Lecture 21 - antibiotics

Question 1

what bacteria caused black death

Answer 1

yersinia pestis
a gram -ve bacterium

Question 2

what does magic bullet refer to

Answer 2

idea by Paul Ehrlich
- wanted a drug that killed targeted pathogen and leave host unharmed

Question 3

what was the first drug developed by Ehrlich

Answer 3

salvarsan
which cured syphilllis

Question 4

what was first commercially available antibiotic

Answer 4

prontosil

Question 5

what are the 4 targets iof antibiotics

Answer 5

• cell wall synthesis inhibitors
• protein synthesis inhibtors
• nucleic acid synthesis inhibitors
• folic acid biosynthesis

Question 6

why must duration of therapy be sufficient in bacteriostatic antibiotic

Answer 6

needs time to allow immune defences to eradicate bacteria

Question 7

whats the name of inhibitors of cell wall synthesis

Answer 7

b-lactam antibiotics
becuase they have a b lactam ring
and they inhibit pepgly synthesis

Question 8

3 examples of b-lactam antibiotics

Answer 8

• benzyl penicillin
• cephalosporin
• carbapenem

Question 9

who discovered penicillin

Answer 9

Fleming

Question 10

how did the first penicillin (penicillin G) have to be administered

Answer 10

injection
cuz destroyed by gastric pH

Question 11

how does penicillin act

Answer 11

acts as competitive inhibitor of penicillin binding protein (e.g. carboxypeptidase) instead of D-ala - D-ala
so pepgly cant be made
- then pepgly precursors build up and trigger hydrolases to lyse the cell

Question 12

how was penicillin modified to allow it to affect gram -ve bact

Answer 12

modified to make it less hydrophobic
e.g. amoxycillin

Question 13

penicillin resistance

Answer 13

b-lactamases
hydrolyse the b-lactam ring so they are inactive

Question 14

2 ways to counteract penicillin resistance

Answer 14

• combine w/ clavulanic acid (a b-lactamase inhibitor)
• synthesis b-lactamase resistant penicillins e.g. methicillin

Question 15

mechanism of carbapenem antibiotics

Answer 15

acylate penicillin binding proteins
so inactivating them
(used to treat b-lactamase producing bacteria; so those resistant to penicillin)

Question 16

how can carbapenem antibiotics target gram-ve ones as well

Answer 16

can enter them via porins

Question 17

how do carbapenem have to be administererd

Answer 17

intravenously

Question 18

2 ways carbapenem resistance arose

Answer 18

1) 3 new enzymes that hydrolyse the b-lactam ring
2) reduce influx or increase efflux of the drug

Question 19

how is MRSA resistant to methicillin

Answer 19

has mecA gene
encodes penicillin binding protein 2A
this has low affinity for B-lactam antibiotics
so they have no effect

Question 20

what is the one antibiotic that can go against MRSA

Answer 20

vancomycin

Question 21

vancomyocin mechnism

Answer 21

bind D-ala-d-ala
preventing transpeptidases catalysing the peptide bond

Question 22

vancomycin resistance how

Answer 22

D-ala exchanged for L-serine or D-lactate

Question 23

what are aminoglycosides

Answer 23

inhibit protein synthesis by binding to 30s ribosomal subunit
bacteriascidal

Question 24

how do aminoglycosides cause cell lysis

Answer 24

creates fissures in outer cell memb
- leakage of intracellular contents
- more antibiotic uptake

Question 25

what are aminoglycosides examples

Answer 25

all the mycins

Question 26

what type of bact is aminoglycosides effective on

Answer 26

aerobic bacteria

Question 27

what are side effects of aminoglycosides

Answer 27

kidner and inner ear toxicity

Question 28

what are tetracyclins

Answer 28

inhibitors of protei synthesis
by binding to 30s subunit
bacteriostatic

Question 29

what type of cell do tetracyclins penetrate

Answer 29

macrophages

Question 30

what are macrolides

Answer 30

inhibitors of protein synthesis
bind to 50s subunit
and ONLY for gram +ve cuz gram - easily resistant

Question 31

how do macrolides work

Answer 31

prevent tRNAs from binding
so polypetide chian cant be made

Question 32

example of inhibitors of nucleic acid synthesis

Answer 32

fluoroquinolones (e.g. ciprfloxcin)

Question 33

how do fluoroquinolones work

Answer 33

bind to DNA gyrase
DNA cant unwind properly
inhibit DNA replication

Question 34

a downside of fluoroquinolones

Answer 34

they affect all bacteria in body
including gut microbiota

Question 35

what type of grug are sulphonamides and trimethoprim

Answer 35

antimetabolites

Question 36

how do sulphonamides act

Answer 36

comp inhib of dihydropeterate
so folate synthesis cant occur

Question 37

3 new antibiotic discovered

Answer 37

• teixobactin - inhibit cell wall biosynth by binding to precursors
• malacidin
• retinoids