Antisepsis and Sterilization

Question 1

What are Nosocomial infections?

Answer 1

are those whose onset and confirmation occur greater than 48 hours after hospital admission. The assumption, therefore, is that they are hospital acquired.

Question 2

What are Healthcare-associated infections?

Answer 2

These can be nosocomial, but also include infections occurring within 6-12 months of systemic antibiotic treatment, residence in a long-term care facility, central IV catheterization, urinary catheterization, or any form of dialysis.

Question 3

Prevalence of nosocomial infection?

Answer 3

Of patients admitted to acute care hospitals, 5-10% will acquire a nosocomial infection, with 25% of these infections occurring in intensive care units. A significant majority, 70%, are due to antibiotic resistance, either of components of the normal flora or pathogens newly acquired from hospital personnel.

Question 4

The single most important method to limit the transmission of nosocomial agents is ____.

Answer 4

proper hand hygiene

Question 5

What is the difference between an antibacterial and an antiseptic agent?

Answer 5

A disinfectant is a physical or chemical agent used to inhibit or destroy microorganisms on inanimate objects (i.e., fomites). An antiseptic is a physical or chemical agent used to inhibit or destroy microorganisms on skin or other tissue. Disinfectants and antiseptics reduce, but do not eliminate, potential pathogens. If the agents inhibit bacterial growth, then they are called bacteriostatic. If the agents destroy or inactivate bacteria, then they are called bactericidal. While there is some overlap in disinfecting and antiseptic agents, many disinfectants are too harsh to use as antiseptics.

Question 6

What do Phenolics and alcohols do in relation to bacteria?

Answer 6

denature proteins and disrupt cell membranes. They are generally ineffective against spores, protozoan cysts, and certain non-enveloped viruses. Phenolics are often too toxic for prolonged exposure to skin, but are the active ingredients in many mouthwashes. Phenol itself has limited use because it is considered a pollutant.

Question 7

What is Chlorhexidine?

Answer 7

a topical phenolic that alters the membrane permeability of bacteria

Question 8

T or F. . Isopropyl alcohol is commonly used as an antiseptic, but its action is slow.

Answer 8

T. Alcohols must contain water to be truly effective, so most alcohol solutions are diluted with water to 70-95% strength.

Question 9

Notes on Iodine and Chlorine

Answer 9

Iodine is a halogen and works by iodinating or oxidizing bacterial proteins. Originally used as a 2% “tincture” in 50% alcohol, iodine is now more commonly packaged in detergents. These agents are termed iodophors, and avoid the staining and allergies associated with the use of tinctures. Chlorine is another halogen that oxidizes proteins and other organic materials. Chlorine works rapidly, but is not suitable for antiseptic use. Instead, it is used at a few parts per million in water to decontaminate water supplies and swimming pools, and is used as a 5% solution in water (hypochlorite) to decontaminate surfaces and glassware. Halogens are effective against bacteria, spores, and most viruses, and are therefore more effective than phenolics or alcohols.

Question 10

How do surfactants work?

Answer 10

Surfactants contain hydrophobic and hydrophilic groups, and are so named because they perturb bacterial cell membranes leading to cell death.

Question 11

What are quats?

Answer 11

Quaternary ammonium compounds (“quats”) are cationic detergents used at 0.1% concentration as antiseptics. However, some bacteria can grow in quats when the surfactant activity is “quenched” by other organic matter, and quats are inactivated by anionic, common detergents. Therefore, quats, which show little activity against viruses and none against spores, are not commonly used today.

Question 12

What is Glutaraldehyde?

Answer 12

an alkylating agent used to disinfect equipment. It first polymerizes and then binds to proteins in the outer membrane of Gram negative bacteria and amino acids found in the peptidoglycan cell wall of Gram positive bacteria. The subsequent alkylation inactivates the proteins, killing the cells.

Question 13

How does ethylene oxide gas work?

Answer 13

Ethylene oxide gas is also an alkylating agent and is used to treat heat-labile equipment. Ethylene oxide gas is explosive, mutagenic, and hazardous to the skin. Therefore, it is used under tightly controlled conditions. Ethylene oxide gas thoroughly kills (i.e., sterilizes) all contaminants.

Question 14

How does hydrogen peroxide work?

Answer 14

Several chemical agents are capable of oxidation, but hydrogen peroxide acts solely in this manner. It attacks the lipid membrane and other cellular components, but is less effective against spores and catalase-positive bacteria.

Question 15

T or F. Chemical agents are used to inhibit or destroy microorganisms (disinfect), but with the exception of ethylene oxide gas, none are capable of completely eliminating all contamination

Answer 15

T

Question 16

Why does moist heat kills more rapidly than dry heat?

Answer 16

because reactive water molecules denature protein by disrupting hydrogen bonds formed between amino acids.

Autoclaving at 15 PSI and 121C for 15 minutes will kill all bacteria, fungi, and viruses. To sterilize by eliminating spores and cysts, the time is extended. For objects or liquids that are not damaged by high heat treatment, autoclaving represents the most efficient way to sterilize.

Baking at high temperatures is another method to sterilize objects. However, because dry air does not conduct heat as well as moist air, higher temperatures and longer times are needed. Minimum standards for dry heat sterilization are 160oC for 2 hours.

Boiling objects does not sterilize them, but it does kill most everything except spores or cysts within 10 minutes. Because the temperature cannot exceed 100oC without added pressure, the boiling time is critical.

Question 17

What is pasteurization and does it sterilize?

Answer 17

does not sterilize. pasteurization involves heating liquids to 55-75C for 30 minutes followed by rapid cooling. Under these conditions, spores are not killed, but the bacterial load is reduced by 90%.

Consequently, pasteurization renders milk and juices safe for consumption and increases their storage life.

Refrigeration and freezing slow the growth of most all pathogens and therefore complement pasteurization as a strategy to ensure food safety and storage. However, refrigeration and freezing have no effect on spores, and therefore do not sterilize even though slow freezing can rupture cells when ice crystals form in the cytoplasm and poke holes in the cytoplasmic membrane.

Question 18

Is Nonionizing radiation sterilizing?

Answer 18

such as ultraviolet (UV) rays is sterilizing because it excites electrons and leads to the formation of new covalent bonds, such as thymine-thymine dimers in DNA. However, because of the long wavelength of nonionizing radiation, it has poor cell penetration properties, limiting its usefulness. Consequently, nonionizing radiation is typically used to disinfect air and surfaces in hospitals.

Question 19

How does ionizing radiation work?

Answer 19

The shorter wavelengths of ionizing radiation (x ray or gamma ray) provide more energy and better cell penetration. The transmitted energy damages DNA but also produces free radicals and creates hydrogen peroxide from cytoplasmic water. Ionizing radiation is used to sterilize disposable surgical supplies and foodstuffs.