"Chemical Disinfection 101"
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BACKGROUND

Today, all healthcare personnel are concerned about improving patient outcomes. One area of concern is surgical site and nosocomial infections. A review of the practices follows as well as what is new in these critical areas.

There are three levels of disinfection; low level; intermediate level; and high level. Environmental disinfectants are used for cleaning inanimate (non-living) items such as floors, walls, tables, etc. These disinfectants are registered by the Environmental Protection Agency (EPA). Environmental disinfectants usually are low and intermediate level. Most often, processing personnel use environmental disinfectants for work areas, sterile storage areas and patient care equipment.

Disinfectants used for patient care devices (e.g. flexible fiber optic scopes) require high level disinfection. High level disinfectants inactive the bacterium TB and some small numbers of spores. The Food and Drug Administration (FDA) regulates the high level disinfectants used for medical devices that will go in a patient. This In-service will not deal with the high level disinfectants.

Hierarchy of Microbes

This chart demonstrates the different groups of microbes (on the left side) and the required minimum processing. The major change in the Hierarchy of Microorganisms is that we now need to recognize prions. On the list they take place at the top, over spores. This is because prions require additional sterilization exposure time, more so than spores. When reading this chart, note that you can always exceed the recommended processing, but cannot do less. In looking at Mycobacteria TB the minimum required processing is high level disinfection. You certainly could sterilize these devices but high level disinfection is the least you could do.

General Disinfectant Guidelines

Items must be thoroughly cleaned following the device manufacturer's written instructions for cleaning. In addition, special cleaning implements may be recommended by the manufacturer. Unless the surface is thoroughly cleaned, the disinfectant may not make contact with all surfaces therefore, disinfection may not occur.

There is much discussion about water quality and its impact on the disinfection process. The quality of your water should be checked for impurities, minerals, salts, etc. Some disinfectant manufacturers require you mix the solution with distilled water. If tap water is used instead, the disinfectant may not work. The temperature can also affect the process; some disinfectants work faster in elevated temperatures. However you should never attempt to elevate the temperature of a disinfectant solution unless the disinfectant manufacturer has provided specific guidelines how this is accomplished and what safety precautions are needed. When measuring disinfectants, make sure you first measure the disinfectant (using a medicine glass or other measuring device). Then you need to know how much water you are adding. Adding too much or too little water can adversely affect the disinfectant's action.

Today, many facilities use a variety of disinfecting agents. Therefore it is critical to always obtain and follow the disinfectant manufacturer's instructions for use, concentration, contact time, rinsing, etc. Some disinfectants are inactivated by soils, others by detergent residues. Therefore rinsing cannot be overlooked because this can also affect the overall process as well. Determine if you need to rinse off the detergent after disinfection.

All surfaces must make direct contact with the disinfectant for a specified period of time. It is important to know the correct contact time so that the disinfectant has time to work. Contact time, temperature and concentration of the chemical can vary with different products. Some chemicals are available for use without mixing (dilution) while others are concentrated and require dilution with water. However, water quality can interfere with the action of the chemicals so it is important to read the disinfectant label to determine what type of water should be used (e.g. tap water versus distilled water) when mixing (diluting) the chemical.

Some disinfectants are bactericidal, others are bacteriostatic and some are both. When you see "bactericidal" on a label it means the product kills bacteria. Bacteriostatic means the product slows or inhibits bacterial growth. Sometimes bacteriostatic disinfectants leave a residual film and the disinfectant is re-activated when it becomes wet.

Before using a disinfectant, make sure it has been approved by your Infection Control Department/Committee for use. Usually, this Committee will review the product for safety, which microorganisms it will inactivate, make sure the product has a valid EPA registration number and provides clean information for the disinfectant's proper use and safety precautions.

What are the Differences Between Disinfectants and Disinfectant Cleaners?

QUAT Disinfectant Cleaner

Some disinfectants are also cleaners. Disinfectant cleaners combine the cleaner (detergent) and disinfectant into a "one-step" process. A disinfectant-cleaner is diluted and then used to remove soils and kill germs all in one application. One step disinfectant-cleaners save labor time and money. Therefore, disinfectants "disinfect" and disinfectant-cleaners "disinfect and clean." If you are uncertain if your product is a disinfectant or disinfectant-cleaner, read the product label carefully. If the label does not mention "cleans and disinfects," then it is probably a disinfectant or sanitizer and not a one-step disinfectant-cleaner.

The types of disinfectants and antiseptics in use in healthcare include:

QUATS also known and Quaternary Ammonium Compounds. These are generally low level disinfectants based upon the active ingredient "benzalkonium chloride". QUATS are mainly used for environmental cleaning. They are effective against Gram positive bacteria, and may be ineffective against some Gram negatives, TB, lipid viruses and spores. Today, there are newer formulations of QUATS which have additives which make them tuberculocidal. Some QUATS have additives which make then tuberculocidal (kills TB).

It is important to read the label on the container for microbial action. The QUATS are relatively non-toxic to humans and are often used in dietary. They usually require mixing with distilled water. The QUATS can be inactivated by inappropriate dilution and the presence of organic matter. In addition, the QUATS can be neutralized or absorbed by gauze, cotton and wool (e.g. Zephiran Chloride). Some QUATS can be somewhat corrosive to metal (instruments).

Clorox Bleach

Chlorine and Iodine - These disinfectants belong to halogen group. Sodium hypochlorite (also known as household bleach) is used in laundry as low to medium level disinfectant. Bleach can also be used for blood spills however, the surfaces must first be cleaned and contaminates removed. Hypoclorites can be inactivated by organic matter (so they are poor cleaners by themselves) and can deteriorate with age and corrode stainless steel (instruments). Chlorines can also damage rubber and some plastics. Chlorine is usually used in concentrations of 1:10 or 1:100 for blood spills. Because of their corrosiveness to metal, the chlorines should never be used on surgical instruments.

Chorine bleach should never be missed with other chemicals (did you every make the mistake of mixing bleach with ammonia at home?) Mixing chlorine bleach with other chemicals can create toxic gases. Chlorine bleach also loses its strength rapidly.

Iodine

Betadine

Iodine - was primarily used as a skin antiseptic. When it was mixed with alcohol it was called a tincture of iodine, when mixed with water it was called Aqueous. Today Iodophor compounds are used which contain iodine but are less harsh to the skin (e.g. Betadine) and are used as skin preps. When iodine is combined with a detergent it can be used as a hand washing agent.

Phenolics - This group of disinfectants is effective against vegetative bacteria, fungi and TB. They are not effective against bacterial spores and some viruses. Phenols usually leave residual film therefore are usually recommended for floors, walls, exterior surfaces. To be effective, the surfaces must be pre-cleaned first.

Phenolic Disinfectant

Detergent residues must be rinsed off first because they can inactivate the disinfectant. The phenols must be measured and diluted carefully. They must remain wet (in contact with the surface of the device) for the specified period of time (10-20 minutes). Phenols can be toxic therefore they are not recommended for food prep areas, nursery or nursery equipment, the OR or porous materials (e.g. rubber tubings) since they cannot be rinsed off. Phenols can cause hyperbilirubinemia (excessive bilirubin in the blood) in infants so they cannot be used on infant bassinets and incubators.

The phenolics can cause skin or mucous membrane irritation if the materials remain in contact with the patient for prolonged periods of time. They can also de-pigment the skin therefore use of personal protective equipment (PPE) is very important.

Alcohol - are effective as antiseptics and sanitizers. Alcohol kills a variety of bacteria viruses, fungi and TB but does not skill spores and some hydrophilic viruses. Alcohol kills variety of bacteria, however to be effective it requires prolonged contact time (5-10 minutes of WET contact). This can be difficult because it evaporates readily

Isopropyl alcohol is the most effective in the 70% concentration. However it should only be used as recommended since it can damage rubber, plastics and some lensed instruments.

As with all disinfectants, alcohol can be inactivated in presence of organic soil so items must be thoroughly cleaned first.

When selecting and using environmental disinfectants, always check:

• Does the product have an EPA Registration Number?
  
• Is it safe for the use intended?
  
• Will it damage the surfaces cleaned with it?
  
• What germs does it kill?
  
• What is the dilution ratio of the product? (How do I mix it correctly?)
  
• Is it a "one-step" disinfectant-cleaner or a disinfectant?
  
• Is it effective in hard (tap) water or do I need to mix it with distilled water?
  
• Is it effective in the presence of organic soil?
  

American Society for Healthcare Central Service Personnel. "Training Manual for Central Service Technicians", 4th Edition, 2001.

Photos taken from web pages of various manufacturers of disinfectants.