Effectiveness of installing an antibacterial filter at water taps to prevent Legionella infections

Effectiveness of installing an antibacterial filter at water taps to prevent Legionella infections
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  G. Imbert a , Y. Seccia b , B. La Scola a,b, * a Unite´ des Rickettsies, CNRS UMR 6020, Faculte´ deme´decine, Marseille, France b Equipe Ope´rationelle d’Hygie`ne Hospitalie`re deL’Assistance Publique de Marseille, Hoˆ pital Nord,Marseille, FranceE-mail address: * Corresponding author. Tel.: C 33 4 91 385517; fax: C 33 4 91830390 Q 2005 The Hospital Infection Society. Published by Elsevier Ltd.All rights reserved.doi:10.1016/j.jhin.2005.01.030 Effectiveness of installing an antibacterial filterat water taps to prevent Legionella infections Sir, Legionella pneumophila  is frequently found inhospital hot water systems, and patients may beinfected by inhalation of the aerosol created whenthe water is run through the taps or shower heads. 1 Risk factors for Legionella infection depend on thepatient’s clinical condition (i.e. immunosuppres-sion) and the degree of colonization within themains. The number of colony-forming units (CFUs)present at the water taps does not appear to bepredictive of infection, 2 but the percentage ofcontaminated tap points appears to be directlyrelated to the incidence of Legionella infection. 3 To prevent Legionella infection, numerousmethods have been applied to eradicate  L. pneu-mophila  from the hospital water circuit: †  hyperchlorination through the use of sodiumhypochlorite, calcium hypochlorite and chlorinedioxide; †  overheating and flushing; †  copper and silver ionization; †  ultraviolet radiation; and †  ozonization.These methods are not always effective,especially in hospitals where piping deadlegs existandmaycontainLegionellawhichthenrecolonizethewater supply. This is particularly true if the pipingcontains biofilms in stagnant areas, 4 as such biofilmsprovide an ideal habitat for Legionellae. Moreover,Legionella may also be present in protozoans inhospital water mains, which makes it even moredifficult to eradicate by chemical means.Apart from cost, these methods have somenegative side effects. Hyperchorination, forexample, is corrosive and leads to production ofthe potentially carcinogenic trihalomethanes. Inoverheating and flushing, there is the potentialdanger of scalding patients. 5 In addition, preventive measures must involvethe hot water systems throughout the hospital,which involves complex installation and/or highoperating costs. Installation of antibacterial filtersat the points where water is used (taps and showerheads) offers some advantages: installation can belimited to the high-risk areas, and installation andmaintenance are simple and inexpensive.Most filters last for a maximum of 15 days andthis is a significant disadvantage. Recently, how-ever, a showerhead filter has been developed with apore size of 0.2  m m (Pall—Aquasafe Shower HeadFilter, AQL3). The filter membrane resists a watertemperature of 60  8 C and has an operating lifespanof one month. 6 Laboratory tests using standardizedmethods have shown that this filter can treat  L. pneumophila  and  Serratia marcescens  at a chal-lenge level of 1 ! 10 7 CFU/cm 2 .We investigated whether installation of this filterineight showerslocatedindifferent departments ofour hospital couldpreventcolonization of thewaterby Legionellae over a period of one month. At thetime of installation, all showers were contaminatedwith Legionellae. In addition, the intent was tocheck whether the integrity of the filters would bepreserved under real conditions involving dailyoperation of the filter. Moreover, it is worth notingthat no other water decontamination system wasused for the entire test period.To determine the number of CFUs present in theshower water before and after installation of thefilter, a 1-L sample was drawn from the hot watercircuit (temperature 40–45  8 C) in sterile bottles withthe addition of sodium thiosulphate at a finalconcentration of 0.01% in order to neutralize thechlorine in the water. After filtering on a membrane(porosity 0.2  m m), the membrane was suspended in10 mL of the srcinal water sample and vortexed for10 min. To reduce contamination by other micro-organisms, 5 mL of this suspension was heat treated(50  8 C for 30 min) in a double boiler. Two 0.1-mLaliquots of the srcinal sample (heat treated or nottreated, diluted 1:10 or undiluted) were used to seedthe surface of a BCYE agar plate. The plates wereincubatedmicro-aerophilicallyat36 G 1  8 Cfor10daysandreadingsweretakenfromthefourthdayonwards.Gram-negativecoloniesthatrequiredthepresenceoflevocistein for growth were identified. 7 Letters to the Editor270  The samples were taken before installation ofthe filter and once a week thereafter for fourweeks. After a month, the filters were changedand additional samples were taken after 15 and30 days.At the completion of the study, all filters werelaboratory tested for integrity and flow (ForwardFlow Test) 8 and all test results were positive. Thenumbers of CFU/L before and after installation areillustrated in Table I.All colonies fell under serum group 3. From themoment the filters were installed, the degree ofwater contamination varied between 10 2 and10 4 CFU/L. For the quantities sampled and thedilutions used, the lower limit for legionelladetection was 50 CFU/L.After installation of the filter, no legionellacolonies were found nor was it possible to detectlegionella 15 and 30 days after the filters werereplaced.The results suggest that, prior to installation ofthe filter, the number of legionella present in thehot water mains was 10 3 –10 4 CFU/mL. As in mostcountries, 9 Italian guidelines permit possible watercontamination containing between 10 2 and10 4 CFU/L of Legionella. Use of the filters made itpossible to eliminate the potential risk of infection.Installation of the filters at points of use made itpossible to forego other methods involving thecostly disinfection of the entire water systemwhich, in any case, may only temporarily resolvethe problem of contamination. References 1. Breiman RF, Fields BS, Sanden GN,  et al . Association of showeruse with Legionnaires’ disease.  JAMA  1990; 263 :2924—2926.2. Best M, Yu VL, Stout J,  et al . Legionellaceae in the hospitalwater supply: epidemiological link with disease andevaluation of a method of control of nosocomial legion-naires’ disease and Pittzburgh pneumonia.  Lancet  1983; 2 :301—310.3. Kool JL, Bergimire-Sweat D, Butler JC,  et al . Hospitalcharacteristics associated with colonisation of water systemsby Legionella and risk of nosocomial Legionnaires’ disease: acohort study of 15 hospital.  Infect Control Hosp Epidemiol 1999; 20 :798—805.4. Murg R, Forster TS, Brown E,  et al . Role of biofilms in thesurvival of  Legionella pneumophila  in a model potable-watersystem.  Microbiology   2001; 147 :3121—3126.5. Yu VL, Liu Z, Stout JE,  et al . Legionella dinfection of waterdistribution systems: principles, problems, and practice. Infect Control Hosp Epidemiol  1993; 24 :567—570.6. Validation Guide (CC107), Pall-Aquasafe Water Filter, Dis-posable Shower Head Filter (AQL3) for Protection AgainstLegionella spp., 2004.7. Linee guida per la prevenzione e il controllo della Legionel-losi. Gazzetta Ufficiale N. 103 del 5/05/2000, Documento 4Aprile 2000-Allegato 2.8. Sterilizing filtration of liquid. PDA. (Parental Drug Adminis-tration).  J Pharmaceutical Sci Technol . Technical Report1998; 26 (Suppl 52):7.9. DitommasoS,BiasinC,GiacomuzziM, etal .PrevenzionedellaLegionellosi: confronto tra linee guida europee ed extraeur-opee.  Giornale italiano delle infezioni ospedaliere  2003; 10 :7—24. G. Salvatorelli a, * , S. Medici b , G. Finzi b , S. DeLorenzi a , C. Quarti c a Department of Biology, University of Ferrara,Italy  b Hospital Management, Policlinico S. OrsolaMalpigli, Bologna, Italy  c Pall Italia s. r. l., via Bruzzesi 38/40, 20146 Milan,Italy E-mail address: * Corresponding author. Address: Dipartimento di Biologia-Sez,Anatomia Comparata, Via Luigi Borsari 46, 44100 Ferrara, Italy.Tel.: C 39 532 291 709; fax: C 39 353 229 1715 Q 2005 The Hospital Infection Society. Published by Elsevier Ltd.All rights reserved.doi:10.1016/j.jhin.2005.04.012 Table I  Colony-forming units per litre in the water flowing from eight showers before installation of the filter (A),after use of the filter for one to four weeks (B, C, D, E), and 15 and 30 days after replacement of the filter (F, G)Water tap A B C D E F GRadiotherapy department 8200  ! 50  ! 50  ! 50  ! 50  ! 50  ! 50Internal medicine ward 9100  ! 50 /  ! 50  ! 50  ! 50  ! 50Diabetology ward 4200  ! 50  ! 50  ! 50  ! 50  ! 50  ! 50Emergency medicine department 4300  ! 50  ! 50  ! 50  ! 50  ! 50  ! 50Service personnel showers 200  ! 50  ! 50  ! 50  ! 50  ! 50  ! 50Cardiology ward 8700  ! 50  ! 50  ! 50  ! 50  ! 50  ! 50Haematology ward 18 600  ! 50  ! 50  ! 50  ! 50  ! 50  ! 50Geriatrics ward 3500  ! 50  ! 50  ! 50  ! 50  ! 50  ! 50 Letters to the Editor 271
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