Supplemental Lecture (98/11/21 update) by Stephen T. Abedon (abedon.1@osu.edu)

 

(1)               Chapter title: Specific Antimicrobials

(a)             A list of vocabulary words is found toward the end of this document

(b)             Methods by which live microorganisms may be removed from a surface, body, or solution, or at least prevented from replicating, include the application of heat, cold, desiccation, osmotic pressure, filtration, ionizing radiation, UV radiation, and chemical agents. By and large none of these methods, as discussed below, are effective in treating disease. Instead they are useful in preventing disease by preventing contamination.

(c)             Found at this site are additional pages of possibly related interest including: [sterilization and disinfection] [control of microbial growth]

(d)             An index to all of the vocabulary words found on this site also exists [index]

(2)               Specific antimicrobials (chemical agents, physical agents)

(a)             Specific physical antimicrobials include:

(i)                  desiccation

(ii)                filtration

(iii)               freezing

(iv)              heat

(v)                moist heat

(vi)              autoclaving

(vii)             pasteurization

(viii)           dry heat

(ix)              ionizing radiation

(x)                UV radiation

(b)             Specific chemical antimicrobials include:

(i)                  alcohols

(ii)                aldehydes

(iii)               halogens

(iv)              heavy metals

(v)                organic acids

(vi)              oxydizing agents

(vii)             phenolic

(viii)           quarternary ammonium compound

(ix)              surfactants

(x)                ultraviolet radiation

(xi)              various gasses

(3)               Death by heat

(a)             Heat is:

(i)                  economical

(ii)                easily controlled

(iii)               kills by denaturing proteins

(iv)              used either moist or dry

(b)             In general, the greater the length of application of heat, the less heat required to do the same job, as can higher heats for shorter durations

(c)             Heat sterilization is used in:

(i)                  canning food

(ii)                autoclaving or baking laboratory supplies

(iii)               autoclaving media

(iv)              flaming inoculating instruments

(4)               Moist heat

(a)             Moist heat is:

(i)                  boiling water

(ii)                unpressurized steam

(iii)               pressurized steam

(iv)              autoclaving

(v)                pasteurization

(b)             Unpressurized generally effective:

(i)                  Unpressurized moist heat is generally effective for killing most microorganisms

(ii)                Exceptions include:

(1)   extreme thermophiles

(2)   endospores

(3)   some viruses

(iii)               Generally, though, boiling is effective for making food and water safe to eat or drink

(iv)              An application of pressure is required to guarantee sterilization since the heat of steam generated by boiling water at normal atmospheric pressure is 100C

(5)               Autoclaving

(a)             Pressurized moist heat:

(i)                  Autoclaving is a method of sterilization employing moist heat at temperatures in excess of that of boiling water at sea level (i.e., 100C)

(ii)                This is done by using high pressure steam

(b)             Autoclaving tends to be used for sterilizing under all circumstances where the high temperatures employed (typically 121C and higher) will not damage the item or substance being sterilized

(c)             Achieving sterilization:

(i)                  Under circumstances where the item or substance is in direct contact with the steam, sterilization will occur after 15 minutes at 121C

(ii)                Higher temperatures may be employed for faster sterilization but only if the item or substance will not break down at these higher temperatures

(d)             Efficacy requires penetration by steam:

(i)                  When heating larger, bulky items or high volume liquids it is necessary to autoclave for longer; Generally, though, once a moist item is up to temperature it takes only 15 minutes for complete sterilization to occur at 121C

(ii)                Anything that impedes the flow of moist heat (trapped air, materials impervious to moisture but not microorganisms, etc.) will not necessarily be sterilized by autoclaving

(6)               Pasteurization

(a)             Pasteurization is a much-less extreme use of moist heat than autoclaving

(b)             Pasteurization does not sterilize nor even disinfect

(c)             Thermodurics are resistant:

(i)                  This is because of the existence of thermoduric microorganisms, ones that are resistant to the application of modest amounts of moist heat for modest lengths of time

(ii)                Fortunately, thermoduric microorganisms tend to be neither pathogenic nor excessively psychrotrophic

(7)               Dry heat

(a)             Dry heat kills by oxidizing organic compounds (i.e., it burns things)

(b)             Higher temperatures required:

(i)                  Sterilization employing dry heat requires much higher temperatures then moist heat

(ii)                Nevertheless, application of dry heat is very useful when sterilizing materials that are resistant to these high temperatures

(c)             Direct flaming employs dry heat (e.g., such as the flaming of a loop)

(d)             Example: baking in oven:

(i)                  Hot-air sterilization is also known as baking in an oven

(ii)                Effective sterilization typically conservatively occurs by two hours at 170C

(8)               Filtration (filter sterilization)

(a)             Filtration is generally employed when sterilizing or disinfecting a solution that is heat-labile

(b)             Alternative if inconvenient to heat:

(i)                  Some substances, such as some biological molecules or air, are difficult or inconvenient to heat

(ii)                These substances may, instead, be filtered

(c)             Membrane filters are routinely used for filtering liquids

(d)             Various filters (especially HEPA or High-Efficiency Particular Air Filters) are used to remove microbes from the air ventilating especially clean environments such as tissue culture hoods

(e)             Note that employing filtration does not necessarily guarantee sterility unless filters which trap even the smallest of microorganisms are employed

(f)               Small pores = low flow rate:

(i)                  Note that the down side of using very fine filters is that this impedes flow through

(ii)                Consequently, there often is a trade-off between rate of flow through the filture and degree of filtration achieved

(9)               Freezing

(a)             Ice crystal disruption:

(i)                  Freezing kills by ice crystal disruption of cells and molecules

(ii)                Freezing slowly is generally more harmful than rapid (or flash) freezing

(b)             There are a number of methods by which microorganism viability is maintained through freezing such as suspension in glycerol or 10% DMSO

(10)           Desiccation

(a)             Loss of water:

(i)                  Desiccation is the loss of water, i.e., drying

(ii)                The verb, to desiccate, means to remove or lose water

(b)             Variation in resistance to:

(i)                  Not all microbes in all settings are equally resistant to desiccation

(ii)                Some bacteria are much more resistant that others (e.g., Mycobacterium tuberculosis)

(iii)               Many viruses and endospores are very resistant to desiccation

(iv)              The presence of capsules can increase resistance to desiccation

(c)             Within various body substances (e.g., pus, mucus, feces) microbes tend to be much more resistant to desiccation

(11)           Ionizing radiation

(a)             Forms free radicals from water:

(i)                  Ionizing radiation, generally, is high energy radiation

(ii)                Ionizing radiation acts by ionizing water, which forms toxins (radicals) that are highly reactive with and destructive of biological molecules such as DNA

(b)             It is important to keep in mind when selecting a source that the ionizing (and therefore killing) power of a given form of radiation may be offset by a lack of tissue penetrating power

(12)           UV radiation (ultraviolet radiation)

(a)             Ultraviolet (UV) light (or radiation, same thing) is damaging to DNA (especially at the 260 nm wavelength)

(b)             UV light is not very penetrating; It is, however, useful for keeping UV resistant surfaces disinfected

(13)           Phenolics

(a)             Derivatives of phenol (a.k.a., carbolic acid)

(b)             Phenolics act by disrupting membranes and denaturing proteins

(c)             Phenolics are especially good at disinfecting in the presence of biological fluids such as pus, saliva, and feces

(d)             They are long lasting and stable

(e)             Cresols are an important group of phenolics and are the active ingredient in Lysol

(f)               Chlorhexidine is a related compound that, when combined with detergent or alcohol, is used as a surgical scrub

(14)           Halogens

(a)             Two halogens, i.e., the second from right on the chemical periodic table, serve as effective, commonly employed antiseptics or disinfectants

(b)             These are iodine and chlorine

(15)           Iodine [tincture, iodophore]

(a)             Molecular iodine damages microorganisms via protein denaturation

(b)             One means by which iodine is employed is as a tincture, an aqueous alcohol solution (a tincture)

(c)             An iodophor is a tincture of iodine which has been combined with an organic compound that causes its (iodine's) slow release

(d)             Betadine and Isodine are brand names of iodophors

(16)           Chlorine [hypochlorite ion]

(a)             Hypochlorite ion:

(i)                  The hypochlorite ion (OCl-) is made by bubbling chlorine gas in water as well upon the dissolving of various salts (Ca(OCl)2 and NaOCl, for example)

(ii)                The hypochlorite ion is a strong oxidizing agent

(b)             Hypochlorite ion is the active ingredient of Clorox bleach

(17)           Halogen-based water purification

(a)             Gaseous chlorine is used extensively to purify water

(b)             Bleach water purification:

(i)                  Adding two to four drops of Clorox bleach, or equivalent, to a liter of water (8 drops per gallon or 16 drops per gallon of cloudy water) and letting it sit for 30 minutes is considered a safe emergency water treatment

(ii)                Let the water sit for longer if temperatures are cold

(iii)               Note, however, be sure to use unscented Clorox because the scent of scented Clorox is poisonous (p. 5 of Jan & Wong, 1999, Y2K Emergency Preparedness Handbook, Ten Speed Press, Berkeley, California)

(c)             Iodine, too, can serve as a water treatment product

(18)           Alcohols

(a)             Alcohols act by disrupting lipid bilayers and denaturing proteins

(b)             Alcohols act rapidly

(c)             Alcohols easily remove themselves from the site of use via evaporation

(d)             Alcohols have a cleansing effect by dissolving lipids so that they may be picked up by wiping

(e)             Alcohols should not be applied to wounds since they can cause tissue damage

(f)               Water solutions work best:

(i)                  Alcohols work best as 60 to 95% solutions with water

(ii)                "Some water must be present for alcohols to disinfect because they act by coagulating (permanently denaturing) proteins, and water is needed for the coagulation reactions. Also, a 70 percent alcohol-water mixture penetrates more deeply than pure alcohol into most materials to be disinfected." (p. 334, Black, 1996)

(iii)               Isopropanol (rubbing alcohol) is superior to ethanol for disinfecting

(g)             Typical spectrum of activity:

(i)                  Like disinfectants in general, alcohols are ineffective against endospores or many viruses

(ii)                "Alcohol disinfects but does not sterlize skin because it evaporates quickly and stays in contact with microbes for only a few seconds. It also does not penetrate deeply enough into pores in the skin. It kills vegatative microorganisms on the skin surface but does not kill endospores, resistant cells, or cells deep in skin pores." (p. 340, Black, 1996) (emphasis mine)

(19)           Heavy metals [heavy metal compounds]

(a)             Metallic silver, mercury, copper, and zinc as well as salts of these metals (i.e., silver nitrate, mercuric chloride, copper sulfate, zinc chloride, and zinc oxide) have antimicrobial activities and are used for various purposes

(b)             Silver nitrate/anti-eye gonorrheal:

(i)                  Only silver nitrate has a recent history of use in humans as an anti-gonorrheal eye treatment of newborns

(ii)                "A few drops of silver nitrate solution were placed in the baby's eyes at the time of delivery to protect against infection by gonocci entering the eyes during passage through the birth canal. For a time, many hospitals replaced silver nitrate with antibiotics such as erythromycin. However, the development of antibiotic-resistant strains of gonococci has led some localities to require the use of silver nitrate, to which gonococci do not develop resistance." (p. 339, Black, 1996)

(20)           Surfactants [surface-active agents, soaps, detergents]

(a)             Soaps are Na+ and K+ salts of fatty acids

(b)             Soaps typically are good degerming agents

(c)             Not germicidal:

(i)                  Soaps, however, are also typically not very germicidal

(ii)                However, free fatty acids are considered, in some circumstances, to be natural antimicrobials and are found, for example, on the surface of the skin

(d)             Detergents are synthetic, soap-like organic compounds

(e)             Varying germicidalness:

(i)                  Detergents tend to vary in terms of their germicidal activity

(ii)                That is, they are not universally as poor germicides as are soaps

(21)           Quats [quaternary ammonium compounds]

(a)             Cationic detergents:

(i)                  Quats are cationic detergents

(ii)                They are ammonium ion derivatives

(b)             Mostly effective killers:

(i)                  Quats kill just about everything except:

(ii)                endospores

(iii)               Mycobacterium tuberculosis

(iv)              Pseudomonas spp. (some Pseudomonas spp. can even grow in solutions of quats, subsisting on them)

(c)             Neutralized by numerous substances:

(i)                  In contrast to phenolics, quats are not very effective in the presence of organic compounds

(ii)                Quats are neutralized by:

(1)   soaps

(2)   various other (anionic) detergents

(3)   the fibers of cotton, gauzes, and bandages

(d)             Brand names quats

(i)                  Zephiran is a brand name for the quat benzalkonium chloride

(ii)                Cepacol is a brand name for the quat cetylpyridinium chloride

(22)           Organic acids

(a)             Various organic acids and their salts are common antimicrobials used in foods

(b)             These include:

(i)                  sorbic acid

(ii)                benzoic acid

(iii)               calcium propionate

(23)           Aldehydes [formaldehyde, formalin, glutaraldehyde]

(a)             Aldehydes employed to control microbial growth include formaldehyde and glutaraldehyde

(b)             These are very potent antimicrobials, especially glutaraldehyde

(c)             Aldehydes kill microorganisms by inactivating proteins

(d)             Formalin:

(i)                  Formalin is what a 37% solution of formaldehyde in water is called

(ii)                Formalin is used for:

(1)   preserving dead tissues

(2)   making toxoids from toxins

(3)   creating whole-killed viral vaccines

(e)             Sterlization:

(i)                  Glutaraldehyde in a 2% solution can actually sterilize

(ii)                Sporicidal activity, however, occurs only after many hours of contact

(24)           Gaseous chemosterilizers [ethylene oxide, propylene oxide, beta-propiolactone]

(a)             Gaseous chemosterilizers include such gasses such as:

(i)                  ethylene oxide

(ii)                propylene oxide

(iii)               beta-propiolactone

(b)             Gaseous chemosterilizers are very penetrating

(c)             Given sufficient length of exposure ethylene oxide can be sterilizing

(d)             Ethylene oxide is used to sterilize disposable lab plasticware

(25)           Oxidizing agents [hydrogen peroxide, ozone]

(a)             Ozone and hydrogen peroxide are examples of compounds whose antimicrobial activity stems from their oxidation of cellular components

(b)             Ozone is a gas which is used in some water purification systems

(c)             Hydrogen peroxide is not a very effective open-wound antiseptic because the host catalase freed in the wound quickly inactivates hydrogen peroxide

(d)             Deep wound oxygenation:

(i)                  Oxidizing agents are effective at oxygenating deep wounds (host catalase catalyzes the conversion of hydrogen peroxide to water and molecular oxygen)

(ii)                This poisons the growth of obligate anaerobes such as Clostridium tetani

(26)           Measures of thermal stability

(a)             Measures of a microorganism's thermal stability include:

(i)                  thermal death point

(ii)                thermal death time

(iii)               decimal reduction time

(b)             Thermal death point (TDP) is equal to the lowest temperature at which all the microorganisms in a liquid culture will be killed in 10 minutes

(c)             Thermal death time (TDT) is a less arbitrary measure of time (than TDP is of temperature) equal to the length of time at a given temperature before all microorganisms in a liquid culture will be killed

(d)             Decimal reduction time (DRT, D value) is the time in minutes at a given temperature until a culture is reduced to 10% of its initial viability

(27)           Vocabulary [index]

(a)             Alcohols

(b)             Aldehydes

(c)             Autoclave

(d)             Beta-propiolactone

(e)             Chemical agents

(f)               Chlorine

(g)             Desiccation

(h)             Detergents

(i)               Dry heat

(j)               Ethylene oxide

(k)             Filter sterilization

(l)               Filtration

(m)           Formaldehyde

(n)             Formalin

(o)             Freezing

(p)             Glutaraldehyde

(q)             Halogen-based water purification

(r)              Halogens

(s)              Heat

(t)               Heavy metals

(u)             Hydrogen peroxide

(v)             Hypochlorite ion

(w)           Iodine

(x)             Iodophore

(y)             Ionizing radiation

(z)              Measures of thermal stability

(aa)          Moist heat

(bb)         Organic acids

(cc)          Oxidizing agents

(dd)         Ozone

(ee)          Pasteurization

(ff)             Phenolics

(gg)          Physical agents

(hh)          Propylene oxide

(ii)              Quarternary ammonium compound

(jj)             Quats

(kk)         Soaps

(ll)              Surface-active agents

(mm)      Surfactants

(nn)          Tincture

(oo)         Ultraviolet radiation

(pp)         UV radiation

(qq)         Various gasses

(28)           Practice questions [index]

(a)             You are autoclaving a gallon of nutrient broth. It takes 42 minutes to bring the water up to temperature. Starting with room temperature water, what is the minimum length of time (in minutes) and temperature (C) you should set your autoclave in order to achieve sterilization? [PEEK]

(b)             Which of the following is not true for alcohol disinfectants (circle only one correct answer)? [PEEK]

(i)                  rapid acting

(ii)                evaporates readily

(iii)               not effective against endospores

(iv)              recommended for wound disinfection

(v)                can kill vegetative cells

(vi)              work best if diluted with water rather than pure

(c)             Why is autoclaving more effective at killing microorganisms than simple water boiling? [PEEK]

(d)             Which of the following is not a problem for quaternary ammonium compounds (circle only one correct answer)? [PEEK]

(i)                  Pseudomonas spp.

(ii)                soap

(iii)               cotton gauze

(iv)             Mycobacterium tuberculosis

(v)                Escherichia coli

(e)             Which of the following does not achieve sterilization (circle only one correct answer)? [PEEK]

(i)                  dry heat

(ii)                Pasteurization

(iii)               autoclave

(iv)              formaldehyde

(v)                ethylene oxide

(f)               UV radiation is a very convenient sterilizing agent. However it has a number of serious draw backs. Name one. [PEEK]

(g)             You treat a pure culture with a weak disinfectant. After one hour 20% of the original culture is dead. After two hours 40% of the original culture is dead. After three hours 60% of the original culture is dead. You suspect that the disinfectant's mode of action is unusual. Why? (assume that there is no problem with your assay method) [PEEK]

(h)             Which of the following circumstance would not be a sufficient reason to choose filter sterilization over heat sterilization? [PEEK]

(i)                  item in need of sterilization is a liquid

(ii)                item in need of sterilization is a heat labile liquid

(iii)               item in need of sterilization cannot conveniently be heated

(iv)              item in need of sterilization is a gas

(i)               Eleven patients received injections of methylprednisolone and lidocaine to relieve pain and inflammation of arthritis at the same orthopedic surgery office. All the patients developed septic arthritis caused by Serratia marcescens. Unopened bottles of mehylprednisolone was preserved with a quat. Cotton balls were used to wipe multiple-use injection vials before the medication was drawn into a disposable syringe. The site of injection on each patient was also wiped with a cotton ball. The cotton balls were soaked in benzalkonium chloride (a quat), and fresh cotton balls were added as the jar was emptied. Opened methylprednisolone and the jar of cotton balls contained S. marcescens. How was the infection transmitted? What part of the routine procedure caused the contamination. (p. 188, Tortora et al., 1995) [PEEK]

(j)               Which of the following is an appropriate wound antiseptic? (choose best answer) [PEEK]

(i)                  70% isopropanol

(ii)                UV radiation

(iii)               an iodophore

(iv)              glutaraldehyde

(v)                ionizing radiation

(vi)              dried cow dung

(k)             If you have to sterilize a clean surface, and could choose the best product (in terms of efficacy) from the following general categories, which would you employ (circle best answer)? [PEEK]

(i)                  a quat

(ii)                a phenolic

(iii)               an aldehyde

(iv)              an antiseptic

(v)                a soap

(vi)              an iodophore

(l)               Why is filter sterilization not necessarily sterilization (short answer) [PEEK]

(m)           __________ is/are especially good at disinfecting in the presence of biological fluids such as pus, saliva, and feces. (choose one correct answer) [PEEK]

(i)                  alcohols

(ii)                quats

(iii)               chlorine

(iv)              UV radiation

(v)                organic acids

(vi)              phenolics

(n)             Which is the least effective as an antimicrobial? (choose one correct answer) [PEEK]

(i)                  boiling water

(ii)                pasteurization

(iii)               unpressurized steam (sea level)

(iv)              pressurized steam

(v)                autoclaving

(vi)              glutaraldehyde

(o)             Which is most applicable as a contaminated-wound antiseptic? (choose one correct answer) [PEEK]

(i)                  phenolics

(ii)                hydrogen peroxide

(iii)               quats

(iv)              alcohols

(v)                aldehydes

(vi)              gaseous chemosterilizers

(p)             Circle all of the antimicrobials which possess the potential to kill all microorganisms of all kinds. [PEEK]

(i)                  phenolics

(ii)                hydrogen peroxide

(iii)               quats

(iv)              alcohols

(v)                gaseous chemosterilizers

(vi)              boiling water

(vii)             pasteurization

(viii)           unpressurized steam (sea level)

(ix)              pressurized steam

(x)                autoclaving

(xi)              glutaraldehyde

(q)             Name a product which employs a halogen as an antimicrobial. [PEEK]

(r)              Name a category of chemical disinfectants which are both highly efficacious in the presence of fecal material and have a long shelf life. [PEEK]

(s)              Normally the interior of sealed containers are not sterilized during autoclaving because the high pressure steam, and therefore moist heat, cannot reach through the seal. Other than unsealing the container, how might you effect the sterilization of its interior using an autoclave? Hint: Disregard any concerns about the durability of the container or limits in autoclave performance. [PEEK]

(t)               Though they differ in terms of their abilities to degerm or disinfect, soaps, quats, and detergents, but not phenolics and halogens, are examples of __________. [PEEK]

(u)             Name a specific chemical germicide capable of achieving sterilization. [PEEK]

(v)             A large volume of liquid requires 30 minutes of autoclaving to raise its temperature to 121 degrees centigrade. Generally, how long must this not yet autoclaved liquid be autoclaved at 121 degrees centigrade to achieve guaranteed sterility? [PEEK]

(w)           _________ is an ineffective wound antiseptic but a good wound oxidizer. [PEEK]

(x)             Given application at the same temperature, which is the more effective sterilizer: [PEEK]

(i)                  dry heat

(ii)                pressurized steam

(iii)               oven baking

(iv)              direct flaming

(v)                all are equally effective

(y)             _________ is an example of a degerming, antimicrobial surfactant, which additionally is an ineffective germicide. [PEEK]

(z)              Name two examples of things that neutralize quats. [PEEK]

(aa)          _________ is an anti-protein, chemical antimicrobial which, in a two percent solution, is capable of sterilizing. [PEEK]

(i)                  formalin

(ii)                tincture

(iii)               ethylene oxide

(iv)              glutaraldehyde

(v)                quaternary ammonium compounds

(bb)         Though effective for making food and water safe to eat or drink, _________ fails to kill extreme thermophiles, endospores, and some viruses. [PEEK]

(29)           Practice question answers [index]

(a)             room temp --[42 min in autoclave]--- 121C --[15 min at temperature]--- sterilization. Thus, 42 + 15 = 57 minutes and 121C.

(b)             iv, alcohols are not recommended for wound disinfection.

(c)             higher temperatures are employed because water boils at a higher temperature when heated under the higher pressures attainable in the autoclave.

(d)             v, Escherichia coli

(e)             ii, Pasteurization

(f)               (i) lack of penetration, (ii) damage to eyes and skin, (iii) destructive to plasticware.

(g)             you are failing to observe the expected exponential decline in viability. Instead, you are seeing a linear decline.

(h)             i, item in need of sterilization is a liquid

(i)               The cotton balls carried the contamination. The problem was that the cotton inhibited the quat so soaking in this disinfectant was not sufficient to kill the S. marcescens already present.

(j)               iii, an iodophore

(k)             iii, an aldehyde.

(l)               In theory you could have filter poor sizes that are sufficiently small that no living organism including viruses could pass through. In practice, however, the smaller the poor size the more difficult it is to pass liquid through the filter and the more easily the filter is clogged. As a consequence, the filter pore size normally employed is sufficiently large that viruses are able to pass through it. Hence, filtration is normally not sterilizing.

(m)           vi, phenolics.

(n)             ii, pasteurization.

(o)             i, phenolics: hydrogen peroxide is inactivated by catalase, quats are less effective in the presence of organics, alcohols cause tissue damage, aldehydes are particularly nasty (not the kind of thing you would appreciate around a wound), how on earth are you going to apply a gaseous chemosterilizers to a wound, assuming you would even want to?

(p)             v, viii, ix, x, xi.

(q)             Clorox bleach, Betadine, Isodine, etc.

(r)              phenolics.

(s)              simply increase the temperature to high enough that dry heat is capable of effecting sterilization, and then, if necessary, autoclave it a long time.

(t)               surfactants.

(u)             glutaraldehyde, ethylene oxide, propylene oxide, beta-propiolactone.

(v)             30 + 15 = 45 minutes

(w)           hydrogen peroxide

(x)             ii, pressurized steam

(y)             soap

(z)              soap, organics, cotton gauze, anionic detergents (quats are cationic detergents), etc.

(aa)glutaraldehyde

(bb)         boiling

(30)           References [index]

(a)    Black, J.G. (1996). Microbiology. Principles and Applications. Third Edition. Prentice Hall. Upper Saddle River, New Jersey. pp. 332-352.

(b)   Tortora, G.J., Funke, B.R., Case, C.L. (1995). Microbiology. An Introduction. Fifth Edition. The Benjamin/Cummings Publishing, Co., Inc., Redwood City, CA, pp. 167-188.