Mode of action and mechanisms of resistance Flashcards
Requirements for antimicrobial activity are…
Adsorption to cell surface
Passage into cell
Interaction with target
Oxidation occurs with which agents?
Peroxygen compounds and halogens
X-linking occurs with which agents?
Aldehydes
Coagulation occurs with which agents?
Aldehydes, Chlorhexidine, Phenols, Ethanol, Mercurials
Oxidation causes…
Strand breakage, binding to DNA or RNA
Degradation of unsaturated fatty acids
Modification of S-S bonds
X-linking causes…
It affects NH2 groups of surface-exposed lysine residues
Coagulation causes…
Extensive X-linking and protein precipitation
How can agents affect the cell wall?
Breakdown the cell wall
Affect integrity of outer membrane
X-link cell wall
How can agents affect the cytoplasmic membrane?
Affect:
- Membrane potential (proton motive force)
- Enzymes
- Membrane permeability
How can agents affect the cytoplasm?
Cause general coagulation Affect: - Ribosomes - Nucleic acids - SH groups - NH2 groups
What is intrinsic/innate resistance?
A natural chromosomally encoded property
What is extrinsic/acquired resistance?
Organisms become resistant
- Phenotypic: response to mode of growth
- Genetic: requires mutation/genetic transfer
Give examples of Innate resistance
Efflux pump
Barrier to penetration
Decreased accumulation
Adaptation
Give examples of Acquired resistance
Phenotypic resistance
Cell density: ‘gang warfare’
Genetic resistance
What is ‘gang warfare’ in relation to cell density
When bacteria only produce virulence factors when there is a ‘quorum’ of cells present