Download concerns about antibiotic resistance

Use of disinfectants and antibacterials in the
home: concerns about antibiotic resistance
Although it is generally agreed that the major cause of antibiotic resistance in clinical
practice is antibiotic overprescribing, some scientists suggest that widespread use of
microbiocides, particularly in consumer products used in the home, may be a
contributory factor. This briefing material has been produced for healthcare
professionals, media and others who are looking for some background
understanding of hygiene issues and/or are responsible for providing guidance to the
public on understanding these issues.
Antibiotic resistance is a serious problem in clinical practice. The emergence of
antibiotic resistant strains (often referred to as “superbugs”) is a trend that goes back
many years – dating almost from the time antibiotics were introduced over 60 years
ago. This trend increasingly limits our ability to successfully treat infectious diseases
and threatens the safety of modern surgery. Today there are bacterial strains that do
not respond to almost all antibiotics.
It is widely agreed that the cause of this trend is the overuse and abuse of antibiotics
in human and animal medicine. Use in animal nutrition has already been legally
restricted or banned in many countries. In the surrounding debate however, some
researchers suggest that widespread use of disinfectants and antibacterials (for both
of which the active ingredients are referred to in this document as microbiocides) in
domestic hygiene and/or personal care products may somehow exacerbate the
trend. This hypothesis however is contradicted by the fact that the history of antibiotic
resistance emergence does not correlate with the patterns of microbiocide use. In
hospitals, where the problems of antibiotic resistance have steadily increased and
are probably the greatest, microbiocide use has tended to decline.
Quite separately, the suggestion is sometimes made that bacteria may also become
resistant to the microbiocides themselves, rendering disinfectants and similar
products ineffective.
These two points are important to address in relation to home hygiene. Even with
ambiguous evidence and where data is lacking, these concerns must be taken into
account when advising the public on how to prevent the spread of infectious disease
in the domestic setting.
How do antibiotics work and how does resistance develop?
In order to understand how exposure to microbiocides might encourage development
of antibiotic resistance, it is first necessary to understand how antibiotics work and
how resistance occurs.
Antibiotics act on bacterial cells by disrupting/inhibiting specific target sites on or in
the cell which are critical for their survival. Different antibiotics work against bacteria
in very different ways which involve different target sites. Thus for example,
penicillins act by preventing the formation of the protective bacterial cell wall, whilst
tetracyclines act by inhibiting microbial protein synthesis.
If a population of bacteria is continuously exposed to low concentrations of
antibiotics, within that population a mutant cell or cells may arise for which the “target
site” is altered in such a way that, although the rest of the population dies, the mutant
cell or cells survive and reproduce. As a result a new population of cells which are
less susceptible to the antibiotic develops. Eventually, through this process, a
population of bacteria emerges which is fully resistant to the antibiotic.
It is important to recognise that “reduced susceptibility” to an antibiotic does not
necessarily mean "resistance" in clinical use.
Could microbiocide use contribute to antibiotic resistance ?
Laboratory studies suggest a number of mechanisms by which microbiocide
exposure can produce changes within a bacterial population which make it less
susceptible to the action of antibiotics. The key question however is:
 Are the changes in antibiotic susceptibility sufficient to compromise their
effectiveness in clinical use?
 Is the evidence sufficient to link the use of microbiocides in the home and
community to the emergence of antibiotic resistance in clinical practice?
Typical mechanisms by which microbiocide exposure could lead to reduced antibiotic
susceptibility include:
Multiresistance through multidrug efflux pumps
Bacteria contain “efflux pumps” in their outer membrane which are switched on in
response to the presence of noxious substances such as microbiocides and
antibiotics in their environment, These allow them to pump the substance out of the
cell. A number of experiments have shown that bacterial populations with increased
pumping activity, selected or induced by exposure to microbiocides such as triclosan,
also show reduced susceptibility to antibiotics.
However:
 It is found that the “reduced susceptibility” to antibiotics is “low level” and unlikely
to compromise the therapeutic effectiveness of the drug.
 It has also been found that this effect is not confined to microbiocides. All kinds of
natural and synthetic substances can also induce this effect, including foods such
as chilli powder, garlic sauce and mustard, and some typical unmedicated
personal products i.e products which do not contain a recognised microbiocide).
These responses can also be caused by physical stresses such as heat or
starvation.
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Multiresistance through shared target sites
As stated above, antibiotics have specific target sites in the bacterial cell. A number
of microbiocides also have specific target sites which are similar to, or the same as,
the target site for one or more antibiotics. An example of this is the microbiocide
triclosan which targets enoyl reductase enzyme in Escherichia coli. It has been
shown that this is also the target enzyme for the antibiotic isoniazid, although in a
different organism, Mycobacterium smegmatis. This gives the theoretical possibility
that persistent exposure to triclosan could select mutant populations which are
clinically resistant to isoniazid
Multiresistance through plasmid-borne resistance
Genes which confer antibiotic or microbiocide resistance can become incorporated
on mobile elements in bacterial cells known as plasmids. These plasmids can
multiply and pass from cell to cell thereby spreading resistance within the whole
microbial population. In some cases a plasmid can contain several genes each
conferring resistance to different agents. Where one of these is a gene for resistance
to a microbiocide, exposure to this microbiocide can lead to selection of a population
containing the multiresistant plasmid. This means that the population will also be
resistant to antibiotics for which the plasmid also bears the genes.
However:
Unlike antibiotics, many or most microbiocides have a non selective action on
bacterial cells i.e. they do not attack specific target sites but e.g. disrupt general
enzyme action or other functions. Non-specific microbiocides include hypochlorites
(bleach), alcohol and peroxides. Multiresistance through shared target sites or
plasmids is only possible for microbiocides which have specific target sites which
means that development of resistance through these mechanisms cannot occur with
these non-specific microbiocides. This likelihood is further reduced by the fact that
agents such as bleach and alcohol are unstable or volatile and thus do not persist in
the environment in an active form.
Although laboratory data suggest that some types of microbiocides have the potential
to encourage the emergence of antibiotic-resistance in microbial populations, there is
no evidence of a link between microbiocide usage and antibiotic resistance in clinical
practice. This conclusion is supported by a number of studies which compare the
prevalence of antibiotic resistant strains in environments where biocides are, or are
not, in use.
 Rutala et al. (2000) found that the frequency of occurrence of antibiotic resistance
in environmental isolates from homes was much lower than for clinical isolates
from a hospital intensive care unit and an outpatient setting where there was
routine extensive use of antibiotics.
 Two studies were carried out to investigate whether antibiotic resistant strains
were more likely to be found in homes where antibacterial products were used
compared with homes where they were not (Marshall et al. 2003, Cole et al.
2003). Samples were collected from houses in the USA and UK of 30 users and
nonusers of antibacterials. Susceptibility tests against antibiotics and antibacterial
agents (triclosan, pine oil, BAC and para-chloro-meta-xylenol) were carried out on
the bacteria isolated. The authors conclude that there was no evidence that
antibiotic resistant strains occurred more frequently in user homes compared with
non-user homes.
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A 1 year study by Aiello et al (2005) showed that household use of antibacterial
cleaning products was not a significant risk factor for occurrence of antibiotic
resistant isolates from hands.
Could microbiocide use encourage the spread of microbiocide resistance ?
Populations of bacteria less easily killed by biocides can be cultivated in the
laboratory, and do from time to time appear in practice. These populations can
withstand higher than usual concentrations of certain biocides. Most often this results
from their strategy aimed at survival under environmental conditions which are
stressful and growth limiting. Where it relates to biocide exposure the altered
susceptibility is found to be insufficient to compromise effectiveness in use where
much higher concentrations are used. In all cases, the resistance is not permanent.
When the biocide or other ‘stress’ is withdrawn, the bacterial population returns to be
as susceptible as it was before.
Recently a consumers’ preference for antimicrobial products has emerged. They
appear to believe these have a “gentler” action – and that “strong” products are more
likely to create superbugs. In fact the reverse is true. It is where germs are exposed
to sublethal concentrations of biocides that problems related to reduced susceptibility
would be more likely to occur.
Conclusions on microbiocides and antibiotic resistance
In view of the concerns about the possibility that use of disinfectants and antibacterial
products in the home could be contributing to the development of antibiotic
resistance, in 2000 the IFH undertook a detailed review of the scientific data related
to the possible links between antibiotic and biocide resistance.1 This review was
updated in 2003 to take account of new evidence which has become available since
2000.2. The IFH also prepared a consensus statement summarising conclusions
regarding this issue.1
The conclusion of the IFH (as also concluded by other reviewers (Russell 2000;
Gilbert and McBain 2003; Aiello and Larsen 2003) is that that although some
laboratory studies have demonstrated links between microbiocide and antibiotic
resistance, there is no equivocal evidence that microbiocide usage contributes to the
development of antibiotic resistance either in clinical practice or in the general
environment; antibiotic use is currently assumed to be the major cause of antibiotic
resistance in clinical practice. This is despite decades of continuous use of
microbiocides in clinical and other situations. There is agreement however that, since
significant questions remain unanswered, it is vitally important that we continue to
research and monitor the situation.
Further, the IFH agrees that, as increases in antibiotic resistance continue to reduce
our ability to treat infections, then infection prevention through hygiene, not only in
hospitals but also in the community, becomes of even greater importance. The
benefits of good hygiene have been demonstrated in clinical settings where good
hygiene has contributed to reduced antibiotic resistance through reduced prescribing.
It is also recognised that good home hygiene has a role on preventing the spread of
antibiotic resistant strains which is increasingly seen as a community as well as a
hospital problem.
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Looking from this perspective, it is argued that if reducing the number of infections
and the spread of resistant strains through effective hygiene is important, then it is
also important to ensure that microbiocide use, as an integral part of good hygiene
practice, is not discouraged in situations where there is real benefit in terms of
preventing spread of infection including the spread of antibiotic resistant strains.
Within a risk-based approach to home hygiene, in situations where failure to achieve
hygiene carries a risk of serious consequences (e.g. food hygiene), or in the
protection of vulnerable groups, we should not be afraid to apply a disinfection
process, either a heat process or an effective chemical disinfectant or antibacterial
which will inactivate pathogens including bacteria and preferably also viruses. For
more details of the IFH risk-based (targeted) approach to home hygiene, see the IFH
information sheet “Developing hygiene practice for the home – the IFH risk-based
approach to home hygiene (targeted hygiene)”.3
On the basis that concerns about antibiotic resistance remain unresolved the
consensus view of the IFH remains as before, which is that there is need to ensure
that microbiocides are used responsibly i.e. in accordance with the IFH
recommendations laid out in the IFH Guidelines, recommendations and training
resources on home hygiene.4,5,6
IFH recommends that, to avoid the possibility of antimicrobial resistance
 Microbiocides should be used prudently not indiscriminately
 Microbiocides should be selected as appropriate to:
 give rapid/effective inactivation of micro-organisms
 avoid build-up of residues which might encourage selection of resistant
strains
IFH reviews and consensus statement on microbiocides and resistance,
Guidelines and training resources
1
Microbial resistance and biocides - a review and consensus statement (2000).
International Scientific Forum on Home Hygiene. Available from http://www.ifhhomehygiene.org/best-practice-review/microbial-resistance-and-biocides-reviewand-consensus-statement-2000
2
Biocide use and antimicrobial resistance in home settings: an update (2004)
International Scientific Forum on Home Hygiene. Available from: http://www.ifhhomehygiene.org/best-practice-review/biocide-usage-and-antimicrobialresistance-home-settings-update-2004
3
Developing hygiene practice for the home – the IFH risk-based approach to home
hygiene (targeted hygiene). http://www.ifhhomehygiene.org/factsheet/developing-hygiene-practice-home-%E2%80%93ifh-risk-based-approach-home-hygiene-targeted-hygiene
4
Guidelines for prevention of infection and cross infection the domestic
environment. International Scientific Forum on Home Hygiene. Available from:
http://www.ifh-homehygiene.com/best-practice-care-guideline/guidelinesprevention-infection-and-cross-infection-domestic
5
Recommendations for suitable procedure for use in the domestic environment
(2001). International Scientific Forum on Home Hygiene.
http://www.ifh-homehygiene.org/best-practice-care-guideline/recommendationssuitable-procedure-use-domestic-environment-2001
6
Home hygiene - prevention of infection at home: a training resource for carers and
their trainers. (2003) International Scientific Forum on Home Hygiene. Available
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from: http://www.ifh-homehygiene.com/best-practice-training/home-hygiene%E2%80%93-prevention-infection-home-training-resource-carers-and-their
Other useful references
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Rutala, W.A., Weber, D.J., Barbee, S.I., Gergen, M.F. and Sobsey, M.D. (2000)
Evaluation of antibiotic resistant bacteria in home kitchens and Bathrooms.
Infection Control and Epidemiology 21, 132.
Marshall, B.M., Roblet, E., Dumont, T., Billhimer, W., Wiandt, K., Keswick, B.,
Levy; S.B. (2003), The Frequency of Bacteria and Antibiotic Resistance in
Homes that Use and do not Use Surface Antibacterial Agents. Abstracts of the
Annual Meeting of the American Society for Microbiology. A-147
Cole, E.C., Addison, R.A., Rubino, J.R., Leese, K.E., Dulaney, P.D., Newell,
M.S., Wilkins, J., Gaber, D,J,. Weininger, T. and Criger, D.A. (2003)
Investigation of antibiotic and antibacterial agent cross resistance in target
bacteria from homes of antibacterial product users and non users. Journal of
Applied Microbiology 95, 664-676.
Cole, E.C., Addison, R.A., Dulaney, P.D., Leese, K.E., Madanat HM, Guffey AM.
Investigation of antibiotic and antibacterial susceptibility and resistance in
Staphylococcus from the skin of users and nonusers of antibacterial wash
products in home environments. International Journal of Microbiology Research,
Vol. 3, Issue 2, 2011
Aiello, A.E. and Larson, E. (2003) Antibacterial cleaning and hygiene products
as an emerging risk factor for antibiotic resistance in the community. The Lancet
infectious diseases, 3. 501-506.
Gilbert, P. and McBain, A. (2003) Potential impact of increased use of biocides
in consumer products on prevalence of antibiotic resistance. Clinical
Microbiological Reviews. 16, 189-208.
Antibacterial cleaning products and drug resistance. Aiello, A.E. Marshall B.
Levy S.B. Della-Latta P., Lin S,X., Larson E. Emerging Infectious Diseases
2005; 11: 1565-1570.
Russell, A.D. and Maillard, J-Y. (2000) Response. American Journal of Infection
Control 28, 204-206.
Bloomfield, S.F. (2002) Significance of biocide usage and antimicrobial
resistance in domiciliary environments. Journal of Applied Microbiology B92/1,
144-157S.
Moore LE, Ledder, RG, Gilbert P, McBain AJ, In Vitro Study of the Effect of
Cationic Biocides on Bacterial Population Dynamics and Susceptibility. Applied
and Environmental Microbiology 2008;74:4825-34.
Meyer B, Cookson B. Does microbial resistance or adaptation to biocides create
a hazard in infection prevention and control? Journal of Hospital Infection.
2010;76:200-5.
Harbath S, Tuan So, S, Horner C, Wilcox MS. Is reduced susceptibility to
disinfectants and antiseptics a risk in healthcare settings? A point/counterpoint
review J Hosp Infect. 2014 Aug;87(4):194-202. doi: 10.1016/j.jhin.2014.04.012.
Epub 2014 Jun 5.
Marshall BM, Robleto E Dumont T Levy SB. The frequency of antibiotic-resistant
bacteria in homes differing in their use of surface antibacterial agents Curr
Microbiol. 2012 Oct;65(4):407-15. doi: 10.1007/s00284-012-0172-x. Epub 2012
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Last updated 2015
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