Antibiotics

Question 1

Name the Aminoglycosides.

Answer 1

Gentamicin, Streptomycin

Question 2

How do the aminoglycosides work?

Answer 2

Bind IRREVERSIBLY to the 16S rRNA in the 30S subunit of the ribsome leading to misreading of the codons along the mRNA. Also interferes with the translocation of tRNA from the A-site to the P-site.

Question 3

What are aminoglycosides used for?

Answer 3

Septicaemia, Nosocomial RTI, complicated UTIs

Question 4

What are the side effects of aminoglycosides?

Answer 4

Nephrotoxicity, Ototoxicity

Question 5

What is the mode of resistance against aminoglycosides?

Answer 5

Enzymatic inactivation (Acetylation, phosphorylation, Adenylation)

Question 6

How do the tetracyclines work?

Answer 6

Bind REVERSIBLY to the A-site on the 16S rRNA site of the 30S subunit of the ribosome. This inhibits the binding of tRNA to the A-site, which in turn inhibits protein synthesis.

Question 7

What are tetracyclines used to treat?

Answer 7

Acne, RTI, Chlamydia, SSTIs, Mycoplasma, Periodontal disease.

Question 8

What are the side effects associated with tetracyclines?

Answer 8

GIT and GIT superinfections, Deposition in bones and teeth (yellow band), Photosensitivity.

Question 9

What are the names of the macrolides?

Answer 9

Erythromycin, Clarithromycin

Question 10

How do the macrolides work?

Answer 10

Bind to the P-site on the 23S rRNA in the 50S subunit of the ribosome. Prevents translocation of the tRNA from the A-site to the P-site. Inhibits peptide bond formation.

Question 11

What is the main mode of resistance against tetracyclines?

Answer 11

Efflux pumps

Question 12

How do lincosamides work?

Answer 12

Similar to the of the macrolides - Bind to the P-site on the 23S rRNA in the 50S subunit of the ribosome. Prevents translocation of the tRNA from the A-site to the P-site. Inhibits peptide bond formation.

Question 13

What do the lincosamides treat?

Answer 13

Staphylococcal Bone & Joint Infections, RTIs, peritonitis, Septicaemia

Question 14

Side effect of Lincosamides?

Answer 14

C. Difficule Infection

Question 15

How does Linezolid work?

Answer 15

Similar to macrolides - Bind to the P-site on the 23S rRNA in the 50S subunit of the ribosome. Prevents translocation of the tRNA from the A-site to the P-site. Inhibits peptide bond formation.

Question 16

What is Linezolid used for?

Answer 16

Last resort antibiotic. Can be used against MRSA

Question 17

How does Fusidic Acid work?

Answer 17

Prevents the turnover of elongation factor (EFG) of the ribosome. Prevents energy needed for translocation

Question 18

What is fusidic acid used for?

Answer 18

Narrow spectrum staphyococcal infections - used topically for skin and eye infections.

Question 19

How does chloramphenicol work?

Answer 19

Inhibits peptidyl transferase in the 23S rRNA region in the 50S subunit, inhibiting peptide bond formation.

Question 20

How do the B-lactams work?

Answer 20

They bind to Penicillin Binding Proteins (PBPs). This prevents cross linking. They get incorporated into the side chain.
They also stimulate autolysins which break down the cell wall.

Question 21

What are B-Lactam side effects?

Answer 21

Hypersensitivity, Neurotoxicity, Renal Failure, Diarrhoea, Psuedomembranous colitis, C. Difficule infections.

Question 22

What is Benzylpenicillin (Pen-G) used for?

Answer 22

Throat infections (nosocomial), endocarditis, and meningitis.

Question 23

What is amoxicillin used for?

Answer 23

RTIs, Oral Infections, Otitis Media, Sinusitis

Question 24

Why are cephalosporins limited in their use?

Answer 24

Risk of C. Difficule infections

Question 25

What are second generation Cephs used for?

Answer 25

Severe infections, and prophylaxis of infections after surgery

Question 26

What are 3rd Gen Cephs used for?

Answer 26

Meningitis, Infantile sepsis, gonorrhoea, nosocomial infections

Question 27

What are carbapenems used for? (imipenem, meropenem)

Answer 27

Septicaemia, HAP, Complicated UTIs and SSTIs.

Question 28

What are the names of the glycopeptides?

Answer 28

Vancomycin, Teicoplanin

Question 29

How do the glycopeptides work?

Answer 29

Binds to D-Ala--D-Ala and prevents cross linking

Question 30

What are the glycopeptides used for?

Answer 30

Systemic Infections caused by B-lactam resistant organisms. Vancomycin can be used to treat C.Difficule when taken orally (because it does't get absorbed)

Question 31

What are the side effects of glycopeptides?

Answer 31

Renal toxicity, Ototoxicity, Blood disorders, Anaphylactoid reactions

Question 32

How does Cycloserine work?

Answer 32

Inhibits enzymes involved in the peptidoglycan synthesis - alanine racemase & D-Ala-D-Ala ligaase

Question 33

What are the side effects of cycloserine?

Answer 33

CNS effects, liver damage, rashes

Question 34

How do polymixins work?

Answer 34

They disrupt the membrane by binding to the Lipid A component of LPS causing disruption of the membrane so cytoplasmic contents leak out.

Question 35

What are polymixins used for?

Answer 35

Gram Negative bacterial infections (Gram positive bacteria do not have LPS)

Question 36

How does daptomycin work?

Answer 36

Aggregates at the membrane of the cell and causes a pore to form, leading to the leakage of cytosolic contents.

Question 37

How do sulfonamides work?

Answer 37

Inhibit dihydropterate synthase.

Question 38

How does trimethoprim work?

Answer 38

Inihibits dihydrofolate reductase

Question 39

What is trimethoprim used to treat?

Answer 39

Acne and UTIs

Question 40

What is the mechanism of action for Fluoroquinolones?

Answer 40

Inhibit DNA gyrase and Topoisomerase IV

Question 41

What are the fluoroquinolones used for?

Answer 41

Chlamydia, Mycobaceteria, RTI, UTI, GIT, Systemic G-ve infections

Question 42

What are the side effects of the flurooquinolones?

Answer 42

GIT, | Interacts with CYP450, therefore interactions with loads of drugs.

Question 43

What is Rifampicin's mechanism of action?

Answer 43

Inhibits DNA polymerase.

Question 44

What is Rifampicin used to treat?

Answer 44

Tuberculosis (1st line in RIPE), Staphylococcal bone and joint infections.

Question 45

What are the side effects of Rifampicin?

Answer 45

Hepatotoxicity, Fever, Rash, Hypersensitivity, Orange-Red colour secretions.

Question 46

How do nitroimidazoles work?

Answer 46

Causes disruption of the DNA

Question 47

What are Nitroimidazoles used for?

Answer 47

C. Difficule infections, Some Genital tract infections, SSTIs where anaerobes are suspected, Abdominal and dental infections.

Question 48

What are the side effects of metronidazole?

Answer 48

GIT, Candida superinfections, CNS: peripheral neuropathy, dizziness, confusion. Hypersensitivity, Genito-urinary.

Question 49

What are the 6 opportunistic bacteria?

Answer 49

``` Enterococcus faecium Staphylococcus aureus Klebsiella pneumonia Acinetobacter buamanii Pseudomonas aeruginosa Enterobacter ```

Question 50

Highlight the mechanisms of resistance against B-lactam drugs

Answer 50

B-lactamases: Limited spectrum - TEM-1 &2, Extended spectrum: CTX-M, NDM-1 (mainly found in E Coli) Altered Target site: MRSA - PBP2 --> PBP2a Altered Uptake: decrease in number and size of pores - only found in G-ve bacteria

Question 51

What is the mode of resistance to Vancomycin?

Answer 51

Altered target site: D-Ala -- D-Ala mutates to D-Ala -- D-Lactate. Means the Vancomycin cannot bind as tighly (x1000 less affinity) due to one less hydrogen bond

Question 52

What is the mode of resistance for Nucleic Acid Synthesis inhibitors?

Answer 52

Altered target site: Enzymes are modified to have less affinity for the drug.