94 terms


complete destruction of all forms of microbial life
destroys most microbial life, reducing contamination on inanimate surfaces. Does not kill spores
destroys most microbial life, reducing contamination on a living surface
the mechanical removal of most microbes from an animate or inanimate surface
Physical Agents
DRY - incineration or dry oven=sterilization or moist-steam under pressure=sterilization or boiling water, hot water and pasteurization-disinfection. RADIATION - Ionizing: x-ray, cathode, and gamma=sterilization or nonionizing: UV=disinfection
Chemical Agents
Gases: sterilization or disinfection
Liquids: Animate-antisepsis or inanimate-disinfection or sterilization
Mecanical Removal Methods
Filtration: Air and liquid both decomination
What are the primary targets od microbial control
microorganisms that can cause infection or spoilage that are constantly present in the external environment
What are the contaminants that need to be controlled
Bacterial vegetative cells and endospores (so resistant, the goal is sterilization)
Fungal hyphae and spores
Protozoan trophozoites and cysts
to kill
Name some "cides" and their functions
Bactericide: chemical that destroys bacteria (not endospores)
Fungicide: a chemical that can kill fungal spores, hyphae, and yeasts
Virucide: a chemical that inactivates viruses
Sporicide: can destroy bacterial endospores
Germicide and microbicide: chemical agents that kill microorganisms
Stasis and static
To stand still
name and functions of some statics
Bacteristatic: prevent the growth of bacteria
Fungistatic: inhibit fungal growth
Microbistatic: materials used to control microorganisms in the body, for example
what are some concerns with microbial control
*Does the application require sterilization, or is disinfection adequate?
*Is the item to be reused or permanently discarded?
*If it will be reused, can it withstand heat, pressure, radiation, or chemicals?
*Is the control method suitable for a given application?
*Will the agent penetrate to the necessary extent?
*Is the method cost- and labor-efficient, and is it safe?
Microbial death
sustained metobolic or structural damage to the point of losing the ability to reproduce.
Factors that Influence the Action of Antimicrobial Agents
1)The number of microorganisms
2)The nature of the microorganisms in the population
3)The temperature and pH of the environment
4)The concentration of the agent
5)The mode of action of the agent
6)The presence of solvents, interfering organic matter, and inhibitors
How do antimicrobial agents work against the cell wall
blocking synthesis, digesting it, breaking down its surface, or cell becomes fragil and is lysed easily
How do antimicrobial agents work against the cell membrane
surfactants (polar molecules) lower the surface tension of the cell membrane
How do antimicrobial agents work against the cells Protein and Nucleic Acid Synthesis:
Binds to ribosomes to stop translation, binds irreversibly to DNA preventing transcription and translation, or mutagenic agents
How do antimicrobial agents work against the cells Protein function
Some modes affect the binding sites of the substate be denaturation by breaking down some of the secondary or tertiary bonds causing complete unfolding, random bonding or incorrect folding or interfering with binding
elevated temperature (exceeding maximum growth temperature
lower temperatures (below the minimum growth temperature)
2 physical states of heat
Dry and moist
Forms of moist heat and the temps and times to kill
Hot and boiling water or steam. ranging from 60 C and 135 C

121C 15 min
125C 10 min
134C 3 min
Forms of dry heat and the temps and times to kill
flame or electric coil 160C to thousands of degrees
121C 600 min
140C 180 min
160C 120 min
170C 60 min
Thermal death time
the shortest length of time required to kill all test microbes at a specified temperature
Thermal death point
the lowest temperature required to kill all microbes in a sample in 10 minutes
what are the practical concerns in the use of heat
* Temp and length of exposure
* Higher temps generally shorter ecposure; lower temps generally require longer exposure
* Thermal Death time
* Thermal Death Point
Common Methods of Moist Heat Control
1) Steam under pressue
2) Nonpressurized steam
3) Pasteurization
4) Boiling water
Steam under pressure
auto clave, pressure cooker, steam under pressure is hotter than free flowing steam or boiling proportional to the amount of pressure. Increased pressure enables temperature to be higher. At normal atmospheric pressure (15 psi) water boils at 100C and stema is the same temp, at higher pressures steam is hotter. 20 psi steam is 109C
intermittent sterilization for substances that cannot withstand autoclaving. Sterilize materials with 100C steam for 30 min.incubate 23-24 hours treat again repeat for 3 consecutive days with incubation periods,
* Used to disinfect beverages
*Heat is applied to liquids to kill potential agents of infection and spoilage, while retaining the liquid's flavor and food value
*Special heat exchangers
-Flash method: expose to 71.6°C -for 15 seconds
*Batch method: expose to 63°C to 66°C for 30 minutes
*Does not kill endospores or thermoduric microbes
boiling water
disinfection. single processing will not kill all resistant cells but will kill most non-spore forming pathogens including resisitant species. Major drawback is that items can be recontaminated after it leaves the water.
dry heat
direct flaming, incineration, hot air sterilization.
Dry Oven
*Usually an electric oven
*Coils radiate heat within an enclosed compartment
*Exposure to 150°C to 180°C for 2 to 4 hours
*Used for heat-resistant items that do not sterilize well with moist heat
Cold and Desiccation
* To slow growth of cultures and microbes in food during processing and storage
* Cold does not kill most microbes; freezing can actually preserve cultures
* Desiccation
* Lyophilization
dehydration of vegetative cells when directly exposed to normal room air
a combination of freezing and drying; used to preserve microorganisms and other cells in a viable state for many years
Are microbes adeversley affected by cold temps
Some are but most are not, some freezing temps actually preserve cultures.
energy emitted from atomic activities and dispersed at high velocity through matter or space
which forms of radiation are used for microbial control
Gamma rays - most penetrating
X rays - intermediate
Ultraviolet radiation - least penetrating
ionizing radiation
Fast-moving alpha or beta particles or high-energy radiation (gamma rays) emitted by radioisotopes. They have enough energy to dislodge one or more electrons from atoms they hit, forming charged ions in tissue that can react with and damage living tissue. Compare nonionizing radiation.
advantages to Ionizing radiation
speed, high penetrating power, and absence of heat
disadvantages to ionizing radiation
main one is potential dangers to machine operators from exposure to radiation and [ossible damage to some materials
nonionizing radiation
excites electrons and causes them to make new covalent bonds, which affects the 3-D structure of Proteins and Nucleic acids
characteristics of UV rays
*Wavelength approximately 100 nm to 400 nm
*Germicidal lamp: 254 nm
*Not as penetrating as ionizing radiation
*Powerful tool for destroying fungal cells and spores, bacterial vegetative cells, protozoa, and viruses
Applications of UV rays
*Usually disinfection rather than sterilization
*Hospital rooms, operating rooms, schools, food prep areas, dental offices
*Treat drinking water or purify liquids
what are the filters made from
thin membranes of cellulose, acetate, polycarbonate, and a variety of plastics
applications of filtration
*Prepare liquids that can't withstand heat
*Can decontaminate beverages without altering their flavor
*Water purification
*Removing airborne contaminants (HEPA filters)
forms of chemical agents
liquid, gaseous, or solid
solutions dissovled in alcohol or water-alcohol
why choose Microbicidal Chemical
*Rapid action even in low concentrations
*Solubility in water or alcohol and long-term stability
*Broad-spectrum microbicidal action without being toxic to human and animal tissues
*Penetration of inanimate surfaces to sustain a cumulative or persistent action
*Resistance to becoming inactivated by organic matter
*Noncorrosive or nonstaining properties
*Sanitizing and deodorizing properties
*Affordability and ready availability
Factors that Affect the Germicidal Activity of Chemicals
*Nature of microorganisms being treated
*Nature of the material being treated
*Degree of contamination
*Time of exposure
*Strength and chemical action of the germicide
what is the concentration and exposure times for chlorine to kill mycobacterium, entamoeba cysts and Hepatits A?
Myco: 50 ppm in 50 secs
Enta: 0.1 ppm in 150 min
Hepatits 3ppm in 30 mins
what is the concentration and exposure times for Ethyl Alcohol to kill S. aureus, E coli and polio
S. Aureus: 70% 10 min
E.coli: 70% 2 min
polio 70% 10 min
what is the concentration and exposure times for Hydrogen Peroxide to kill S. Aureus, Gonorrhoeae and herpes
S. aureaus: 3% at 12.5 secs
Gonorrhoeae: 3% at 0.3 secs
Herpes: 3% at 12.8 secs
what is the concentration and exposure times for Quantery ammonium compound to kill S. Aureus and Salmonella
s. aureus: 450 ppm at 10 min
salmonella 300 ppm at 10 min
what is the concentration and exposure times for Ethylene Oxide Gas to kill Strep and Influenza
Strep: 500 mg/1 for 2.4 min
Flu: 10,000 mg/1 for 25 h
Halogen Antimicrobial Chemicals
*Fluorine, bromine, chlorine, and iodine group VII on periodic table
*Microbicidal and sporicidal with longer exposure
*1/3 of anitmicrobial agents are halgoens
Chlorine compounds:
liquid and gaseous chlorine, hypochlorites, chloramines
*Kills bacteria and endospores
*Also kills fungi and viruses
*Example: Household bleach
Iodine compounds
free iodine and iodophors
*Topical antiseptic
Phenol coefficient
compares a chemical's antimicrobic properties to those of phenol
what do low and hig concentrations of phenol do to a microbe
Low: inactivate certain critical enzyme systems
High: cellular poisons
most widely used phenolic
*Complex organic base containing chlorine and two phenolic rings
*Targets cell membranes and protein structure
*At moderate to high concentrations, it is bactericidal for both gram-positive and gram-negative bacteria but inactive against spores
*Mild, low toxicity, rapid action
what are the only alochol anitmicrobial agents sutible for microbial control?
isopropyl and ethyl alochols
What does an alcohol antimicrobial agent depend on?
concentration (50-95% typically)
What can and can't alcohol antimicrobial agents destroy
cannot destyor spores but can destroy resistant vegetative forms
What are alcohol anitmicrobial agents most effective on inactivating: Enveloped or non-enveloped viruses
What are dermicdal effects due to?
direct and indirect actions of oxygen
What does oxygen form that is toxic?
Hydroxl free radicals
What does hydogen peroide kill
bacteria, viruses and fungus
Can hydrogen peroxide kill spores?
in high concentrations yes
What do detergents act as?
Which is more powerful anionic or cationic detergents?
Cationics are genrally more effective, anionics are limited
What are detergents
polar molecules with a positively charged head and at least one long uncharged hydrocarbon chain. the head contains a central nitrogen nucleus with various alkyl
What are the heavy metal compounds used?
Hg, Ag, Au, Cu, As, and Zn
which heavy metals are still used?
Hg and Ag
oligodynamic action
the ability of very small amounts of heavy metals to exert antimicrobial activity
How do heavy metals work?
inds to functional groups of proteins and inactivates them
What are the drawbacks to using metals in microbial control
*Can be very toxic to humans
*Often cause allergic reactions
*Large quantities of biological fluids and wastes neutralize their actions
*Microbes can develop resistance to them
What are the 2 more common aldehydes
Glutaraldehyde and formaldehyde
What are aldehydes
-CHO functional group on the terminal carbon (strong reducing group)
* Yellow acidic liquid with an odor
* cross linking protein molecules on the cells surface
* amino acids are alkylated
* irreversibly disrupt the activity of enzymes within the cell
an irritating, acidic, gas used in laboratory disinfectants and preservatives
Gaseous Sterilants and Disinfectants
*Ethylene oxide (ETO)
*Propylene oxide
*Chlorine dioxide
Ethylene oxide
gas used to sterilize heat sensitive ingredients
Propylene oxide
alkylates proteins; sterilize heat sensitive items
Chlorine dioxide
effective, rapid-acting environmental surface disinfectant or chemical sterilant.
what is the primary source used in certain drugs for chemotherapy
what are some aniline dyes and what are they used for
crystal violet and malachite green very active against gram positive species of bacteria and various fungi
What are some yellow acridine dyes and what are they used for
acriflavine and proflavine sometimes used for antisepsis and wound treatment
Why aren't dyes used very often
they have limited applications because they stain and have a narrow spectrum of activity
why are acids and alkalis limited in applications
they are corrosive, caustic and hazardous in nature