Chap 7 Flashcards
Sepsis
refers to bacterial contamination
Asepsis
absence of significant contamination
Aseptic surgery techniques
prevent the microbial contamination of wounds
Sterilization
removing and destroying all microbial life
Commercial sterilization
killing Clostridium botulinum endospores from canned goods
Disinfection
destroying harmful microorganisms
Antisepsis
destroying harmful microorganisms from living tissue
Degerming
the mechanical removal of microbes from a limited area
Sanitization
lowering microbial counts on eating utensils to safe levels
Biocide (germicide):
treatments that kill microbes
Bacteriostasis:
inhibiting, not killing, microbes
The usual definition of sterilization is the removal or destruction of all forms of microbial life; how could there be practical exceptions to this simple definition?
Disinfectants and Antiseptics do not kill or remove all bacteria and viruses. Prions and endospores have a high resistance to all forms of sterilization; sterilization implies to the absence of prions.
Effectiveness of treatment depends on
- Number of microbes
- Environment (organic matter, temperature, biofilms)
- Time of exposure
- Microbial characteristics
If the rate of killing is the same, how long will it take to kill all the members of a larger population compared to a smaller population
It will take longer to kill all members of a larger population than a smaller population
How is it possible that a solution containing a million bacteria would take longer to sterilize than one containing a half-million bacteria?
A larger number of bacteria will require more time to be completely killed, as the process of sterilization is a slow one.
Actions of Microbial Control Agents
- Alteration of membrane permeability
- Damage to proteins (enzymes)
- Damage to nucleic acids
Would a chemical microbial control agent that affects plasma membranes affect humans?
A microbial agent that targets the plasma membrane of the microorganism would not be advised because humans also have a plasma membrane.
Thermal death point (T D P):
lowest temperature at which all cells in a liquid culture are killed in 10 min
Thermal death time (T D T):
minimal time for all bacteria in a liquid culture to be killed at a particular temperature
Decimal reduction time (D R T)
Minutes to kill 90% of a specific population of bacteria at a given temperature
What does moist heat sterilization do?
Moist heat coagulates/denatures proteins
Moist heat sterilization involves
- Boiling
- Free-flowing steam
Autoclave
steam under pressure
How does autoclave sterilization work?
- 121 C at 15 psi for 15 min
2.Kills all organisms and endospores - Steam must contact the item’s surface
In moist heat sterilization, large containers require
longer sterilization times
What is used to indicate sterility in moist heat sterilization?
Test strips
Why are containers only filled to 75% of their capacity in an autoclave?
Liquids boil vigorously
Pasteurization
reduces spoilage organisms and pathogens
High-temperature short-time (HTST)
72 C for 15 sec
Thermoduric organisms
survive heat
Dry heat sterilization kills by
oxidation
Examples of dry heat sterilization
Flaming
Incineration
Hot-air sterilization
Filtration
Passage of substance through a screenlike material
Filtration is used for
heat-sensitive materials
High-efficiency particulate air (H E P A) filters remove
microbes > 0.3 micrometers in diameter
Membrane filters remove
microbes > 0.22 micrometers
Membrane filters with pore sizes as small as 0.01 micrometers can filter out
viruses and large proteins
Physical methods of microbial control
- Low temp
- High pressure
- Dessication
- Osmotic pressure
Examples of low temperature having a bacteriostatic effect
Refrigeration
Deep-freezing
Lyophilization (freeze drying)
High pressure denatures
proteins
Desiccation
absence of water prevents metabolism
how does osmotic pressure help control microbes?
uses high concentrations of salts and sugars to create hypertonic environment; causes plasmolysis
Plasmolysis
shrinkage of the protoplasm of a plant cell and is caused due to the loss of water in the cell
protoplasm
the colorless material comprising the living part of a cell, including the cytoplasm, nucleus, and other organelles.
Ionizing radiation examples
(X - rays, gamma rays, electron beams)
How does ionizing radiation inhibit microbial growth?
- Ionizes water to create reactive hydroxyl radicals
- Damages D N A by causing lethal mutations
Nonionizing radiation
ultraviolet, 260 nm
How does non-ionizing radiation control microbial growth?
Damages D N A by creating thymine dimers
How do microwaves affect microbes?
kill by heat; not especially antimicrobial
How is microbial growth in canned foods prevented?
using heat and creating a vacuum to destroy microorganisms and prevent recontamination
Why would a can of pork take longer to sterilize at a given temperature than a can of soup that also contained pieces of pork?
Solid foods heat unevenly because of the uneven distribution of moisture.
What is the connection between the killing effect of radiation and hydroxyl radical forms of oxygen?
These radicals are produced from ionizing radiation that take electrons from other molecules.
4 Principles of Effective Disinfection
1.Concentration of disinfectant
2.Organic matter
3.p H
4.Time
What is a Use-Dilution test?
minimal inhibitory concentration of an antimicrobial to inhibit or kill the bacteria/fungi
a laboratory method used to assess the effectiveness of a liquid disinfectant on hard, nonporous surfaces by exposing a standardized test carrier (like a stainless steel cylinder) coated with a known bacteria to a specific dilution of the disinfectant for a set time, then checking if the bacteria are still viable after incubation
Explain the process of Use-Dilution Tests
- Metal cylinders are dipped in test bacteria and dried
- Cylinders are placed in disinfectant for 10 min at 20 C
- Cylinders are transferred to culture media to see if bacteria survived treatment.
Disk-Diffusion Method is used to
Evaluates efficacy of chemical agents
How does the disk diffusion method work?
- Filter paper disks are soaked in a chemical and placed on a culture
- Look for zone of inhibition around disks
If you wanted to disinfect a surface contaminated by vomit and a surface contaminated by a sneeze, why would your choice of disinfectant make a difference?
vomit typically contains a wider variety of microorganisms, including bacteria, viruses, and parasites, which might require a disinfectant with a broader spectrum of killing power, while a sneeze usually contains primarily viruses and some bacteria, potentially allowing for a more targeted disinfectant depending on the suspected pathogen.
Which is more likely to be used in a medical clinic laboratory, a use-dilution test, or a disk-diffusion test?
the disk-diffusion test is the standard method for determining a bacteria’s susceptibility to antibiotics, which is a crucial aspect of patient care in a clinical setting.
Phenol and phenolics injure
lipids of plasma membranes, causing leakage
Bisphenols are made of
two phenol groups connected by a bridge
The two phenols connected by a bridge in bisphenols are
Hexachlorophene and triclosan
Function of bisphenols
Disrupt plasma membranes
What are biguanides?
a class of oral medications that help control blood sugar levels, and include metformin
Chlorhexidine is a type of
Biguanide
Chlorhexidine and biguanides are used in
surgical hand scrubs; can clean the skin after an injury, before surgery, or before an injection.
what do biguanides do?
Disrupt plasma membranes
What are essential oils
Mixtures of hydrocarbons extracted from plants
Peppermint oil, pine oil, orange oil
uses of essential oils
Used for centuries in traditional medicine and for preserving food
What causes the microbial action in essential oils?
primarily due to phenolics and terpenes
Essential oils have stronger activity against
gram-positive bacteria; effectiveness against viruses not studied to date
How does iodine affect microbes
Impairs protein synthesis and alters membranes
Iodine tincture
solution in aqueous alcohol
Iodophor
Iodine combined with organic molecules
How does chlorine affect microbes?
Oxidizing agents; shut down cellular enzyme systems
Bleach
hypochlorous acid (H O C l)
Chloramine
chlorine + ammonia
What do alcohols do to microbes?
Denatures proteins and dissolves lipids
Alcohols have no effect on
endospores and nonenveloped viruses
Ethanol and isopropanol require
water
Oligodynamic action of heavy metals and their compounds
very small amounts exert antimicrobial activity
What do heavy metals and their compounds to to microbes?
Denature proteins
Heavy metals and their compounds
Ag, Hg, Cu, Zn
Silver nitrate is used to prevent
ophthalmia neonatorum
Mercuric chloride prevents
mildew in paint
Copper sulfate is an
algicide
Zinc chloride is found in
mouthwash
soap
Degerming; emulsification
Acid-anionic sanitizers
Anions react with the plasma membrane
Quarternary ammonium compounds quats
Cations are bactericidal, denature proteins, disrupt plasma membrane
Sulfur dioxide prevents
wine spoilage
organic acids inhibit
metabolism
Sorbic acid, benzoic acid, and calcium propionate prevent
molds in acidic foods
Nitrites and nitrates prevent
endospore germination
What are Bacteriocinsproteins?
proteins or peptides produced by bacteria that can kill or inhibit the growth of other bacteria
Nisin and natamycin (pimaricin) prevent spoilage of
cheese
Examples of antibiotics
nisin, natamycin, bacteriocinsproteins
How do aldehydes prevent microbial activity?
Inactivate proteins by cross-linking with functional groups
When are aldehydes used?
preserving specimens and in medical equipment
Formaldehyde and ortho-phthalaldehyde
Glutaraldehyde is one of the few liquid chemical sterilizing agents
one of the few liquid chemical sterilizing agents
Glutaraldehyde
How does chemical sterilization work?
Gaseous sterilants cause alkylation-replacing hydrogen atoms of a chemical group with a free radical
what sterilization technique Cross-links nucleic acids and proteins?
Chemical sterilization
What is used to sterilize heat-sensitive material?
Ethylene oxide
Plasma
Fourth state of matter, consisting of electrically excited gas
How does plasma help sterilize?
Free radicals destroy microbes
Plasma sterilization is used for what kind of instruments?
Tubular instruments
What are supercritical fluids?
CO2 with gaseous and liquid properties
What are supercritical fluids used to sterilize?
medical implants
Peroxygens and Other Forms of Oxygen are what kind of agents?
oxidizing agents
Peroxygens and Other Forms of Oxygenare used to sterilize
contaminated surfaces and food packaging
Examples of Peroxygens and Other Forms of Oxygen
O3, H2O2, and peracetic acid
Why is alcohol effective against some viruses and not others?
Enveloped viruses have a lipid membrane, while nonenveloped viruses are those without a lipid membrane. Generally, nonenveloped viruses are more resistant to disinfectants. Isopropyl alcohol works against enveloped viruses but not against nonenveloped viruses.
Is Betadine an antiseptic or a disinfectant when it is used on skin?
Yes, Betadine is both an antiseptic and a disinfectant when used on skin:
- Antiseptic: Betadine prevents the growth of bacteria that cause infections.
- Disinfectant: Betadine kills bacteria, fungi, and viruses on the skin by damaging their proteins
What characteristics make surface-active agents attractive to the dairy industry?
Acid-Anionic Sanitizers: important in cleaning dairy utensils and equipment; Non-toxic; non-corrosive; and fast acting.
What chemical disinfectants can be considered sporicides?
PGBEP
1.Phenols; 2.Glutaraldehyde; 3.B-Propiolactone;
4.Ethylene oxide ;
5.Peroxy acids.
What chemicals are used to sterilize?
Alcohol.
Chlorine and Chlorine Compounds.
Formaldehyde.
Glutaraldehyde.
Hydrogen Peroxide.
Iodophors.
Ortho-phthalaldehyde (OPA)
Peracetic Acid.
Effect against endospores Glutaraldehyde
Fair
Effect against endospores chlorines
Fair
Effect against endospores alcohols
poor
Effect against endospores iodine
poor
Effect against endospores phenolics
poor
Effect against endospores chlorhexidine
none
Effect against endospores bisphenols
none
Effect against endospores quats
none
Effect against endospores silver
none
Effect against mycobacteria Glutaraldehyde
Good
Effect against mycobacteria chlorines
Fair
Effect against mycobacteria alcohols
Good
Effect against mycobacteria Iodine
Good
Effect against mycobacteria Phenolics
Good
Effect against mycobacteria Chlorhexidine
Fair
Effect against mycobacteria Bisphenols
None
Effect against mycobacteria Quats
none
Effect against mycobacteria Silver
none
The presence or absence of endospores has an obvious effect on microbial control, but why are gram-negative bacteria more resistant to chemical biocides than gram-positive bacteria?
Gram-negative bacteria are generally more resistant to chemical biocides than gram-positive bacteria because they possess an outer membrane, which acts as a protective barrier, preventing many chemicals from easily penetrating the cell and reaching their target sites within the bacteria;
Gaseous sterilants cause alkylation-
replacing hydrogen atoms of a chemical group with a free radical
