Control Of Microbial Growth Flashcards
Sterilization
Absolute removal or destruction of all microbial life and viruses - all microorganism must be removed including endspores
Disinfection
Destruction of pathogenic microorganism - kills most but not all microbes
Antisepsis
Disinfection of living tissue - requires less harsh of a chemical treatment
Degerming
Removal of most microbes from a limited area
Sanitization
Lowering the microbial counts on a surface such that they are at a safe level
Bacteriocidal
An agent that kills microbes
Bacteriostatic
An agent that stops the growth of microbes
Asepsis (aseptic)
This is when an area is free of significant contamination
Heat
Kills microbes by destroying their fundamental enzymes- bacteriocidal
Boiling
Disrupts the protein structure and accomplishes disinfection
Autoclave
Uses 15psi of pressure and 121°c of steams.kills all endospores and organisms. Best method for sterilization
Pasteurization
Eliminates pathogens and reduce microbial counts -classic treatment is 63°c for minutes
HTST pasteurization
High temperature , short-time:72°c for 15 second
UHT pasteurization
Ultra - high temperature: 140° for 3 seconds
Dry heat sterilization
Several method, kill via oxidation
Direct flaming
Sterilize inoculation needles and crops, metallic instruments must be red to be considered sterile
Incineration
Effective way to sterilize and dispose of contaminated materials
Drying oven
Non - temperature sensitive materials are kept at 170°c for 2 hours
Filtration
Vacuum is used to force liquid through a filter with very small pores,used to sterilize temperature sensitive liquid.
Air filtration
High efficiency particulate Air(HEPA)filters used in some operating room to remove all microbes langer then 0.30 micrometer in diameter
Refrigeration
Slows or stops microbial growths,and freezing stops microbial growth
High pressure
High pressure, disturbs protein/ molecular structure, it is bacteriocidal but does not accomplish sterilization
Desiccation
Used to control microbial growth so it is bacteriostatic, occurs through removal of water (drying), microbes can remain viable in a dehydrated state.
Osmotic pressure
Movement of water from high to low concentration, it can kill some bacteria so it’s both bacteriocidal and bacteriostatic
Radiation
Destroys DNA, x- ray and gamma rays penetrate materials, uv and high energy electron beams are used on surfaces.
Microwaves
Use longer wavelengths,not of high energy to kill organism directly but the high temperature created by the microwaves are used disinfect materials
The disk diffusion method
- ) a disk of filter paper is soaked in the chemical disinfectant
- ) the dish is placed on an agar plate that has been inoculated with bacteria.
- ) the chemical will diffuse from the paper to the plate
- ) the plate is incubated until the bacteria grow
- ) the zone of clearance around the bacteria is used to determine the effectiveness of the disinfectant
Phenolics and bisphenols
Disrupts The plasma membrane and denature protein making it bacteriocidal. Very effective, long lasting and stable with other organic compounds making it suitable for disinfection of surfaces entamimated by saliva, pus and feces. These are mixed with other compound to Lower their toxicity
Phenolics examples
Lysol used for household disinfection
Bisphenol example
Hexachlorophene- useful against bacteria that cause skim infection, use with caution because it may cause neurological disorders
Triclosan - used in personal hygiene products and cosmetics
Biguanides - chlorhexidine
Attacks the plasma membrane, it has broad spectrum of activity and is used to control the skin and mucous membranes.it is bacteriocidal but does not kill endospores
Halogens
These are chlorine and iodine, they impair protein synthesis and alter membrane. Used as household bleach and iodine which is a every effective antiseptic.
Chlorine
Used as gas or combined with other chemical. it is a strong oxidizing agent that destroys enzymes.
Iodine
Most effective antibiotics, available as tincture in solution in aqueous alcohol and lodophore a combination of Iodine and organic molecule.
Alcohols
Denature proteins, disrupts lipid membranes, it does not kill endospores or non-enveloped viruses. Ethanol and isopropanol are 2 types of alcohol most commonly used.
Heavy metal
Metals such as copper, silver, zinc, and mercury can inhibit microbes. They are bacteriostatic
Silver nitrate (1%)
Used as an antiseptic, eye drop for newborn to protect against gonorrhea of the eye
Silver sulfadiazine
Combination of silver and sulfadiazine drug used as a tropical cream for burns
Soaps and detergents
Surface agents - Do not work as antiseptics, they are important in the mechanical removal of microbes, soap break up the oil on the skin and the water washes it away , therefore they are good Degerming agents
Quaternary ammonium compounds (quats)
Cationic detergents: kills most bacteria, fungi and some viruses, they are less effective against gram negative and affect the plasma membrane.
Gaseous chemosterilizer
Chemical gas used for sterilization
Gaseous chemosterilizer example
Ethylene oxide kills all microbes including endospores and viruses, is highly penetrating and requires 4-18 hours of exposure
Oxidizing agents
Oxidize and denature proteins, it is useful against anaerobic organisms
Hydrogen peroxide
Common antiseptics for wounds
Ozone
Used with chlorine to disinfect water
Benzoyl peroxide
Used as an antiseptic on skin, kills anaerobic bacteria living in tissue
