A disinfectant is a chemical agent that kills microorganisms on inanimate objects and surfaces. It is similar to an antiseptic,
except that antiseptics are used on living tissue. Some disinfectants are also antiseptics and vice versa. Disinfectants do not typically kill bacterial spores, although some disinfectants such as hydrogen peroxide (H2O2) and chlorine can kill bacterial spores when applied in high concentrations.
(LIANE RISS/GETTY IMAGES)
Disinfectants are biocidals, and biocidal activity is measured by the minimum bactericidal concentration (MBC). When a microorganism
is first exposed to a disinfectant and subculturing is not possible, it is deemed to have been killed. The concentration at
which the microorganism is killed is known as biocidal activity. The effects of antibiotics, such as penicillin and cephalosporin, are also described in terms of biocidal activity (1).
Several forums and publications have claimed that disinfectants must be rotated in biotechnology and pharmaceutical manufacturing
settings to prevent the target organisms from developing resistance. Chapter <1072>, "Selection of a Disinfectant for Use
in a Pharmaceutical Manufacturing Environment," in USP 30 addresses disinfectant rotation. It states that:
The development of microbial resistance to antibiotics is a well-described phenomenon. The development of microbial resistance
to disinfectants is less likely, as disinfectants are more powerful biocidal agents than antibiotics and are applied in high
concentrations against low populations of microorganisms usually not growing actively, so the selective pressure for the development
of resistance is less profound. However, the most frequently isolated microorganisms from an environmental monitoring program
may be periodically subjected to use dilution testing with the agents used in the disinfection program to confirm their susceptibility.
The Japanese Pharmacopoeia, British Pharmacopoeia, and European Pharmacopoeia do not currently address the issue of disinfectant rotation.
Annex 1 of the European Commission's Good Manufacturing Practice (GMP) Guidelines, "Manufacture of Sterile Medicinal Products" states, "Where disinfectants are used, more than one type should be employed.
Monitoring should be undertaken regularly in order to detect the development of resistant strains" (2).
But, the US Food and Drug Administration does not mention the rotation of disinfectants in its equivalent guideline Sterile Drug Products Produced by Aseptic Processing—Current Good Manufacturing Practice (3). This discrepancy raises the question of whether the technique of rotating disinfectants has a sound scientific rationale.
Many people use inaccurate expressions when they refer to disinfectants. For example, it is common to confuse sanitizers with
disinfectants. Although these agents are similar, they are not the same. Disinfection targets pathogenic microorganisms, and sanitation kills all microorganisms. Table I presents a glossary of terms, as published by Gilbert and McBain and FDA, to dispel confusion
Table I: Glossary of terms.
The biotechnology and pharmaceutical industries usually clean equipment with a detergent and use a disinfectant to reduce
or eliminate microbial contamination. These industries usually call the process of reducing microbial contamination "disinfection,"
but the correct term is "sanitation" or "sanitization." As a side note, the probability of finding a true pathogen in an environment
that complies with current good manufacturing practice (CGMP) is quite low.
This article uses the following definitions, which are described in references 5 and 6:
Resistance is the property of a microorganism that can survive but not grow, either alive or in stasis, at the recommended exposure
conditions and use concentration of a disinfectant.
Tolerance is the relative capacity of a microorganism to survive and grow at or beyond the recommended exposure conditions and use
concentration of a disinfectant.
Susceptibility is the failure of a microorganism to survive exposure to a disinfectant at the recommended conditions and concentration.
Reduced susceptibility is the property of a microorganism that is not killed by the usual disinfectant concentration and exposure conditions, but
does not survive a higher concentration or different conditions.