L5 - Antibacterial chemotherapy

Question 1

Is food poisoning due to the virus or the toxin?

Answer 1

can be both

often toxin present WITHOUT virus

Question 2

What is endogenous infection?

Answer 2

disease from commensal microbiota

Question 3

What is exogenous infection?

Answer 3

disease from microbes that do not reside in the body e.g. TB

Question 4

define antibiotics?

Answer 4

natural substances produced by one micro-organism that kill/inhibit another

Question 5

define antibacterial agents?

Answer 5

compounds capable of killing/inhibiting bacteria - include semisynthetic/synthetic

Question 6

define antibacterial drugs?

Answer 6

compounds that show selective toxicity against bacterial cells

Question 7

define antibacterial chemotherapy?

Answer 7

use antibacterial drugs to treat bacterial infections

Question 8

what are the recurring themes of antibacterial action?

Answer 8

substrate analogues
steric hindrance
enzyme inactivation
disruption/subversion

Question 9

what is selective toxicity?

Answer 9

organism is killed without any damage to the host

Question 10

What are the recurring themes for selective toxicity?

Answer 10

gets into bacterial cells more easily than mammalian

targets structures not present/different in mammalian cells

pro-drug only activated in bacteria

Question 11

Names of 2 segments of antibiotic discovery?

Answer 11

Golden age - 1945-1970

Discovery void - 1990-2021

Question 12

what % of antibacterial drug prescriptions are for oral use in primary care?

Answer 12

> 80-90%

Question 13

What % of antibiotics prescribed are inappropriate?

Answer 13

50%

Question 14

What is the process for uncomplicated infections?

Answer 14

choice of drug based on physical examination

empiric “best-guess” therapy

Question 15

What is the process for complicated infections?

Answer 15

Hospitalised
refine drug choice based on lab diagnosis
susceptibility testing

Question 16

What are 3 types of antibac susceptibility tests?

Answer 16

Disk diffusion assay
Etest - MIC
Broth/agar dilution

Question 17

What is MIC?

Answer 17

minimum inhibitory concentration

Question 18

What are factors that influence the choice of antibacterial drugs for therapeutic use?

Answer 18

Plasma concentration/half life

tissue distribution/concentration at site

dosing forms (oral/topical/IV)

potential adverse side effects

Question 19

What are pharmacokinetics (PK)?

Answer 19

what the body does to the drug

Question 20

What are pharmacodynamics (PD)?

Answer 20

What the drug does to the bacterium

Question 21

What are pharmacokinetic considerations (CSF, urine)?

Answer 21

Cerebrospinal fluid:
B-lactams (good)
Aminoglycosides, vancomycin (bad)

Urine:
B-lactams, Trimethropin (good availability)
macrolides (bad)

Question 22

Why is combination therapy good?

Answer 22

broad spectrum - single agent may not cover everything

boost activity via synergism

reduce resistance

Question 23

What are adverse effects of antibiotics?

Answer 23

antibiotics resistance

endotoxin release (when lots of bacteria die at once = clinical deterioration - septic shock

superinfection e.g. C.diff

Question 24

What happens in C.diff infection?

Answer 24

antibiotic-associated diarrhoea

gut flora ruined by antibiotics