Copyright © 2004 WA Rutala Prions (CJD) and Processing of Reusable Medical Products William A....

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Transcript of Copyright © 2004 WA Rutala Prions (CJD) and Processing of Reusable Medical Products William A....

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Copyright 2004 WA Rutala Prions (CJD) and Processing of Reusable Medical Products William A. Rutala, Ph.D., M.P.H. University of North Carolina (UNC) Hospitals and UNC School of Medicine Slide 2 Copyright 2004 WA Rutala Prions and Processing of Reusable Medical Products Topics l Rationale for United States recommendations Epidemiological studies of prion transmission Infectivity of human tissues Efficacy of removing microbes by cleaning Prion inactivation studies Risk associated with instruments l Recommendations to prevent cross-transmission from medical devices contaminated with prions Slide 3 Copyright 2004 WA Rutala Transmissible Spongiform Encephalopathies (TSEs) of Humans l Kuru l Gertsmann-Straussler-Scheinker (GSS) l Fatal Familial Insomnia (FFI) l Creutzfeldt-Jakob Disease (CJD) l Variant CJD (vCJD), 1995 Slide 4 Copyright 2004 WA Rutala CJD Slide 5 Copyright 2004 WA Rutala Prions and Processing of Reusable Medical Products l Rationale for US recommendations Epidemiological studies of prion transmission Epidemiological studies of prion transmission via surgical instruments Infectivity of human tissues Efficacy of removing microbes by cleaning Prion inactivation studies Risk associated with instruments Slide 6 Copyright 2004 WA Rutala Transmissibility of Prions l Transmission Not spread by contact (direct, indirect, droplet) or airborne Not spread by the environment Experimentally-all TSEs are transmissible to animals, including the inherited forms Epidemiology of CJD: sporadic-85%; familial-15%; iatrogenic- 1% (primarily transplant of high risk tissues, ~250 cases worldwide) Slide 7 Copyright 2004 WA Rutala Iatrogenic Transmission of CJD l Contaminated medical instruments Electrodes in brain (2) Neurosurgical instruments in brain (4) l Dura mater grafts (>110) l Corneal grafts (3) l Human growth hormone and gonadotropin (>130) Slide 8 Copyright 2004 WA Rutala Prions and Processing of Reusable Medical Products Historical Perspective l CJD and other TSEs exhibit an unusual resistance to conventional chemical and physical decontamination methods l Until recently, all medical/surgical instruments from CJD patients received special prion reprocessing l Draft guidelines of the CDC (Favero, 1995) suggested a risk assessment consider cleaning and prion bioburden that results from contact with infectious tissues Slide 9 Copyright 2004 WA Rutala Prions and Processing of Reusable Medical Products l Rationale for US recommendations Epidemiological studies of prion transmission Epidemiological studies of prion transmission via surgical instruments Infectivity of human tissues Efficacy of removing microbes by cleaning Prion inactivation studies Risk associated with instruments Slide 10 Copyright 2004 WA Rutala CJD and Medical Devices l Six cases of CJD associated with medical devices 2 confirmed cases-depth electrodes; reprocessed by benzene, alcohol and formaldehyde vapor 4 unconfirmed cases-CJD following brain surgery, index CJD identified-1, suspect neurosurgical instruments l Cases occurred from 1953-1980 in UK, France and Switzerland l No cases since 1980 and no known failure of steam sterilization Slide 11 Copyright 2004 WA Rutala Prions and Processing of Reusable Medical Products l Rationale for US recommendations Epidemiological studies of prion transmission Epidemiological studies of prion transmission via surgical instruments Infectivity of human tissues Efficacy of removing microbes by cleaning Prion inactivation studies Risk associated with instruments Slide 12 Copyright 2004 WA Rutala Risk of CJD Transmission l Epidemiologic evidence (eye, brain, pituitary) linking specific body tissue or fluids to CJD transmission l Experimental evidence in animals demonstrating that body tissues or fluids transmit CJD Infectivity assays a function of the relative concentration of CJD tissue or fluid Slide 13 Copyright 2004 WA Rutala Risk of CJD Transmission Risk of InfectionTissue HighBrain (including dura mater), spinal cord, and eye LowCSF, liver, lymph node, kidney, lung, spleen, placenta, olfactory epithelium NoPeripheral nerve, intestine, bone marrow, whole blood, leukocytes, serum, thyroid gland, adrenal gland, heart, skeletal muscle, adipose tissue, gingiva, prostate, testis, tears, nasal mucus, saliva, sputum, urine, feces, semen, vaginal secretions, and milk High-transmission to inoc animals >50%; Low-transmission to inoc animals >10-20% but no epid evidence of human inf Slide 14 Copyright 2004 WA Rutala Prions and Processing of Reusable Medical Products l Rationale for US recommendations Epidemiological studies of prion transmission Epidemiological studies of prion transmission via surgical instruments Infectivity of human tissues Efficacy of removing microbes by cleaning Prion inactivation studies Risk associated with instruments Slide 15 Copyright 2004 WA Rutala CJD: DISINFECTION AND STERILIZATION l Effectiveness must consider both removal by cleaning and inactivation Probability of a device remaining capable of transmitting disease depends on the initial contamination and effectiveness of cleaning/disinfection/sterilization. Device with 50ug of CJD brain with a titer of 6 log 10 LD 50 /g would have 5 x 10 4 infectious units Slide 16 Copyright 2004 WA Rutala CJD: DISINFECTION AND STERILIZATION l Effectiveness of cleaning Cleaning results in a 4 to 6 log 10 reduction of microbes and ~2 log 10 reduction in protein contamination Recent data: alkaline detergents reduce 5 log 10 prions (FDA, 2003, J Hosp Infect, 2004); enzymes that digest prions at 70 o C reduce 5-6 log 10 prions (J Inf Dis, 2003) Ideally, in the future new alkaline/enzymatic cleaners and routinely available sterilization processes will lead to sterilization methods for prion-contaminated medical devices Slide 17 Copyright 2004 WA Rutala Prions and Processing of Reusable Medical Products l Rationale for US recommendations Epidemiological studies of prion transmission Epidemiological studies of prion transmission via surgical instruments Infectivity of human tissues Efficacy of removing microbes by cleaning Prion inactivation studies Risk associated with instruments Slide 18 Copyright 2004 WA Rutala Decreasing Order of Resistance of Microorganisms to Disinfectants/Sterilants Prions Spores Mycobacteria Non-Enveloped Viruses Fungi Bacteria Enveloped Viruses Slide 19 Copyright 2004 WA Rutala Prion Inactivation Studies l Problems Investigators used aliquots of brain tissue macerates vs. intact tissue (smearing, drying); weights of tissue (50mg-375mg) Studies do not reflect reprocessing procedures in a clinical setting (e.g., no cleaning) Factors that affect results include: strain of prion (22A), prion conc in brain tissue, animal used, exposure conditions, validation and cycle parameters of sterilizers, resistant subpopulation, different test tissues, different duration of observations, screw cap tubes with tissue (air), etc Slide 20 Copyright 2004 WA Rutala Ineffective or Partially-Effective Disinfectants: CJD l Alcohol l Ammonia l Chlorine dioxide l Formalin l Glutaraldehyde l Hydrogen peroxide l Iodophors/Iodine l Peracetic acid l Phenolics Slide 21 Copyright 2004 WA Rutala CJD: Ineffective Disinfectants Examples l Glutaraldehyde (5%) Partially effective l Iodine (2%) ~1 log decrease in 30m l Hydrogen peroxide (3%) ~ 1 log decrease in 60m l Formaldehyde (3.7%) ~ 1 log decrease in 60m Slide 22 Copyright 2004 WA Rutala Ineffective or Partially Effective Processes: CJD l Gases Ethylene oxide Formaldehyde l Physical Dry heat UV Microwave Ionizing Glass bead sterilizers Autoclave at 121 o C, 15m Slide 23 Copyright 2004 WA Rutala CJD: Ineffective Sterilants Examples l Steam sterilization (gravity) 121 o C and 132 o C-< 4 log 10 decrease at 15m l Ethylene oxide 88%, 4h l Glass bead sterilizers 240 o C for 15m l Dry heat 160 o C for 24h Slide 24 Copyright 2004 WA Rutala Effective Disinfectants (>4 log 10 decrease in LD 50 with 1 hour) l Sodium hydroxide 1 N for 1h (variable results) l Sodium hypochorite 5000 ppm for 15m l Guanidine thiocyanate 4M l Phenolic (LpH) 0.9% for 30m Slide 25 Copyright 2004 WA Rutala Effective Processes: CJD l Autoclave 134 o C-138 o C for 18m (prevacuum) 132 o C for 60m (gravity) l Combination (chemical exposure then steam autoclave, potentially deleterious to staff, instruments, sterilizer) Soak in 1N NaOH, autoclave 134 o C for 18m Soak in 1N NaOH, autoclave 121 o C for 30m Slide 26 Copyright 2004 WA Rutala Prions and Processing of Reusable Medical Products l Rationale for US recommendations Epidemiological studies of prion transmission Epidemiological studies of prion transmission via surgical instruments Infectivity of human tissues Efficacy of removing microbes by cleaning Prion inactivation studies Risk associated with instruments Slide 27 Copyright 2004 WA Rutala Disinfection and Sterilization l EH Spaulding believed how an object will be D/S depended on the objects intended use CRITICAL-objects that enter normally sterile tissue or the vascular system should be sterile SEMICRITICAL-objects that touch mucous membranes or skin that is not intact requires a disinfection process (high level disinfection) that kills all but bacterial spores (prions?) NONCRITICAL-objects that touch only intact skin require low-level disinfection Slide 28 Copyright 2004 WA Rutala Prions and Processing of Reusable Medical Products l Rationale for US recommendations Epidemiological studies of prion transmission Epidemiological studies of prion transmission via surgical instruments Infectivity of human tissues Efficacy of removing microbes by cleaning Prion inactivation studies Risk associated with instruments Slide 29 CJD : potential for secondary spread through contaminated surgical instruments Slide 30 Copyright 2004 WA Rutala Risk Assessment l High risk patient-certain patients capable of transmitting infection. l High risk tissue-CJD