Lecture 6: Growth Control Flashcards
What methods are available to control microbial growth?
Sterilization: Kill all microbes
Disinfection: Inhibit growth on inanimate surface
Antisepsis: Inhibit growth on living tissue
What are the methods of sterilization?
Heat, Radiation, Filters
What is the heat sterilization?
Denatures macromolecules making them lose structure/function
- Decimal Reduction Time: 10-fold reduction
- Thermal death time: Time to KILL ALL microbes
What equipment will you use for heat sterilization?
Autoclave
- Up to 121 degrees Celsius
- Uses steam to get endospores to hatch (endospores resistant to 150 degrees celsius)
What method is used for heat growth control?
Pasteurization
-Rapid heating/cooling
Does not KILL ALL microbes but REDUCES number
What are the types of radiation sterilization?
UV Radiation
-mutates DNA
Ionizing Radiation
-Radicals tear proteins/lipids apart
What is UV radiation sterilization?
Expose to UV waves
Advantage: Practical and Safer
Disadvantage: Sterilize surface only
What is Ionizing radiation sterilization?
Expose to Electromagnetic radiation
Advantage: Cold sterilization penetrate solid/liquid
Disadvantage: DANGEROUS
What is filter sterilization?
Sterilization without heat that uses filters
Advantage: Safe and useful for heat sensitive microbe
Disadvantage: Cant use on solids
What are Depth Filters?
Filter sterilization uses glass fibers to make 3d spiderweb
What are membrane and nucleopore filters?
Filter sterilization uses strong polymers to trap microbe
Nucleopore filters use polycarbonate film with specific and controllable pore sizes to trap microbe
What is a chemical that kills or inhibits microbial growth?
Antimicrobial agent
What are the classifications of antimicrobial agents?
Target Organism
-Bacterio-, Fungi-, Viri-
Action
- static= stop growth (plateau total+viable cell count)
- cidal= kills cells (decrease viable cell count)
- lytic=kills+lyses cells (decrease total cell count)
What is targeted by bacteriostatic, bateriocidal, and bateriolytic antimicrobial agents?
Bacteriostatic-ribosomes, prevent protein synthesis
Bacteriocidal-bins specific cellular targets
Bacteriolytic-cell wall+membranes=lysis
What is the Minimum Inhibitory Concentration (MIC)?
Amount of chemical needed to inhibit growth
What kinds of antimicrobial agents would you use on inanimate surfaces and external body surfaces?
Inanimate surfaces
-Sterilants and Disinfectants
External Body Surfaces
-Antiseptics (germicides)
What do sterilants do? What would you use them for?
KILL ALL microbial cells and endospores
Use on heat-sensitive equipment
What do Disinfectants do? What would you use them for?
Kill ALL microbial cell but NOT endospores
Used on home surfaces
What do Antiseptics (germicides) do? What would you use them for?
Kill Microbial cells or inhibit growth (non-toxic)
Used in Handwashing soaps
What are the different structural classes of antimicrobial drugs which kill and inhibit microbial growth INSIDE the body?
B-Lactam = 52% Fluoroquinolones = 24% Macrolide = 20% Other = 4%
What class of drug is penicillin?
B-Lactam
What are some of the targets of antimicrobial drugs?
DNA translation
RNA Elongation
DNA Gyrase (only in bacteria)
Folic Acid Synthesis
Cell Wall Synthesis
Who is Paul Ehrlich and what is selective toxicity?
Paul Ehrlich responsible for magic bullet approach to antimicrobial drugs
Selective toxicity is the goal of antimicrobial drugs
-inhibit or kill microbial pathogens and don’t harm human
What are Sulfa antimicrobial drugs? What is its mechanism and spectrum?
Synthetic Antimicrobial Drug
- Mechanism: Interfere with folic acid synthesis (DNA)
- Spectrum: Broad, Gram + and Gram -
