Sporicides for Clostridium difficile: the devil is in the detail

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Journal of Hospital Infection 77 (2011) 187e188

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Journal of Hospital Infection

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Guest Editorial

Sporicides for Clostridium difficile: the devil is in the detail

M.H. Wilcox a,*, A.P. Fraise b, C.R. Bradley b, J. Walker c, R.G. Finch d

aMicrobiology, Leeds Teaching Hospitals & University of Leeds, Old Medical School, Leeds General Infirmary, Leeds, UKbHospital Infection Research Laboratory, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UKcBiosafety Unit, Research Department, Health Protection Agency, Microbiology Services, Porton Down, Salisbury, UKdUniversity of Nottingham & Nottingham University Hospitals NHS Trust, Clinical Sciences Building, City Hospital Campus, Nottingham, UK

a r t i c l e i n f o

Article history:Received 25 October 2010Accepted 31 October 2010Available online 31 January 2011

Keywords:DisinfectantsIn vitro assaysQuality assessmentSporicides

* Corresponding author. Address: Microbiology,University of Leeds, Old Medical School, Leeds GeneUK. Tel.: þ44 113 392 6818; fax: þ44 113 392 2696.

E-mail address: mark.wilcox@leedsth.nhs.uk (M.H

0195-6701/$ e see front matter � 2010 The Hospitaldoi:10.1016/j.jhin.2010.10.017

s u m m a r y

A taskforce has now been formedwith representatives from the Department of Health’s AdvisoryCommittee onAntimicrobial Resistance andHealthcare Associated Infection (ARHAI), theHospitalInfection Society (HIS), theDepartment of Health (England) and theHealth Protection Agency. Theaims of the ARHAI/HIS Taskforce on Sporicidal Disinfectants are: to develop an accepted standardfor laboratory testing of disinfectants which claim to have activity against C. difficile spores; todevelop a network of laboratorieswith capability to perform in vitro assays of sporicidal activity ofdisinfectants; and to explore the creation of a national quality assessment scheme for laboratorieswhich perform in vitro assays of sporicidal activity of disinfectants.

� 2010 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.

Environmental contamination is a key component of the trans-mission route for Clostridium difficile.1e3 The increased incidence ofC. difficile infection (CDI) and attendant morbidity, mortality andhealthcare costs has created a clear need for practicable and effectiveenvironmental disinfection methods. Current guidelines advocatechlorine-based disinfection to remove viable C. difficile spores fromcontaminated surfaces, based on in vitro and in situ studies.4e6 Forexample, High Impact InterventionNumber 7 in the Saving Lives carebundle guidance recommends ‘environmental disinfection witha chlorine based or other sporicidal disinfectant’.7 There are signifi-cant drawbacks to the continuous use of chlorine-based disinfec-tants. Users will want to explore other agents, but it may be difficultfor them to determinewhat is an acceptable and effective alternative.The need to ensure adequate cleaning as well as user and environ-ment safety, including minimisation of surface damage, are keyfactors in determining product acceptability. There are many prod-ucts available that claim to be effective at killing C. difficile, yet it is notclearwhich of these are (most) fit for purpose, namely rapid killing ofsurface-adherent C. difficile spores, in the presence of organic matter.

Given the challenges ofmanipulating and testing C. difficile, thereis unfortunately significant scope to obtain misleading results on

Leeds Teaching Hospitals &ral Infirmary, Leeds LS1 3EX,

. Wilcox).

Infection Society. Published by Els

the apparent efficacy of disinfectants. For example, water may beshown to be cidal against C. difficile vegetative bacteria (because ofthe effects of dissolved oxygen against obligate anaerobic bacteria),but this of course does not equate to any useful disinfectant activityagainst C. difficile spores. Long exposure times, which far exceed thelikely few minutes of contact time achievable in practice, may berequired to effect spore killing. Also, assessment of disinfectantactivity without the challenge imposed by a soil is of minimalusefulness, since it is likely that spores will invariably be found insitu in association with organic matter. Hence, the current testingand reporting scenario for disinfectant activity against C. difficile isconfusing, both for the average (healthcare professional or other-wise) consumer who is unaware of the importance of such details,and for the specialist for whom the detail may not be provided.Testing standardisation that also has in situ relevance is required toenable greater transparency of choice.

A taskforce has now been formed with representatives fromthe Department of Health’s Advisory Committee on AntimicrobialResistance and Healthcare Associated Infection (ARHAI), theHospital Infection Society (HIS), the Department of Health(England) and the Health Protection Agency. The ARHAI/HISTaskforce on Sporicidal Disinfectants aims: to develop an acceptedstandard for laboratory testing of disinfectants which claim tohave activity against C. difficile spores; to develop a network oflaboratories with capability to perform in vitro assays of sporicidalactivity of disinfectants; and to explore the creation of a nationalquality assessment scheme for laboratories which perform in vitroassays of sporicidal activity of disinfectants. Key to this process

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will be interaction at a European level where there is ongoingwork to develop a European Norm for disinfectants with activityagainst anaerobic spores including C. difficile. Interaction with theEuropean process means that timescales are difficult to estimatebut it is hoped that this work should be complete in 12e24months.

Although there is a current European Normmethod (EN 13704)for testing the activity of biocides against spores, this test usesBacillus subtilis as the test organism and does not require activityagainst any anaerobic spores. This EN was developed for use infood hygiene, domestic and institutional settings and was neverapproved for use in connection with medical services. Key factorsfor the accuracy of disinfectant test methods include the prepar-ation of a standardised spore inoculum, use of a soil (dirt) chal-lenge, realistic exposure times, adequate neutralisation/removalof disinfectant prior to assay for remaining viable spores, andefficient culture of C. difficile. Once a standard in vitro test methodhas been achieved, a desirable goal will be to validate adequatelyin situ those disinfectants considered suitably active againstC. difficile spores in vitro. The important stepping stone is a stan-dard method that yields reproducible results. To this end, weenvisage that UK laboratories participating in a quality assessmentscheme agree to have the results of their tests made publiclyavailable (e.g. on the internet). The overriding objective of thisinitiative is to provide clarity to healthcare workers about disin-fectant efficacy, and so to improve the standard of disinfection ofenvironments contaminated with C. difficile. The devil is in thedetail but should be easier to spot.

The ARHAI/HIS Taskforce on Sporicidal Disinfectants will bepleased to receive feedback on its stated aims (comments please toSue Hollinshead, e-mail: sue.hollinshead@his.org.uk).

Conflict of interest statementNone declared.

Funding sourceTravel expenses for meetings of the Taskforce are paid byHospital Infection Society.

References

1. McFarland LV, Mulligan ME, Kwok RY, Stamm WE. Nosocomial acquisition ofClostridium difficile infection. New Engl J Med 1989;320:204e210.

2. Samore MH, Venkataraman L, DeGirolami PC, Arbeit RD, Karchmer AW. Clinicaland molecular epidemiology of sporadic and clustered cases of nosocomialClostridium difficile diarrhea. Am J Med 1996;100:32e40.

3. Fawley WN, Wilcox MH. Molecular epidemiology of endemic Clostridium difficileinfection. Epidemiol Infect 2001;126:343e350.

4. Fawley WN, Underwood S, Freeman J, et al. Efficacy of hospital cleaning agentsand germicides against epidemic Clostridium difficile strains. Infect Control HospEpidemiol 2007;28:920e925.

5. Wilcox MH, Fawley WN, Wigglesworth N, Parnell P, Verity P, Freeman J.Comparison of effect of detergent versus hypochlorite cleaning on environ-mental contamination and incidence of Clostridium difficile infection. J HospInfect 2003;54:109e114.

6. Mayfield JL, Leet T, Miller J, Mundy LM. Environmental control to reduce trans-mission of Clostridium difficile. Clin Infect Dis 2000;31:995e1000.

7. Department of Health (England). Saving Lives: reducing infection, delivering cleanand safe care. High Impact Intervention Number 7: Care bundle to reduce the riskfrom Clostridium difficile. London: DoH; 2007.