Antibiotics: Mode of Action

Question 1

what is the physical control of microbial growth?

Answer 1

heat sterilisation, radiation sterilisation

Question 2

what is the chemical control of microbial growth?

Answer 2

antiseptics and disinfectants, natural antimicrobials and synthetic antimicrobials

Question 3

what are the different methods of infection control?

Answer 3

disinfection of non-sterilisable surfaces and equipment, heat sterilisation of all compatible equipment, handwashing technique, ppe

Question 4

what are disinfectants

Answer 4

strong chemical agents that inhibit or kill microorganism

Question 5

what are antiseptics

Answer 5

disinfecting agents with sufficiently low toxicity for host cells and can be used on skin

Question 6

what are sterilants

Answer 6

kill both vegetative cells and spores when applied to materials for appropriate times and temperatures

Question 7

what is the most important thing for an antiseptic?

Answer 7

to have selective toxicity - toxicity to microorganisms but not human cells

Question 8

what are the uses of antiseptics?

Answer 8

treatment of skin infections, prevention of infections in cuts and wounds, cleaning the skin area of surgery, prophylaxis and treatment of infections in mucosal areas, as a scrub for surgeons

Question 9

what are the 3 classifications of antiseptics?

Answer 9

those that denature proteins, those that cause osmotic disruption of the cell, those that interfere with specific metabolic processes

Question 10

what do phenols, iodine and alcohols do?

Answer 10

denature proteins and DNA bases

Question 11

what do cationic detergents do?

Answer 11

interfere with plasma membranes permeability and cause leakage of enzymes and metabolites

Question 12

what do oxidising compounds do?

Answer 12

oxidise functional molecules in the microorganisms

Question 13

what are iodophores?

Answer 13

iodine and other free halogens which oxidise the -SH groups of proteins and enzymes

Question 14

what are iodophores used as?

Answer 14

either as an antiseptic or disinfectant to kill vegetative bacteria, fungi, mycobacteria etc.

Question 15

what are alcohols used as?

Answer 15

antiseptics and disinfectants to kill vegetative bacteria and fungi by denaturing proteins and disturb the membrane permeability

Question 16

what is chlorhexidine used as?

Answer 16

an antiseptic

Question 17

what types of bacteria is chlorhexidine most effective against?

Answer 17

gram+ cocci

Question 18

give an example of an oxidising agent

Answer 18

hydrogen peroxide

Question 19

what is the health warning with antiseptics, disinfectants and sterilant users?

Answer 19

they accumulate in the environment or in the patients/caregivers body

Question 20

what is the definition of an antibiotic?

Answer 20

a chemical substance produced by one organism that is destructive to another

Question 21

what are the two forms of antibiotics

Answer 21

bacteriostatic and bacteriocidal

Question 22

what are the cellular targets of antibiotics?

Answer 22

cell wall, cell membrane, nucleic acid, protein synthesis

Question 23

what are the properties of the ideal antimicrobial agent?

Answer 23

selective toxicity, cidal activity, long plasma half-life, good tissue distribution, low binding to plasma proteins, oral and parenteral preparations, no adverse drug interactions

Question 24

what are the antimicrobial targets?

Answer 24

inhibition of: cell wall synthesis, protein synthesis, nucleic acid replication and transcription, injury to plasma membrane, inhibition of synthesis of essential metabolites

Question 25

what molecules prevent cross linking of the cell wall?

Answer 25

beta-lactams e.g., penicillin

Question 26

how does penicillin inhibit the cell wall synthesis

Answer 26

it binds to penicillin binding proteins
inhibition of cross-linking of cell wall
accumulation of precursor cell wall units
cell lysis

Question 27

what molecules prevents vertical linking of the peptidoglycan?

Answer 27

glycopeptides e.g., vancomycin

Question 28

how does vancomycin work?

Answer 28

bind to terminal D-ala residues and prevents incorporation of sub-unit into growing peptidoglycan

Question 29

what does transpeptidation do?

Answer 29

prevents cross-linking of the cell wall so the molecule does not have stability

Question 30

how do you inhibit the protein synthesis?

Answer 30

inhibit ribosomal subunits

Question 31

how do you inhibit nucleic acid?

Answer 31

inhibit DNA gyrase so it cannot wind and therefore inhibit packing of DNA and cell functions

Question 32

what is the antibiotic resistance cycle?

Answer 32

increase antibiotic use, increase in resistant strains, ineffective empiric therapy, increased hospitalisation, increased healthcare, limited treatment alternatives so more antibiotic use

Question 33

what does misuse of antibiotics include?

Answer 33

outdated or weakened antibiotics, antibiotics for common cold, antibiotics in animal feed, failing to complete prescribed regimen, using someone elses leftover prescription

Question 34

what are the resistance mechanisms of bacteria?

Answer 34

blocking entry, inactivating enzymes, alteration of target molecule, efflux of antibiotic

Question 35

give an example of how antibiotic resistance works with penicillin

Answer 35

the B-lactam ring in penicillin is broken by penicillinase

Question 36

what is the effect of antibiotic resistance on overall antibiotic effectiveness?

Answer 36

originally the effect of antibiotics decrease the number of bacteria by 4 logs but then it increases again so the net loss of bacteria is only 1 log