Control of bacterial growth Flashcards
What are ways we can control bacterial growth
- Physical
- Chemical
- Biological
Sterilization
Kill everything and spores
Decontamination
treat to make them safe to handle
Disinfection
Control pathogens on inanimate objects
Antisepsis
Control pathogens in living tissues
Sanitization
Lower microbe load
Sepsis
Bacterial contamination
Sepsis
Bodies reaction to bacterial infection
“cidal”
Kill microbes
“static”
Don’t kill, but won’t grow
Factors influencing effectiveness of agents
- Number of microbes
- Environment
- Time of exposure
- Microbial features
Modes of actions of antibacterials
- Alteration of membrane permeability
- Damage to proteins
- Damage nucleic acids
What are physical methods of killing bacteria
- Heat
- Radiation
- Filtration
Thermal death point
Lowest temp where all microbes are killed in 10 min
What type of heat is most effective
Moist heat
Types of dry heat
- Flaming
- Incineration
- Hot air sterilization
Types of moist heat
- Boiling at 100C (doesn’t kill spores)
- Steam under pressure (autoclave) kills spores
- Pasteurization
What is autoclaving
121C at 15 PSI for 15min or higher
What is pasteurization
Use for liquids sensitive to heat but kills pathogens and prolongs shelf life. Can be HTST or ultra high temp
Types of radiation
- Ionizing
- Nonionizing
Ionizing radiation
X rays and gamma rays. Generate electrons, OH, and H to disrupt nucleic acids and proteins
Nonionizing radiation
UV rays. Thymine dimers
Filtration
Sterilize heat sensitive liquids. Filters exclude bacteria. HEPA filters
Type of chemicals used to combat microbes
- Cidal
- Static
Phenols
Active in presence of organic compounds and stable for a long time. Disrupts cytoplasmic membrane
Phenol coefficient
Every other chemical is compared to the effectiveness of phenol. If it is greater than 1 it is more effective if less it is less effective
Triclosan
Chlorinated diphenyl. Can become resistant to it as well as antibiotic resistant from it
Chlorhexidine
Synthetic cationic antiseptic effective against bacteria but not spores. Used as presurg antiseptic, wound flush, and teat dip
Halogen
Iodine and chlorine product
Types of iodine
- Tincture (in alcohol)
- Iodophore (in organic molecule; betadaine)
What type of alcohol is more effective
Isopropanol
Heavy metal antimicrobial
- Silver nitrate
- Mercury chloride
- Copper sulfate
- Zinc chloride
Soaps
Not antiseptic, mechanically remove bacteria
Quarternary ammonium compounds
Derivative of ammonia. good for Gram +
Hydrogen peroxide
Useful for deep wounds to kill anaerobes not on superficial wounds
Benzoyl peroxide
Treat wounds for anaerobes
Peracetic acid
Kills spores in food
Aldehydes
Formaldehydes etc. Inactivates bacteria
Ethylene oxide
Gaseous sterilizers. Effective against all microbes over time. Denatures protein and sterilizes medical equipment
