Chapter 5 Flashcards
introduced methods to prevent
infection of wounds
Joseph Lister
Applied what directly onto damaged tissues, where it prevented infections
carbolic acid (phenol)
introduced as a surgical antiseptic
Listerine
Oral antiseptic names after Lister
Listerine
removal of all microorganisms
Sterilization
is free of microbes including endospores and
viruses (but does not consider prions)
sterile
elimination of most or all pathogens
* Some viable microbes may remain
Disinfection
used on inanimate objects
Disinfectants
kill bacteria
Bactericides
kill fungi
Fungicides
inactivate viruses
Virucides
used on living tissue
Antiseptics
reduce pathogens to levels considered safe
to handle.
Decontamination:
examples of Decontamination:
Washing, use of heat or chemicals
substantially reduced microbial population that meets accepted health standards
Sanitization
process of delaying spoilage of foods and other
perishable products
Preservation:
growth-inhibiting
bacteriostatic
brief heating to reduce number of spoilage organisms, destroy pathogens without changing characteristics of product
Pasteurization
routine control
washing and scrubbing with soaps and detergents
cooking
foods, cleaning surfaces, and refrigeration
Pathogens more likely found in hospital setting.
healthcare-associated infections (HAIs)
Pathogens more likely found in hospital setting are in what
Feces, urine, respiratory droplets, bodily secretion
more susceptible to infection
Weakened patients
are used in patient
care to prevent infection of both patients and personnel.
Standard Precautions
highly transmissible or epidemiologically important
pathogen
Transmission-Based Precautions
very difficult to destroy
prions
prevent contamination of samples,
workers and environment
Aseptic techniques
For work with microbes not known to cause disease in healthy people
BSL-1
For work with moderate-risk microbes that cause
disease but have limited potential for transmission
BSL-2
Procedures for work with pathogens that cause
serious or potentially fatal disease through inhalation
BSL-3
Procedures for work with easily transmitted deadly
pathogens
BSL-4.
Perishables retain quality longer when
contaminating
microbes destroyed, removed, inhibited
most common and reliable mechanism for retaining perishables
heat treatment
approved to treat certain foods without altering
irradiation
can prevent spoilage (regulated by FDA
due to risk of toxicity)
Chemical additive
Ensure drinking water free of pathogens
Water Treatment Facilities
Choice of effective procedure depends on what numerous factors
- Type and number of microbes
- Environmental conditions
- Risk of infection
- Composition of infected item
Multiple highly resistant microbes
- Bacterial endospores
- Protozoan cysts and oocysts
- Mycobacterium species
- Pseudomonas species
- Non-enveloped viruses
most resistant, only extreme heat or chemical treatment destroys them
Bacterial endospores
resistant to disinfectants;
excreted in feces; causes diarrheal disease if ingested
Protozoan cysts and oocysts
waxy cell walls makes resistant to many chemical treatments
Mycobacterium species
resistant to and can actually grow in some disinfectants
Pseudomonas species
lack lipid envelope; more resistant to disinfectants
Non-enveloped viruses
Fraction of population what during given time interval
dies
is the population bigger or smaller with more time
bigger
Removing organisms by what reduces time to sterilize
washing
helps remove biofilms
scrubbing
gauges commercial effectiveness
Decimal reduction time
Time required to kill 90% of
population under specific
conditions
Decimal reduction time
can interfere with heat penetration, action of chemicals
Dirt, grease, body fluids
Microorganisms in what are more resistant
biofilm
can influence effectiveness
pH, temperature
come in contact with body tissues
Critical items
what level of sanitization must Critical items be
sterile
contact mucous membranes but do not penetrate body tissues
Semicritical instruments
what level of sanitization must Semicritical instruments be
Must be free of viruses and vegetative bacteria
contact unbroken skin only
Non-critical instruments
inappropriate for plastics and other sensitive items
heat
provides alternative, but damages some types of
plastic
Irradiation
cannot be used to treat moisture-sensitive material
Moist heat, liquid chemical disinfectants
can be used on materials that cannot withstand heat treatment
Filtration, irradiation, and high-pressure treatment
irreversibly denatures protein
Moist heat
destroys most microorganisms and viruses
boiling
does boiling kill endospores and sterilize
no
destroys heat-sensitive pathogens, spoilage
organisms
Pasteurization
most products classify as what kind of Pasteurization
High-temperature-short-time (HTST)
shelf-stable boxed juice and
milk; known as “ultra pasteurization”; packaged in sterile containers
Ultra-high-temperature (UHT)
used to sterilize using pressurized steam
autoclave
does autoclave kill endospores and sterilize
yes
Physical methods to Destroy Microorganisms and Viruses
steam must enter item and displace air
Tape with a heat-sensitive indicator can confirm heating
how to make sure steam enters item and displace air
– Place long, thin containers on their sides
– Do not close containers tightly
can confirm lack of microbial growth after autoclaving
Biological indicators
industrial-sized autoclave
retort
Designed to destroy Clostridium botulinum endospores
Commercial Canning Process
what uses retort
Commercial Canning Process
Cells grow in low-acid anaerobic conditions and produce
botulinum toxin
what endospores remain in Canned food
Endospores of some thermophiles may survive
Usually not a concern; only grow at temperatures well above normal storage
Less effective than moist heat; longer times, higher
temperatures necessary
Dry heat
a method of dry heat sterilization
Incineration
Oxidizes cell to ashes
Incineration
Used to destroy medical waste and animal carcasses
Incineration
example of Incineration
Laboratory inoculation loop sterilized by flaming
types of Filtration of fluids
Membrane filters
Depth filters
Small pore size (0.2 µm) to remove bacteria
Membrane filters
– Thick porous filtration
material (e.g., cellulose)
– Larger pores
– Electrical charges trap cells
Depth filters
High-efficiency particulate air (HEPA) filters remove nearly
all microbes over 0.3 micrometer from air
Filtration of air
radio waves,
microwaves, visible and UV light, X rays, and gamma rays.
Radiation: electromagnetic radiation:
are wavelength and frequency inversely or directly proportional
inversely
does High frequency or low frequency have more energy
High frequency
can remove electrons from atoms
Ionizing radiation
Destroys DNA, damages cytoplasmic membranes and
produce ROS (reactive oxygen species)
Ionizing radiation
– Used to sterilize heat-sensitive materials
High energy gamma-rays
Generally used after packing
High energy gamma-rays
FDA has approved for spices and dried herbs, fruits,
vegetables, and grains (insect control), pork (parasite control), and poultry, beef, lamb, and pork (bacterial control)
High energy gamma-rays
destroys microbes directly b y damaging DNA
Ultraviolet radiation
Used to destroy microbes in air, water, and on surfaces
Ultraviolet radiation
downsides of Ultraviolet radiation
Poor penetrating power
– Thin films or coverings can limit effect
– Cannot kill microbes in solids or turbid liquids
– Most glass and plastic block
heat food unevenly, so cells can survive
Microwave ovens
kill by generated heat, not directly
microwaves
Decreases number of microorganisms in commercial food products by Employs high pressure up to 120,000 psi
High Pressure Processing (HPP)
Products maintain color, flavor associated with fresh food
High Pressure Processing (HPP)
Destroys microbes by denaturing proteins and altering cell
permeability
High Pressure Processing (HPP)
types of moist heat
boiling
pasteurization
pressurized steam
types of dry heat
incineration
dry heat ovens
types of filtration
filtration of fluids
filtration of air
types of radiation
ionizing radiation
ultraviolet radiation
can disinfect and, in some cases, sterilize
Germicidal chemicals
do Germicidal chemicals react irreversibly with proteins, DNA, cytoplasmic membranes, or viral envelopes. or reversibly
irreversibly
useful for treating large surfaces and heat-sensitive items
Germicidal chemicals
types of Germicidal chemicals
- Sterilants
- High-level disinfectants
- Intermediate-level disinfectants
- Low-level disinfectants
destroy all microorganisms
Sterilants
destroy viruses, vegetative cells
High-level disinfectants
destroy vegetative bacteria,
mycobacteria, fungi, and most but not all viruses
Intermediate-level disinfectants
destroy fungi, vegetative bacteria except mycobacteria, and enveloped viruses
Low-level disinfectants
things to note about Germicidal Chemical
- Toxicity
- Activity
- Compatibility
- Residues: can be toxic or corrosive
- Cost and availability
- Environmental risk: Agent may need to be neutralized before disposal
60–80% aqueous solutions of ethyl or isopropyl alcohol
Alcohols
what don’t Alcohols kill
endospores, some naked viruses
Damage membranes, denature essential proteins
Alcohols
Commonly used as antiseptic and disinfectant
alcohol
benefits of alcohol
non-toxic, inexpensive, no residue
limitations of alcohol
- Evaporates quickly, limiting contact time
- Can damage rubber, some plastics, and others
inactivates proteins and nucleic acids
Aldehydes
Immersion in what for 10–12 hours kills all microbial life
type of Aldehyde: 2% alkaline glutaraldehyde
is 2% alkaline glutaraldehyde toxic
yes
Effective germicide that kills most microbes quickly
type of Aldehyde: Formaldehyde
Used to kill bacteria and inactivate viruses for vaccines
type of Aldehyde: Formaldehyde
is Formaldehyde a carcinogen
yes
Extensive use as antiseptics that Stays on skin, mucous membranes
Biguanides
type of Biguanides
Chlorhexidine
is Chlorhexidine toxic
Relatively low toxicity
Destroys vegetative bacteria, fungi, some enveloped viruses
Chlorhexidine
what is Chlorhexidine used in
skin cream, prescription
mouthwash
Useful gaseous sterilant – applied with special chamber
Ethylene oxide
Destroys microbes including endospores and viruses
Ethylene oxide
Penetrates fabrics, equipment, implantable devices like Pacemakers, artificial hips
Ethylene oxide
Ethylene oxide is useful in sterilizing what
heat- or moisture-sensitive items
Ethylene oxide is used for what lab items
Petri dishes, pipettes
Ethylene oxide limitations
- toxic (must be extensively aired), explosive,
mutagenic and potentially carcinogenic - Must be eliminated by heated forced air for 8 to 12 hours
oxidize proteins, cellular components
halogen
Destroys all microorganisms and viruses
- Used as disinfectant
type of halogen: chlorine
what dilution of chlorine is most effective
- 1:100 dilution
Very low levels disinfect drinking water
chlorine
Can react with organic compounds in water
chlorine
Kills vegetative cells, unreliable on endospores
type of halogen: iodine
Used as tincture
type of halogen: iodine
antimicrobial chemical dissolved in alcohol in
alcohol
tincture
High concentrations too toxic to be used medically
Metal Compounds
still used as an antiseptic: creams, bandages
silver
once widely used as preservatives
Compounds of mercury, tin, copper
Unstable form of oxygen
Ozone (O3)
Decomposes quickly and Powerful oxidizing agent
Ozone (O3)
Ozone (O3) is an alternative for what
chlorine
powerful oxidizers used as sterilants
Peroxygens
are Peroxygens biodegradable
yes
Readily biodegradable, no residue
are Peroxygens toxic
Less toxic than ethylene oxid
Hydrogen peroxide is most effective on what
More effective on inanimate object (vs. tissues)
does Hydrogen peroxide damage materials
Doesn’t damage most materials, no residue
more potent than H2O2
Peracetic acid
Effective on organic material
Peracetic acid:
Sterilizes in less than 1 hour; useful on wide range of material
Peracetic acid
one of earliest disinfectants
Phenol (carbolic acid)
Has unpleasant odor and irritates skin
Phenol (carbolic acid)
kill most vegetative bacteria but not all viruse
Phenolics
benefits of Phenolics
Wide activity range, reasonable cost, non-toxic for skin applications, remain effective in presence of detergents and organic contaminants
type of Quaternary Ammonium Compounds
Cationic (+ charged) detergents
Positive charges of quats attracted to negative charges of cell surface
Cationic (+ charged) detergents
benefits of Cationic (+ charged) detergents
Low toxicity, disinfection of food preparation surfaces
what resists Cationic (+ charged) detergents
Pseudomonas
where are Cationic (+ charged) detergents found
personal care products
Food preservatives must be non-toxic for safe ingestion
Chemical preservatives
- Affect cell membrane function
- Control molds and bacteria in foods
Weak organic acids (benzoic, sorbic, propionic)
used in processed meats
Nitrate and nitrite
Inhibit endospore germination and vegetative cell growth
Nitrate and nitrite
are Nitrate and nitrite carcinogenic
yes when converted to nitrosamines by
cooking or intestinal bacteria
inhibits growth of pathogens and spoilage organisms by slowing or stopping enzyme reactions
Refrigeration
preserves by stopping all microbial growth
Freezing
killed by ice crystal formation, but many survive and can grow once thawed
microbial cells
water exits bacterial cells
plasmolysis
bacteria that grow in high salt environments
Staphylococcus aureus
freeze drying foods
Lyophilization
stops microbial growth but does not reliably kill
Drying
