Chapter 5 (quiz 6)

laminar flow hoods

A continuous flow of incoming and outgoing air is filtered through the HEPA filters to contain microor- ganisms within the cabinet.

formalin

Formaldehyde is used as a gas or an aqueous 37% solution (119)

Peroxygens

Hydrogen peroxide and peracetic acid are powerful oxidizing agents that under controlled conditions can be used as sterilants.

general-purpose disinfectants

Intermediate-level and low-level disinfectants

electromagnetic radiation

Radio waves, microwaves, visible and ultraviolet light rays, X rays, and gamma rays;This energy travels at the speed of light in waves and has no mass.

retort

The commercial canning process uses pressurized steam in an industrial-sized autoclave (114)

Degerming

a treatment used to decrease the number of microbes in an area, particularly the skin

Decontamination

a treatment used to reduce the number of pathogens to a level considered safe to handle.

tinctures

alcohol-based solutions

Quaternary ammonium compounds

also commonly called quats, are cationic (positively charged) detergents that are non- toxic enough to be used to disinfect food preparation surfaces (121)

Peracetic acid

an even more potent germicide than hydrogen peroxide. A 0.2% solution of peracetic acid, or a combination of peracetic acid and hydrogen peroxide, can be used to sterilize items in less than 1 hour.

Ethylene oxide

an extremely useful gaseous sterilizing agent that destroys all microbes, including endospores and viruses, by reacting with proteins. As a gas, it penetrates well into fabrics, equipment, and implantable devices such as pacemakers and artificial hips. Useful for heat or moisture sensitive items.

Ozone (O3)

an unstable form of oxygen that is a powerful oxidizing agent. It decomposes quickly, however, so it must be generated on-site, usually by passing air or oxygen between two electrodes. Ozone is used as an alternative to chlorine for disin- fecting drinking water and wastewater.

Protozoan cysts and oocysts

are stages in the life cycle of certain intestinal protozoan pathogens such as Giardia lamblia and Cryptosporidium parvum. These disinfectant resistant forms are excreted in the feces of infected animals. They are readily destroyed by boiling.

Benzoic, sorbic, and propionic acids

are weak organic acids that are sometimes added to foods such as bread, cheese, and juice to prevent microbial growth. At a low pH, these weak acids alter cell membrane functions and interfere with energy transformation.

flash autoclaving

autoclaving at higher temperature By increasing the temperature to 135°C, sterilization is achieved in only 3 minutes (113)

Highly resistant microbes include:

bacterial endospores, protozoan cysts, oocysts, Mycobacterium species, Pseudomonas species, Naked viruses (110)

Sterilants

can destroy all microorganisms, including endo- spores and viruses. Sterilants are used to treat heat- sensitive critical instruments such as scalpels.

Halogens include

chlorine and idoine

Semicritical instruments

come into contact with mucous mem- branes, but do not penetrate body tissue. These items, including gastrointestinal endoscopes and endotracheal tubes, must be free of all viruses and vegetative bacteria including mycobacteria.

Critical instruments

come into direct contact with body tissues. These items, including needles, scalpels, and biopsy forceps, must be sterilized to avoid transmission of all infectious agents.

Pseudomonas species

common environmental organ- isms are not only resistant to some chemical disinfectants, but in some cases can actually grow in them.

disinfection by-products (DBPs)

compounds that are formed when disinfectants such as chlorine react with naturally occurring chemicals in the water (110)

phenolics

derivatives of phenol, have greater germicidal activity, which enables effective use of more dilute and there- fore less irritating solutions. Phenolic compounds are the active ingredients in LysolTM.

Intermediate-level disinfectants

destroy all vegetative bacteria including mycobacteria, fungi, and most, but not all, viruses. They are used to disinfect non-critical instruments such as stethoscopes.

High-level disinfectants

destroy all viruses and vegetative micro- organisms, but they do not reliably kill endospores. They can be used to treat semicritical instruments such as gastrointestinal endoscopes.

Low-level disinfectants

destroy fungi, vegetative bacteria except mycobacteria, and enveloped viruses. They do not kill endospores, nor do they reliably destroy naked viruses.

aldehydes glutaraldehyde, orthophthalaldehyde (OPA), and formaldehyde

destroy microorganisms and viruses by inactivating proteins and nucleic acids.

chlorine

destroys all types of microorganisms and vi- ruses but is too irritating to skin and mucous membranes to be used as an antiseptic.

Sanitized

generally implies a substantially reduced microbial population that meets accepted health standards.

membrane filters

have microscopic pores that allow liquid to flow through while trapping particles that are too large to pass through the pores

autoclave

heat water in an enclosed vessel that achieves temperatures above 100°C

flaming

heating until red hot

nosocomial infection

hospital-acquired infections

iodophore

in which the iodine is linked to a carrier molecule that releases free (unbound) iodine slowly. Iodophores are not as irri- tating to the skin as tincture of iodine nor are they as likely to stain.

Physical methods

include heat treatment, irradiation, filtration, and mechanical removal (washing).

Chlorine dioxide (ClO2)

is a strong oxidizing agent that is increasingly being used as a disinfectant and sterilant. It has an advantage over chlorine-releasing compounds in that it does not react with organic compounds to form trihalomethanes or other toxic chlorinated products.

Phenol (carbolic acid)

is important historically because it was one of the earliest disinfectants, but its use is now lim- ited because it has an unpleasant odor and irritates the skin.

decimal reduction time or D value

is the time required for killing 90% of a population of bacteria under specific conditions (111)

Lyophilization

is widely used for preserving foods such as coffee, milk, meats, and vegetables. In the process of freeze-drying, the food is first frozen and then dried in a vacuum.

Metal compounds

kill microorganisms by combining with sulf- hydryl groups (—SH) of enzymes and other proteins, thereby interfering with their function (122)

Naked viruses

lack a lipid envelope and are more resistant to disinfectants

Chlorhexidine

most effective of a group of chemicals called biguanides, is extensively used in antiseptic products. It adheres to and persists on skin and mucous membranes, is of relatively low toxicity, and destroys a wide range of microbes, including vegeta- tive bacteria, fungi, and some enveloped viruses.

high- temperature-short-time (HTST) method

most pasteurization protocols employ this method, milk is heated to 72 degrees celsius and held for 15 seconds

what is a sterile item?

one that is absolutely free of microbes, includ- ing endospores and viruses. It is important to note, however, that the term sterile does not consider prions. These infectious protein particles are not destroyed by standard sterilization procedures (108)

incineration

oxidizes the cell components to ashes

Processes used to control microorganisms are either ___ or ___

physical or chemical

high-efficiency particulate air (HEPA) filters

remove nearly all microorganisms that have a diameter greater than 0.3 mm from air.

Non-critical instruments

surfaces pose little risk of infection because they only come into contact with unbroken skin.

commercially sterile

the fact that the endospores of some thermophiles may survive.

Preservation

the process of delaying spoilage of foods or other perishable products.

Disinfection

the process that eliminates most or all pathogens on or in a material.

Depth filters

trap material within thick filtration material such as cellulose fibers or diatomaceous earth.

Iodine

unlike chlorine, does not reliably kill endospores, but it can be used as a disinfectant. It is used as a tincture in which the iodine is dissolved in alcohol

Chemical methods

use any of a variety of antimicrobial chemicals.

ultra-high-temperature (UHT) method

used on single-serving containers of cream. This process is designed to render the product free of all microorganisms that can grow under normal storage conditions, it is technically not a type of pasteurization (113).

pasteurization

uses a brief heat treatment to reduce the num- ber of spoilage organisms and kill pathogens.

antiseptics

when disinfectants are for use on skin

wavelength

which is the distance from crest to crest (or trough to trough) of a wave (115)

frequency

which is the number of waves per second.

Hydrogen Peroxide

The effectiveness of hydrogen peroxide (H2O2) as a germicide depends in part on whether it is used on living tissue, such as a wound, or on an inanimate object. This is because all cells that use aerobic metabolism, including the body's cells, produce the enzyme catalase, which inactivates hydrogen peroxide by breaking it down to water and oxygen gas (120)

electromagnetic spectrum

The full range of wavelengths

sterilization

The process of removing or destroying all microorganisms and viruses on or in a product (108)

aseptic technique

The use of specific methods to exclude contaminating microorganisms from an environment

disinfectants

Those used for disinfecting inanimate objects