Control of Microbial Growth Flashcards
Used phenol (carbolic acid) as anti-septic for surgery
Lister
Introduced hand-washing with chlorinated lime solutions to reduce puerperal fever in obstetric clinics (anti-septic procedures)
Semmelweis
Aseptic Technique
Techniques used to prevent microbial contamination
Sterilization
- Destruction or removal of ALL viable microorganisms
- Includes vegetative cells and endospores
Disinfection
Reducing number of pathogens to the point where they don’t cause disease
Antiseptics
Chemicals applied to living tissues to reduce pathogens
Disinfectants
Chemicals applied to inanimate objects to reduce pathogens
Bacteriostatic
Inhibits growth, often reversible
Bacteriocidal
- Prevents growth by killing, leaving cells intact (no lysis)
- Total count constant, viable count reduced
Bacteriolytic
- Kills by cell lysis
- Turbidity/cell number decreases
Physical Control (Heat)
Dry - Flame/incinerate, hot air
Moist - Autoclave, boil, pasteurize
Physical Control (Radiation)
Ionizing - X-rays, gamma rays, electron beams
Non-ionizing - UV
Physical Control (Filtration)
Filters out microbes (0.2 um removes most microbes)
Moist heat sterilization
- Kills by denaturing proteins
- Steam must contact item’s surface
Pasteurization
- Reduces spoilage organisms and pathogens
- High temperature for a short period of time
- Thermoduric organisms survive, but cannot grow
Chemical Control (Phenol and Phenolics)
-Disrupts plasma membranes, inactivating enzymes, denaturing proteins
Chemical Control (Bisphenols)
- E.g. triclosan
- Disrupts plasma membrane, stops fatty acid synthesis
Chemical Control (Alcohols)
- Denature protein, dissolve lipids
- Requires water
- Bacteriocidal
Chemical Control (Iodine)
- Tinctures: In aqueous alcohol
- Iodophors: In organic molecules
- Alter protein synthesis and membranes
Chemical Control (Chlorine)
- Bleach (Hypochlorous acid)
- Chloramine: Chlorine + Ammonia
- Oxidizing agents
- 2 drops of Clorox per liter; let sit for 30 min
Chemical Control (Biguanide compounds)
- Bacteriostatic and bactericidal
- Used as both antiseptic and disinfectant
- Destroys cell membrane
- Effective against most bacteria (except pseudomonads, endospores, and some viruses)
- E.g. chlorhexidine digluconate
Chemical Control (Surfactants)
- Soap (Physical removal)
- Acid-anionic detergents (Sanitizing: lower counts on eating utensils)
- Quaternary ammonium compounds (Bactericidal, denature proteins, disrupt plasma membrane)
Disk-Diffusion Method
- Disk of filter paper is soaked with chemical
- Placed on agar plate that has been incubated
- Look for lack of growth near disks
