METHODS OF MICROBIAL CONTROL (DISINFECTION AND STERILIZATION)) Flashcards
- a Greek Physician (460-377 BC) Disproved the idea that disease was a punishment for sins
- He advocated irrigation of wounds with wine or boiled water foreshadowing antisepsis
Hippocrates
a Greek Doctor who practiced medicine in Rome, boiled instruments used in caring wounded Roman gladiators.
Galen
a German Physician, and regarded as “saviour of mothers” who advocated the use of hand disinfection using chlorine lime solutions in obstetrics clinics. He is considered an early pioneer of antiseptic procedures.
Ignaz Semmelweiz
French Chemist and Microbiologist conducted
experiments that proved germs as causes of certain diseases
Louis Pasteur
a British Surgeon reduced the mortality rate of his patients by using a carbolic solution spray. He used it on wounds, on equipment in contact with wound, and on hands of the operating team.
Joseph Lister
What is the difference between
STERILIZATION and DISINFECTION?
Sterilization: Complete destruction of ALL FORMS of microbial life of including endospores. An All or nothing process
Disinfection: Elimination of a defined scope of microorganisms, including some endospores
What is the difference between
DISINFECTANT and ANTISEPTIC?
Disinfectant: Chemical agents applied to inanimate objects
Antiseptic: Chemical agents applied to the skin for the purpose of eliminating or reducing the number of bacteria present. It does not kill endospores.
Complete destruction of ALL FORMS of microbial life of including endospores. An All or nothing process
sterilization
Elimination of a defined scope of microorganisms, including some endospores
disinfection
Chemical agents applied to inanimate objects
Disinfectant
Chemical agents applied to the skin for the purpose of eliminating or reducing the number of bacteria present. It does not kill endospores.
Antiseptic
Microbial factors that contribute to their varied resistance
Endospores of bacteria
Cell wall of Mycobacteria
Viruses with lipid envelopes
Organisms that form biofilm
Prions
what will happen if there are presence of organic matter during disinfection
May inactivate disinfectants
May prevent full penetration and contact of disinfectant to the surface to be disinfected
The critical aspect in sterilization and disinfection
Contact time
factor that influence the degree of killing that has has a parallel relationship with effectiveness
temperature
Contact time can be influenced by:
▪ Bio burden of the material to be disinfectedor sterilized
▪ Type of microorganisms
▪ Presence of organic material
▪ Temperature at which the disinfectant is used
factor that influence the degree of killing that affects the effectiveness of a disinfectant
pH
disinfectants should be used at what temperature
20-22C
Disinfecting biofilms may require increased
disinfectant’s/sterilant’s:
▪ Concentration
▪ Contact time
factor that influence the degree of killing that is a community covered with a protective material that
shields them from external factors
Biofilm
what is the common mistake when using disinfectants
two disinfectants are better
than 1
- Materials that invade sterile tissues or enter the vascular system
- May produce infection if contaminated
What is the type of disinfection/sterilization?
Critical materials; Sterilization
Materials that come in contact with mucus membranes and non-intact skin
What is the type of disinfection/sterilization?
Semi-critical materials; High level disinfection agents
Iodine containing. Used at 0.1-0.2% concentration. Some iodine containing disinfectants can also be used as antiseptic agents.
What is the disinfection level and the agent used?
Low; Iodine
Objects that come in contact with intact skin but not mucus membranes
What is the type of disinfection/sterilization?
Non-critical materials; Intermediate to low level
disinfection
Biological detergent contains enzymes, non-biological does not. Used to remove soil and surface debris from items.
What is the disinfection level and the agent used?
Basic cleaning; Detergent
Used on hard surfaces as a disinfectant or on the skin as an antiseptic. Greater than 70% v/v solution required. Denatures cell membranes and dehydrates cells.
What is the disinfection level and the agent used?
Intermediate; Alcohol
10% concentration required. 2 types of bleach: CHLORINE AND PEROXIDE. Both peroxide and chlorine bleaches can corrode metal objects if left in contact for too long. Can irritate skin and mucous membranes.
What is the disinfection level and the agent used?
Intermediate to low; Bleach
0.2% concentration required for HLD. Corrosion of metal objects can occur with long contact time. Environmentally safe waste produced after processing.
What is the disinfection level and the agent used?
High to intermediate; Peracetic acid
0.2% concentration required for HLD. Can irreversibly bin proteins to the surface of processed objects, thorough washing required before sterilant treatment. Can irritate skin and mucous membranes.
What is the disinfection level and the agent used?
High; Glutaraldehyde
Enumerate the factors that influence the degree of killing
Concentration of disinfectants
Presence of organic matter
Nature of surface to be disinfected
Temperature
Contact time
pH
Biofilms
Compatibility of disinfectants
What method only destroys vegetative bacteria and what is its temperature and contact time?
Boiling; 100 degreed celsius, 10-15 minutes
what is the temperature and contact time of autoclave for sterilization of culture media, utensils, glass pipettes, and instruments for assays
-121 degrees celsius, 15psi, 15 minutes
Method that is the fastest and simplest method of sterilization that kills organisms, including spore-forming bacteria except PRIONS.
Autoclave
What is the principle of autoclave
moist heat or steam under pressure
what is the temperature and contact time of autoclave for decontamination of medical wastes and used instruments.
-132 degrees celsius, 15psi, 30-60 minutes
what is the biologic indicator in autoclave
Geobacillus stearothermuphilus
Method that is used in the sterilization of high-protein culture media such as Lowenstein Jensen medium for Mycobacteria
Inspissation
Mode of action of inspissation
Thickens the medium through evaporation
Method used to sterilize milk, dairy products, and alcoholic beverages, eliminates food borne pathogens and organisms responsible for spoilage, cannot eliminate bacterial spores.
Pasteurization
Temperature and contact time of inspissation
75-85 degrees, 2 hours, 3 consecutive days
Method that uses dry heat in killing microorganisms through protein denaturation. Suitable for the sterilization of heat-stable objects not penetrated by moist heat. Used to sterilize glasswares, oil products, petrolatum, or powders.
Oven
Temperature and contact time of oven
160-170 degrees, 1.5-2 hours
Method that is used in direct heating. Sterelizes inoculating loops and needles
Flaming
Biologic indicator in oven
Bacillus subtilis var. niger
Temperature for hazardous materials in Incineration
870-980 degrees celsius
Most common method for treating infectious wastes and infected laboratory animal. Destroys prions. Burns materials into ashes at 300-400 degrees celsius.
Incerination
Method used to control the spread of communicable diseases
Cremation
Temperature in cremation
1800 degrees farehnheit (982 degrees celsius)
Method of choice for the sterilization of heat-sensitive compounds or solutions such as antibiotic solutions, toxic chemicals, radioisotopes, vaccines and carbohydrates.
Filtration
What type of filtration uses cellulose acetate/cellulose nitrate membrane with a vacuum
liquid filtration
WHAT CHEMICAL METHOD?
- Precipitates bacterial protein
- Kills bacteria
- Irreversible
Bactericidal
What type of filtration uses 0.45um and 0.80um pores membrane filters
Filtration of bacteria, yeast, and molds
What type of filtration uses HEPA filters that remove organisms larger than 0.3um from isolation rooms, operating rooms, and biological safety cabinets.
Air filtration
Method that uses low energy and is used to sterilize exposed surface air, operating rooms, biosafety cabinets, nurseries, and cafeterias.
Non-ionizing radiation
Method that has a short wavelength, and has high energy. Destroys vegetative cells and endospores of both prokaryote and eukaryote cells. Used to sterilize disposable supplies.
Ionizing radiation
WHAT CHEMICAL METHOD?
- Applied typically to the skin
- Inhibits sepsis formation
Antiseptic
WHAT CHEMICAL METHOD?
- Applied to inanimate objects
Disinfectant
WHAT CHEMICAL METHOD?
- Inhibits the growth of microorganisms
- Reversible
Bacteriostatic
WHAT CHEMICAL METHOD?
MOA: inactivation of proteins and nucleic acids
Has irritable factor and carcinogenic - not recommended for routine disinfection and sterilization
Formaldehyde
WHAT CHEMICAL METHOD?
MOA: inactivation of DNA or RNA
Rapid killing action, not activated by organic matter, but does not penetrate organic matter well.
Used as sterilant or disinfectant depending on the CONTACT TIME
glutaraldehyde
WHAT CHEMICAL METHOD?
MOA: denaturation of protein, dissolution of lipid membrane, and dehydration of cells
Has excellent in-vitro activity against most gram-positive and gram-negative bacteria
Used both as antiseptic and disinfectant
Alcohol
WHAT CHEMICAL METHOD?
MOA: Free iodine degrades microbial cell walls and cytoplasm, denatures and coagulates chromosomal materials.
Used as skin preparation agents for blood collection sites.
Halogens
WHAT CHEMICAL METHOD?
MOA: antibacterial effect is attributed to the oxidative effects of hypochlorous acids formed when chloride ions are dissolved in water
Inexpensive and has a broad spectrum activity
Oldest and most commonly used disinfectants
Chlorine and chlorine compounds
WHAT CHEMICAL METHOD?
MOA: destroys plasma membranes and denatures cell proteins
Has a broad spectrum activity, but not sporicidal
Effective in the presence of organic matter and remains active for long periods of time when applied on surfaces
The first widely used disinfectant and antispetic
Phenol and Phenolic compounds
Most commonly used gas for sterilization
MOA: alkylation of nucleic acids in the spore and vegetative cells
Ethylene Oxide
Active against all vegetative microorganisms and fungal spores
Used to sterilize medical equipment
Peracetic acid
WHAT CHEMICAL METHOD?
MOA: disrupts cell membranes of bacteria resulting in leakage of cell contents
Used as surface-active agents
Inactivated by organic matter
Quaternary Ammonium Compounds
Combined H2O2 and peracetic acid vapors is used in the pharmaceutical and medical devices industries.
Hydrogen peroxide and peracetic acid
Active against all vegetative microorganisms, bacterial endospores, and fungal spores.
Used as sterilant in the pharmaceutical and medical devices industries.
Hydrogen peroxide
Sporicidal disinfectants
Glutaraldehyde
Hydrogen peroxide
Ethylene oxide
Combined Hydrogen peroxide and peracetic acid
Disinfectants inactivated by organic matter
Alcohol
Chlorine and Chlorine compounds
Quaternary Ammonium Compounds
What number of biosafety level where organisms with known potential of infecting healthy individuals
BSL 1
What number of biosafety level where organisms acquired through ingestion, percutaneous, and mucous membrane exposure
BSL 2
What number of biosafety level where organisms possible for aerosol transmission
BSL 3
What number of biosafety level where organisms that may expose extreme risk to laboratory workers and may cause life threatening disease
BSL 4
Category where agents that pose the greatest health threat, easily transmitted, highly infectious, and high mortality rate
Category A
Category where moderately easy to disseminate or transmit. Moderate morbidity and low mortality
Category B
Category where organisms that can be engineered for mass destruction in the future. High mortality and morbidity rates.
Category C
