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B1: An introduction to the Different Classes of Antimicrobials (Definition…
B1: An introduction to the Different Classes of Antimicrobials
Definition of Antimicrobial Activity
Bacteriostatic
Cell stop dividing but remain viable
Bacteriocidal
Cells are killed but dead cells remain
Bacteriolytic
Cells are killed and broken down
Minimum Bactericidal Concentration (MBC)
Lowest concentration of an antimicrobial agent that kills 99.9% original inoculum
Minimum Inhibitory Concentration (MIC)
Highest dilution antibiotic prevents overnight visible growth
Different classes of antimicrobials
Antibiotic
Systemic Antimicrobial Action, Low host toxicity, Targeted selective toxicity, Naturally occurring or synthetic, Bacteriostatic or Bacteriocidal
Non-Antibiotic antimicrobial
Antiseptic, Disinfectant, Preservative
Ex Vivo
(outside body) use only, High host toxicity, Broad, Non-selective toxicity, Chemical agents classed as
biocides
, Bacteriostatic, Bacteriocidal, Bacteriolytic
Choice of biocide
Likely risk from type of microorganisms
Types of microorganisms, Levels of contamination :unlock: treatment outcome
Efficacy must be investigated in stimulated tests to guide biocide choice
Factors affecting biocide choice are:
: :check: Properties of biocide
:check: Microbial Challenge
:check: Intended Application
:check: Environmental factors
:check: Toxicity of the agent
Entry of Biocide into the Cell
Interact and Enter the cell
Electrostatic/Hydrophobic infections
Porin Channels, Diffusion
No specific receptors/uptake mechanism
Affinity :unlock: Efficacy
Mechanism of Action: Biocide
Influenced by environmental factors
Action inserted through structural damage and interactions with other cellular components
Resistance to Biocides
Intrinsic (i.e.neutral)
Acquired (i.e. achieved by mutation and plasmid/vector transfer)
Gram-negative bacteria
are often more resistant
Resistance to biocides not often seen as biocide is short lasting