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.
