Antimicrobial Modes of Action

Question 1

what are the requirements for antimicrobial activity

Answer 1

adsorption to cell surface, passage into cell, interaction with target

Question 2

what antiinfectives undergo oxidation

Answer 2

peroxygen compounds, halogens

Question 3

what antiinfectives undergo x-linking

Answer 3

aldehydes

Question 4

what antiinfectives undergo coagulation

Answer 4

aldehydes, chlohexidine, phenols, ethanol, mercurials

Question 5

what happens during oxidation mode of action

Answer 5

strand breakage, binding to DNA or RNA, degredation of unsaturated fatty acids, modification of S-S bonds

Question 6

what happens during the x-linking mode of action

Answer 6

NH2 groups of surface-exposed lysine residues

Question 7

what happens during the coagulation mode of action

Answer 7

extensive x-linking and protein precipitation

Question 8

what happens when biocide concentration and exposure time are increased

Answer 8

bacteriostatic = sub-lethal, bacteriocidal=lethal

permeability changes, reversible enzyme inhibition, structural damage, leakage, autolysis, lysis, cytoplasm coagulation

Question 9

what disinfectants act on the cell wall of bacteria

Answer 9

low conc phenol, fomaldehyde

Question 10

what disinfectants work on -SH groups in DNA

Answer 10

glutaraldehyde, hydrogen peroxide, iodine

Question 11

what disinfectants work on -NH2 groups

Answer 11

formaldehyde, glutaraldehyde

Question 12

what disinfectants work on ribosomes

Answer 12

H2O2

Question 13

what disinfectants work on nucleic acid

Answer 13

acridine dyes, cimetidine

Question 14

what disinfectants work on coagulation

Answer 14

high conc chlorhexidine, phenol, Hg salts

Question 15

what disinfectants work on proton motive force

Answer 15

parabens, some phenols

Question 16

what disinfectants work on cell membrane permeability

Answer 16

cetrimidine, chlorhexidine, phenol

Question 17

what disinfectants work on membrane ATPase

Answer 17

chlorhexidine

Question 18

what disinfectants work on electron transport systems

Answer 18

hexachlorophane

Question 19

what disinfectants work on enzymes with-SH groups

Answer 19

Hg, Ag agents

Question 20

what is intrinsic/innate resistance

Answer 20

natural chromosomally encoded property

Question 21

what is extrinsic or acquired resistance

Answer 21

organism becomes resistant

Question 22

what is phenotypic extrinsic resistance

Answer 22

response to mode of growth

Question 23

what is genetic extrinsic resistance

Answer 23

requires mutation/ genetic transfer

includes co-resistance

Question 24

what type of resistance are efflux pumps

Answer 24

innate resistance

Question 25

what happens with efflux pumps

Answer 25

antimicrobials pumped out of cell via pumps in the cell wall

Question 26

what barriers to penetration do bacteria have

Answer 26

spore coat, waxy fatty acids, presence of OM/structure/porins, peptidoglycan

Question 27

what decreased accumulation mechanisms do bacteria have to disinfectants

Answer 27

efflux pumps, degredation/modification of biocide

Question 28

what adaptations do bacteria have toward disinfectants

Answer 28

altered/absence f metabolic pathway

Question 29

what bacteria has acquired phenotypic resistance

Answer 29

``` legionella pneumophila (legionnaire's disease) exists as parasite inside protozoa, isolated from water sources where outbreaks have occurred, intracellular bacteria more resistant to biocides than planktonic bacteria ```

Question 30

what are biofilms

Answer 30

acquired phenotypic resistance provide barrier to biocide, facilitates cell-cell communication, allows 3D community to develop, increased genetic exchange

Question 31

how does acquired genetic resistance occur (chromosomal mutation)

Answer 31

``` changes in protein, fatty acid or phospholipid composition decreases efficacy changes in lentgth of O-chain of LPS changes in number and/or size of porins modified target, altered pathway increased efflux ```

Question 32

how does acquired resistance via efflux upregulation occur

Answer 32

widespread resistance to multiple solvents, detergents and antibiotics partly under control of mar operon (marA=activator, marR=repressor) inactivation of marR or over-expression of marA induces mar phenotype