Microbiology Chapter 7: The Control of Microbial Growth

Alcohols

*effectively kill bacteria and fungi but not endospores and nonenveloped viruses.* *alcohol usually denature protein*, but it can also disrupt membranes and *dissolve many lipids.* alcohols are unsatisfactory antiseptics when applied to wounds --> cause coagulation of a layer of protein under when bacteria continue to grow

Ionizing radiation

*high-energy (carries more energy) radiation w/ a wavelength less than 1 nm*; causes ionization. X rays and gamma rays are examples and high energy electron beams.

Commercial sterilization

*sufficient heat treatment to kill* endospores of Clostridium botulinum in canned food.

What is thermal death point (TDP)?

*the lowest temp* at which all the *microorganisms* in a particular suspension will be killed in 10 minutes.

How many states of matter are there? What are they?

4 liquid, gas, solid and *plasma*

High-effeciency particulate air (HEPA) filters

a *screenlike* material that removes particles larger than 0.3 mcm from the air.

ultra-high-temperature (UHT) treatment

a method of treating food w/ high temps [140-150C] for very short times to make the food sterile so that it can be stored at room temperature.

Membrane filters

a screenlike material w/ pores small enough to retain microorganisms; a 0.45 mcm filter retains most bacteria.

Chlorine dioxide (chemical sterilization)

a short-lived gas that is usually manufactured at the place of use. has been used to fumigate enclosed building areas contaminated w/ endospores of anthrax. *most common use* in water treatment prior to chlorination.

Hypochlorite

a strong oxidizing agent that prevents much of the cellular enzyme system from functioning.

Isopropanol

aka rubbing alcohol slightly superior to ethanol as an antiseptic and disinfectant and more easily obtained than ethanol

C. diff and viruses that lack a lipid envelope are resistant to what?

alcohol-based hand sanitizers

________ are the most effect antimicrobials (formaldehyde, glutaraldehyde). What is their mechanism of action & preferred use?

aldehydes mechanism of action: protein denaturation preferred use: glutaraldehyde (Cidex) is less irritating than formaldehyde and is used for disinfecting medical equipment.

Chlorine (Cl2)

as a gas or in combo w/ other chemicals, is another widely used disinfectant. its germicidal action is caused by the HOCl that forms when chlorine is added to water. used in swimming pools and sewage systems to disinfect water.

Surface-active agents, aka surfactants, do what? What agents do they include?

can decrease surface tension among molecules of a lipid include soaps and detergents

copper sulfate is used to destroy what?

chiefly destroy green algae that grow in reservoirs, stock ponds, swimming pools, and fish tanks

Chloramines

combo of chlorine and ammonia used to sanitize glassware and eating utensils and to treat dairy and food-manufacturing equipment.

Xgel, a hand sanitizer, does not contain alcohol, but what instead?

copper

UV light

damages the DNA of exposed cells by causing bonds to form b/t adjacent pyrimidine bases, usually thymines, in DNA chains. These *thymine dimers* inhibit correct replication of the DNA during cell reproduction. the most effective UV wavelengths for killing microorganisms are about 260 nm.

Phenolics

derivatives of phenol that contain a *molecule* of phenol that has been chemically altered to reduce its irritation qualities or increase its antibacterial activity in combo w/ a soap or detergent.

Bisphenols

derivatives of phenol that contain two phenolic *groups* connected by a bridge (bis = two) one bisphenol is an ingredient in prescription lotion that is used for surgical and hospital microbial control procedures. --> used to control growth of staphylococci and streptococci in newborns

Antisepsis

destruction of *vegetative pathogens* on living tissue. treatment is almost always by chemical antimicrobials.

Disinfection

destruction of vegetative pathogens on inanimate objects. may make use of physical or chemical methods.

Sterilization

destruction or removal of all forms of microbial life, (including endospores but with the possible exception of prions.) usually done by steam under pressure or sterilizing gas, such as ethylene oxide.

Equivalent treatments

different methods that have the same effect on controlling microbial growth.

Biguanides

effective against gram +/- bacteria. best known biguanide: *chlorhexidine* is frequently used for microbial control on skin and mucous membranes.

Microwaves

electromagnetic radiation w/ wavelength b/t 10^21 and 10^-3 m.

Gamma rays

emitted by certain radioactive elements such as cobalt. penetrate deeply but may require hours to sterilize large masses.

Phenol

first used by Lister to perform aseptic surgeries. is used in sewage systems now, but rarely used in surgery because of it's odor and it causes irritation to the skin.

If a mouthwash bottle ________ when shaken it probably contains a ________

foams quat

High-energy electron beams

have much lower penetrating power but usually require only a few seconds of exposure. used to sterilize pharmaceuticals and disposable dental and medical supplies, and catheters. *as a protection against bioterrorism, the postal service often uses electron beam radiation to sterilize certain classes of mail.*

High pressure applied to liquid suspensions

if the press. is high enough, it alters the molecular structures of proteins and carbs, resulting in the rapid inactivation of vegetative bacterial cells.

What is plasma r/t it being a state of matter?

is a state of matter in which a gas is excited, in this case by an electromagnetic field, to make a mixture of nuclei w/ assorted electrical changes and free electrons.

Disk-diffusion method

is used in teaching laboratories to evaluate the efficacy [the ability to produce a desired or intended result.] of a chemical agent. a disk of filter paper is soaked w/ a chemical and placed on an agar plate that has been previously inoculated and incubated with the test organism.

Glutaraldehyde

less irritating and more effective than formaldehyde. used to disinfect hospital instruments, inc endospores and respiratory therapy equipment

Nitrates/nitrites (chemical food preservatives)-mechanism of action & preferred use

mechanism of action: active ingredient is nitrite, which is produced by bacterial action on nitrate. Nitrite inhibits certain iron-containing enzymes of anaerobes. preferred use: meat products such as ham, bacon, hot dogs or sausage.

Quats (surface-active agents)-mechanism of action & preferred use

mechanism of action: enzyme inhibition, protein denaturation, and disruption of plasma membranes preferred use: antiseptic for skin, instruments, utensils, rubber goods.

Ethylene oxide and other gaseous sterilants (chemical sterilization)-mechanism of action & preferred use

mechanism of action: inhibits vital cellular function preferred use: mainly for sterilization of materials that would be damaged by heat

Supercritical fluids (chemical sterilization)-mechanism of action & preferred use

mechanism of action: inhibits vital cellular functions preferred use: esp useful for sterilizing organic material implants.

Plasma sterilization (chemical sterilization)-mechanism of action & preferred use

mechanism of action: inhibits vital cellular functions preferred use: esp useful for tubular medical instruments

Soaps and detergents (surface-active agents)-mechanism of action & preferred use

mechanism of action: mechanical removal of microbes through scrubbing preferred use: skin degerming and removal of debris

Organic acids (chemical food preservatives)-mechanism of action & preferred use

mechanism of action: metabolic inhibition, mostly affecting mold; action not r/t their acidity preferred use: sorbic acid and benzoic acid effective @ low pH; parabens used in cosmetics, shampoos; calcium propionate used in bread

Acid-anionic sanitizers (surface active agents)-mechanism of action & preferred use

mechanism of action: not certain; may involve enzyme inactivation or disruption preferred use: sanitizers in dairy and food-processing industries

Peroxygens and other forms of oxygen-mechanism of action & preferred use

mechanism of action: oxidation preferred use: contaminated surfaces; some deep wounds, in which they are very effective against oxygen-sensitive anaerobes.

Use-dilution test

metal or glass cylinders are dipped into standardized cultures of the test bacteria grown in liquid media, removed and dried at 37C for a short time. (the dried cultures are the placed into a soln of the disinfectant at the conc. recommended by the manufacturer and left there for 10 minutes at 20C. following this exposure, the cylinders are transferred to a medium that permits the growth of any surviving bacteria.) *the effectiveness of the disinfectant can be determined by the number of cultures that grow.*

Zinc chlorine is a common ingredient in _______. Zine pyrithione is a common ingredient in _______.

mouthwashes antidandruff shampoos

Organic acids such as sorbic acid and calcium propionate inhibit mold growth how?

not by affecting the pH but by interfering w/ the mold's metabolism or the integrity of the plasma membrane.

Nisin (antibiotic)

often added to cheese to inhibit the growth of certain endospore-forming spoilage bacteria present naturally in small amounts in dairy products

Iodine (I2)

one of the oldest and most effective antiseptics it is active against all kinds of bacteria, many endospores, various fungi, and some viruses. iodine impairs protein synthesis and alters cell membranes.

Halogens

particularly iodine and chlorine which are effective antimicrobial agents.

high-temperature short-time pasteurization

pasteurizing at 72C for 15 *seconds.*

Newer products being sold inc what r/t silver being used as an antiseptic?

plastic food containers infused w/ silver nanoparticles, which are intended to keep food fresher, and silver-infused athletic shirts and shorts, which are claimed to minimize odors

What produces the effect of oligodynamic results?

produced by the action of heavy metal ions on microbes when the metal ions combine w/ the sulfhydryl groups on cellular proteins, denaturation results

Degerming

removal of microbes from a limited area, such as the skin around an injection site. mostly a mechanical removal by an alcohol-soaked swab.

Non-ionizing radiation

short-wavelength radiation that does not cause ionization; UV radiation is an example.

Hot air sterilization

sterilization by the use of an oven at 170C for approx. 2 hours.

Quaternary ammonium compounds (quats) properties

strongly bactericidal against gram + bacteria ad less active against gram - bacteria quats are fungicidal, amebicidal, virucidal against enveloped viruses. they do not kill endospores or mycobacteria. they change the cell's permeability and cause the loss of essential cytoplasmic constituents, such as K+.

What is oligodynamic action?

the ability of very small amounts of heavy metals, esp silver and copper, to exert antimicrobial activity.

What is thermal death time (TDT)?

the minimal length of time for all bacteria in a particular liquid culture to be killed at a given temperature.

What factors influence the effectiveness of antimicrobial treatments?

the number of microbes: the more the longer it will take. environmental influences: most disinfectants work better in warm environments.

What is autoclaving?

the preferred method of sterilization in health care environments, unless the material to be sterilized can be damaged by heat or moisture.

Flaming

the process of sterilization an inoculating loop by holding it an open flame.

What are nitrosamines?

the reaction of nitrites with amino acids that can form certain carcinogenic products

Ethanol

the recommended optimum concentration of ethanol is 70%, but conc b/t 60%-95% seem to kill as well. pure ethanol is less effective than aqueous solns b/c denaturalization requires water.

Desiccation

the removal of water. microorganism cannot grow or reproduce w/o water but once it has water available it will resume growth and division.

What is decimal reduction time (DRT, or D value)?

the third concept r/t bacteria heat resistance. DRT is in the time, in minutes, in which 90% of a population of bacteria at a given *temperature* will be killed.

Silver sulfadiazine is a topical cream commonly used for what?

the treatment of burns

Osmotic pressure

the use of high concentrations of salts and sugars to preserve food is based on the effects of osmotic pressure.

Acid-anionic sanitizers properties

their sanitizing ability is r/t the negatively charged portion of the molecule, which reacts w/ the plasma membrane.

When is plasma (matter) used?

to clean surgical equipments w/ tiny holes such as those used in throscopic or laparoscopic surgeries

What is the primary use of mercurials?

to control mildew in paints

What are the two main functions of nitrite?

to preserve the red color of the meat by reacting w/ blood components in the meat the prevent germination and growth of any botulism endospores that might be present

Sanitization

treatment is intended to lower microbial counts on eating and drinking utensils to safe public health levels. may be done with high-temp washing or by dipping into a chemical disinfectant.

Sodium hypochlorite

used as a household disinfectant and bleach and as disinfectant in dairy, food-processing establishments and *hemodialysis systems.*

Chlorine dioxide solution

used as a surface disinfectant b/c it doesn't leave residual tastes or odors has a broad spectrum of activity against bacteria and viruses and at high concentrations, chlorine dioxide can be used as an antiseptic

Calcium hypochlorite

used to disinfect dairy equipment and restaurant eating utensils. used in hospitals in the 1840s by Semmelweis to control hospital infections after childbirth.

Pasteurization (milk)

used to eliminate pathogenic microbes. it also lowers microbial numbers, which prolongs milk's good quality under refrigeration.

What is UV light used to disinfect?

vaccines and other medical products germicidal lamp commonly found in hospital rooms, nurseries, OR and cafeterias.

Formalin

was once used extensively to preserve biological specimens and inactivate bacteria and viruses in vaccines.

What is emulsification?

when soap breaks the oily film into tiny droplets -->the water and soap together lift up the emulsified oil and debris and float them away as the lather is washed off.