Reduced susceptibility to a disinfectant does not mean that the agent or the disinfection method fails. Most of the evidence
for resistance to disinfectants, antiseptics, and sanitizers is laboratory-based. Little, if any, evidence has been gleaned
from real-life situations. Resistance in laboratory situations means reduced susceptibility.
Common disinfectants, antiseptics, and sanitizers are used at high concentrations in real-life to attain swift microbicidal
action and produce effects such as disruption of the cellular membrane or wall, inactivation of critical enzymes, and degradation
of DNA or RNA. At lower concentrations, these substances inhibit microorganisms' growth.
Rotation of disinfectants in the pharmaceutical and biotech industries has been promoted to prevent the development of bacterial
resistance. The argument is that one disinfectant should be replaced by another that has a different mode of action. This
recommendation is derived from experience with antibiotics that does not apply directly to disinfectants, antiseptics, and
sanitizers. The reported resistance to common disinfectants does not occur at use concentrations, and is more accurately considered
reduced susceptibility (96, 97).
This assessment agrees with a report issued by CDC on Oct. 28, 1997, which said, "Antibiotic resistant microorganisms are
susceptible (or killed) to chemical germicides. The mechanisms by which chemical germicides and antibiotics work are completely
different and there does not seem to be a relationship between antibiotic resistance and chemical germicide effectiveness"
Because common disinfectants are used on lifeless objects rather than on living tissue, they are used at concentrations that
exceed the MIC or MBC by several orders of magnitude. Consequently, a decrease in susceptibility by a factor of two or more,
which is important to an antibiotic, has no relevance to the effectiveness of a common disinfectant.
Rotation of a common disinfectant and a sporicidal helps ensure that bacterial spores do not take hold in manufacturing and
aseptic areas. But the rotation of common disinfectants such as those based on phenol-derivatives (except TLN), aldehydes,
and oxidizing agents, has no scientific basis. If antibiotic-like disinfectants are used, however, rotation is a necessity.
The development of resistance to antibiotics has been extrapolated to common disinfectants, antiseptics and sanitizers, and
the general environment. A misunderstanding of the vocabulary related to disinfectant and antibiotic susceptibility tests
seems to be the justification for this extrapolation. The elemental differences between disinfectants' and antibiotics' mechanisms
of action and the methods used to evaluate their efficacy are often left unconsidered. The lack of standard terminology for
interpreting studies can result in inaccurate interpretations of the data.
José E. Martínez is a consultant at JEM Consulting Services, Box 4956 PMB 652, Caguas, PR 00726, tel. 787.349.3857, email@example.com
Submitted: Apr. 29, 2008. Accepted: Aug. 3, 2008.
What would you do differently? Submit your comments about this paper in the space below.
1. P. Gilbert and A.J. McBain, "Potential Impact of Increased Use of Biocides in Consumer Products on Prevalence of Antibiotic
Resistance," Clin. Microbiol. Rev.
16 (2), 189–208 (2003).
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3. FDA, Sterile Drug Products Produced by Aseptic Processing—Current Good Manufacturing Practice (Rockville, MD, Sept. 2004).
4. FDA, Center for Food Safety and Applied Nutrition, "Comprehensive List of Terms," available at
http://www.cfsan.fda.gov/~dms/a2z-term.html, accessed Jan. 18, 2009.