Sterilization, disinfection and containment - Kozel Flashcards
Define sterilization.
Use of physical or chemical agent to destroy all microbial formes, including spores.
Define disinfection.
Use of physical or chemical agents todestroy most microbial forms, bacterial spores or other relatively resistant organisms may remain viable.
Define antisepsis.
Use of chemical agents on skin or other living tissue to inhibit or eliminate microbes, no sporicidal action is implied.
Define biocide.
A general term describing a chemical agent, usually with broad spectrum, that inactivates microbes.
What are the factors influencing disinfectant potency?
- Concentration - effective concentration varies with disinfectant. There is a general inverse correlation between concentration and time required to kill
- Time - usually more time is better.
- pH - can dramatically influence potency
- Temp.- killing rate doubles for every 10 degrees centigrade that temp increases.
- presence of extraneous materials - these can bind or inactivate the disinfectant.
- microorganism - significant differences between microbes.
What microbes are the most vulnerable to disinfectants?
Lipid enveloped viruses.
From least resistant to most, list microbes.
- prions
- coccidia
- mycobacteria
- cysts
- small, non-enveloped viruses
- trophozoites
- gram-neg bacteria
- fungi
- large non-enveloped viruses
- gram-pos bacteria
- lipid enveloped viruses
Name some types of antiseptics and disinfectants.
- ethylene oxide and aldehydes
- oxidizing agents
- halogens
- phenolic compounds
- quaternary ammonium compounds
- alcohols
What are some types of ethylene oxide and aldehyde disinfectants?
- Formaldehyde - environmental decontamination; used in gaseous form or dissolved in water.
- Glutaraldehyde - chemical sterilization of equipment.
- Ethylene oxide - gaseous sterilization of heat sensitive materials.
What is the mechanism of action of ethylene oxide and aldehyde disinfectants?
They alkylate and cross-link macromolecules like proteins, DNA or RNA.
What are some oxidizing agents used as disinfectants?
- Ozone - disinfection of air systems.
- Hydrogen peroxide - cleansing of wounds, disinfection of implants, prostheses, etc.
- Peracetic acid - chemical sterilant.
What is the mechanism of action of the oxidizing agent type of disinfectants?
They oxidize proteins and cause DNA breakage.
Name some halogen disinfectants.
- Iodine - used as skin disinfectant.
2. Chlorine - chemical decontamination.
What is the mechanism of action of halogen disinfectants?
They oxidize proteins.
Name some types of phenolic compound type disinfectants.
- Chlorhexidine - skin disinfection.
2. Triclosan - antibacterial soaps, inumerable other uses.
What is the mechanism of action of phenolic compound disinfectants?
They disrupt the lipid containing membranes and denature proteins.
Name some quaternary ammonium compound type of disinfectants.
- Benzalkonium chloride like Lysol - skin disinfection and hard surface cleaning.
What is the mechanism of action of quaternary ammonium compound disinfectants.
They act as a surfactant. Their amphoteric properties disrupt membranes.
Name a type of alcohol disinfectant.
- Isopropyl alcohol (70%) - skin decontamination, disinfection of fomites. 100% alcohol is less effective at killing.
What is the mechanism of action of alcohol?
It denatures proteins.
What are some ways that bacteria resist antiseptics and disinfectants.
- intrinsic resistance due to microbe variability and also physiological adaptation such as biofilms.
- decreased uptake - silver compounds.
- Efflux of agent - seen with quaternary ammonium compounds and chlorhexidine.
- Inactivation of agent - seen with chlorhexidine, formaldehyde and mercurials.
What is temperature required to kill most pathogenic bacteria?
60 degrees Celcius.
What is the temperature required to kill vegetative forms of all bacteria and fungi?
80 degrees Celsius.
What is the temperature required to kill spores of pathogens?
100 degrees celsius.
What is the temperature required to kill all bacterial spores?
120 degrees celsius.
Describe some methods of using heat to kill microbes.
- Pasteurization - 72°C
- Boiling - 100°C
- Autoclave - Steam under pressure (the heat kills not the pressure) - 120°C
- Dry heat - 180°C, very inefficient
- incineration
Name 2 types of physical agents used to kill or remove microbes.
- Radiation
2. Filtration
Describe radiation.
- UV irradiation like sunlight or UV lights. This is used to control airborne or surface contamination - can’t penetrate solids.
- Ionizing radiation like X-ray and gamma emitters. This is used for sterilization of small, heat-sensitive articles.
Describe filtration.
- Filter sterilization of heat-labile liquids - no removal of viruses or other small forms like some toxins - these can fit through pores.
- HEPA filtration of air - effective and even works for viruses.
Describe the biosafety levels.
There are 4 levels.
- BSL-1 - basic level of containment with no special primary or secondary barriers used for work with well-characterized agents not known to consistently cause disease in healthy adults.
- BSL-2 - used in labs whose work involves broad spectrum of indingenous moderate-risk agents such as Hep B and HIV. Risks are skin, ingestion or mucous membrane exposure.
- BSL-3 - used in labs whose work involves indigenous exotic agents with potential for aerosol transmission. All work is done in a biosafety cabinet or other physical containment device.
- BSL-4 - used in labs whose work involves dangerous and exotic agents that pose a high risk of aerosol-transmitted lab infections and life-threatening diseases. All work is done in specialized safety cabinets.
Give some specific examples of how to sterilize in the lab or medical setting.
- packages of surgical dressings - autoclave w/dry cycle
- liquids containing live virus - fix w/bleach then autoclave
- thermometer used in peds clinic - alcohol
- glass flasks of bacterial culture media - autoclave
- plastic pipettes in plastic wrappers - ionizing radiation
- pathogen contaminated glassware - autoclave
Give some specific examples of how to sterilize in the lab or medical setting.
- 200 mL of tissue culture media - filter sterilize
- biosafety hood to change HEPA filters - formaldehyde gas
- skin at site of lumbar puncture - Iodine
- skin at site of venipuncture - alcohol
- raw milk - pasterurize
- lab bench after routine use for bacterial culture - phenol based disinfectant
