three categories of growth control

• bacteriostatic
• bacteriocidal
• bacteriolytic 

bacteriostatic

• stops growth
• cells survive
• same cell count
• same optical density

bacteriocidal

• stops growth
• cells die
• cells disappear from the microscope
• optical density remains the same

bacteriolytic 

• cells lyse and break open
• cells disappear under the microscope
• optical density decreases

sterilants

• kills everything
• kills spores as well

disinfectants

• kill everything EXCEPT spores

sanitizers

• kill many microorganisms
• does not kill ALL microorganisms

antiseptics

• kill many microorganisms
• does not kill ALL microorganisms
• is mild enough to be applied to human skin

factors that affect antimicrobial agents

• time exposure
• concentration 

MIC

• minimum inhibitory concentration
• fill tubes with differing concentrations, inoculate all tubes with same organism
• the MIC is the lowest concentration where the growth stops
• if there is no growth at multiple concentrations, the lowest is the MIC

agar diffusion array test

• done by adding antibiotic discs to petri plates covered by a particular microorganism
• zone of inhibition shows how affect the antibiotic is to teh microorganism
• large zone = is sensitive
• medium sized zone = inhibited
• no zone or super small = is resistent

bacterial targets for antimicrobial agents

• peptidoglycan cell wall
• penicillin targets peptidoglycan synthesis
• 70S ribosome 
• RNA polymerase (different from eukaryotic RNA polymerase)

fungal targets for antimicrobial agents

• chitin cell wall
• special lipids that are not found in humans
• (usually targeting fungi damages human cells because they are similar to Eukaryotic cells)

ways microorganisms gain antibiotic resistence

• acquisition of resistence genes either by: 
• mutation OR 
• horizontal gene transfer

components of horizontal gene transfer

• can be plasmids,
• transposons,
• pathogenicity islands

common ways microorganisms evade antibiotics

• enzyme degrades the antibiotic
• can change the outer membrane permeability
• can pump the antibiotic out of the cell
• can change the target protein (by mutation)