Table 10-4.Micro-organisms and Levels of Disinfection
for that particular product. The following are some of
the criteria for effective chemical disinfection:
The degree of microbial kill or deactivation
The composition and texture of the item being
The technical requirement and ease of use of the
Regardless of the product selected, there is no
single chemical or heat agent available today that will
meet all these criteria. As always, follow label
directions precisely. Give strict attention to the
proper use of the product regarding mixing, dilution,
method and duration of the application, temperature
requirements, shelf-life, and if applicable, reuse life.
Organic Debris Present
Blood, saliva, and other organic material may
contribute to the failure of a germicidal process by
either direct inactivation of the disinfectant or the
actual layering of the micro-organisms on the
instruments or equipment, thereby preventing
penetration of the germicide.
LEVELS OF DISINFECTION
Type and Concentration of the Germicide
The EPA classifies disinfectants as high,
intermediate, or low level, based on the effectiveness
and contact time of the solution and the biocidal
activity of an agent against bacterial spores,
mycobacterium tuberculosis, lipid and nonlipid
viruses, and vegetative bacteria. Table 10-4 describes
the level of disinfection required to kill the
Generally, when all other variables are constant,
the higher concentrations of a chemical agent are more
effective and require a shorter time to disinfect. Use
of dilutions other than those specified by the
manufacturer adversely affect some intermediate-
level disinfectants, specifically iodophors. In all
instances, follow the manufacturers recommendations.
GENERAL CATEGORIES OF LIQUID
FACTORS INFLUENCING GERMICIDAL
A large variety of liquid disinfectants are available
today, and it is probable that many new ones will
become available in the future. When selecting a
product, make sure that the label has an EPA
registration number on it. Table 10-15, is a guide to
chemical agents for disinfection and sterilization.
Since they may be subject to change, be sure to read the
manufacturers instructions before using. Next, we
will discuss the four most commonly used chemical
agents, glutaraldehyde and chlorine dioxide based
solutions, iodophors, and phenolics.
The factors associated with the micro-organisms,
as well as those associated with the surrounding
physical and chemical environment, influence the
antimicrobial efficiency of the germicides. They are
Nature of the Material
The easiest surface to disinfect is a smooth,
nonporous, and cleanable one. If the materials are
incompatible with disinfectant, damage and corrosion
These agents are available in several formulations
differing in pH, concentration, use in dilution, and
exposure time. They are classified as high-level
disinfectants or sterilants.
Always wear impermeable gloves and protective
eyewear when handling these solutions. Irritation of
the hands is common and personnel are always at risk
of splashes occurring whenever liquids are being
Under a given set of circumstances, the higher the
level of microbial contamination, the longer the
required exposure to the disinfectant is needed.
Additionally, resistant micro-organisms require
longer exposure times.
Bacterial Tubercle Nonlipid
In the absence of gross organic contamination.