(02) Antisepsis and Sterilization Flashcards
Koch’s Postulates
- Microbe must be present in all disease cases
- Microbe must be isolated from the infected host and grown in a pure culture
- When pure culture is introduced to susceptible host the disease must be reproduced
- Microbe must be isolated from purposefully infected host
Nosocomial Infections
- assumption?
Infections whose onset and confirmation occur greater than 48 hours after hospitalization.
- Assumption is that these were acquired while in the hospital
What infections fall under the category of Healthcare-associated infections
- Nosocomial
- Infections occurring within 6-12 months of systemic antibiotic treatment
- Residence in Long-Term Care facility
- Central IV catheterization
- Urinary Cathertization
- Dialysis
How many hospital associated infections are due to:
- nosocomial infection
- antibiotic resistance
Nosocomial = 5-10%
Antibiotic Resistance = 70%
3 Reasons for high rates of Hospital Associated Infections.
- Prevalence of Pathogen
2 .Prevalence of compromised patients
- Patient to Patient transmission by hospital personnel
Differentiate disinfectants and antiseptics
- which is more harsh?
- Disinfectants are used an inanimate things
- antiseptics are used on skin
- Disinfectants are typically too harsh to use on skin
Differentiate bacteriostatic and bacteriocidal agents
Bacteriostatic
- Inhibits growth
Bacteriocidal
- Destroys or inactivates bacteria
What is the only chemical agent capable of eliminating all contamination?
Ethylene Oxide Gas
How do phenolics and alcohols aid in eliminating contamination?
- effective against?
- Ineffective against?
Action:
- Denature Proteins
- Disrupt Cell membranes
Effective against:
- Bacteria
- Enveloped viruses?
Ineffective against:
- Spores
- Protozoan cysts
- non-enveloped viruses
How do halogens work to aid in eliminating contamination?
- Effective against?
- Oxidize (iodinate or chloronate) proteins
Effective against:
- Bacteria
- Spores
- Most Viruses
How do surfactants work to aid in eliminating contamination?
- what are quats?
- Use hydrophobic and hydrophilic groups to disrupt cell membrane
- quats = Quaternary Ammonium Salts, these are largely ineffective
Hydrogen Peroxide
- how does it clean?
- NOT effective against?
- Attacks the Lipid Membrane
NOT Effective against:
- Spores
- Catalase (+) bacteria
Glyceraldehyde
- how does it work?
- what is it used for?
- Alkylating Agent
- Used to Disinfect equipment
Sterilization
- define
- best accomplished by…
Definition:
- Complete Killing or Removal of All living organisms from an item or area
Best accomplished by PHYSICAL METHODS
How would the plot of bacterial death vs. time look?
- It would be an exponential graph
**e.g. 90% (9/10) reduction of bacteria in 10 min means 99.9% (999/1000) reduction of bacteria in 30 min.
T or F: mixed microbial populations will alter death rate kinetics
True
What are the physical methods of bacterial control?
- Temperature
- Filtration
- Radiation
Which is more effective at killing bacteria autoclaving or baking?
why?
Autoclaving:
- Uses steam and pressure
(15 min at 121ºC and 15PSI)
Baking:
- Uses dry heat (pressure not needed to raise BT or h2o)
(160º for 2 hours)
AUTOCLAVING MORE EFFICIENT - wet heat is a more rapid killer than dry heat
Why is wet heat a more rapid killer than dry heat?
Wet heat has H2O which can denature protein by disrupting hydrogen bonds between amino acids
T or F: like baking and autoclaving, boiling an object STERILIZES it
FALSE, it does not kill spores or cysts (pretty much everything else is killed within 10 min)
Describe the Process of Pasteurization
- does it sterilize?
- Heat liquids to 55-75ºC for 30 minutes, then rapidly cool them
DOES NOT STERILIZE
- spores are not killed, bacterial load reduced by 90%
*Make liquids safe for consumption
What does refrigeration and freezing do to prevent bacterial growth?
- does they sterilize?
- Slow bacterial growth
- Freezing may kill some bacteria by ice crystals on cytoplasm puncturing cell membrane but DOES NOT STERILIZE (no effect on spores
Filtration
- what does it remove?
- What can it not remove?
- Removes live and deal BACTERIA from liquids
- VIRUSES remain in the liquid (these can be removed by boiling)
Nonionizing Radiation
- How does it work?
- What can it DISINFECT?
- Excites electrons to form thymidine dimers in DNA
- Disinfect air and Surfaces (poor penetration so it doesn’t work on other things)
Ionizing Radiation
- Can it sterilize?
- how does it work?
- YES, it can sterilize disposable surgical supplies and foodstuffs
Action:
- Damages DNA
- Produces Free Radicals and H2O2
