Antibiotics

Question 1

What is selective toxicity?

Answer 1

Ability of the drug to target the invader and not the host

Question 2

Define Bactericidal

Answer 2

Drug which kills the bacteria

Question 3

Define Antibacterial

Answer 3

Drug which kills or inhibits the growth of bacteria

Question 4

Define minimum [bactericidal]

Answer 4

Lowest [drug] to kill bacteria

Question 5

Define minimum [inihbitory]

Answer 5

lowest [drug] to inhibit growth of bacteria

Question 6

Define bacteriostatic

Answer 6

drug which prevents growth of bacteria

Question 7

Define Empirical treatment

Answer 7

antibiotic therapy used before a specific bacteria has been identified

Question 8

How are antibacterials selected?

Answer 8

What is the pathogen?
Bacteriostatic or bactericidal?
Pharmacokinetics?
Dose?
Route of admin?
Contraindications?
Allergies?
Side effects?
Need for monitoring?

Question 9

What are the mechanisms of action of antibacterials?

Answer 9

Selective toxicity

Question 10

How do cell wall targetting antibiotics work?

Answer 10

Inhibit the 2 enzymes which catalyse the formation of the cell wall (transglycosylase and transpeptidase). Transglycosylase likes the glycan portion of the cell wall together and transpeptidase the peptide portion

Question 11

Which group of drugs target the cell wall synthesis?

Answer 11

Beta-Lactams - inhibit transpeptidase function competitively by mimicing AA structure
Vancomycin - inhibits transpeptidase by covering the peptide chain

Question 12

What are the 4 beta-lactam classes?

Answer 12

Penicillins, Carbapenems, Cephalosporins, Monobactams

Question 13

How do polymyxins work?

Answer 13

They disrupt the cell membrane and cause lysis. Not very selective

Question 14

How do protein synthesis inhibitors work?

Answer 14

Chloraphenicol - binds to 50S portion and inhibits formation of peptide bond
Erythromycin - Binds to 50S portion and prevents translocation along mRNA
Tetracyclines - interfere with attchment of tRNA to mRNA
Streptomycin - Changes shape of 30S portion causing mRNA misreads

Question 15

How do folate inhibitors work?

Answer 15

Sulfonamides target the enzyme which catalyses PABA to Folate

Question 16

How do antibacterials affect DNA/RNA formation?

Answer 16

Quinolones - inihibit topoisomerases which prevents supercoiling
Nitroimidazoles - Causes DNA fragmentation
Nitrofurantoin - Causes DNA and RNA fragmentation
Rifampicin - inhibits DNA-dependant RNA polymerase (prevents mRNA synthesis)

Question 17

What are the mechanisms of antibiotic resistance?

Answer 17

Efflux pump - removes the drug from the bacterial cell
Alteration of enzyme pathways
Alteration of drug binding site
Production of enzyme which inactivates the drug

Question 18

Class, mechanism of action, selective toxicity, functions and limitations of Benzyl penicillin

Answer 18

Beta-lactam - penicillin
Competitive inhibition of transpeptidase
Targets cell wall of bacteria
Throat infections, Pneumonia, Cellulitis
Side effects - Diarrhoea, nausea, vomiting

Question 19

Class, mechanism of action, selective toxicity, functions and limitations of flucloxacillin

Answer 19

Beta-lactam - penicillin
Competitive inihibition of transpeptidase
Targets cell wall of bacteria
Pneumonia, chest infections
Nausea, vomiting, indigestion

Question 20

Class, mechanism of action, selective toxicity, functions and limitations of amoxicillin

Answer 20

Beta-lactam - penicillin
Competitive inihibition of transpeptidase
Targets cell wall of bacteria
Chest infections, dental abscesses, UTIs
Diarrhoea, nausea

Question 21

Class, mechanism of action, selective toxicity, functions and limitations of co-amoxiclav

Answer 21

Beta-lactam - penicillin
Competitive inihibition of transpeptidase
Targets cell wall of bacteria
Middle ear infections, Respiratory tract infections, UTIs, Joint and bone infections, Dental infections
Diarrhoea, itching/redness of mouth, armpits, genitals, nausea/vomiting

Question 22

Class, mechanism of action, selective toxicity, functions and limitations of ceftriaxone

Answer 22

Beta-lactam - Cephalosporin
Competitive inihibition of transpeptidase
Targets cell wall of bacteria
Pneumonia, UTI, intra-abdominal infections
Diarrhoea, dizziness, abdominal pain

Question 23

Class, mechanism of action, selective toxicity, functions and limitations of ceftazidime

Answer 23

Beta-lactam - Cephalosporin
Competitive inihibition of transpeptidase
Targets cell wall of bacteria
Septicaemia, pneumonia, meningitis
Abdominal pain, diarrhoea, dizziness

Question 24

Class, mechanism of action, selective toxicity, functions and limitations of erythromycin

Answer 24

Macrolide
Binds to 50S portion and prevents translocation along mRNA
Targets bacterial ribosomal function
Chest infections, skin problems (acne), STIs
Nausea, vomiting, stomach cramps, loss of appetite, indigestion

Question 25

Class, mechanism of action, selective toxicity, functions and limitations of ciprofloxacin

Answer 25

Fluoroquinolones Inhibits DNA replication by binding to DNA topoisomerase Bacterial DNA Pneumonia, Gonorrhoea, typhoid fever Tendon damage (tendonitis), nausea, diarrhoea

Question 26

Class, mechanism of action, selective toxicity, functions and limitations of doxycycline

Answer 26

``` Tetracycline Interferes with tRNA/mRNA attachment Bacterial ribosome Malaria, chest infections, STIs Headaches, nausea/vomiting, sensitive to sunlight ```

Question 27

Class, mechanism of action, selective toxicity, functions and limitations of trimethoprim

Answer 27

``` Sulfonamides Prevents folic acid synthesis PABA to Folate does not occur in humans UTIs, Acne, chest infections Nausea, diarrhoea, headaches ```

Question 28

Class, mechanism of action, selective toxicity, functions and limitations of metronidazole

Answer 28

Nitroimidazole DNA fragmentation Targets Bacterial DNA Skin infections, Bacterial vaginosis, pelvic inflammatory disease

Question 29

Class, mechanism of action, selective toxicity, functions and limitations of meropenem

Answer 29

``` Beta-lactam - carbapenem Competitive inhibition of transpeptidase Cell wall synthesis Meningitis, pneumonia, anthrax Diarrhoea, abdominal pain, headache ```

Question 30

Class, mechanism of action, selective toxicity, functions and limitations of Clarithromycin

Answer 30

Macrolide Binds to 50S portion and prevents translocation along mRNA Targets bacterial ribosomal function Chest infection, stomach ulcers, cellulitis

Question 31

Class, mechanism of action, selective toxicity, functions and limitations of gentamicin

Answer 31

Aminoglycoside Binds to 30S region of ribosome and causes misreading of bacterial proteins Bacterial ribosomes Meningitis, pneumonia, UTIs

Question 32

Class, mechanism of action, selective toxicity, functions and limitations of vancomycin

Answer 32

``` Glycopeptide Prevents Ala-Ala elongation of peptides Bacterial ribosome Colitis, Diarrhoea, Intestinal infections Dizziness, nausea ```