russell, hugo & ayliffe's (principles and practice of disinfection, preservation and...

229

Microbicides – the Double-edged Sword: Environmental Toxicity and Emerging Resistance

Jean-Marie Pagès1, Jean-Yves Maillard2, Anne Davin-Regli1 and Susan Springthorpe3

1 UMR-MD1, Aix-Marseille Université Transporteurs Membranaires, Chimiorésistance et Drug-Design, Facultés de Médecine et de Pharmacie, Marseille, France2 Cardiff School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, Wales, UK3 Centre for Research on Environmental Microbiology, University of Ottawa, Ottawa, Ontario, Canada

11

Introduction

The worldwide dissemination of multidrug-resistant (MDR) pathogens has severely reduced the efficacy of our antibiotic arsenal and increased the frequency of therapeutic failure. Today, antibiotic resistance is a major concern in the anti-infective treatment of both humans and animals. Misuse and overuse of antibiotics is widely blamed as the sole reason for this widespread resistance, although microbicide usage has recently been impli-cated as a possible contributing factor [1].

The development and use of microbicidal products are of immense benefit to human and animal health, and to associated economic activities [1]. However, the widespread use of microbi-cidal products also entails a number of negative aspects such as the potential for toxicity to humans and the environment and their sublethal environmental residues leading to the emergence of microbial resistance [1].

In a global context, microorganisms are regularly exposed to natural or anthropogenic physical and chemical elements detri-mental to their growth and survival. Antimicrobials (e.g. antibiotics, peptides, hydrogen peroxide) from natural sources

usually exert their inhibitory effects within their immediate vicin-ity. In contrast, humans have been much less discriminating in how they use both natural and synthetic antibiotics and micro-bicides in increasing ways. This mounting and widening use is fueled primarily by a better understanding of microbe-led degradation of our surroundings and continuing discoveries of microbial pathogens and their potential for serious harm. Of course, the widespread press coverage of these issues and their negative impacts on human health have provided microbicide manufacturers in particular unprecedented marketing opportu-nities [2]. The widening varieties and increasing quantities of such chemicals that we use in domestic and professional settings will ultimately enter the waste stream.

All types of microorganisms, with their relatively small but pliable genomes and short generation times, have evolved a number of strategies to deal with damaging chemicals. While some possess intrinsic resistance to such chemicals, others deal with them by acquiring mobile resistance-conferring genetic ele-ments through horizontal gene transfer, modifying membrane permeability, overexpressing efflux pumps, detoxification outside the cell, or by altering or multiplying cellular targets [2]. Chapter 6.1 provides more information on this topic and also discusses

Russell, Hugo & Ayliffe’s: Principles and Practice of Disinfection, Preservation and Sterilization, Fifth Edition. Edited by Adam P. Fraise, Jean-Yves Maillard,

and Syed A. Sattar.

© 2013 Blackwell Publishing Ltd. Published 2013 by Blackwell Publishing Ltd.

Introduction, 229Applications of biocidal products and fate in the environment, 230Differences and similarities in antimicrobial actions, 231Microbicide concentration and bacterial susceptibility, 231Microbicides and antimicrobial resistance in bacteria, 232Conclusions, 233References, 234

Section 1 Principles

230

Applications of biocidal products and fate in the environment

Microbicides are a very diverse group of chemicals [1]. Such chemicals are rarely used on their own and are often a part of a formulation to optimize or increase their delivery, activity or to negate side effects such as smell, toxicity or corrosiveness. Yet, most studies on the development of microbial resistance to microbicides are based on the chemical alone and rarely on for-mulations containing it [12].

Microbicides have a wide variety of applications – including infection control, water and wastewater treatment, food pro-duction and preparation for market, microbial control in manufacturing and other industries, and disinfection or preser-vation of degradable substances – everything from household cleaners, personal care products and consumer plastics to trans-portation vehicles, building substrates and oil and gas exploration. Increases in microbicide use are forecast to continue. Conse-quently, the risks of microbicide use leading to the selection of resistant organisms followed by their selection and dissemination are of increasing concern [1, 2, 12].

In the healthcare setting, microbicidal products are used for the disinfection of medical devices, environmental surfaces, disinfection of skin and mucosa (antisepsis) as well decontamina-tion of hospital wards. The Spaulding classification [13], which takes into account the degree of infection risk from a particular item (divided into critical, semi-critical and non-critical) and the level of disinfection required, holds true today, with some recent concerns on its relevance to current products and practices [14–19].

While the significance of environmental surfaces as vehicles for pathogens is still questioned by some, there is increasing evi-dence that such surfaces can be potential means of spread of a variety of pathogens in healthcare settings, in particular [20, 21]. This increasing appreciation of environmental surfaces in the spread of pathogens has spawned the development and aggres-sive marketing of a wide range of microbicide-containing surfaces (see Chapter 20). Then there is the burgeoning market-ing of microbicidal wipes for use on skin and environmental surfaces [22, 23].

Microbicides are used in numerous consumer products such as cosmetics, personal care products, household products and textiles. In the European Union (EU) the use of microbicides as preservatives in cosmetics is regulated by the Cosmetics Directive (see Chapter 18). The use of microbicides in household products such as dishwashing liquids and powders, liquid soaps, shampoos and many others has seen recent and substantial increases in use with claims against innumerable pathogens. Antimicrobial sur-faces are also being sold for use in domestic settings, such as cutting boards, plastic containers for food storage, toilet seats, shower curtains and various textiles as examples.

Microbicide use is, of course, common in food preserva-tion and for environmental hygiene in settings where food is

terms such as “resistance”, “cross-resistance”, “co-resistance”, “tol-erance” and “reduced susceptibility”.

One of the most important factors in the development and spread of microbial resistance (or enhancing survival) in the envi-ronment is whether or not a toxic chemical is maintained for any significant period at sublethal concentrations to allow the selec-tion for and persistence of resistance, through gene expression, mutation, etc. Since mutation itself is a random event, it is the selection that is important in driving entrenchment and spread of resistance. This is widely recognized for antibiotics as anti-biotic resistance emerges and disseminates almost immediately following their field applications [3–5]. Serious concerns about antibiotic resistance and its impact on nosocomial, community-acquired and foodborne pathogens are now well recognized and have been raised at both national and international levels as well as in the popular press.

Bacteria in particular can also increase their mutation rate significantly during the starvation phase due to failures in mis-match repair; the resulting “mutator” phenotype that arises is then already primed for secondary mutations [6]. Mismatch repair mutants often undergo more conjugation and recombina-tion events [7]. This might readily contribute to the development of antimicrobial resistance; conversely, cells primed to further mutations are also more vulnerable to extinction. Direct linkage between mismatch repair mutants and antimicrobial resistance was suggested previously but only recently has any potential link been demonstrated [8]; in this case, overexpression of an efflux pump resulted simultaneously in antibiotic resistance, protection against reactive oxygen species and a decrease in mutation rate. It is worth noting that “mutator” phenotypes might be selected within a host to whom antibiotics may also be administered [9].

This chapter aims to put into context the use of microbicides and subsequent effects on bacteria in particular and the conse-quences for the environment. It should be noted that while the main focus has been and continues to be on human pathogens, pathogens of economically important animals and crops, as well as those of wildlife, are likely to be significantly affected as well. Aquatic species might be especially vulnerable. While it is not the main target of this chapter to discuss hazards to persons from occupational or other microbicide exposure, it is pertinent that this be mentioned as a part of the downside of microbicide use. Microbicidal products are often used in high concentrations and direct toxic exposures, especially of young children, are not uncommon. These chemicals can also give rise to numerous side effects in those who use them regularly [10], and even low-level exposures through food and water by ingestion of the microbi-cides or their toxic and mutagenic by-products are recognized risks [11], although reports remain scarce. There are some regula-tions on the presence of by-products in the environment, notably in drinking water where the presence of trihalomethanes as by-products of water disinfection is regulated. However, the only hazards regulated are those that are recognized and many more disinfectant by-products remain to be investigated.

231

Chapter 11 Microbicides – the Double-edged Sword: Environmental Toxicity and Emerging Resistance

Chapter 4). Electrophilic microbicides react with critical enzymes and inhibit growth and metabolism, with cell death occurring immediately or after several hours of contact. For example, the modification of functional groups from proteins and nucleic acids by oxidation or precipitation are characteristic of heavy metals (copper, silver, mercury), halogens (chlorine, bromine), oxidizers (ozone, peroxides), aldehydes, carbamates and isothia-zolones [32]. Membrane-active microbicides directly affect cell membranes by a lytic effect (e.g. surfactants, phenols, bigua-nides, alcohols, quaternary ammonium compounds (QACs)) or a protonophoric interaction (e.g. weak acids, parabens, pyrithiones). This quite simple classification of the mechanisms of action does not consider that some microbicides have multiple effects. For example, QACs also bind to, and denature (solubilization and depolymerization), proteins and enzymes [32, 34–37]. Microbicides, especially those used as sporicides, are highly reactive and are thought to disrupt many functions and structures simultaneously (see Chapter 4).

The key mechanisms of bacterial resistance to antibiotics are well understood, but the same cannot be said about how bacteria become resistant to microbicides [12]. However, it turns out that the strategies used by bacteria to survive the deleterious effects of sublethal levels of antibiotics and microbicides have much in common [2, 12, 33, 38, 39]. This alone suggests that, in general terms and in theory, resistance developed originally against an antibiotic may manifest itself as resistance to a micro-bicidal chemical as well and vice versa. However, the available evidence shows that while bacteria with reduced susceptibility to microbicides also show an increased resistance to antibiotics, antibiotic-resistant bacteria have not been shown to develop increased insusceptibility to microbicides. This may well be because microbicides are often used in higher concentrations and they also have the ability to attack multiple targets on bacterial cells simultaneously.

It is important to understand the molecular and genetic bases for the selection of antibiotic-resistant bacteria by microbicides and to have a clear picture of the corresponding health risks. It is equally important to decipher the genetic, biochemical and physi-ological bases of mechanisms conferring microbicide resistance to pathogens in order to combat the emergence and dissemina-tion of resistant pathogens that limit the efficiency of our antibacterial weapons [1].

Microbicide concentration and bacterial susceptibility

Effects of Low Concentrations of a MicrobicideAlthough microbicide concentration is key to its effective use [12, 40], it is crucial to remember that the microbicide concentration applied may not necessarily be the level the target pathogen encounters. Therefore, it is very important to consider how the microbicide is delivered.

produced, manufactured and served. In the EU, microbicides used during food production are regulated under the Biocidal Products Directive (see Chapter 14.1). Microbicides are applied in the decontamination of carcasses; in 2008, the European Food Safety Authority BIOHAZ panel noted the lack of infor-mation on the ability of such microbicides to generate microbial resistance and cross-resistance [24, 25]. Disinfection of water in recreational areas regularly relies on the use of chemical disin-fectants (see Chapter 19.5). The use of disinfectants for potable water is regulated by the Drinking Water Directive (98/83/EC) in the EU.

In animal husbandry, farm buildings, barns, equipment and vehicles are all chemically disinfected to reduce the risk of spread of animal pathogens. It is often difficult to assess the effectiveness and real benefits of such applications and to get accurate meas-ures on the types and amounts of chemicals used for these purposes in order to properly determine any potential impacts on humans and the environment. On farms, the use of microbicide-containing teat-dips is common and so is the use of preservatives for eggs and semen.

A large range of microbicide use includes the disinfection/decontamination of environmental surfaces, their use as anti-biofouling agents during industrial processes, the preservation of building materials (including antimicrobial coating or impreg-nated surfaces), water disinfection and wastewater treatment. In the EU, the amounts of microbicides used for these different applications cannot be estimated because of the absence of reporting requirements. The European Commission has pro-duced an assessment of human and environmental risks linked to the use of microbicides (report available at http://ec.europa.eu/environment/biocides/pdf/report_use.pdf; accessed July 2011). This overview is based on the minimum annual production/import volumes of microbicides in the EU.

High concentrations of microbicides have been reported in river water and wastewater effluents [26–28]. The bisphenol tri-closan in these environmental locations has been particularly well investigated, and concentrations have been found ranging from 1.4 to 40,000 ng/l in surface water, up to 85,000 ng/l in wastewater and 133,000 µg/kg in biosolids from wastewater treatment plants [29]. These concentrations are high enough to produce a selective pressure on the microbial microcosm. Long-term exposures to low concentrations of microbicides have been found to change the bacterial composition of complex micro-cosms [30, 31].

Differences and similarities in antimicrobial actions

While microbicides are a very diverse group of chemicals [1], the focus here is on commercially-produced bactericidal/bacteriostatic agents. In contrast to how antibiotics exert their antimicrobial action, microbicides as a class are often much less discriminating in the targets they attack [32, 33] (see also


232

this is not always the case. Examples where bacteria are likely exposed to microbicide levels that might be stressful include wastes from cooling towers, farms, pulp and paper mills, and various industries including gas and oil drilling. The injection of largely undisclosed mixtures of microbicides (including alde-hydes) and other toxic chemicals during the fracking (hydraulic fracturing) process for gas extraction has recently drawn public concern for the safety of groundwater.

As mentioned above, triclosan has been found at low con-centrations in a number of settings [27, 29]. Often those concentrations are at the stressful level for bacteria. To date, there have been no antimicrobial susceptibility studies investigating microbial microcosms in these environments.

The acquisition of resistance determinants in the environment is of concern. Environmental bacterial isolates from a reed bed exposed to QACs from a wool-finishing mill have been shown to have high levels of resistance to QACs, and class 1 integron inci-dence was significantly higher for bacteria pre-exposed to QACs [54]. Gaze et al. [55] reported a high prevalence of class 1 inte-grons and demonstrated the potential importance of detergents. These authors estimated that more than 1 × 1019 bacteria carrying class 1 integrons enter the UK environment from sewage sludge each year. The presence of conjugative plasmids has also been associated with co-resistance between a number of microbicides such as cationic compounds, metallic salts (e.g. organomercuri-als) and antibiotics [50, 56, 57].

However, to date, there have not been any comprehensive studies linking microbicides in the environment and antibiotic resistance.

Microbicides and antimicrobial resistance in bacteria

General ConsiderationsMicrobicide resistance in bacteria has been described since the 1950s and a number of mechanisms for such resistance have been described (see Chapter 6.1). Most of the evidence regarding bac-terial resistance to microbicides comes from laboratory-based studies, which report a change of susceptibility in a wide range of bacterial pathogens such as Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Salmonella enterica, etc. against a wide range of microbicides (see Chapter 6.1). The role of bacterial biofilms in bacterial survival and persistence has been particularly well addressed (see Chapter 6.2). Evidence for the effects of microbicides on altering antibiotic susceptibility profiles in situ is scarce. In a study performed in the community, a significant relationship was highlighted between high MICs to QACs, high MICs to triclosan and resistance to one or more antibiotics [58]. More recently, an outbreak of Mycobacterium massiliense in a number of hospitals in Brazil linked antibiotic resistance with glutaraldehyde resistance [59].

Some resistance mechanisms expressed in bacteria constitu-tively or as a result of environmental stresses, notably exposure

The reduced availability of a microbicide through bacterial biofilms [2, 41, 42] has already been mentioned (see Chapter 5). What is often less apparent are the other factors that affect the bioavailability of a microbicide, such as formulation and the pres-ence of organic matter and diluent (e.g. ionic content of water/hard water). Microbicides are used in formulations (i.e. microbi-cidal products) usually, but not always, at a high concentration for application on surfaces or the disinfection of liquids (i.e. application of microbicides in suspension). With advances in formulations and delivery methods, one might consider that a microbicide delivered should be thought of as a dose (concentra-tion × volume) rather than simply as concentration. For example, some microbicides are recommended by manufacturers to be applied on a surface via the use of a wipe. Test data are rarely, if ever, obtained using a wipe test, and when results are available using a wipe efficacy test, microbicidal efficacy has been shown to be limited [22, 23, 43]. The nature and cleanliness of the micro-bicide applicator and how it is used are key to the dose of microbicide that will be delivered to the surface. The microbicide volume delivered on a surface is also important to consider as well as the time for application. The exposure time recommended in standard tests (see Chapter 12) is often not representative of microbicide application on surfaces in reality [22, 23, 44, 45]. In practice, failure to deliver sufficient microbicide to kill the target organisms will result in microorganisms surviving on the surface [46] and their possible selection [2, 47, 48], and, depending on the delivery method, it might result in distributing microorgan-isms over a wider area [22]. It is thus paramount that label instructions include accurate information on product dilution, usage (including detailed procedure and minimum contact time required) and storage.

Numerous reports on bacterial resistance to microbicides have been based on measuring the minimum inhibitory concentration (MIC). MICs are largely used for determining antibiotic suscep-tibility; for microbicides MICs provide evidence of the alteration of bacterial susceptibility to a microbicide (see Chapter 6.1). However, there can be considerable variations in the MIC values for a microbicide exposure within a single species or even among laboratories working with the same strain. Where the MIC of a microbicide differs widely from its minimum bactericidal con-centration (MBC), the use of a concentration close to the MIC might result in selection for microorganisms with reduced sus-ceptibility; this is particularly pertinent when the type of microorganism present is unknown [12]. In many studies the level of microbial resistance could be increased following repeated exposure to low concentrations of a microbicide or to its increas-ing (gradient) concentrations [2, 49–53].

Concentrations of Microbicides in the EnvironmentVirtually all antimicrobials or their by-products are eventually discharged into the environment, either directly to water or through sewage treatment plant effluents. In many instances the volume of water or sewage is large enough that the concentration(s) of microbicides might be below stressful levels for bacteria, but

233


S. enterica cells to triclosan was able to modify expression of regulator genes (soxS) involved in the genetic control of antibi-otic resistance [75].

Physiological and Metabolic ChangesA change in bacterial physiology, including small colonies, altera-tion of growth rates and altered gene expression, have been described during bacterial exposure to microbicides [82]. Expo-sure to isothiazolones changed metabolic processes in P. aerugi-nosa [49]. Serratia marcescens insusceptibility to a QAC was proposed to be dependent in part on a number of biosynthetic pathways [83]. In S. enterica, a “triclosan resistance network”, which constitutes an alternative pathway to the production of pyruvate and fatty acid, has been described [76]. Likewise, in S. aureus, a modification of the membrane lipid composition associ-ated with the alteration of expression of various genes involved in fatty acid metabolism has been associated with triclosan resist-ance [84]. A change in metabolic pathways in bacteria exposed to triclosan is, overall, not surprising when one considers the specific mechanism of action of triclosan at a low concentration [85, 86].

Conclusions

The emergence of microbicide resistance and the persistence of mobile genetic elements containing resistance genes have impor-tant implications for human and animal health in terms of surviving pathogens and the potential dissemination of antimi-crobial resistance. The selective pressure exerted by exposure to microbicides has been associated with the selection of less sus-ceptible or resistant bacteria. This has been exacerbated with increasing use and sometimes misuse of microbicides worldwide. A large number of studies have reported the resistance to micro-bicides in specific applications including healthcare, consumer products, food production and animal husbandry [1].

Microbicides used in a very large number of applications will eventually be released in the environment together with their by-products, despite existing regulations (e.g. BPD and REACH, see Chapter 14.1). In the environment, sewage and biosolid residuals combine with microbial pathogens and various chemicals, includ-ing microbicides and antibiotics. It is disappointing that, to date, there have been no investigations on the antimicrobial pheno-types of bacteria isolated from these environments.

There are now genetic and bacteriological data to demonstrate the involvement of microbicides in the selection of resistant bac-terial strains. Such information strongly indicates that prudence in the use of microbicides is needed in order to preserve their efficacy and to limit the emergence and dissemination of resistant bacteria.

This chapter dealt with bacteria and did not address the devel-opment of resistance to other classes of microorganisms such as fungi, protozoa and viruses (see Chapters 8 and 9). For those microorganisms, investigations in the development of resistance following microbicide exposure are scarce.

to microbicides, have a broad spectrum of action and contribute not only to resistance to microbicides but also to resistance to unrelated compounds such as antibiotics [12, 60]. For example, to reduce the intracellular concentration of antibacterial mole-cules under an inhibitory concentration threshold, Gram-negative bacteria can regulate the permeability of their membranes by decreasing the expression of porins (membrane pore-forming proteins involved in antibiotic uptake) and altering the lipopoly-saccharide structure or overexpressing efflux pumps [12, 60–63]. These modifications contribute to the resistance against antibiot-ics and microbicides [2, 64, 65].

Expression and Overexpression of Efflux Pumps and Other SystemsEfflux pumps, because of their broad-spectrum substrates, are increasingly associated with resistance [66–68]. In Salmonella, triclosan-selected strains have been shown to be less susceptible to antibiotics than the wild-type [69, 70]. Changes in antibiotic susceptibility profiles have also been observed following expo-sure to a low concentration of other microbicides [67, 68]. In triclosan-selected Stenotrophomonas clones, the overexpression of an efflux pump (SmeDEF) involved in antibiotic resistance has been described [71]. Other investigations described P. aeru-ginosa overexpressing multidrug efflux systems during exposure to chlorhexidine [72]. Expression and overexpression of other multigenic systems such as soxRS and oxyR [73] have also been implicated in bacterial resistance. In S. aureus, Huet et al. [74] described that transcription of efflux pump genes is stimulated during exposure of clinical isolates to low concentrations of a variety of microbicides and dyes. In a recent study, Bailey et al. [75] demonstrated that the exposure of E. coli and S. enterica cells to triclosan induces a species-specific response correspond-ing to an increase of the expression of efflux pump genes. A recent report showed that the triclosan resistance could involve distinct mechanisms including the overexpression and mutagen-esis of fab1 and the production of the active efflux pump AcrAB/TolC in Salmonella [76]. In bacterial biofilms, triclosan could also upregulate the transcription of acrAB, of marA (the major regulator of the genetic cascade controlling multidrug resist-ance) and of the cellulose synthesis coding genes bcsA and bcsE. In E. coli exposure to polyhexamethylene biguanide induced the alteration of transcriptional activity in a number of genes, notably in the rhs gene involved in repair/binding of nucleic acid [77]. Some of the mechanisms that play a major role in micro-bicide and antibiotic resistance are controlled by diverse genetic cascades that share common key gene regulators (soxS, marA) [60, 78, 79]. A transcriptional analysis has demonstrated that paraquat is able to induce the expression of several genes that are directly involved in antibiotic resistance [80]. In addition, activation of the soxRS regulon with paraquat treatment increased resistance to ampicillin, nalidixic acid, chlorampheni-col and tetracycline in laboratory strains of E. coli and S. enterica. The soxRS regulon was also connected to antibiotic resistance in clinical strains [81]. In a recent study, the exposure of E. coli and


234

Resistance, Scientific Opinion of the Panel on Biological Hazards, published 2

April 2008; adopted 6 March 2008.

25 EFSA (European Food Safety Authority) (2008) Scientific opinion of the panel

on biological hazards on a request from the European Food Safety Authority on

foodborne antimicrobial resistance as a biological hazard. EFSA Journal, 765,

1–87.

26 Pedrouzo, M. et al. (2009) Ultra-high-performance liquid chromatography

and mass spectrometry for determining the presence of eleven personal

care products in surface and wastewaters. Journal of Chromatography A, 1216,

6994–7000.

27 Kumar, K.S. et al. (2010) Mass loadings of triclosan and triclocarbon from four

wastewater treatment plants to three rivers and landfill in Savannah, Georgia,

USA. Archives of Environmental Contamination and Toxicology, 58, 275–285.

28 Wilson, B. et al. (2009) The partitioning of triclosan between aqueous and

particulate bound phases in the Hudson River Estuary. Marine Pollution Bul-

letin, 59, 207–212.

29 SCCS (Scientific Committee on Consumer Safety) (2010) Preliminary Opinion

on Triclosan (Antimicrobial Resistance), March 23, http://ec.europa.eu/health/

scientific_committees/consumer_safety/docs/sccs_o_023.pdf.

30 McBain, A.J. et al. (2004) Effects of quaternary-ammonium based formulations

on bacterial community dynamics and antimicrobial susceptibility. Applied and

Environmental Microbiology, 70, 3449–3456.

31 McBain, A.J. et al. (2003) Exposure of sink drain microcosms to triclosan: popu-

lation dynamics and antimicrobial susceptibility. Applied and Environmental

Microbiology, 69, 5433–5442.

32 Maillard, J.-Y. (2002) Bacterial target sites for biocidal action. Journal of Applied

Microbiology, 92 (Suppl.), 16–27.

33 Russell, A.D. (2003) Biocide use and antibiotic resistance: the relevance of labo-

ratory findings to clinical environmental situations. Lancet Infectious Diseases,

3, 794–803.

34 Aiello, A.E. and Larson, E. (2003) Antibacterial cleaning and hygiene products

as an emerging risk factor for antibiotic resistance in the community. Lancet

Infectious Diseases, 3, 501–506.

35 Aiello, A.E. et al. (2005) Antibacterial cleaning products and drug resistance.

Emerging Infectious Diseases, 11, 1565–1570.

36 Aiello, A.E. et al. (2007) Consumer antibacterial soaps: effective or just risky?

Clinical Infectious Diseases, 45 (Suppl. 2), 137–147.

37 Levy, S.B. (2000) Antibiotic and antiseptic resistance: impact on public health.

Pediatric Infectious Disease Journal, 19 (Suppl.), 120–122.

38 Russell, A.D. (2002) Antibiotic and biocide resistance in bacteria: comments and

conclusion. Journal of Applied Microbiology, 92 (Suppl.), 171–173.

39 Sheldon, A.T., Jr. (2005) Antiseptic “resistance”: real or perceived threat? Clinical

Infectious Diseases, 40, 1650–1656.

40 Russell, A.D. and McDonnell, G. (2000) Concentration: a major factor in study-

ing biocidal action. Journal of Hospital Infection, 44, 1–3.

41 Anderson, G.G. and O’Toole, G.A. (2008) Innate and induced resistance mecha-

nisms of bacterial biofilms. Current Topics in Microbiology and Immunology, 322,

85–105.

42 Tart, A.H. and Wozniak, D.J. (2008) Shifting paradigms in Pseudomonas aeru-

ginosa biofilm research. Current Topics in Microbiology and Immunology, 322,

193–206.

43 Panousi, M.N. et al. (2009) Use of alcoholic wipes during aseptic manufacturing.

Letters in Applied Microbiology, 48, 648–651.

44 Williams, G.J. et al. (2009) The use of sodium dichloroisocyanurate, NaDCC, in

Welsh ITUs. Journal of Hospital Infection, 72 (3), 279–281.

45 Cheeseman, K.E. et al. (2009) Evaluation of the bactericidal efficacy of three

different alcohol hand rubs against 57 clinical isolates of Staphylococcus aureus.

Journal of Hospital Infection, 72, 319–325.

46 Maillard, J.-Y. (2011) Innate resistance to sporicides and potential failure to

decontaminate. Journal of Hospital Infection, 77, 204–209.

47 Chapman, J.S. (2003) Disinfectant resistance mechanisms, cross-resistance, and

co-resistance. International Biodeterioration and Biodegradation, 51, 271–276.

48 Maillard, J.-Y. (2005) Antimicrobial biocides in the health care environment:

efficacy, policies, management and perceived problems. Therapeutics and Clini-

cal Risk Management, 1, 307–320.

References

1 SCENIHR (Scientific Committee on Emerging and Newly Identified Health

Risks) (2009) The antibiotic resistance effect of biocides, adopted by the

SCENIHR on January 19, 2009. http://ec.europa.eu/health/ph_risk/committees/

04_scenihr/docs/scenihr_o_021.pdf

2 Maillard, J.-Y. (2007) Bacterial resistance to biocides in the health care environ-

ment: should it be of genuine concern? Journal of Hospital Infection, 65 (Suppl.

2), 60–72.

3 Falagas, M.E. and Bliziotis, I.A. (2007) Pandrug-resistant Gram-negative bacte-

ria: the dawn of the post-antibiotic era? International Journal of Antimicrobial

Agents, 29, 630–636.

4 Jansen, W.T. et al. (2006) Bacterial resistance: a sensitive issue complexity of the

challenge and containment strategy in Europe. Drug Resistance Update, 9,

123–133.

5 Chopra, I. et al. (2008) Treatment of health-care-associated infections caused

by Gram-negative bacteria: a consensus statement. Lancet Infectious Diseases, 8,

133–139.

6 Llorens, J.M.N. et al. (2010) Stationary phase in Gram negative bacteria. FEMS

Microbiology Reviews, 34, 476–495.

7 Feinstein, S.I. and Brooks, K.B. (1986) Hyper-recombining recipient strains in

bacterial conjugation. Genetics, 113, 13–33.

8 Guelfo, J.R. et al. (2010) A MATE-family efflux pump rescues the Escherichia

coli 8-oxoguanine-repair-deficient mutator phenotype and protects against

H2O2 killing. PLoS Genetics, 6 (5), e1000931.

9 Jolivet-Gougeon, A. et al. (2011) Bacterial hypermutation: clinical implications.

Journal of Medical Microbiology, 60, 563–573.

10 Preller, L. et al. (1996) Disinfectant use as a risk factor for atopic sensitization

and symptoms consistent with asthma: an epidemiological study. European

Respiratory Journal, 9, 1407–1413.

11 Bove, G.E. et al. (2007) Case control study of the geographic variability of

exposure to disinfectant byproducts and risk for rectal cancer. International

Journal of Health Geographics, 6, 6–18.

12 Maillard, J.-Y. and Denyer, S.P. (2009) Emerging bacterial resistance following

biocide exposure: should we be concerned? Chemica Oggi, 27, 26–28.

13 Spaulding, E.H. (1968) Chemical disinfection of medical and surgical materials,

in Disinfection, Sterilization and Preservation (eds C.A. Laurence and S.S. Block),

Lea & Febiger, Philadelphia, pp. 517–531.

14 Allerberger, F. et al. (2002) Routine surface disinfection in health care facilities:

should we do it? American Journal of Infection Control, 30, 318–319.

15 Dettenkoffer, M. et al. (2004) Does disinfection of environmental surfaces influ-

ence nosocomial infection rates? A systematic review. American Journal of Infec-

tion Control, 32, 84–89.

16 Dharan, S. et al. (1999) Routine disinfection of patients’ environmental surfaces.

Myth or reality? Journal of Hospital Infection, 42, 113–117.

17 Rutala, W.A. and Weber, D.J. (2001) Surface disinfection: should we do it?

Journal of Hospital Infection, 48 (Suppl. A), 64–68.

18 Rutala, W.A. and Weber, D.J. (2004) The benefits of surface disinfection. Ameri-

can Journal of Infection Control, 32, 226–231.

19 Boyce, J.M. (2007) Environmental contamination makes an important

contribution to hospital infection. Journal of Hospital Infection, 65 (Suppl. 2),

50–54.

20 Talon, D. (1999) The role of the hospital environment in the epidemiology of

multi-resistant bacteria. Journal of Hospital Infection, 43, 13–17.

21 Hota, B. (2004) Contamination, disinfection and cross-colonization: are hospi-

tal surfaces reservoirs for nosocomial infection? Clinical Infectious Diseases, 39,

1182–1189.

22 Williams, G.J. et al. (2009) Limitations of the efficacy of surface disinfection in the

healthcare settings. Infection Control and Hospital Epidemiology, 30, 570–573.

23 Siani, H. et al. (2011) Efficacy of “sporicidal” wipes against Clostridium difficile.

American Journal of Infection Control, 39, 212–218.

24 EFSA (European Food Safety Authority) (2008) Assessment of the Possible Effect

of the Four Antimicrobial Treatment Substances on the Emergence of Antimicrobial

235


69 Karatzas, K.A. et al. (2008) Phenotypic and proteomic characterization of mul-

tiply antibiotic-resistant variants of Salmonella enterica serovar Typhimurium

selected following exposure to disinfectants. Applied and Environmental Micro-

biology, 74, 1508–1516.

70 Karatzas, K.A. et al. (2007) Prolonged treatment of Salmonella enterica serovar

Typhimurium with commercial disinfectants selects for multiple antibiotic

resistance, increased efflux and reduced invasiveness. Journal of Antimicrobial

Chemotherapy, 60, 947–955.

71 Sánchez, P. et al. (2005) The biocide triclosan selects Stenotrophomonas mal-

tophilia mutants that overproduce the SmeDEF multidrug efflux pump. Anti-

microbial Agents and Chemotherapy, 49, 781–782.

72 Fraud, S. et al. (2008) MexCD-OprJ multidrug efflux system of Pseudomonas

aeruginosa: involvement in chlorhexidine resistance and induction by

membrane-damaging agents dependent upon the AlgU stress response sigma

factor. Antimicrobial Agents and Chemotherapy, 52, 4478–4482.

73 Dukan, S. and Touati, D. (1996) Hypochlorous acid stress in Escherichia coli:

resistance, DNA damage, and comparison with hydrogen peroxide stress.

Journal of Bacteriology, 178, 6145–6150.

74 Huet, A.A. et al. (2008) Multidrug efflux pump overexpression in Staphylococcus

aureus after single and multiple in vitro exposures to biocides and dyes. Micro-

biology, 154, 3144–3153.

75 Bailey, A.M. et al. (2009) Exposure of Escherichia coli and Salmonella enterica

serovar Typhimurium to triclosan induces a species-specific response, including

drug detoxification. Journal of Antimicrobial Chemotherapy, 64, 973–985.

76 Webber, M.A. et al. (2008) Triclosan resistance in Salmonella enterica serovar

Typhimurium. Journal of Antimicrobial Chemotherapy, 62, 83–91.

77 Allen, M.J. et al. (2006) The response of Escherichia coli to exposure to the

biocide polyhexamethylene biguanide. Microbiology, 152, 989–1000.

78 Li, X.Z. and Nikaido, H. (2009) Efflux-mediated drug resistance in bacteria: an

update. Drugs, 69, 1555–1623.

79 Oethinger, M. et al. (1998) Association of organic solvent tolerance and fluoro-

quinolone resistance in clinical isolates of Escherichia coli. Molecular Microbiol-

ogy, 16, 45–55.

80 Pomposiello, P.J. et al. (2001) Genome-wide transcriptional profiling of the

Escherichia coli responses to superoxide stress and sodium salicylate. Journal of

Bacteriology, 183, 3890–3902.

81 Koutsolioutsou, A. et al. (2005) Constitutive soxR mutations contribute to

multiple-antibiotic resistance in clinical Escherichia coli isolates. Antimicrobial

Agents and Chemotherapy, 49, 2746–2752.

82 Seaman, P. et al. (2007) Small-colony variants: a novel mechanism for triclosan

resistance in methicillin-resistant Staphylococcus aureus. Journal of Antimicrobial


83 Codling, C.E. et al. (2004) Identification of genes involved in the susceptibility

of Serratia marcescens to polyquaternium-1. Journal of Antimicrobial Chemo-

therapy, 54, 370–375.

84 Tkachenko, O. et al. (2007) A triclosan-ciprofloxacin cross-resistant mutant

strain of Staphylococcus aureus displays an alteration in the expression of several

cell membrane structural and functional genes. Research in Microbiology, 158,

651–658.

85 Gomez Escalada, M. et al. (2005) Triclosan inhibition of fatty acid synthesis and

its effect on growth of E. coli and P. aeruginosa. Journal of Antimicrobial Chemo-

therapy, 55, 879–882.

86 Gomez Escalada, M. et al. (2005) Triclosan-bacteria interactions: single or mul-

tiple target sites? Letters in Applied Microbiology, 41, 476–481.

49 Abdel Malek, S.M. et al. (2002) Antimicrobial susceptibility changes and T-OMP

shifts in pythione-passaged planktonic cultures of Pseudomonas aeruginosa

PAO1. Journal of Applied Microbiology, 92, 729–736.

50 Langsrud, S. et al. (2003) Bacterial disinfectant resistance – a challenge for the

food industry. International Biodeterioration and Biodegradation, 51, 283–290.

51 Tattawasart, U. et al. (1999) Development of resistance to chlorhexidine diace-

tate and cetylpyridinium chloride in Pseudomonas stutzeri and changes in anti-

biotic susceptibility. Journal of Hospital Infection, 42, 219–229.

52 Thomas, L. et al. (2000) Development of resistance to chlorhexidine diacetate

in Pseudomonas aeruginosa and the effect of “residual” concentration. Journal of

Hospital Infection, 46, 297–303.

53 Walsh, S.E. et al. (2003) Development of bacterial resistance to several biocides

and effects on antibiotic susceptibility. Journal of Hospital Infection, 55,

98–107.

54 Gaze, W.H. et al. (2005) Incidence of class-1 integrons in a quaternary ammo-

nium compound-polluted environment. Antimicrobial Agents and Chemother-

apy, 49, 1802–1807.

55 Gaze, W.H. et al. (2011) Impacts of anthropogenic activity on the ecology of

class 1 integrons and integron-associated genes in the environment. ISME

Journal, 5, 1253–1261.

56 Beveridge, T.J. et al. (1997) Metal–microbe interactions: contemporary

approaches. Advances in Microbial Physiology, 38, 177–243.

57 Misra, T.K. (1992) Bacterial resistances to inorganic mercury salts and organo-

mercurials. Plasmid, 27, 4–16.

58 Carson, R.T. et al. (2008) Use of antibacterial consumer products containing

quaternary ammonium compounds and drug resistance in the community.

Journal of Antimicrobial Chemotherapy, 62, 1160–1162.

59 Duarte, R.S. et al. (2009) Epidemic of postsurgical infections caused by Myco-

bacterium massiliense. Journal of Clinical Microbiology, 47, 2149–2155.

60 Poole, K. (2007) Efflux pumps as antimicrobial resistance mechanisms. Annals

of Medicine, 39, 162–176.

61 Pagès, J.M. et al. (2008) The porin and the permeating antibiotic: a selective

diffusion barrier in Gram-negative bacteria. Nature Reviews. Microbiology, 6,

893–903.

62 Nikaido, H. (2003) Molecular basis of bacterial outer membrane permeability

revisited. Microbiology and Molecular Biology Reviews, 67, 593–656.

63 Piddock, L.J. (2006) Clinically relevant chromosomally encoded multidrug

resistance efflux pump in bacteria. Clinical Microbiology Reviews, 19, 382–402.

64 Thorrold, C.A. et al. (2007) Efflux pump activity in fluoroquinolone and tetra-

cycline resistant Salmonella and E. coli implicated in reduced susceptibility to

household antimicrobial cleaning agents. International Journal of Food Microbi-

ology, 113, 315–320.

65 Tumah, H.N. (2009) Bacterial biocide resistance. Journal of Chemotherapy, 21,

5–15.

66 Maira-Litrán, T. et al. (2000) An evaluation of the potential of the multiple

antibiotic resistance operon (mar) and the multidrug efflux pump acrAB to

moderate resistance towards ciprofloxacin in Escherichia coli biofilms. Journal

of Antimicrobial Chemotherapy, 45, 789–795.

67 Randall, L.P. et al. (2007) Commonly used farm disinfectants can select for

mutant Salmonella enterica serovar Typhimurium with decreased susceptibility

to biocides and antibiotics without compromising virulence. Journal of Antimi-

crobial Chemotherapy, 60, 1273–1280.

68 Randall, L.P. et al. (2004) Effect of triclosan or a phenolic farm disinfectant on

the selection of antibiotic-resistant Salmonella enterica. Journal of Antimicrobial


russell, hugo & ayliffe's (principles and practice of disinfection, preservation and...

Documents