STERILIZATION AND DISINFECTION

How is it used? to sterilize heat-tolerant items

(e.g. some surgical instruments, implants, ultrasound probes, anesthesia equipment, glassware, surgical dressings, gloves...)

How is pH a factor?

-changes in pH (away from neutral) may: -alter the agent efficacy on the bacteria: Increases in pH improve the microbial control of some agents (e.g. glutaraldehyde) and diminishes the microbial control of others (e.g. phenols) -influence the agent diffusion across the bacterial membrane: pH affects the ionization of the agent --Non-ionic molecules are more lipid soluble and will diffuse across the membrane easier than ionic or polar molecules

Characteristics of Quats

-ex: Benzalkonium chloride -mechanism of action=Disrupt the cell membrane by solubilizing the proteins -usage= Cleaning/disinfecting hard, non-porous surfaces (e.g. walls, floors, doorknobs, elevator buttons, bathroom fixtures...) -Active against most active against Gram (+) bacteria

What has to be done first in terms of organic matter?

-generally, the organic matter has to be removed first by cleaning, then the surface can be disinfected

What is antiseptic?

-kills or prevents growth of microorganisms primarily on the skin and mucous membranes by using chemical agents

What is sterilization?

-kills or removes all microbes, including bacterial spores (highly resistant) Includes: moist heat (autoclaving), dry heat (oven), filtration, gas sterilization (ethylene oxide), and gamma radiation

PHENOLS AND PHENOLIC COMPOUNDS (e.g. Carbolic acid, Lysol)

-low concentration- membrane leakage and irreversible inactivation of membrane functions (e.g. inactivating enzymes); high concentration- precipitate cell wall proteins disinfect noncritical items (e.g. bedside tables and bedrails, lab surfaces, bedpans, linens, crutches, BP cuffs...) FYI: Use of phenols/phenolic compounds is questionable in nurseries due to reported increases in infant bilirubin levels; if used on nursery floors, proper dilution must be made; use on other nursery objects (e.g. bassinets, incubators...) is suggested only when unoccupied, followed by thorough rinsing.

How is the location of organism is factor?

-only surfaces that come into direct contact with the agent will be disinfected/sterilized (are you using equipment with multiple pieces (e.g. endoscope) that need to be disassembled?)

At what pH is glutaraldehyde a poor disinfectant?

-pH 4 -good at pH 8 -Effects of pH on efficacy of disinfection. If glutaraldehyde is used as a disinfectant, its pH must be alkaline in order to achieve maximum efficacy in killing bacteria.

What factors are considered in selection of microbial control methods?

-treatment site (i.e. are you only treating the skin surface, or will you penetrate the skin?) -susceptibility of the microbe that you are attempting to control (i.e. does the microbe have structural elements- e.g. spores, waxy cell wall, cysts- that will hinder its destruction?) -environmental conditions (i.e. what is the temperature, pH?; temperature/pH affects microbial death rates and efficacy of antimicrobial methods) -Let's focus on the important considerations that need to be made in selecting chemical agents.

What is disinfection?

-use of disinfectants to kill many (but not all) microbes on inanimate objects; does NOT guarantee elimination of all pathogens; Spores and some viruses may survive Includes: ultraviolet (UV) light, heat, alcohol, and bleach

*Moist heat is also effective at killing spores.

. Spores of Clostridium botulinum can be destroyed in 4 minutes at 121°C under moist heat and pressure. If a lower temperature is used (e.g. 100°C), it would take about 6 hours.

When is it best to use alcohol based hand sanitizers?

Alcohol-based hand sanitizers are the most effective and preferred method for basic hand hygiene (not prior to surgery) if hands are not visibly dirty. Recommended use: 1) sanitizers with at least 60% alcohol are recommended; 2) rubbing the product over the entire surface of the hands (including fingers) until your hands are dry. For maximum effect, hands should be washed prior to use of hand sanitizer.

What are sterilization methods?

Bacteria have a minimum, ideal, and maximum temperature at which they grow and function best. Increasing the temperature above the maximum generally results in a bactericidal response because the increase in temperature denatures proteins, which affects bacterial function.

ANIONIC AGENTS (Surfactants/soaps

Decrease ability of bacteria to attach to surfaces; potential damage to bacterial membranes; antimicrobial properties can be enhanced with the addition of antibacterial substances (e.g. Triclosan...) Clean skin, clothing (laundering)... active at an acidic pH and are effective on Gram (+) bacteria; not effective against G

How is the oven used?

How is it used? to sterilize anhydrous fats, oils, powders, metal instruments subject to corrosion

How is gamma radiation used?

How is it used? to sterilize microbiological plasticware (disposable pipettes, pipette tips, petri dishes...), various dental/medical supplies (e.g. surgical gloves, catheters, sutures, syringes...), human tissue grafts...

What is microbial control?

Microbial control refers to the inhibition or prevention of growth of microbes. Control of microbes can be achieved through physical methods, chemical agents (antimicrobial agents) or a combination of both.

Is it important to have proper hygiene with stethoscope?

Stethoscopes can be reservoirs for microbes because of their repeated use during the course of a day. Failure to disinfect them could be as problematic as not adhering to hand hygiene • The American Journal of Infection Control (2017) reported that healthcare providers rarely perform stethoscope hygiene between patient encounters, regardless of the emphasized necessity of doing so o Infection control guidelines from the CDC and Prevention state that re-usable medical equipment must undergo disinfection between patients o Authors of a study published in the American Journal of Infection Control reported that even after educating clinicians (in their study) about the method, importance and necessity of stethoscope hygiene, there was still no occurrences of compliance o **there are numerous studies on this same subject that report similar results

chlorine/iodine

oxidizing cellular molecules (e.g. enzymes), resulting in diminished function and survival Chlorine: used in water treatment (in gas and liquid form); when it is in the form of hypochlorite (bleach) it can be used in a number of ways (e.g. post cleaning of blood spills, disinfectant for manikins, floors, countertops...) Iodine: generally used as a tincture or an iodophor; Betadine (used in skin prep prior to surgery) Have some ability to kill spores

ALCOHOLS (e.g. isopropyl alcohol, ethanol

) water-soluble solutions that disrupt bacterial cell membranes by denaturing proteins and disorganizing lipids -Ethanol is great antiseptic for the skin and may be used as a disinfectant on some surfaces. -Isopropyl alcohol can also be used on the skin and is recommended for disinfection of thermometers; it is a slightly better disinfectant, and has better activity against some bacteria -Hand sanitizers (which contain alcohol) have some efficacy as a disinfectant when the hands are not visibly dirty or greasy (washing hands with soap and water is best). -Ethanol and isopropyl alcohol are not viable for sterilizing medical or surgical instruments (because they cannot kill spores) Not effective against spores

Is pasteurization a sterilization method?

**Pasteurization is not a method of sterilization, but is a method of slowly increasing the heat of substances (e.g. milk, wine, beer...) just enough to destroy bacteria that would cause spoilage • accomplished by short exposure to 60-65°C which kills most vegetative bacteria; longer exposure will kill all pathogens, notably Mycobacterium

For example with 90% ethanol?

- Using a higher concentration of ethanol (90%) does not effectively kill bacteria on surface, but inactivates them. 90% ethanol quickly coagulates bacterial surface proteins, which prevents the alcohol from penetrating the bacterial cells to kill them.

What selection of antimicrobial chemical agents?

-Antimicrobial chemical agents include antiseptics and disinfectants (refer to p. 2 for definitions). In selecting the most effective agent, several factors must be considered:

How is a type of organism a factor?

-Consider the type of organism(s) present, the structural characteristics (e.g. does the bacterium possess structures that will enhance its resistance- spores, waxy cell wall, capsules?), number (how contaminated is the area?), and any info of the organism based upon culture characteristics

What is gas sterilization (ethylene oxide)?

-Ethylene oxide (gas) is used to sterilize items that are sensitive to moisture and heat (i.e. items that cannot be sterilized by steam); kills both microbes and spores • Because it is a gas, it is highly flammable and the sterilized item must be allowed to "degas" post- sterilization; Levels of residual ethylene oxide are tested before product is deemed "ok" for use How is it used? To sterilize items such as: surgical sutures/staples, catheters, specula, syringes, fiber optic endoscopes, surgical telescopes; can also sterilize some plastic

Why is microbial control important?

-Healthcare-associated infections (HAI; i.e. infections acquired while receiving medical or surgical treatment) are common threats to public health and patient safety. -According to the CDC, about 1 in 25 U.S. hospital patients acquires a HAI. To address this issue, several national initiatives and action plans have been instituted which have made a significant impact on the reduction of the most common types of HAI (i.e. catheterassociated urinary tract infections, surgical site and bloodstream infections, pneumonia, and Clostridium difficile infections). -A clear understanding of the methods of microbial control is critical in the reduction and potential elimination of HAI.

What is an example of length of exposure?

-Illustration of contact time on container and evaluation of contact time on disinfectant efficacy

In preventing transmission of communicable disease, what has to be removed?

-In preventing transmission of communicable diseases, only the potential pathogen has to be removed (e.g. preparation of milk via pasteurization).

How is temperature a factor?

-Increases in temperature generally enhance the agent's ability to kill bacteria (e.g. disinfection of a blood spill on the surface at room temp will be faster than a blood spill in a refrigerator); However, disinfectant efficacy can be hindered by temperatures that are too high or too low

How is concentration a factor?

-Many chemicals are used at very high concentrations (to increase killing of target organisms) -Some are more effective at lower doses (ex. Ethanol more effective @ 70% than 95%) -altering concentration may affect contact time (how long the chemical has to be in contact with the microbe in order to be effective) -: Efficacy of 70% ethanol vs. 90% on surfaces; recommended for maximum efficacy (50-80%).

How is length of exposure a factor?

-Not all microorganisms die at the same time when exposed to an agent (i.e. the longer the time of exposure to an agent, the greater the reduction in microbes) -For disinfectants: the maximum length of exposure is when all bacteria are killed; it is important to determine the appropriate length of time for each agent used (most disinfectants will provide info on the container about the contact time required for maximum efficacy) - Contact time is the amount of time that the surface (that you are disinfecting) needs to stay wet in order to be effective; follow the instructions listed by the product manufacturer

What is an example of pH?

-The image below illustrates manual cleaning of an endoscope with water and an enzymatic cleaner. - Post cleaning, the endoscope is to be disinfected. In this example, we are using glutaraldehyde to illustrate the effects of pH on efficacy of disinfection.

For example with 70% ethanol?

-Using a diluted concentration of ethanol (70%) effectively kills bacteria on surface. 70% ethanol also coagulates bacterial surface proteins, but at a slower rate. Therefore, alcohol can penetrate the bacterial cells and kill them.

What is germicide?

-agents (e.g. antimicrobials, disinfectants, sporicides, sanitizers, sterilants) that kill disease causing microorganisms (including bacteria, viruses etc.)

What is the presence of organic matter or biofilms?

-association of microbes with organic substances (e.g. serum, blood, pus, feces, sputum, vomit) or biofilms can decrease the activity of the agent; organic matter may form less active (inert) complexes with the agent, and reduce the agent's ability to adequately kill the microbes

What does hand hygiene involve?

Hand hygiene involves: routine hand washing (with soap and H2O), use of antiseptic washes or gel rubs, and/or surgical antisepsis (hand/forearm wash prep for surgery), which has been shown through numerous studies to reduce the incidence of infections.

PHYSICAL METHODS OF MICROBIAL CONTROL AND THEIR MECHANISM OF ACTION

PURPOSE: use of physical means to destroy or remove contaminants (in this discussion, bacteria). Include: moist heat (autoclave), dry heat (oven/incinerator), filtration (removal of microbes with use of filters), gamma radiation, gas sterilization (ethylene oxide). Some of these methods results in sterilization (refer to terms on p.2). This info in this section will focus on the sterilization methods of microbial control.

What is filtration?

Passage of a solution through sterile membrane filters to remove microbes from solution; The filter must contain components that minimize adhesion of the solution to the filter and have a pore-size that prevents passage of microbes • must be followed by aseptic transfer of the sterilized solution to a sterile container and sealed • All downstream use of the solution must be aseptic How is it used? To sterilize thermolabile solutions (solutions that are subject to decomposition in heat)

What is the sterilization by heat?

STERILIZATION BY HEAT **Heat is the most reliable and universally applicable method of sterilization, and is generally the sterilization method of choice. Although heat can kill bacterial vegetative cells, spores are quite resistant to heat. **In order to destroy spores, very high temperatures are necessary. Heat sterilization is a gradual process that results in exponential death of microbes.

What must be evaluated since microbes display a range of resistance?

Since microbes display a range of resistances to chemical agents, it is necessary to evaluate the efficacy of the agent to select the one that will best control microbial growth. The effective and efficient use of disinfectants in healthcare facilities is an important in prevention of healthcare-related infections. Historically, evaluation of disinfectant efficacy is achieved by comparing it to the activity of phenol (broad spectrum disinfectant that can denature cell wall proteins and inactivate membrane-bound enzymes, resulting in altered permeability and death of the cell; used as the historical standard because it has an overall damaging effect on microorganisms).

When should proper hand hygiene be implemented?

The times below are generalities. The CDC has detailed guideline available on their website. • before eating • before and after direct contact with patient (e.g. taking BP/pulse, physical exams...) • after touching an inanimate surface/object with your bare hands • after contact with body fluids, mucous membranes, wound dressings, or non-intact skin • during patient care when moving hands from a contaminated body site to clean body site • before surgical procedures • before putting on sterile gloves/after removing gloves • after restroom use

HEAVY METALS (high molecular weight-e.g. silver arsenic, zinc, mercury,copper)

alters the 3D-structure of bacterial proteins, which compromises protein function and survival of the bacteria; several exhibit toxicity and use in humans has become limited Historically, silver (as silver nitrate) was used as a prophylaxis for opthalmia neonatorum (neonatal conjunctivitis). Today, antibiotics are often used; is silver sulfadiazine is used as a topical cream for burns

CHLORHEXIDINE

antiseptic that disrupts cell membranes and denatures proteins; May be combined with gluconate, which enhances bacterial uptake to clean skin (e.g. handwashing, surgical scrubs...) and in oral rinses does not kill spores

HYDROGEN PEROXIDE

oxidizes bacterial enzymes which interfere with bacterial metabolism and kills the bacteria; the combination of hydrogen peroxide with peracetic acid (another oxidizer), has been shown to be a much stronger disinfectant to disinfect environmental surfaces and to clean wounds (although there is some debate on the efficacy of this) bactericidal activity is greater against anaerobic bacteria

How to function dry heat?

application of heat with no moisture involved; used to sterilize materials that can be damaged by moist heat or cannot be sterilized by moist heat (e.g. powders, sharps) • ** liquids cannot be sterilized by dry heat because they would just "boil away" IMPORTANT MOIST HEAT INFO INDICATED BY ** STERILIZATION BY HEAT **Heat is the most reliable and universally applicable method of sterilization, and is generally the sterilization method of choice. Although heat can kill bacterial vegetative cells, spores are quite resistant to heat. **In order to destroy spores, very high temperatures are necessary. Heat sterilization is a gradual process that results in exponential death of microbes. MBLDD: Sterilization and Disinfection Carolyn Roberson, Ph.D. 2020 12 • FUNCTION: denatures bacterial proteins and exerts oxidative damage but takes longer to sterilize in comparison to moist heat (dry heat requires higher temperatures, which takes more time to achieve because no pressure is involved) • Examples include: o incineration (uses a flame or heating coil; e.g. Bunsen burner) or ovens o ** Oven sterilization is the main method of dry heat, and the standard parameters for dry heat sterilization (and for killing spores) is 150-180°C for 2-4 hours

FORMALDEHYDE GLUTARALDEHYDE ETHYLENE OXIDE

attach alkyl groups to bacterial proteins and DNA resulting in nonfunctional molecules and ultimate death of the bacteria Formaldehyde: used as an embalming agent and to disinfect the internal pathways of dialysis machines Glutaraldehyde is a 10x more effective disinfectant than formaldehyde and is the **only cold chemical sterilizing agent recommended by the CDC for use on respiratory therapy equipment; Glutaraldehyde is also used in cleaning endoscopes and spirometer tubing Effective against spores Glutaraldehyde is a cold sterilization method

It is recommended that the item to be autoclaved is...

cleaned (decontaminated) of any debris 1st via cleaning (manual or machine), disinfected, and then prepped for autoclaving (appropriate wrappings, containers...)

What is gamma radiation?

the emission of gamma rays by radioactive elements (e.g. Cobalt-60) to produce free radicals which disrupt bonds in DNA, resulting in inhibition of bacterial cell division and subsequent cell death • **deeply penetrating method of sterilization that can kill microbes throughout the product and packaging with no need for pressure or vacuum suction; kills vegetative cells, viruses, and most endospores • emission of the radiation is in doses that are measured in kiloGray (kGy) units; Post radiation exposure, the products are verified to ensure that they have received the correct dosage of radiation for sterilization (via dosimeters which are calibrated regularly) • Exposure occurs over several hours • **there is no residual radioactivity post irradiation

What is the function of moist heat autoclave?

use of saturated steam under pressure and is the preferred method of heat sterilization o Each item to be sterilized must be directly exposed to the steam at the required temperature and pressure • FUNCTION: **Moist heat is more effective than dry heat because it penetrates the bacterial cells to kill the bacteria by denaturing their proteins and melting their lipids o One of the most common methods of applying moist heat is through use of the autoclave o ** The most efficient temperature/pressure to destroy microbes in the autoclave is 121°C and 15 psi (pounds per square inch) of pressure for about 15-20 minutes; Times can vary based upon the size of the load that is to be autoclaved.

What is the most common mode of transferring pathogens?

via the hands