Lecture 11 - Microbial Control Flashcards
Four possible outcomes microbial control outside the body
sterilization
disinfection
antisepsis
decontamination
what is the primary targets of microbial control?
microorganisms capable of causing infection or spolage
Considered the most resistant microbial entities
bacterial endospores
Destruction of endospores is the goal of ____.
sterilization
most resistant type of microbial forms
- prions
least resistant type of microbial forms
- enveloped viruses
A process that destroys or removes all viable microorganisms, including viruses.
sterilization
any material that has been subject to sterilization
sterile
sterilized products are essential to human well being (3)
- surgical instruments
- syringes
- commercially packaged foods
The use of a physical process or a chemical agent to destroy vegetative pathogens but not bacterial endospores.
disinfectection
are normally only used on inanimate objects
disinfectants
the growth of microorganisms in blood and other tissues
sepsis
any practice that prevents the entry of infectious agents into sterile tissues and prevents infection
asepsis; aseptic techniques
chemical agents that kill microorganisms
germicide and microbicide
chemical that destroys bacteria except for those in endospore stage
bactericide
kills fungal spores, hyphae, and yeasts
fungicide
inactivates viruses, especially on living tissue
virucide
capable of killing endospores
sporicide
Prevent the growth of bacteria on tissues or objects in
the environment
bacteriostatic agents
Inhibit fungal growth
fungistatic chemicals
Chemicals used to control microorganisms in the body (antiseptics and drugs)
microbistatic agents
Any cleansing technique that mechanically removes
microbes and debris
• Reduces contamination to safe levels
sanitization
- reduction of the # of microbes on the skin
- involves scrubbing the skin or immersing it in chemicals or both
- emulsifies oils on the outer cutaneous layer
- mechanically removes potential pathogens on the outer layers of the skin
antisepsis/degermation
expected to come into contact with sterile tissues
critical medical devices
comeinto contact w/t mucosal membranes
semi critical medical devices
those that not touch the patient or are only expected to touch intact skin
non critical medical devices
factors that affect death rate (7)
- # of microorganisms
- nature of the microbes the population
- type of microbial growth
- tempt and pH of environment
- concentration of the agent
- mode of action of the agent
- presence of solvents, interfering organic matter, and inhibitors
• Cellular targets of physical and chemical agents:
- cell wall
- cell membrane
- DNA RNA
- proteins
how protein can be altered (3)
- complete denaturation
- different shape
- blocked active site
are inserted into the lipid bilayer to disrupt it and create abnormal channels that alter permeability and cause leakage both into and out the cell
surfactant molecules
the most widely used method of microbial controls
heat
other methods of microbial control
radiation
filtration
ultrasonic waves
cold
Hot water, boiling water, steam
Temperature ranges from 60°C - 135°C
moist heat
air with a low moisture content that has been heated by a flame or electric heating coil
160c - 1000c
dry heat
exhibit the greatest resistance to disinfection methods
bacterial endospores
destruction of spores usually requires
temperatures above boiling
vary in their sensitivity to heat
vegetative cells
the shortest length of time required to kill all test microbes at a specified temperature
thermal death time
the lowest temperature required to kill all microbes in a sample in 10 minutes
thermal death point
methods of moist heat
boiling water, pasteurization, non pressurized steam, steam under pressure
2 methods for dry heat
hot air and incineration
merely retards the activities of most microbes.
cold treatment
dehydration of vegetative cells directly exposed to normal room air
desiccation
a combination of freezing and drying
lyophilization
Energy emitted from atomic activities and dispersed at high velocity
through matter or space
radiation
radiation suitable for microbial control
gamma rays
x rays
UV radiation
– Bombardment of microbes with radiation
irradiation
– Radiation ejects orbital electrons from an atom, causing ions to form
– Causes the most damage to proteins
ionizing radiation
– Excites atoms, raising them to a higher energy state
– Leads to the formation of abnormal bonds within molecules such as DNA
– UV: Form pyrimidine dimers
non ionizing radiation
An effective method to remove microbes from air and liquids
• Fluid is strained through a filter with openings large enough for liquid to pass through, but too small for microbes to pass through
filtration
when is filtration used
- when liquids cannot withstand heat
- decontaminating milk andbeer
- water purification
- removing airborne contaminants
- Adding large amounts of salt or sugar to foods creates a hypertonic environment.
- causes plasmolysis in bacteria
- makes it impossible for microbes to multiply
osmotic pressure
antimicrobial chemicals
solid
liquid
gaseous
solvents containing pure water as the solvent
aqueous solution
antimicrobial chemicals dissolved in pure alcohol or water alcohol mixtures
tinctures
– Rapid action in low concentrations
– Solubility in water or alcohol and long-term stability
– Broad-spectrum microbicidal action without toxicity to human and animal tissues
- Penetration of inanimate surfaces to sustain a cumulative or persistent action
desirable qualities of a germicide
- resistance to becoming inactivated by organic matter
- noncorrosive or nonstaining properties
- sanitizing and deodorizing properties
- affordability and ready availability
desirable qualities of a germicide
critical items that are not heat sterilizable
high level germicides
used to disinfect semi critical items (respiratory equipment and thermometers)
intermediate-level germicides
used to clean noncritical materials (electrodes and straps)
low-level germicides
5 factors that affect the microbicidal activity of chemicals
- nature of microorganisms being treated.
- nature of material being treated
- degree of contamination
- time of exposure
- strength and chemical action of the germicide
Fluorine, bromine, chlorine, iodine,
microbicidal, and sporicidal
the active ingredients in 1/3 of all antimicrobial chemicals
halogens
types of chlorine based products
- gaseous chlorine
- hypochlorites
- chloramines
hypochlorites
bleach
chloramines
alternative to chlorine
types of iodine based products
free iodine
iodophors
– All classes of organisms are killed by iodine if proper concentrations and exposure times are used
– Not adversely affected by organic matter
iodophors
applications of iodine
Aqueous iodine
Iodine tincture
Iodine tablets
Iodophors
– First used as the major antimicrobial chemical
– Toxic and irritating side effects
phenol
– Destroy vegetative bacteria, fungi, and some viruses
– Able to act in the presence of organic matter
phenolics
applications of phenol
- cresols
- bisphenols
- triclosan
- chlorhexidine
what alcohols are appropriate for microbial control
ethyl and isopropyl
destroys vegetative microbial forms but not endospores, more effective against enveloped viruses than non-enveloped viruses
alcohol
- Germicidal effects are due to toxic reactive oxygen
* Bactericidal, virucidal, fungicidal, and sporicidal at high concentrations
hydrogen peroxide
Skin and wound cleansing, bedsore care, mouthwashes
antiseptic
Soft contacts, surgical implants, plastic equipment, etc.
disinfectant
used for small industrial items and larger enclosed spaces
vaporized hydrogen peroxide
similar effects to hydrogen peroxide
ozone
Limited microbicidal power
• Activity due to amphipathic nature of the molecule
surfactants
Disinfectants: mixed with cleaning agents to sanitize a variety of objects and surfaces
– Preservatives for ophthalmic solutions and cosmetics
quaternary ammonium compounds
– Weak microbicides
– Pseudomonas grows abundantly in soap dishes
– Mainly used for mechanical removal of microbes
– More germicidal when combined with chlorhexidine or iodine
soaps
toxic minute quantities
oligodynamic
have significance as germicides
mercury and silver
drawbacks to heavy metal compounds
- toxic to humans if ingested
- cause allergic reactions
- neutralized by biological wastes
- microbes can develop resistance to microbes
Rapid, broad spectrum, accepted as a sterilant
– Retains potency in the presence of organic matter
glutaraldehyde
– Formalin: aqueous solution
– Intermediate- to high-level disinfectant
– Extremely toxic
formaldehyde
– Similar to glutaraldehyde
– Less irritating
– Does not destroy endospores
ortho-phthaldehyde (OPA)
– Chemiclave: chemical sterilization
– Explosive, causes damage to lungs, eyes, and mucous membranes
ethylene oxide
– Used for water treatment
– Used to disinfect Congress after the anthrax attacks in 2001
chlorine dioxide
Incorporated into solutions and ointments to treat skin infections.
dyes
used for antisepsis and wound treatment
yellow acridine dyes
limited applications of dyes
- stain
- narrow spectrum of activity
• Detergents, cleansers, and deodorizers
aqueous ammonium oxide
- Used in food preservation
* Acetic acid, propionic acid, lactic acid, benzoic acid, and sorbic acid
organic acids
Excreted in the urine of 75% of Americans
• Detectable levels in groundwater sources
• Creates dioxin-like compounds when exposed to sunlight
• Promotes resistance to triclosan and other antibiotics
triclosan
can penetrate a solid barrier, bombard a cell, enter it, and dislodge electrons from molecules - proteins damage
ionizing
enters a cell, strikes molecules, and excites them (formation of abnormal bonds)
nonionzing
