminoglycosides bind to 30S subunit?

Answer 15

Streptomycin and spectinomycin

Question 16

What aminoglycosides bind to 30S and 50S?

Answer 16

Kanamycin and tobramycin

Question 17

What do aminoglycosides do?

Answer 17

Cause mid-reading of mRNA producing abnormal proteins

Insertion of abnormal proteins into the cytoplasmic membranes leads to membrane destabilisation and bacterial cell death

Question 18

What do aminoglycosides treat?

Answer 18

Plague
Enterococcal endocarditis
Sever sepsis
Tuberculosis (combination)

Question 19

What are the adverse side effects?

Answer 19

Nephrotoxicity
Neuromuscular blockade
Ototoxicity

Question 20

What does chloramphenicol bind to?

Answer 20

50S subunit - inhibits peptidyl transferase activity

Oral and IV

Question 21

What are the adverse side effects of chloramphenicol?

Answer 21

Bone marrow suppression and gravy baby syndrome

Question 22

What are the two types of macrolides?

Answer 22

Azalides and ketolides

Question 23

How does azithromycin work?

Answer 23

Binds to the 23S rRNA at the peptidyl transferase centre of the 50S ribosomal subunit - causes premature dissociation of the peptidyl tRNA from the P site

Question 24

What are the two molecules acting synergistically in streptogramins?

Answer 24

Quinupristin (30%) and dalfopristin (70%) - enhances binding
Binds to 50S subunit - inhibit peptide bond formation

Question 25

What does streptogramins treat?

Answer 25

Vancomycin resistance, skin and soft tissue infections caused by S.Aureus

Question 26

What are the two lincosamids developed for clinical use?

Answer 26

Clindamycin and lincomycin

Question 27

How do lincosamides work?

Answer 27

Inhibits peptidyl transferase but don’t share a binding site with chloramphenicol

Question 28

What are lincosamids active against?

Answer 28

Gram positive aerobes but not gram negative aerobes

Question 29

What are most antibacterial agents that affect protein synthesis?

Answer 29

Bacteriostatic