Decontamination of fibreoptic endoscopes

ffournal of Hospital Infeetion (1985) 6. 363-368

L E A D I N G ARTICLE

D e c o n t a m i n a t i o n of fibreoptic e n d o s c o p e s T h e effective d e c o n t a m i n a t i o n o f e n d o s c o p e s r e q u i r e s the interaction of clinician, e n d o s c o p y n u r s e a n d microbiologist. T h e clinician m a y have one or two i n s t r u m e n t s only, and will r e q u i r e a fast d e c o n t a m i n a t i o n rate b e t w e e n patients; the n u r s e will r e q u i r e a process w h i c h is n o t laborious and t i m e - c o n s u m i n g to c a r r y out; a n d the m i c r o b i o l o g i s t will n e e d assurance t h a t the process is effective against t h e m i c r o - o r g a n i s m s e n c o u n t e r e d . In short, the p r o c e d u r e m u s t be endoscopically functionali n u r s e acceptable, a n d microbiologically feasible. T o achieve these criteria, a c o m p r o m i s e will almost certainly be required. W h a t is required? S h o u l d the i n s t r u m e n t be sterile, or disinfected? Sterilization r e q u i r e s the r e m o v a l or killing of all m i c r o - o r g a n i s m s , including spores. Disinfection, o n the o t h e r hand, is the r e m o v a l of vegetative forms of bacteria and u n d e r certain c i r c u m s t a n c e s m a y include fungi, viruses, or even to a l i m i t e d extent spores. H o w e v e r , the precise effect of t h e disinfection process will be d e p e n d e n t on the disinfectant, e x p o s u r e time, a n d the degree of p r e c l e a n i n g of the i n s t r u m e n t . E n d o s c o p e s will not w i t h s t a n d the sterilizing effect o f s t e a m u n d e r pressure, a n d t h e r e f o r e cannot be autoclaved. E x p e r i m e n t s using low t e m p e r a t u r e steam, and low t e m p e r a t u r e steam plus f o r m a l d e h y d e as a sterilizing s y s t e m have also resulted in u n a c c e p t a b l e d a m a g e to the endoscopes (Babb e t al., 1981). T h u s , the only effective sterilization process is c o n t r o l l e d e x p o s u r e to ethylene oxide gas. T h i s process is p r o l o n g e d , a n d requires a p e r i o d of post exposure aeration, m a k i n g t h e process i m p r a c t i c a b l e f o r r o u t i n e use. It is i m p o r t a n t to stress that the ethylene oxide sterilization r e q u i r e s carefully controlled conditions to ensure efficacy. U n d e r w h a t c i r c u m s t a n c e s m i g h t sterilization be advisable? U s e o f the e n d o s c o p e on patients w i t h k n o w n c o m m u n i c a b l e infection is obviously to be avoided. H e p a t i t i s B has been t r a n s m i t t e d via the e n d o s c o p e (Birnie et al., 1983) . a n d endoscopes invariably b e c o m e c o n t a m i n a t e d w i t h H B s A g when used on H B s A g positive patients ( B o n d & M a n c a n d a , 1978) b u t the clinical risk is p r o b a b l y low ( O , C o n n o r & Axon, 1983). T h e r e have b e e n no r e p o r t s of the t r a n s m i s s i o n of Mycobacteriurn tuberculosis via g a s t r o ' intestinal e n d o s c 0 p e s , b u t Leers (1980) r e p o r t e d t r a n s m i s s i o n of this agent via a f i b r e o p t i c b r o n c h o s c o p e . T h e a e t i o l o g y o f t h e a c q u i r e d i m m u n e deficiency s y n d r o m e ( A I D S ) i s still p o o r / y u n d e r s t o o d , and: the possibility of t r a n s m i s s i o n of the causal agent via e n d o s c o p y has t o be e n t e r t a i n e d u n t i l m o r e is:known o f its susceptibility xo c h e m i c a l d i s i n f e c t a n t s . I n t h e s e t h r e e 0195-67011851040363 "1.06 $03.00/0

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circumstances, it seems reasonable that the endoscope is ethylene oxide sterilized before further use. A fourth situation where a sterile instrument may be indicated is when heavily immuno-suppressed patients are to be endoscopically examined, for example leukaemia and cancer patients on marrow suppressive therapy (Greene et al., 1974). Routine disinfection in this circumstance may not be adequate to reduce numbers of contaminating organisms such as Pseudomonas spp. below the level that makes infection in the immunosuppressed patient a rare event. For most purposes, an adequate disinfection procedure will be preferred. This will involve a two-stage process, namely the initial cleaning (in itself a disinfection procedure), followed by the use of an effective chemical agent. Manual cleaning is the simplest method, but is probably the least efficient (Babb et al., 1981). It is impossible to control the process, which will depend considerably on the competence of the individual performing the task. In a busy clinic, it may simply involve cleaning of the insertion tube, and the suction/biopsy channel. T h e use of the manufacturer's recommended cleaning apparatus, for example the ' K e y m e d ' trolley, will improve cleaning efficiency, but is f a r from ideal. Unless t h e cleaning apparatus itself is cleaned, the potential for re-contamination of the endoscope remains. This particularly applies to brushes, trays and automated systems. The recommendations of the Endoscopy Committee of the British Society of Gastroenterology (Axon & Cotton, 1983) represent the minimal acceptable cleaning between patients. Namely a detergent clean, brushing of the suction channel and brushing of the tip of the instrument. T h e air/water channel should then be flushed with water, followed by air. Finally, the shaft of the endoscope is i m m e r s e d in a disinfectant, which is aspirated into the suction channel and left for 2rain, before rinsing and drying. A simple and inexpensive apparatus for disinfection is the Leeds disinfector ( O ' C o n n o r et':al., 1982). T w o connected perspex c h a m b e r s are involved, one of which takes the shaft of the endoscope and the o t h e r acts as a reservoir for glutaraldehyde. T h e disadvantage of this relatively simple apparatus is failure t o disinfect the air channel; This is a fault: common to most of the m o r e sophisticated cleaning/disinfection machines currently available. Meuwisson et al. (1983) described a : s i m p l e system involving placing of the insertion tube into a long acrylic tube, and attaching:irrigation tubing to the three o p e n sleeves on t h e control b o x (applicable to Olympus scopes only). Detergent; disinfectant or water is then p u m p e d t h r o u g h all the channels, followed by warm air. Babb, B r a d l e y & Ayliffe (1984) evaluated four machines currently available i n the U . K . These i were the ' K e y m e d ' Fibrescope: Disinfectant Irrigator,; the A M S C O Pu!star ::!200 Endoscope~Processor,~the Pauldrach Endocleaner and the Wolf fibrescopeDisinfector:2070; The~onlymachine offering automatic all-channel irrigation in ,this ~study was:the ' K e y m e d ' machine, w h i c h u n f o r t u n a t e l y : will:only process Olympus endoscopes. T h e

D e c o n t a m i n a t i o n of: e n d o s c o p e s

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disadvantage of this machine is that the insertion tubes m u s t be cleaned manually. Failure of commercial~ ctisinfection machines to clean the air channel is anomalous, as this is the v e r y channel that is m o s t likely to b e c o m e blocked d u r i n ~ use, and is also often t h e most difficult to clean manually. T h e efficiency of individual machines is b u t one factor in the overall process. T h e cycle time can be varied on m o s t machines to suit the disinfectant, or (and m o r e often) the user. It is i m p o r t a n t that cycle times for between patient and end of list disinfection processes are established on microbiological and not convenience grounds. T h e evaluation of disinfection is imprecise, and there is no general agreement oh the m e t h o d of choice. Should in-use tests be relied upon (Babb, Bradley & Ayliffe, 1984) or is it preferable to contaminate the instrument with a k n o w n organism and m o n i t o r its removal (Coates & Death, 1982; F e l m i n g h a m e t al., 19.85)? T h e latter m e t h o d has the advantage that the conditions u n d e r experimental consideration can be controlled. However, the use of a simple aqueous or broth culture is probably invalid, since m u c u s and other organic material encountered during use will make bacterial decontamination m o r e difficult. T h e value of egg a l b u m i n for in-vitro work has been r e c o m m e n d e d in at least one study ( F e l m i n g h a m et al., 1985). T h e fall qn n u m b e r s of bacteria is usually expressed a s the n log10 reduction. T h e significance of n will depend o n the initial degree of contamination. At the beginning and end of the list the r e d u c t i o n in count should lead to 'none detectable'. Hovcever, for practical purposes, a between patient logl0 reduction of greater than 3 is probably sufficient. T h e implications for possible litigation of two standards of decontamination (i.e., with respect to being the first or second patient on a list)will need to be considered. It is i m p o r t a n t to stress that a thorough disinfection process is required a t the b e g i n n i n g of the endoscopy hst, as well as at the end. F e l m i n g h a m et al. (1985) noted h e a v y bacterial c o n t a m i n a t i o n of the endoscope channels after overnight storage, d e s p i t e a d e q u a t e end of list disinfection. A suitable disinfectant m u s t satisfy t h e following criteria: I t s h o u l d be microbiologically effective, r a p i d in action, not significantiy affected by organic material, n o t ~tamage theen'doscope, a n d n o t c a u s e hypersensitiyitY reactions in the us'ers. A c h e m i c a l agent satisfying a l l t h e s e criteria ha s y e t to be described. T h e consensus of opinion i s t h a t a 2 % , alkaline buffered glutaraldehyde solution is the disinfectant o f choice (Babb e~ al i, 1981;;Axon &~Cotton, 11933 ;~F a v e r o , 1983; F e l m i n g h a m e t al.,: 1 9 8 5 ) . ~Recent evidence indicates ~that: glutaraldehyde :.inactivates : t h e . v i r u s • associated !with A I D S (Spire e t a l . , 1984), :The m a i n d i s a d v a n t a g e of glutaraldehyde t h e i r . ' is frequent occurrence: of~ skin sensitivity ~and conjunctival :irritation ~ a m o n g : users ( O ' C o n n o r ~&iAxoni! 11983 )' : 0 t h e r ~glutaraldehyde ipreparations~:mayl :also corr0de instruments, and s h o u l d be~thoroughlY tested~ ~before r 0 u t i n e : use

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(Babb, B r a d l e y & Ayliffe, 1981). O t h e r p r o p r i e t a r y a l d e h y d e m i x t u r e s m a y also be effective; b u t less i r r i t a n t ( F e l m i n g h a m et al., 1985). T h e use of a closed s y s t e m will go s o m e w a y to obviating the h y p e r s e n s i t i v i t y reaction. T o avoid irritation of t h e e n d o s c o p i s t ' s eyes', a d e q u a t e rinsing is essential, p a r t i c u l a r l y with the n e w e r fully i m m e r s i b l e endoscopes. P o v i d o n e - i o d i n e solution is in t h e o r y a useful disinfectant for endoscopes. H o w e v e r , t h e microbicidaI activity is a f u n c t i o n of the free iodine (not t h e available i o d i n e ) p r e s e n t , and this level is n o t only critical, b u t can be difficult to calculate for a specific p r o d u c t . I n consequence, care m u s t be taken.to ensure t h a t the correct dilution is used (Favero, 1983). I n particular, preparations of povidone--iodine antiseptics m u s t n o t be used for e n d o s c o p e disinfection. C o n t a m i n a t i o n o f p o v i d o n e - i o d i n e solutions w i t h Pseudomonas cepacia has been well d o c u m e n t e d ( C r a v e n et al., 1981). P o v i d o n e - i o d i n e has a n u m b e r of o t h e r disadvantages w h e n used; it is sticky and difficult to remove, subject to inactivation b y organic material, and m a y stain the endoscope. Solutions of buffered h y p o c h l o r i t e have been investigated b y a n u m b e r of workers (Babb et al., 1981; C o a t e s & Death, 1982; F e l m i n g h a m et al., 1985). C o n c e n t r a t i o n s of a r o u n d 2000 p p m available chlorine are r e q u i r e d for reliable in-use disinfection. Such concentrations are liable to be corrosive to the endoscopes. Alcohol at 7 0 % v/v in w a t e r is an effective disinfectant; however, in-use studies have shown that c o n t a m i n a t i o n m a y persist (Axon et al., 1974). Alcohols are non-sporicidal, and of limited anti-viral efficacy. T h e y are flammable, a n d p r o l o n g e d contact m a y cause d a m a g e to lens c e m e n t a n d h a r d e n i n g of plastics (Favero, 1983). H o w e v e r , t h e y are useful as d r y i n g agents, and should be c o n s i d e r e d for between patient use as an adjunct to o t h e r disinfecting agents. U s e d after a water rinse, t h e y will assist r a p i d aird r y i n g of the endoscope channels. Chlorhexidine-containing solutions, hexachlorophane and most q u a t e r n a r y a m m o n i u m c o m p o u n d s (including c e t r i m i d e alone or with chlorhexidine) s h o u l d n o t be used for endoscope disinfection. L a b o r a t o r y studies on the q u a t e r n a r y a m m o n i u m c o m p o u n d ' D e t t o x A B C ' were initially e n c o u r a g i n g (Gilbert, A1-Hiti & S m i t h , 1982). I n - u s e studies have been less c o n v i n c i n g (Babb et al., 1981; F e l m i n g h a m et al., 1985). ' D e t t o x A B C ' is, however, n o n - i r r i t a t i n g , and m a y have a place f o r b e t w e e n - p a t i e n t cleaning. I t should n o t be used f o r start a n d end of:list disinfection, T h e i n t r o d u c t i o n of totally i m m e r s i b l e e n d o s c o p e s will go s o m e way to e n s u r i n g a d e q u a t e d i s i n f e c t i o n : H o w e v e r , t h e y m a y a l s o e n g e n d e r a false sense of security unless all channels a r e cleaned~ a n d c h a r g e d with disinfectant. Unless e x p e n s i v e closed a u t o m a t i c s y s t e m s are u s e d , there will be an increased r i s k o f staff e x p o s u r e t o irritant c h e m i c a l s , b o t h d u r i n g use, and d u r i n g cleaning. ~A n a u t o m a t i c a l l - c h a n n e l d i s i n f e c t i n g m a c h i n e is available f o r d i s i n f e c t i n g these i n s t r u m e n t s , b u t w i l l n o t take o t h e r makes of endoscopes,

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Against the background of the vast numbers of endoscopic investigations c a r r i e d o u t a n n u a l l y , t h e i n c i d e n c e o f i n f e c t i o n is low, a l t h o u g h p r o b a b l y u n d e r r e p o r t e d . I t is a p p a r e n t t h a t for c e r t a i n p r o c e d u r e s , s u c h as endoscopic retrograde cholangio-pancreatography (ERCP) additionaI m e a s u r e s n e e d to b e t a k e n , s u c h as t h e a d m i n i s t r a t i o n o f p r o p h y l a c t i c a n t i b i o t i c s ~( A x o n & C o t t o n , 1983). P r o c e d u r e s f o r t h e r o u t i n e d~s~lfection o f g a s t r o i n t e s t i n a l f i b r e s c o p e s a r e f a r f r o m ideal. C o - o p e r a t i o n b e t w e e n i n s t r u m e n t m a n u f a c t u r e r s s h o u l d l e a d to t h e p r o d u c t i o n o f d i s i n f e c t i o n m a c h i n e s t h a t c a n b e u s e d f o r all m a k e s o f e n d o s c o p e s . N e w a n d i m p r o v e d c h e m i c a l a g e n t s a r e still r e q u i r e d . R i g i d p r o t o c o l s o f p r o v e n ePficacy n e e d to b e a v a i l a b l e . T h e g u i d e l i n e s o f t h e Endoscopy Committee of the British Society for Gastroenterology (Axon & C o t t o n , 1983) are a m o v e in t h e r i g h t d i r e c t i o n , b u t o n l y o u t l i n e t h e p r o b l e m . A m u l t i - p r o f e s s i o n a l a p p r o a c h is r e q u i r e d , i n v o l v i n g clinical m i c r o b i o l o g i s t s , e n d o s c o p y n u r s e s , e n d o s c o p i s t s a n d t h e i n d u s t r y to p r o v i d e e q u i p m e n t , r e a g e n t s a n d m e t h o d s t h a t a r e effective a n d p r a c t i c a l . A s t u d y of 52 e n d o s c o p y c e n t r e s in B r i t a i n in 1980 s h o w e d t h a t 30 c e n t r e s ( 5 8 % ) w e r e u s i n g a n i n a d e q u a t e m o d e o f d i s i n f e c t i o n ( A x o n et al., 1981). I n 1985, h o w m u c h h a s c h a n g e d ? G. L. R i d g w a y

Department of Clinical Microbiology, University College Hospital, Grafton Way, London W C I E 6.4 U

References Axon, A. T. R., Banks, J., Cockel, R., Deverill, C. E. A. & Newmann, C. (1981). Disinfection in upper-digestive-tract endoscopy in Britain. Lancet i, 1093-1094. Axon, A. R. T. & Cotton, P. B. (1983). Endoscopy and infection. Gut 24, 1064-1066. Axon, A. T. R., Phillips, I., Cotton, P. B. & Avery, S. A. (1974). Disinfection of gastrointestinal fibre-endoscopes. Lancet i, 656-658. Babb, J. R., Bradley, C. R. & Ayliffe, G. A. J. (1981). Sporicidal activity of glutaraldehydes and hypochlorites and other factors influencing their selection for the treatment of medical equipment. Journal of Hospital Infection 1, 63-75. Babb, J. R., Bradley, C. R., Deverill, C. ,E. A., Ayliffe, G. A. J. & Melikian, V. (1981). Recent advances in the cleaning and disinfection of fibreoptics, ffournal of Hospital Infection 2, 329-340. Babb, J. R., Bradley, C. R. & Ayliffe, G. A. J. (1984). Comparison of automated systems for the cleaning and disinfection of flexible endoscopes, ffournal of Hospital Infection 5, 213-226. Birnie, G. G., Quigley, E. NI., Clements, G. B., Foiler, E. A. C. & Watkinson, G. (1983). Endoscopical transmission of Hepatitis B virus. Gut 24, 171-174. Bond, W. W. & Mancanda, R. E. (1978). Viral hepatitis B infection risk in flexible fibre optic endoscopy. Gastrointestinal endoscopy 24, 225-230. Coates, D. & Death, J. E. (1982).:!Use of buffered hydrochlorite solution for clisinfecting fibrescopc.:,, ffournal of Clinical Pathology 35, 296-303. Craven, D. E., Moody,. B.; Conolly, M: G., Kollisch, N. R., Stottmeier, K. D~:& McCabe, W. R. (1981). Pseudobacteraemia Caused bypovidone-iodine solution cor~ta'~ninated with Pseudomonas cepacia?New England ffournal of Medicine!305, 621"623. Favero, M. S. (1983). Chemical disinfection of medical and surgical materials. In

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Disinfection, Sterilization and Preservation 3rd edn, (Black, S. S., Ed.), pp. 469--492. Lean and Febiger, Philadelphia. Felmingham, D., Mowles, J., Thomas, K. & Ridgway, G. L. (1985). Disinfection of gastrointestinal fibreoptlc endoscopes, ffournal of Hospital Infection 6, 379-388. Gilbert, P., A1-Hiti, M. M. & Smith, P. M. (1982).. A laboratory evaluation of a new disinfectant cleaner for fibre-optic instruments. Microbios 33, 53--64. Greene, W. H., Moody, M., Hartley, R., Effman, E., Aisner, J., Young, V. M. & Wiernik, P. H. (1974). Oesophagoscopy as a source of Pseudomonas aeruginosa sepsis in patients with acute leukaemia: the need for sterilization of endoscopes. Gastroenterology 67, 912-919. Leers, W.-D. (1980). Disinfecting endoscopes: how not to transmit Mycabacteriu.m tuberculosis by bronchoscopy. Canadian Medical Association Journal 123, 275-283. Meuwisson, S. G. M., MaeLaren, D. M., Rijsberman, W. & Boshvizen, K. (1983). A simple method for cleaning flexible fibre-optic endoscopes by 'all-channel perfusion', ffournal of Hospital Infection 4, 81-86. O'Connor, H. J. & Axon, A. T. R. (1983). Gastrointestinal endoscopy: infection and disinfection. Gut 24, 1067-1077. O'Connor, H. J., Rothwell, J., Maxwell, S., Lincoln, C. & Axon, A. T. ~R. (1982). New disinfecting apparatus for gastrointestinal fibre-endoscopes. Gut 23, 706--709. Spire, B., Barr6-Sinoussi, F., Montagnier, L., Chermann, J. (1984). Inactivation of lymphadenopathy associated virus by chemical disinfectants. Lancet ii, 899-901.