Chapter 11 Disinfectants and Antiseptics

Why is alcohol not recommended for high-level disinfection?

Because it is not virucidal against naked (nonenveloped viruses) or bacterial spores, and because it is inactivated in the presence of organic debris.

Characteristics of the ideal disinfecting agent:

Broad-spectrum antimicrobial activity, nonirritating and nontoxic to animal and human tissue, easily applied to inanimate objects and without causing corrosion or stains, stable and not easily inactivated, and inexpensive.

How does chlorhexidine work?

By damaging the cell membrane of the pathogen, lysing the cell. It remains more active than chlorine or iodine in the presence of organic material including blood, but through cleaning of the application site is still recommended for it to achieve maximal effectiveness.

High-level, intermediate-level/ Low-level disinfectants

Designations that generally refers to the ability of the disinfectant to kill pathogens with different levels of susceptibility to kill pathogens with different levels of susceptibility.

Disinfection

General term that refers to the destruction of pathogenic microorganisms

Biofilm

Generated by bacteria when they attach to a surface (such as within the joint or box hinge of a surgical instrument, or in crevices of an endoscope) and develop a glycocalyx "shell" around themselves.

What are phenols effective against?

Gram-positive bacteria, but generally ineffective against gram-negative bacteria, viruses, fungi and spores.

What are quaternary ammonium compounds effective against?

Gram-positive bacteria, but they are ineffective against bacterial spores, and have poor efficacy against fungi and gram-negative bacteria. Although they can destroy enveloped viruses, they are ineffective against nonenveloped viruses such as parvovirus.

Non-enveloped viruses

"Naked" virus core without a surrounding lipid envelope.

Iodophor

A combination of molecular iodine and a carrier molecule that releases the iodine over time, prolonging the antimicrobial activity.

Hydrogen peroxide

A commonly available 3% solution has historically been used to debride (remove) necrotic tissue and kill bacteria. But is weakly bactericidal and probably provides most of its benefit by removing devitalized tissue to make the environment less suitable for bacterial growth. Although the foaming action of oxidizing agents in wounds is dramatic, these compounds are not virucidal and may actually damage tissue that is healthy or marginally viable. For that reason, 3% hydrogen peroxide has fallen out of favor as an antiseptic on tissues.

Glutaraldehyde

A high-level disinfecting chemical sterilizer with a wide spectrum of activity against bacteria, viruses, fungi, and bacterial spores. IT has a similar chemical structure to formaldehyde but with less of the irritation and non of the potential carcinogenic effects.

Chlorhexidine

A member of a class of antiseptics known as biguanides, is one of the most commonly used disinfectant and antiseptic compounds in veterinary medicine.

Phenols (Lysol)

A part of a larger group of related compounds found in mouthwashes, surface disinfectants, and many household disinfectants such as Lysol, pine oil, and similar cleansers.

Triclosan

A phenol that has been incorporated into a variety of soaps, disinfectants, deodorants, shampoos, medical supplies, and even some plastics to decrease bacterial growth. Phenols are sparingly used in veterinary medicine.

Accelerated hydrogen peroxide

A variant of hydrogen peroxide that has been successfully marketed as a proprietary compound for use as a disinfectant. Contains a lower concentration of hydrogen peroxide (0.5%), surfactants that break down the surface tension of water and allow penetration, wetting agents that allow liquids to spread out over a surface, and a chelator.

Vinegar solution is primarily ______________________ _____________________ and is sometimes recommended for yeast infections in otitis externa (ear inflammation cause by bacterial or yeast infections). Because better products are available that have greater efficacy and less tissue irritation, this produce is not often recommended today for use in veterinary medicine.

Acetic acid

Vegetative bacteria

Actively growing bacteria not in a spore state.

What two forms can bacteria and fungi exist in?

Actively growing vegetative state or a more static spore form.

How long does alcohol have to be in contact with the skin to be effective against bacteria and fungi?

Alcohol must be applied in sufficient quantities and remain in contact with the skin or site for 1-3 minutes to be effective against bacteria, several minutes are required for fungi.

What trade name is accelerated hydrogen peroxide been incorporated into commercial disinfectant products under?

Clorox

Peroxymonosufate

Another oxidizing agent that has been used to disinfect pools and hots tubs but has also been formulated with potassium to be used as a surface disinfectant.

Germicide

Any chemical agent that kills microorganisms, but because microorganisms include viruses, bacteria, protozoa, and fungi, the term germicide is too nonspecific and should not be used by veterinary professionals.

Topical iodine and ionophores antifungal agents

Are effective against the dermatophytes that cause ringworm.

Vegetative bacteria and enveloped viruses

Are usually very susceptible to disinfectants or antiseptics and therefore could by killed by low-level disinfectants.

Pseudomonas

Bacteria that is highly resistant to disinfection and antiseptics because of their ability to produce and immerse themselves in a biofilm. These bacteria attach to living tissue, implants, or catheters and begin to exude microscopic glycocalyx material made of protein, deoxyribonucleic acid, and polysaccharides in which the bacteria can proliferate protected from the disinfecting agents.

Enveloped viruses include:

Canine distemper virus (paramyxo virus), feline herpes virus, rabies (rhabdovirus), influenza virus (orthomyxovirus), and poxviruses (smallpox, cowpox).

Non-enveloped viruses include:

Canine parvovirus, feline panleukopenia virus (it is a parvovirus), feline calicivirus, and papillomavirus (produces warts).

Disinfectants

Chemical agents that kill or prevent the growth of microorganisms on inanimate objects such as surgical equipment, floors, and tabletops.

Antiseptics

Chemical agents that kill or prevent the growth of microorganisms on living tissues.

Sanitizers

Chemical agents that reduce the number of microorganisms to a "safe" level without eliminating all microorganisms.

Sterilizers

Chemicals or other agents that destroy all microorganisms.

As an external ear preparation, ________________________________ is considered quite safe but if the compound gains access to the middle ear it is considered ototoxic.

Chlorhexidine

Why is combining chlorhexidine with other cleaning products not advised?

Chlorhexidine can be inactivated by anionic and nonionic detergents soaps, and the minerals in hard water.

Halogens

Chlorine compounds belong to a larger group of compounds known as this.

When is chlorine readily inactivated?

Chlorine is the most commonly used disinfectant for fighting enteric viruses such as parvovirus, it is readily inactivated in the presence of any organic material such as feces, blood, and pus. The free chlorine ion needed to denature the pathogen proteins combines instead with organic material.

Although iodine can be inactivated by organic material, especially blood, to some degree, it is still considered to be better at maintaining its antiseptic activity in the presence of organic material than ______________________________.

Chlorines

Quaternary ammonium compounds or "quats"

Cleansing agents (cationic surfactants) with germicidal activity, used in veterinary medicine to disinfect the surfaces of floors, walls, and vehicles utilized in livestock and eff-laying operations.

The manufacturer of _________________________________ claims strong bactericidal, virucidal, along with some fungicidal activity for these products.

Clorox

At what concentrations do alcohol concentrations work best?

Concentrations of 70-90%, but concentrations in excess of 95% are less effective because very high alcohol concentrations lack the water needed to effectively denature the proteins of the pathogen and produce the disinfection.

What are the down sides of using chlorine disinfectants?

Contact with high concentrations of sodium hypochlorite bleach can cause bleaching of colors and fabric deterioration. Chlorine is also corrosive to most metals, except high-quality stainless steel, and if left in contact for an extended period of time can pit or damage metal tabletops or surfaces, providing reservoirs for debris accumulation and proliferation of pathogens.

_________________________________ typically are more potentially toxic to veterinary patients, staff, or clients because they are intended for use on nonliving tissue and hence may be more concentrated form of an antiseptic or may have chemical characteristics that produce irritation or tissue damage.

Disinfectants

What two alcohols are among the most common antiseptics applied to the skin?

Ethyl alcohol and isopropyl alcohol

What is the difference between ethyl alcohol and isopropyl alcohol?

Ethyl alcohol has slightly better virucidal activity, but isopropyl alcohol has slightly better bactericidal activity.

True or False, glutaraldehyde 2% solutions are inactivated by organic debris, and it is not effective in the presence of hard water.

False, glutaraldehyde 2% solutions are not inactivated by organic debris, and it is effective in the presence of hard water.

True of False, Alcohol is also effective against bacterial spores?

False, it is not.

Iodine is potentially effective against bacterial spores is what?

If the iodine solution remains moist and in contact with the site for more then 15 minutes.

Nosocomial infections

Infections acquired during a period of hospitalization, are especially difficult to control because any oraganism that can suvive the routine cleaning, sterilization of instruments, use of antiseptic on patients, and widespread application of disinfectants must be a very tough, resistant organism.

What level are chlorine compounds classified as?

Intermediate-level disinfectants because they can kill the vegetative form of bacteria, algae, fungi, and both enveloped and nonenveloped viruses, including parvovirus. It is not however effective against bacterial spores.

What is the most common iodophor used?

Iodine complexed with polyvinylpyrrolidone, or PVP, a combination more commonly known as povidone-iodine

Surgical scrubs

Iodophors combined with a detergent or nonionic surfactant (soap like compounds that break the surface tension of water and allow easier interactions between organic material and chemicals).

Why shouldn't alcohol be applied to open wounds?

It can cause pain and may also facilitate survival of pathogens.

What is chlorhexidine used for?

It is used for a variety of purposes, including cleaning cages, treating teat infections in cattle, surgical preparation as a scrub, and maintaining oral hygiene in companion animals. Its wide range of uses is likely related to its low tissue irritation and its bactericidal (both gram positive and gram negative) and fungicidal properties. Is not considered effective against nonenveloped viruses like pravovirus and has debatable effectiveness against enveloped viruses.

How is glutaraldehyde used?

It is used primarily as a disinfectant on equipment that cannot be heat sterilized, such as endoscopes, but has also been widely used to cold-sterilize clinical instruments (product called Cidex).

What does the coagulum do?

It may seal in or protect underlying bacteria, thereby preventing topical disinfectants from reaching the organisms. The infection could then spread to underlying tissues.

What side effects does glutaraldehyde share with formaldehyde?

It shares some the tissue irritation, odor, and corrosion characteristics, a veterinary technician should take special precautions when working with this compound by wearing safety goggles and gloves, and working in a well-ventilated area. Any equipment, like endoscopes, disinfected with glutaraldehyde must be thoroughly rinsed with sterile water before use in or on living tissue.

What is one of glutaraldehyde's advantages?

Its ability to kill bacteria normally protected from disinfectants by biofilm. It can penetrate the biofilm and reach the bacteria, plus cause the bacteria colony to detach from the surface of the instrument and be flushed away.

What are the advantages of alcohol?

Its low cost, general lack of toxicity when applied topically, and bactericidal activity against gram positive bacteria and gram negative bacteria.

Bactericidal chemicals

Kill bacteria

Fungicidal chemicals

Kill fungi

Sporicidal

Kill microbial spores

Protozoacidal chemicals

Kill protozoa

Virucidal chemicals

Kill viruses

Benzalkonium chloride

Major quaternary ammonium compound used in veterinary medicine. Is the key ingredient in the disinfectant Roccal-D.

Potassium peroxymonosulfate (PPMS)

Marketed as Trifectant comes mixed with surfactant, organic acids, and buffers in a dry powder or tablet form that has been dissolved in water. The manufacturer claims that it is virucidal, including against nonenveloped, bactericidal, and fungicidal, even in the presence of organic material and hard water.

What do disinfectants need to be?

Microbicidal rather than microbiostatic because inanimate objects do not have an immune system to eliminate organisms not killed.

Alcohols

Most commonly used as part of an aseptic technique to disinfect surgical sites, injection sites, and sites with low-disinfectant requirement.

Do saline solutions added to chlorhexidine affect its antimicrobial properties?

No, the saline solution does cause chlorhexidine to precipitate but apparently does not affect the antimicrobial properties.

Iodine compounds and iodophors

Not commonly used as topical antiseptics before surgical procedures or for aseptic disinfection of tissue. They are bactericidal, virucidal, fungicidal, and sporicidal because of the free iodine, which diffuses into the pathogen cell and disrupts metabolism and protein structure and synthesis.

coagulum

Open wounds usually contain a serum exudate that is rich in protein. Alcohol denatures the structure of this protein, causing it to form a superficial barrier also called this.

__________________________________ are not as easily inactivated by organic material as detergents, quaternary ammonium compounds, and chlorine solutions.

Phenols

The older preparations of free iodine included what?

Products such as tincture of iodine or topical iodine solutions.

What side effects can occur with use of phenols (lysol)?

Prolonged contact with concentrated solutions may damage the skin. For example, bid perches, disinfected with phenols may cause lesions on the feet of birds. Dermal ulceration has been reported in reptiles kept in cages that are consistently disinfected with phenols. Dogs may develop skin lesions when runs are cleaned with phenols and not adequately rinsed. Phenols themselves are hard to adequately rinse from surfaces, especially slightly porous surfaces, and therefore tissue irritation from contact of residues are a common problem. Ingestion can result in severe liver damage.

Ovidone-iodine

Provides a low level to intermediate level of disinfection that is slightly less than that of the level of disinfection that is slightly less than that of the older free-iodine solutions because less free iodine is avialable from the iodophor at any given moment during the slower release process.

The powder formulation of Potassium peroxymonosulfate (PPMS)

Said to have no environmental residue problems and has low toxicity if applied topically or swallowed.

What do most disinfectants and antiseptics tend to be?

Sanitizers because sterilization is something only attained on inanimate objects.

What are antiseptics and disinfectants sometimes described as?

Sanitizers or sterilizers

What are chlorine disinfectants most commonly available as?

Sodium hypochlorite (formula=NaOCl) found in the common, inexpensive household bleach and often referred to be the particular proprietary name Clorox.

How is sodium hypochlorite solutions diluted?

Sodium hypochlorite solution is not very stable after they have been diluted because the chlorine evaporates into the air, reducing the quantity of free chlorine available for disinfection. In addition, exposure to light breaks down the disinfecting compound.

What is alcohol's main mechanisms of action against pathogens?

Solubilizing (dissolving) lipid membranes and by denaturing (altering structure) of proteins. For enveloped viruses, this means alcohol destroys the vital lipid envelop these viruses need to enter the hose cell. For bacteria alcohol denatures either the pathogen's surface proteins or essential metabolic proteins needed by the pathogen to survive. Non enveloped viruses (canine parvovirus), will be largely unaffected by alcohol.

Acetic acid

Sometimes used as a 0.25% solution to kill Pseudomonas organisms, as well as a variety of other gram-positive and gram-negative bacteria.

What have a significant effect on glutaraldehydes?

Temperature, and pH, that's why it is important that cold-sterilization baths or solutions used to clean endoscopes are kept at room temperature and at neutral to alkaline pH. For example, dlutaraldehyde is sporicidal at an alkaline pH (above 8) but generally not at an acidic pH.

Why are quaternary ammonium compounds not used as antiseptics?

The active ingredients bind to gauze and cotton commonly used to apply antiseptics to skin or tissue, and the Center for Disease Control and Prevention, no loner recommends them for antisepsis.

How do chlorine compounds work?

The chlorine ions liberated from the disinfecting compounds kill the pathogens by denaturing protein structure and chemically inactivating essential enzyme systems needed by the pathogen.

What is the difference between antiseptics and disinfectants referred to?

The difference refers to the degree of microbial destruction achieved.

What does the envelope in the enveloped viruses do?

The envelope around the enveloped virus does not protect the virus but is an essential component of the virus and is readily disrupted by detergents and disinfectants.

What are other common sites for the creation of biofilm or nosocomial infections?

The urinary tract (associated with the use of infected or contaminated urinary catheters), respiratory tract (associated with improperly disinfected endotracheal tubes), surgical sites (improper surgical prep or contaminated instruments), wounds (failure to clean bandages or areas around the wound site, and intravenous (IV) catheter insertion sites (failure to use adequate aseptic technique when inserting the catheter).

Iodine solutions

These are iodine antiseptics without the added surfactant, so a povidone-iodine product without surfactant would be a solution.

How do quaternary ammonium compounds work?

They act rapidly at the site of application and normally are not irritating to the skin or corrosive metals. They readily bind to organic materials, rendering them less effective against many pathogenic microorganisms within or under such debris.

What inactivates quaternary ammonium compounds?

They are inactivated by contact with other detergents and soaps, the application site cleaned with soap or other surfactant must be rinsed thoroughly to remove residue before the quaternary ammonium antiseptic is applied. Hard water reduces the antimicrobial activity of quaternary ammonium compounds. Therefore, proper cleansing, rinsing, and drying of the site before the application of the quaternary ammonium compound are essential to maintaining its effectiveness.

Why are Phenols not commonly used as antiseptics for preparing surgical sites in veterinary medicine?

They are more toxic if taken into the body and they are also not used because they have a slower onset of action than povidone-iodine or chlorhexidine.

Why are cationic soaps and detergents less recommended for use?

They combine readily with proteins, fats, and phosphates and therefore will be easily inactivated by the presence of serum, blood, tissue debris.

Why must cleansers (detergents or surfactants) be used before application of the disinfectant?

They have to remove the organic material, before the disinfectant is used.

How do oxidizing compounds work?

They work primarily by denaturing proteins and lipids of microorganisms, however they can potentially have similar effects on mammalian cells, and for that reason the use of different agents sparks continued debate.

What does it mean when a disinfectant is described as sporicidal?

This means the chemical is capable of killing the pathogen when it is in its resistant or dormant state.

True or False, higher than recommended concentrations of iodine in iodophors are actually less effective than diluted iodophor concentrations because the free iodine is not released as readily at higher than recommended concentrations.

True

True or False, the chlorine solution should remain in contact with the site several minutes to ensure adequate destruction of pathogens. According to Oregon State University Biological Safety bulletin, a 10% bleach solution left in contact with the site for 10 minutes at room temperature should produce adequate disinfection. At lower temperatures, a longer period of contact would be needed to achieve the same degree of disinfection.

True

True or False, the presence of scrub soap is not appropriate for any use inside the body, and if such a need for iodine antiseptics is indicated (flushing an abscess), a solution without detergent must be used.

True

True or False, Bacterial spores are designed to be able to survive in a dormant state for years to decades so that under appropriate conditions they can switch to the vegetative state and begin multiplying again.

True, for example, Clostridium tetani, the bacteria agent of tetanus, and Bacillus anthracis, the bacterial agent of anthrax, have been shown to exist as spores buried in the ground for decades, only to be reactivated on exposure to appropriate conditions.

True or False, Alcohol has no cleaning ability (it does not act like a soap).

True, therefore it should not be used to cleanse the site or equipment of fecal matter, blood, mucus, urine, or organic debris. Organic debris dramatically reduces the effectiveness of both ethyl and isopropyl alcohol. In addition, blood left on instruments will denature if soaked in alcohol and will become more tightly adhered to the equipment or instruments being disinfected.

Ethylenediamine tetraacetic acid (EDTA) and Tris buffer

Two products that are compounded and used together to irrigate ear infections, wounds, or fistulas, infected with Pseudomonas. They are considered effective against a fairly narrow spectrum of gram-negative bacteria and Staphylococcus aureus.

Enveloped viruses

Viruses surrounded by a thin phospholipid/protein envelope used to enter a host cell.

When does biofilm becomes a great concern?

When it forms on metal bone implants (plates and internally placed pins or screws) used to immobilize broken bones. If a surgically placed metal implant becomes infected with biofilm-producing bacteria , the infection prevents bone healing and the implant usually has to be surgically removed.

Of all the antiseptic agents, _______________________________ produces the largest and fastest reduction in bacterial counts within 1 to 3 minutes of contact.

alcohol

What soaps work well to liquify or solubilize (dissolve) dirt, fat, and microorganism membranes (made of phospholipids) so that they can be washed away.

anionic cleansers

Non-enveloped viruses, bacteria or fungi in their spore form, and protozoal oocysts (cyst containing the zygote of the protozoan parasite) are all difficult to kil and would require ___________________________ _________________________________.

high-level disinfectants

Like chlorine, ______________________________ ______________________________ are classified as halogens.

iodine compounds

Instead of free-iodine compounds, _________________________ are used instead, which are far less irritating and provide a longer duration of antiseptic or disinfecting action.

iodophors

iodophors are often referred as what?

surgical scrubs

Why should neither iodophor solution or scrub be used in the peritoneal cavity?

the irritation and trauma caused by the free iodine, high concentrations of iodine should be avoided on denuded skin because of the potential for significant irritation and systemic absorption of iodine.