antimicrobial drugs

Question 1

what are antibiotics

Answer 1

• substances produced by microorganisms that inhibit the growth of other organism/ microbe

Question 2

what are examples of microbes that produce antibiotics

Answer 2

• fungi (penicillin, cephalosporium)
• gram positive bacteria rods (polymyxin)
• actinomycetes

Question 3

what are the five mechanisms of antibiotics that affect pathogen

Answer 3

1. inhibit cell wall synthesis
2. inhibit protein synthesis
3. inhibit nucleic acid synthesis
4. affect/disrupt membrane permability
5. inhibit metabolite synthesis

Question 4

what are the antibiotics that inhibit cell wall synthesis

Answer 4

• beta lactams examples include penicilin (amoxcillin), cephalosporins, carbapenems
• beta lactams inhibit enzyme involved in peptidoglycan synthesis- bacteria cells undergoes osmotic lysis.
• beta lactams all have beta lactam ring- attachment site can vary
• glycopeptides which inhibit assembly of subunits to form peptidoglycan cell wall examples vancomycin

Question 5

what bacteria organisms does beta lactam and glycopeptides not work on

Answer 5

• mycoplasma
• legionella
  -chlamydia
• do not have a cell wall

Question 6

what 3 antibiotics inhibit protein synthesis

Answer 6

• aminoglycosides (gentamicin)
• macrolide (erythromycin)
• tetracyclines

Question 7

how do macrolide antibiotics work

Answer 7

• prevent peptide bond being formed between adjacent amino acids in ribosome
• example erythromycin

Question 8

what antibiotics cause injury to plasma membranes and how do they work

Answer 8

• cause changes to membrane permabillity- causes cell lysis and loss of metabolites
• polymyxin B (antibacterial) or fluconazole (antifungal)

Question 9

what antibiotics inhibit synthesis of nucleic acids and how

Answer 9

• quinolones (ciprofloxacin)
• interfere with dna replication and transcription

Question 10

how do quinolones work

Answer 10

• inhibit enzyme dna gyrase- DNA supercoiled in bacteria

Question 11

what antibiotics inhibit metabolite synthesis

Answer 11

• antifolates such as trimethoprim ( inhibit synthesis of folates)
• act as competitive inhibitor

Question 12

what is an example of an antibiotic which inhibits folate synthesis

Answer 12

trimethoprim

Question 13

what is an example of an quinolones

Answer 13

ciprofloxacin

Question 14

what are 3 factors that influence antibiotic efficacy

Answer 14

• distribution
• metabolism
  -excretion

Question 15

how do we give antibiotics

Answer 15

• external (topical) or systemic (blood stream)
• systemic drugs can be administered intravenously, intramuscularly or orally

Question 16

what are 5 safety concerns with regards to antibiotics

Answer 16

1. toxicity (aminoglycosids can cause reversible renal failure or irreversible deathness). liver failure, pseudomembranous colitis
2. interact with other medications e.g. neutralise effects of contraceptive pill
3. foetal damage/risk to pregnancy- tetracycline causes discolouration of teeth in children and may cause liver damage in pregnant women
4. hypersensititvity reactions- anaphylactic reactions to penicillin
5. amr

Question 17

what is the action of beta lactamases

Answer 17

• break down beta lactam antibiotic

Question 18

why are susceptible bacteria more advantagerous to resistant

Answer 18

• susceptible bacteria grow/divide faster than resistant bacteria- allows them to outnumber the resistant bacteria- resistant bacteria biological disadvantage

Question 19

when can resistant bacteria be a biological advantage compared to susceptible

Answer 19

• antibiotics= selective pressure
• antibiotics kill susceptible bacteria, resistant survive
• resistant divide and multiply growing their population
• this disadvantage leads to an advantage when there is a selective pressure

Question 20

how can we reduce resistant?

Answer 20

• reducing antibiotic spectrum- so keeping it narrow
• narrower the spectrum the less selective pressure exerted

Question 21

what are examples of narrow spectrum antibiotics

Answer 21

trimethoprim (inhibits synthesis of folic acid)- uti

Question 22

what is an example of a wide spectrum antibiotic

Answer 22

• cefotaxim
  -ceftriaxone
  -meropenem
  ( all beta lactams)

Question 23

before a patient starts on antibiotics you need to..

Answer 23

-send of all lab tests
- review in 48 hours
- ask question does patient need antibiotic

Question 24

when should you stop antibiotic course

Answer 24

-if lab test is sent and the result shows that there is no bacterial infection
- no need to complete course as theres no bacteria which would mutate

Question 25

how long does most infections resolve in

Answer 25

5 days

Question 26

what are some antibiotic resistant mechanisms

Answer 26

• bypass pathway- e.g. using a different pathway to synthesis a metabolite such as folate so different enzymes used
• enzyme modification (production of beta lactamases)
• altered target site
• mutations in porings which allow antibiotic to get in, mutation does not less antibiotic in cell

Question 27

what is the evolution of resistance

Answer 27

• deletion of nucleotides
  -alteration of dna (mutation)
• acquisition of dna (plasmids, naked dna, transposons)

Question 28

what are the major groups of antibiotics

Answer 28

• beta lactams
• gylcopeptides
  -aminoglycosids
  -macrolide
• tetracycline
• quinolones