Chapter 9 mock smartbook

Antimicrobial chemical

A chemical agent used to kill or inhibit the growth of microorganisms

Disinfectant

A chemical agent used on inanimate objects to destroy vegetative pathogens

Antiseptic

A chemical agent safe for application to living tissues to reduce microbial growth

Sterilant

A chemical capable of destroying all forms of microbial life, including endospores

Preservative

A chemical that inhibits microbial growth to prevent spoilage of products

Chemical control

The use of chemical agents to limit or eliminate microorganisms

Aqueous solution

A solution in which water is used as the solvent for an antimicrobial chemical

Tincture

A solution in which alcohol or an alcohol-water mixture is used as the solvent

Protein denaturation

Loss of protein structure and function caused by chemical disruption

Enzyme inactivation

Chemical interference with enzymatic activity essential for metabolism

Nucleic acid damage

Damage that interferes with DNA or RNA synthesis or structure

Cell wall disruption

Chemical damage that weakens or destroys the microbial cell wall

Cytoplasmic membrane damage

Loss of selective permeability that leads to cell death

High-level germicide

A chemical that kills endospores and can act as a sterilant with proper exposure

Intermediate-level germicide

A chemical that kills fungal spores, Mycobacterium tuberculosis, and viruses

Low-level germicide

A chemical that kills vegetative bacteria, vegetative fungi, and some viruses

Critical items

Medical devices that enter sterile tissues and require high-level disinfection or sterilization

Semicritical items

Devices that contact mucous membranes and require intermediate-level disinfection

Noncritical items

Items that only contact intact skin and require low-level disinfection

Nature of the microorganism

Different microbes vary in susceptibility to chemical agents

Degree of contamination

Higher numbers of microbes reduce disinfectant effectiveness

Organic matter

Blood or debris that can block or inactivate chemical agents

Contact time

The length of exposure required for effective microbial killing

Chemical concentration

Germicidal effectiveness depends on proper strength.

Temperature

Higher temperatures generally increase chemical activity

pH

Acidity or alkalinity of the environment can alter effectiveness

Broad-spectrum activity

Ability to act against a wide range of microorganisms

Rapid action

Effectiveness at low concentrations in short time periods

Low toxicity

Minimal harm to humans or animals.

Surface penetration

Ability to reach microorganisms on complex surfaces

Stability

Ability to maintain effectiveness over time

Resistance to organic matter

Ability to remain active in dirty environments

Noncorrosive

Does not damage materials or equipment

Sanitizing capability

Ability to reduce microbial populations to safe public-health levels

Affordability

Cost-effective and readily available

Alcohol

A hydrocarbon containing one or more –OH groups used as antiseptics

Ethyl alcohol

An alcohol commonly used for skin degerming

Isopropyl alcohol

A widely used alcohol for antiseptic purposes

Optimal alcohol concentration

60–80% alcohol for maximum protein denaturation

Mode of action of alcohols

Disrupt membranes, reduce surface tension, and denature proteins

Limitation of alcohols

Rapid evaporation reduces contact time and effectiveness

Chlorhexidine

A mild, low-toxicity antiseptic containing chlorine and phenolic rings

Target of chlorhexidine

Bacterial membranes, cell walls, and proteins

Uses of chlorhexidine

Surgical scrubs, skin prep, and mucous membrane irrigation

Limitation of chlorhexidine

Not uniformly effective against all viruses and fungi

Halogens

Chemical elements with strong oxidizing properties used as disinfectants

Chlorine

A halogen that kills most microbes and slowly kills endospores

Hypochlorous acid (HOCl)

The active antimicrobial compound formed when chlorine reacts with water

Mode of action of chlorine

Permanently denatures enzymes and halts metabolism

Limitation of chlorine

Activity reduced by light, alkaline pH, and organic matter

Iodine

A halogen effective against most microbes and slowly effective against endospores

Free iodine (I₂)

The active antimicrobial form of iodine

Iodophor

An iodine-alcohol complex that releases iodine slowly

Mode of action of iodine

Disrupts protein bonding and metabolism

Limitation of iodine

Can be irritating and toxic with prolonged exposure

Oxidizing agent

A chemical that produces free radicals toxic to cells

Hydrogen peroxide

An oxidizing agent used for wound cleansing and disinfection

Peracetic acid

A strong oxidizing agent used as a sterilant

Mode of action of oxidizers

Damage proteins, membranes, and DNA via free radicals

Limitation of oxidizing agents

Can be broken down by catalase-producing microbes, less stable in light/heat, activity reduced by organic matter, and strong solutions can damage tissues and materials.

Phenol (carbolic acid)

A disinfectant derived from coal tar

Mode of action of phenols

Disrupt cell walls, membranes, and enzymes

Phenol coefficient

A measure comparing disinfectant effectiveness to phenol

Limitation of phenols

Toxicity makes them unsafe as antiseptics

Aldehydes

Organic compounds containing a terminal –CHO group

Glutaraldehyde

A high-level disinfectant capable of killing endospores

Mode of action of aldehydes

Irreversibly disrupt enzymes and proteins

Limitation of glutaraldehyde

Unstable at high pH and temperature

Ortho-phthalaldehyde (OPA)

A safer, effective alternative to glutaraldehyde.

Ethylene oxide

A gaseous sterilant used on heat-sensitive medical equipment

Mode of action of ethylene oxide

Alkylates DNA and proteins, blocking replication

Limitation of ethylene oxide

Toxic, explosive, and carcinogenic

Why are alcohols ineffective against endospores?

Endospores lack lipid membranes needed for alcohol disruption

Why are enveloped viruses more susceptible to alcohol?

Alcohol dissolves lipid envelopes present in enveloped viruses.

Why does organic matter reduce disinfectant effectiveness?

It inactivates chemicals and shields microorganisms

Which chemicals were recommended by the WHO in 2020 for surface disinfection?

Chlorine and ethyl alcohol

What is the primary goal of chemical control methods?

To reduce or eliminate microbial populations using chemical agents

How do antimicrobial chemicals differ from physical control methods?

Antimicrobial chemicals kill or inhibit microbes using chemical reactions rather than heat or radiation

Why are disinfectants not considered sterilizing agents?

They typically do not destroy endospores or all forms of microbial life

Why can antiseptics be applied to living tissue while disinfectants cannot?

Antiseptics are formulated to have lower toxicity to human cells

What distinguishes a sterilant from a disinfectant?

A sterilant destroys all microbial life, including endospores

Why is chemical control preferred for many medical instruments?

Many instruments are heat-sensitive and cannot withstand physical sterilization

What determines whether a chemical is classified as high-, intermediate-, or low-level?

The range of microorganisms it can eliminate

Why are critical items required to undergo high-level disinfection or sterilization?

Because they enter sterile body tissues and pose a high risk of infection

Why are semicritical items treated differently from critical items?

They contact mucous membranes rather than sterile tissues.

What level of germicide is sufficient for noncritical items?

Low-level germicides

Why is Mycobacterium tuberculosis used as a benchmark for intermediate-level disinfection?

Because it is more resistant than most vegetative bacteria

How does microbial susceptibility influence chemical effectiveness?

Some microbes are naturally more resistant to chemical agents

Why does a higher degree of contamination reduce disinfectant activity?

More microbes require longer exposure or higher chemical concentrations

How does organic matter interfere with chemical disinfection?

It can neutralize chemicals or shield microorganisms

Why is proper contact time essential for chemical control?

Insufficient exposure may not allow complete microbial killing

How does chemical concentration affect microbial killing?

Too little is ineffective, while optimal concentrations maximize killing

Why do higher temperatures generally enhance germicidal activity?

Chemical reactions occur more rapidly at higher temperatures

How does pH influence chemical disinfectants?

Extreme pH levels can increase or decrease chemical activity

Why is broad-spectrum activity desirable in a disinfectant?

It allows effectiveness against many different microorganisms

Why is low toxicity an important characteristic of disinfectants and antis

To prevent damage to human tissues and surfaces

Why must disinfectants be stable over time?

Chemical breakdown reduces effectiveness during storage and use

Why is resistance to organic matter important in hospital disinfectants?

Medical environments often contain blood or bodily fluids

What is meant by sanitization?

Reduction of microbial populations to levels considered safe by public health standards

Why is cost an important factor when selecting a disinfectant?

Disinfectants must be affordable for routine and widespread use