Glossary of Infection Control / Antiseptic Terminology

INFECTION CONTROL:

Nosocomial or hospital acquired infections are a major issue to hospitals resulting in millions of dollars of non-reimbursed costs being incurred each year.  To minimize the chances of patients and healthcare workers being infected by microorganisms (bacteria, yeast, fungi, etc.) in the healthcare environment, antiseptic (synonym is antimicrobial) agents are used to both kill and suppress the growth of these organisms.

Related to the concept of infection is the concept of sterility.  An object is considered sterile if it is free of all living microorganisms including spores (dormant forms of microorganisms typically resistant to being killed by antimicrobial agents) with a probability of 1 in 1 million.

Definitions / Related terms:

Sterile field – any area that has been rendered sterile by the placement of a sterile barrier, such as a drape.  This can be the area around a surgical incision, or any area where a sterile procedure is preformed, such as a central line dressing change or a PICC insertion.

Sterile technique – the method through which contamination with microbes is prevented during a surgical procedure.

MICROBIOLOGY:

From an infection control standpoint, microorganisms are often categorized a number of different ways as follows:

Pathogenic – microorganisms capable of producing disease

Nonpathogenic – not disease causing

Resident – present as part of the natural ecology of the skin; relatively difficult to remove using soap and water

Transient – not normally found on the skin; relatively easy to remove with soap and water

Microorganisms that cause the greatest problems and concern for individuals in the hospital responsible for managing infection rates are those that are both transient and pathogenic.

Specific to bacteria:

Gram positive – because of their chemical nature, these bacteria turn dark violet or purple on being exposed to the Gram staining method in the laboratory

Gram negative – because of their chemical nature, these bacteria do not turn dark violet or purple on being exposed to the Gram staining method in the laboratory

Before describing the differences between these antiseptic agents, a number of parameters by which these products are evaluated need to be defined:

Broad Spectrum – an antimicrobial or antiseptic containing formulation that kills a wide variety of microorganisms

Fast Acting – an antimicrobial or antiseptic containing formulation that kills microorganisms rapidly.  The fastest acting antiseptics are the alcohols (either ethyl or isopropyl) or combination formulations that contain alcohol.

Substantive – an antimicrobial or antiseptic containing formulation that kills a large number of microorganisms.  The most substantive antiseptics are again the alcohols (either ethyl [EtOH] or isopropyl [IPA]) or combination formulations that contain alcohol.

Persistent – an antimicrobial or antiseptic containing formulation that maintains the number of microorganisms present on a treated area of skin at a reduced number or level for an extended period of time.

Two terms are used in the context of substantivity or persistence namely; 

Bactericidal = cidal – the ability of an antiseptic containing formulation to reduce the number of microorganisms it is exposed to.  Other synonymous terms sometimes used are germicide and microbicide.

Bacteriostatic = static – the ability of an antimicrobial containing formulation to prevent an increase in the number of microorganism it is exposed to.

There are two ways in which the reduction in the number of microorganisms on the skin is measured or reported:

Percent reduction – if there are 1,000,000 microorganisms on a portion of skin prior to an antimicrobial containing formulation is applied and only 10,000 microorganisms after application, the percent reduction is 990,000/1,000,000 X 100 or 99%.

Log reduction – because microorganisms reproduce geometrically (1 turns into 2 which turn into 4 which turn into 8 which turn into 64 etc.), microbiologists often transform the actual count of microorganisms onto a logarithmic scale and then report the reduction.  In the above example, the log of 1,000,000 is 6; the log of 10,000 is 4.  The log reduction is 2.  Because of the magnitude of the numbers of bacteria present and the numbers that are removed or killed by the various agents, the log reduction approach is always easier to comprehend than the percent reduction approach;  data presented in the percent reduction format are almost always misleading to all but the most knowledgeable clinicians.

When a competitor reports efficacy data in terms of percent vs. log reduction, it’s usually because the product didn’t perform particularly well.  The reporting of percent reduction data is usually a flag that the product(s) tested aren’t particularly effective.

There are generally two types of tests that are conducted to evaluate the effectiveness or efficacy of an antimicrobial containing product:

In vitro efficacy testing – vitro means glass.  In vitro testing means that the testing was done in a nonbiological environment such as a test tube or Petri dish.

In vivo efficacy testing – vivo means life.  In vivo testing means that the testing was done in a biological environment such as actual skin.

CLAIMS (INDICATIONS) ALLOWED BY THE FDA FOR ANTIMICROBIAL PRODUCTS:

Regardless of the drug product, the FDA has three criteria for allowing them to be marketed; they must be safe, effective for their claimed or indicated use, and chemically stable.

The allowable active ingredients, claims or indications and regulatory requirements for antiseptics used in healthcare settings are addressed by the FDA in a “Tentative Final Monograph” or “TFM”. 

The FDA actually publishes many “Tentative Final” and “Final” monographs, but in the world of antiseptics, the TFM is actually FDA’s TFM entitled “Topical Antimicrobial Drug Products for Over-the-Counter Human Use; Tentative Final Monograph for Health-Care Antiseptic Drug Products”.

The above TFM recognizes three claims or indications and defines them as follows:

1. Antiseptic handwash or health-care personnel handwash drug product.  An antiseptic containing preparation designed for frequent use; it reduces the number of transient micro-organisms on intact skin to an initial baseline level after adequate washing, rinsing, and drying; it is broad spectrum, fast acting and, if possible, persistent.
2. Patient preoperative skin preparation drug product.  A fast acting, broad spectrum, and persistent antiseptic containing preparation that significantly reduces the number of micro-organisms on intact skin. The FDA recognizes “patient preoperative skin preparation” as a broad category which includes preparation of the skin prior to surgery and other applications such as skin prepping prior to injection, catheter care, and intravenous site preparation.
3. Surgical hand scrub drug product. An antiseptic containing preparation that significantly reduces the number of micro-organisms on intact skin; it is broad spectrum, fast acting, and persistent.
   

ANTIMICROBIAL AGENTS:

There are five commonly used antimicrobial agents used to disinfect the skin in a healthcare environment.  With the exception of IPA (see below), these agents are always part of a chemical formulation which include varying amounts of detergents (degreasing / foaming agents), emollients, thickening agents, and fragrances.  The actual antimicrobial agents or active ingredients in these formulations as they might be called are as follows:

1. Polyvinylpyrrolidone or Povidone-Iodine or Povidone or PVP-I
2. Isopropyl Alcohol or IPA
3. Ethyl Alcohol or EtOH or Alcohol*
4. Chlorhexidine Gluconate or CHG
5. Triclosan or Irgasan

PVP-I has long been considered the antimicrobial of choice in the hospital setting.

The alcohols are extremely substantive and in an indirect way, quite persistent.  Once evaporated, an antiseptic cannot be considered “persistent”, but with so few bacteria present after application, they have considerably difficulty re-establishing large populations.

CHG is fast becoming the antimicrobial of choice for a number of reasons.

Triclosan is the antiseptic found in many consumer products; e.g. Dial soap; not particularly persistent or substantive.  You’ll usually see their efficacy results reported in terms of percent vs. log reductions.

PRODUCT CONFIGURATIONS:

To enable customers to use antiseptic formulations for the various claimed uses, manufacturers have developed a number of product configurations, both with respect to the formulations themselves and in the device delivery systems that accompany the formulations:

Solution or topical solution – simply liquid that is dispensed from a bottle or packet.

Foam – liquid that is combined with a gas (typically air) as it is dispensed from a bottle or aerosol can.

Gel – liquid that is typically dispensed from a bottle and is highly viscous.  The advantage of gels is that they tend to stay where they’re applied and don’t run off and pool under the patient.  For iodine-containing formulations, pooling can lead to chemical burns.  For alcohol-containing formulations, pooling can lead to fire when electrocautery equipment is used.

Impregnated or Pre-impregnated – usually a liquid or possibly a gel that has been presaturated onto typically a polyurethane foam applicator device.