Sterilization and Disinfection

Filtration

- physical removal of microbes, sterile filtration - Not cidal not static - HEPA filters for air (disinfects the air)

Specific Disinfectants (all cidal)

1. Phenol and its derivatives 2. Organic solvents 3. Aldehydes 4. Gaseous agents 5. Quaternary Ammonium Compounds 6. Halogens 7. Biguanides and Bisphenols 8. Heavy metals 9. Oxidizing agents

Chemical Methods of Controlling Microbial Growth

1. Time - the longer the better 2. Temperature - warm is better 3. pH - usually acidic is better (lower pH) 4. Extraneous material - usually impairs ex. vomit may prevent agent from working 5. Concentration - depends on agent (higher better) 6. Microbe susceptibility - gram, growth stage, other ex. adjust chemical agent for bacteria (endospores,mycobacterium)

Phenol coefficient

>1 stronger than phenol <1 weaker than phenol

Osmotic pressure

Creates a hypertonic environment Similar to desiccation except you use a chemical agent to take out the water STATIC - salt or sugar solutions used in preservation - the efficacy depends on the microbe - fungi are typically resistant ( to osmotic pressure)

Radiation

Damage to the cell's DNA CIDAL

Ionizing

Damaging free radicals Breaks DNA into pieces/strands sterilizing/cidal - strong penetration - used for disposable plastic items, in some preparations of food Ex. Gamma Rays and X-Rays

Death Rate

Death rate is usually exponential Most microbes die really quick but there are a few that are resistant, more microbes, longer to kill

Iodine

Degerming agent Mixed with Iodophors, allow for easier application and slow release

Biguanides and Bisphenol's

Degerming agents inhibits lipid synthesis, broader spectrum of activity - hexachlorophene (clean babies with) - triclosan ex. colgate, old spice, dawn b. used mainly on the skin

Quaternary Ammonium Compounds

Disinfectant polar, against peptidoglycan more effective against gram +, NH4+

Chlorine

Disinfects Forms Hypochlorous Acid when added to water denatures things in water

Gaseous agents

Ethylene oxide and propylene oxide -long exposure, penetrates - sterilize things that are heat sensitive - good against +/-

Form of Desiccation (2 ways)

Freeze Drying aka lyophilization preserves static *freezing water expands and kills* good way of preserving bacteria Osmotic pressure - creates a hypertonic environment

Physical Control of Microbial Growth

Heat *cidal* 1. Autoclave 2. Boiling 3. Pasteurization 4. Dry Heat Non-heat 1. Filtration 2. Low temperature 3. Desiccation 4. Osmotic pressure 5. Radiation

Dry Heat (2 ways)

Hot air oven - will provide sterilization (not as efficient as autoclave) · 170oC for 2 hours Incineration - will provide sterilization

Oxidizing agents

Hydrogen peroxide - denatures proteins - used as an antiseptic

Halogens

Iodine and chlorine

Measurement of efficacy

Thermal death point (constant time, variable temp) Thermal death time(constant temp, variable time) Decimal reduction time (like TDT but only kill some) 10,000 to 1,000 killing off 90%

Non ionizing

UV - pyrimidine dimers Disinfecting Causes Damage to DNA (we have repairable enzymes, doesn't break DNA into pieces) - restrictions = does not penetrate well - mainly used on air and surfaces

disinfectant

an agent used to decrease the number of organisms on an inanimate object *doesnt clean* We DONT use disinfectants as antiseptics harsh ex. bleach,phenol,alcohol

antiseptic

an agent used to decrease the number of organisms on living tissue* hydrogen peroxide* killing *open wound* microbes from living tissue * sepsis - the presence of microbes in blood / tissues

Phenol and its derivatives

carbolic acid a. damages cell membranes, denatures proteins (non polar, gram -) b. works well in the presence of extraneous organic material c. rarely used because it irritates tissue and smells bad sanitizing agent - it doesn't lose its activity in the presence of extraneous organic material ex. lysol, pinesol doesn't kill endospores

Heat

denatures enzymes (coagulation and oxidation)

Organic solvents

disrupts plasma membranes and denatures proteins non polar alcohols disinfectant no residue isopropyl and ethyl alcohol used most often 70% most effective conc. for alcohol effective against enveloped viruses doesn't kill endospores

Heavy metals

mercuric chloride, mercurochrome, merthiolate (antiseptic) mercury silver copper a. react with chemical groups on proteins - inactivates enzymes- oligodynamic action (small conc. to make effective antiseptic) stings b. examples . silver compounds - silver nitrate, newborn babies, dressings (used on burns) . copper compounds - copper sulfate, algacide, fungicide

Autoclave

moist heat under pressure sterilization kills endospores restrictions heat sensitive material - powder, heat-liable proteins, plastic ex. canned foods, glassware *items are wrapped to ensure they remain sterile* *cidal*

Degerming

physical removal of microbes from skin

Low temperature

refrigeration slow growth static preservation

Sterilization

removal of all life or living organisms kills endospores

Mechanical scrub

scrubbing with an antiseptic soap (degerming/ sanitizing)

Sanitization

the removal of debris and microbes from objects to safe public health levels *hand sanitizers* ex.lysol cleans and disinfects

Disinfection

the removal of the majority of living organisms or potentially harmful organisms

Preservation

to prevent deterioration by microbial action *canned foods* salt, sugar, vinegar

Aldehydes

very strong disinfectants denature proteins by cross-linking R groups can be used as a preservative glutaraldehyde - a liquid sterilizing agent works against +/- kills endospores

Boiling

will kill all vegetative cells, but not endospores 100 degrees C - 10 min *Disinfects*

Pasteurization

will kill most disease and spoilage causing organisms (preservation) doesn't kill all vegetative cells

Mechanism of action

Microbicidal (germicidal) - kills the bacteria, destroys the microbe directly Microbiostatic - prevents the growth of microbe (not killing just stoping growth)

Evaluation of Disinfectant Efficacy

Phenol coefficient Filter paper method - disk diffusion

Desiccation

Removal of water necessary to take in nutrients static the efficacy depends on the microbe Fungi are usually resistant ex. meats, fruits, jerky, preservation