Chapter 7 - The Control of Microbial Growth Flashcards
Define: Aseptic techniques
Include examples
practices and procedures to prevent contamination from microbes (ex: use fire source, spray disinfectant)
Compare: Sepsis vs. Asepsis
Sepsis
- microbe contamination
Asepsis
- absense of significant contamination
Compare: Sterilization vs. Disinfection
Sterilization
- removing and destroying ALL microbial life (kills all active cells + endospores)
Disinfection
- destroys MOST microbes (doesnt kill endospores)
- usually applies to non-living objects (counter/surfaces)
Define: Antisepsis
destorying harmful microbes from living tissue/body wounds
Define: Degerming
Include: How its accomplished, examples
physical removal of microbes from a limited area
- accomplished by soaps/detergents
- Ex: hand washing, wiping skin with alcohol swab
Define: Sanitization
Include: examples
cleansing of fomites to remove enough microbes to achieve levels safe for public health
Ex: Restaurant industry lowers microbial count (doesnt kill eveything) on plates and eating utensils to safe levels
Compare: Biocide (germicide) vs Biostatic (bacteriostatic)
Include: Examples of biocide
Biocide (germicide)
- chemical treatement that kill microbes; can be target specific
- Ex: bactericide, fungicide, viricide
Biostatic (bacteriostatic)
- treatment that inhibits growth of microbes
List several factors (4) that affect the rate of microbial death
1. # of microbes (population load)
- higher the population load = longer time to kill
2. environment (pH, nutrients, temp)
- ideal environment will take longer to kill
3. time of exposure to disinfectant
4. microbial characteristics
- range from most resistant microbes (difficult to kill) to most sesnsitive microbes (easy to kill)
Know the 2 most resistant “microbes” (to chemical agents) and the 2 most senstive “microbes” (to chemical agents)
MOST RESISTANT
- prions
- bacteria containing endospores
LEAST RESISTANT
- Gram positive bacteria
- Viruses with lipid envelops
Name four ways chemical agents are able to control microbial growth
(Hint: How do these chemical agents harm the microbe?)
1. Alter cell membrane permeability
- damage CM of bacteria = distrupt homeostasis
2. Damage to proteins (enzymes)
3. Damage to nucleic acids (DNA)
- damage DNA -> damage RNA -> damage protein structure -> loss of protein structure/FXN
4. Inhibit/alter metabolism
- damage cell resp -> little/no energy (ATP)
Understand the concepts of Thermal Death Point (TDP) and Thermal Death Time (TDT)
Thermal Death Point (TDP)
- lowest temperature (variable) at which all cells in a liquid culture are killed in 10 minutes (fixed)
Thermal Death Time (TDT)
- minimal time (variable) for all bacteria in a liquid culture to be killed at a certain temperature (fixed)
Examples: Boiling H2O at 100C for 10 minutes
What is the TDP and what is the TDT?
TDP = 100C
TDT = 10 minutes
Describe this Physical Method: Dry Heat
Include: Mechanism of Action, Examples, Applications
Mechanism of Action:
- Kills via oxidation (disrupt CW)
-> also seen with halogens
Examples:
- Bake Sterilization (BS)
- Hot-Air Sterilization (HAS)
- Direct Flaming (DF)
- Incineration (I)
Application/Uses:
- Glassware (BS, HAS)
- Metal instruments (DF)
- Prions (I)
Describe this Physical Method: Moist Heat
Include: Mechanism of Action, Examples, Applications, MISC (Types of Pastuerization and Advantages of Pastuerization)
Mechanism of Action:
- Kills via protein (enzyme) denaturation
Examples:
- Boiling (B)
- Autoclave (A)
-> Inv steam under pressure (psi)
-> Kills ALL organisms and endospores - Pasteruization
-> Inv use of various combination of temp and heating times
Application/Uses:
- Glassware (B, A)
- Metal Instrucments (A)
- Lab Media/Plates/Tubes (A)
- Food/Beverages; Dairy/Juices (P)
MISC:
Types of Pastuerization:
- Bulk-liquid pasteurization
- High-temperature short time (HTST)
- Ultra-High-Temperature (UHT)
Advantages of Pasteurization:
- Kills pathogens (but not spores)
- Extends shelf life
- Keep quality taste
Describe this Physical Method: Low Temperatures
Include: Mechanism of Action, Examples, Applications
Mechanism of Action:
- Low temperature has a bacteriostatic effect (suppress growth)
Examples:
- Refridgeration (R)
-> Extends shelf life - Deep-Freezing (DF)
- Lyophilization (L)
-> Freeze drying method (powder) used for long-term/indefinitie preservation
Application/Uses:
- Medications/Antibiotics (R)
- Hormones (R)
- Meats (DF)
- Some foods/Microbial culture (L)
Describe this Physical Method: Filtration
Include: Mechanism of Action, Examples, Applications
Mechanism of Action:
- Passage of substances/fluids through screen-like membrane
Examples:
- High-Efficiency Particulate Air (HEPA) Filter
-> Removes tiny microbes - Membrane Filters
-> Removes VERY TINY microbes (viruses, large proteins)
Application/Uses:
Used for heat sensitive materials:
- Vaccines
- Serum
- Enzymes
Describe this Physical Method: Dessication
Include: Mechanism of Action, Applications
Mechanism of Action:
- Removal of water
-> no water = Pvt metabolism = no cell resp = no ATP (energy)
Examples:
- x
Application/Uses:
- Salami/Pepperoni
Describe this Physical Method: Osmotic Pressure/Imbalance
Include: Mechanism of Action, Applications
Mechanism of Action:
- Removal of water
-> Uses high concentration of salts/surgars (solutes) to create hypertonic envuronemtn = draws water away = cell (path) shrink/die
Examples:
- x
Application/Uses:
- Salami/Pepperoni
Describe this Physical Method: Radiation
Include: Mechanism of Action, Examples, Applications
Mechanism of Action:
- Destroy/damage DNA (of microbe)
Examples:
- Ionizing Radiation (destory DNA)
-> Types: X-rays, Gamma Rays, Electron Beams (high E) - Nonioninzing Radiation (damage DNA)
-> Types: UV light (medium/high E)
Application/Uses:
- Disposable syringes/gloves/masks/surgical sutures (IR)
- Cleaning hospital rooms via germicidal UV lamp (NR)
Which example of moist heat involves pressure?
Autoclave (inv steam under pressure to kill ALL organisms and endospores)
List (3) desirable attributes of a chemical agent
- Safe (must be non-toxic to humans, animals, plants)
- Effective at Low Concentrations (high concentrations can cause bodily harm)
- Wide Range Uses (kills everything)
List (4) factors affecting the level of disinfection (by chemical agent)
- Concentration of chemical agents (conc vs. dilute)
- Time of exposure to chemical agent
- pH of chemical agent (want chem agent ot be acidic)
- Type of microbes/microbial characteristics (most resistant to most sensitive microbes)
What method is uses to evaluate the efficacy of chemical agents (to microbes)?
Describe how this method is carried out
What is one advantage and disadvantage to this method?
Disk Diffusion Method
- paper disk soaked in chemical agent and placed on culture
- look for zone of inhibition
- Advantages: evaluate several agents at once
- Disadvantage: chemical agents diffuse into agar at different rates
Describe this Chemical Method: Phenols, Phenolics, Bisphenols, Biguanides
Include: Mechanism of Action, Examples, Applications
Mechanism of Action:
- Disruption of plasma membrane
-> Cell leakage = disrupt homeostasis
Examples:
- Phenol (1)
-> Rarely used, highly irritating to skin & strong odor - Phenolics (2)
-> Derived from Phenol - Bisphenols (3)
- Biguanides (4)
Application/Uses:
- Hand soaps (3)
- Skin disinfection/Surgical hand scrubbing (4)
Describe this Chemical Method: Halogens
Include: Mechanism of Action, Examples, Applications
Mechanism of Action:
- Kills via oxidation
-> Also seen with dry heat
Examples:
- Iodine
-> Tincture (iodine + alcohol): antiseptic solution for disinfection - Chlorine
-> Bleach: exist gas/liquid form; used for disinfection
Application/Uses:
- Minor wounds (T)
- Before/After surgery (T)
- Water (B)
- Household supplies (B)
- Glassware (B)
Describe this Chemical Method: Alcohol
Include: Mechanism of Action, Examples, Applications
Mechanism of Action:
- Denature proteins
- Dissolve lipids
Examples:
- Isopropanol
-> Bactericidal/Fungicidal
-> More effective in water (ex: 70%)
Application/Uses:
- Surfaces
- Hands
Describe this Chemical Method: Surface-Active Agents
Include: Mechanism of Action, Examples, Applications
Mechanism of Action:
- Disrupt cell membranes
Examples:
- Soap/Detergent (S/D)
- Acid-anionic sanitizers (AAS)
- QUATS
Application/Uses:
- Skin degerming agent (S/D)
- Sanitization of large metal containers in food-processing industries (AAS)
- Used on hospital instruments, utenzils, rubber goods (QUATS)
Describe this Chemical Method: Chemical Food Perservatives
Include: Mechanism of Action, Examples, Applications
Mechanism of Action:
- Inhibit metabolism (OA)
- Pvt endospore germination in foods (N)
Examples:
- Organic acids (OA)
-> Pvt mold/bactria in food/cosmetics - Nitries/Nitrates (N)
-> Pvt growth C. botulinum in food
Application/Uses:
- Food/cosmetics (OA)
- Cold cuts, hot dogs (N)
Describe this Chemical Method: Chemical Sterilization
Include: Mechanism of Action, Examples, Applications
Mechanism of Action:
- Causes alkylation (uses gas to serilize)
-> Formation of free radicals (toxic)
Examples:
- Ethylene Oxide (gas)
Application/Uses:
- Large, heat sensitive material/Mattresses
Describe this Chemical Method: Plasma Sterilization
Include: Mechanism of Action, Examples, Applications
Mechanism of Action:
- Causes alkylation
-> formation of free radicals (toxic)
Examples:
- Plasma
-> Better penetration power and more expensive that Ethylene Oxide (regular gas)
Application/Uses:
- Tubular Medical Instruments
-> Surgical steel rods/plates
Define/Describe: Plasma
fourth stage of matter consisting of electrically excited (charged/ionic) gas
