ch 11- microbial control

decontamination

destruction, removal, or reduction in number of undessirable microbes

ex: asepsis, disinfection, sanitization, sterilization, degermation

sepsis

the growth of microbes on living tissue; ex: infected wound, blood infection

asepsis

techniques that prevent microbes from entering sterile tissues, ex: using sterile needles and cleansing the skin with iodine before surgery

disinfection

destruction of vegetative pathogens on inanimate objects. ex: 5% bleach, boiling water

sanitization

cleansing technique that removes microbes and debris from inanimate objects. ex: laundry, dish washing

degermation

technique that removes microbes and debris from living tissue. ex: surgical hand scrub, alcohol wipes

sterilization

the removal/destruction of all viable (alive, able to grow) pathogens. ex: autoclaving and ionizing radiation

desiccation

gradual removal of water from cells = metabolic inhibition by altering enzymes. lyophilization (freeze drying)

lyophilization

freeze drying; preservation. form of desiccation

filtration

physical removal of microbes from heat sensitive substances or gas with a filter

radiation

energy emitted thru atomic activities and are dispersed at high velocity thru matter and space

• ionizing

• nonionizing

ionizing radiation

deep penetrating energy that breaks phosphodiester backbone of DNA by making e- leave their orbit

• gamma, x, cathode

nonionizing radiation

little penetrating power from atomic activities. UV rays cause thymine dimers which interfere with DNA replication

moist heat

lower temp, moisture, lots of energy and shorter time. coagulation and denaturing of proteins stops cellular metabolism. ex: autoclaving and pasteurization

dry heat

high temp for long time dehydrates the cell, denatures the protein. incineration

autoclaving

form of moist heat control - sterilization with steam, under pressure.

• denatures proteins, destroys DNA and membrane

• 15 PSI / 121 C / 10-40 min

• destroys endospores, viruses, but not prions

pasteurization

form of moist heat control. not sterilizing, only kills NON spore forming bacteria and not endospores, but does lower microbe count.

• heat is applied to kill microbes in food without destroying flavor or value

• flash: 71.6 C for 15 sec

• Ultra - sterile milk: 134 for 2-5 sec

flash pasteurization

pasteurization at 71.6C for 15 sec. does not kill endospores, only non spore formers and lowers overall microbe count

ultrapasteurized

134C for 2-5 sec produced sterile milk

what does boiling contaminated water kill?

boiling contaminated water can kill most vegetative pathogens (viruses, fungi, and protozoa like Giardia). but does NOT kill prions and endospores

microbiostatic

slows the rate of microbial growth, like in cold temp control (refrigeration 0-15C and freezing <0C)

microbicidal agents

antimicrobial agent that kills a certain group of microorganisms

• disinfection: use of a chemical agent to destroy vegetative pathogens but not bacterial endospores

• antisepsis: chemical agents on exposed body surfaces (wounds, incisions) to destroy/inhibit vegetative pathogens

halogens (germicide)

• chlorine - Cl2, hypochlorite bleach, chloramine

  • denatures proteins by breaking disulfide bonds

  • intermediate level

  • unstable in sunlight and inactivated by organic matter

  • sewage, wastewater, water, inanimate objects

• iodine - I2, iodophors (betadine)

  • chelation - iodine is attached to an organic molecule. low concentration and slow release kills microbe over time

  • mild medical and dental degermation, disinfectant, and ointment

  • interferes w disulfide bonds of proteins

phenol (germicide)

• carbolic acid is acrid and poisonous, oxidizes your skin and burns it

• joseph lister used it to clean medical instruments

• it disturbs the cell wall, membrane, and precipitate proteins

• low-intermediate level

• bactericidal, fungicidal, virucidal (NOT SPORICIDAL)

• lysol and triclosan are antibacterial additives to soap

• toxicity of phenolics makes them questionable antiseptics (on living tissue)

alcohols (germicide)

• only ethyl and isopropyl are for microbial control

• intermediate level

• concentrations of 50+% dissolve membrane lipids and coagulate proteins of vegetative bacterial cells and fungi

• water is needed for proteins to coagulate, thus alc shows greater microbicidal activity at 70% than 100% concentration

hydrogen peroxide

• this germicide produces highly reactive hydroxyl (-OH) free radicals that damage protein and DNA while also decomposing to O2 gas - toxic to anaerobes

• antiseptic at low concentrations; strong solutions are sporicidal

detergents

• this germicidal category is a surfactant (lowers surface tension), polar molecules

• quats: quaternary ammonia compounds act as surfactants that alter membrane permeability of some bacteria and fungi

• very low level

soap

• alkaline compounds

• mechanically remove soil and grease containing microbes

• weak microbicides, destroy only highly sensitive forms like gonorrhea, meningitis, and syphilis

organic metals

• organic mercury

• silver sulfadiazine ointment

• silver nitrate (AgNaO3)

• metallic silver

• colloidal silver (tiny silver particles floating in a liquid)

organic mercury

thimerosal (merthiolate) and nitromersal (metaphen) are weak antiseptics and infection preventives

• can be preservatives in cosmetics and ophthalmic (eye)solutions

• tinctures are effective but bad choice for broken skin due to toxicity

• mercurochrome is the poorest antiseptic

silver disulfadiazine ointment

• added to dressings to prevent infection in 2nd and 3rd degree bun patients

• its a yellow ointment containing silver salts and a sulfa drug (antibiotic)

metaphen

nitromersal

merthiolate

thimerosal

silver nitrate

• topical germicide for mouth ulcers and root canals

• 1-2% solutions can be antiseptic but they discolor skin and other tissues

metallic silver

• incorporated into catheters to prevent UTI in the hospital

• paint, plastics, steel to control microbial survival on:

  • toilet seats, stethoscopes, walls and floors in homes

• silver binds to fungi enzymes, stops metabolism (bc it looks like phospholipid?)

colloidal silver

• colloid = tiny particles of silver in liquid

• mild germicidal ointments or rinses for the mouth, eyes, nose, and vagina

mercurials

• disrupt sulfhydryl groups in proteins = inactivate proteins

• organic mercury like thimerosal (merthiolate) and nitromersol (metaphen) = weak antiseptics, prevent infection

• mercurochrome

• 0.001-0.2% tinctures