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Sterilization & Disinfection

Sterilization & Disinfection. Allison McGeer, MSc, MD, FRCPC. How can microorganisms be killed?. Denaturation of proteins (e.g. wet heat, ethylene oxide) Oxidation (e.g. dry heat, hydrogen peroxide) Filtration Interruption of DNA synthesis/repair (e.g. radiation)

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Sterilization & Disinfection

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  1. Sterilization & Disinfection Allison McGeer, MSc, MD, FRCPC

  2. How can microorganisms be killed? • Denaturation of proteins (e.g. wet heat, ethylene oxide) • Oxidation (e.g. dry heat, hydrogen peroxide) • Filtration • Interruption of DNA synthesis/repair (e.g. radiation) • Interference with protein synthesis (e.g. bleach) • Disruption of cell membranes (e.g. phenols)

  3. Factors that influence efficacy of disinfection/sterilization • Contact time • Physico-chemical environment (e.g. pH) 3 Presence of organic material 4 Temperature 5 Type of microorganism 6 Number of microorganisms 7 Material composition

  4. Ideal sterilization/disinfection process • Highly efficacious • Fast • Good penetrability • Compatible with all materials • Non-toxic • Effective despite presence of organic material • Difficult to make significant mistakes in process • Easily monitored

  5. Spaulding Classification

  6. Bacterial endospores Mycobacteria (tuberculosis) Non-lipid (small) viruses (polio) Fungi Vegetative bacteria (Salmonella) Lipid viruses (Herpes, HepB, HIV) sterilization high level disinf low level disinf Types of microorganisms and levels of disinfection

  7. Steam Ethylene oxide Peracetic acid (.2%) Hydrogen peroxide gas plasma Vapourized hydrogen peroxide Ozone Sterilization

  8. Clean items Package items Load sterilizer Monitor Physical (time/temp/pressure) Chemical Biological Sterilization process

  9. Steam: Geobacillus stearothermophilus Dry heat: B. atrophaeus (formerly B. subtilis) ETO: B. atropheus Peracetic acid: G. stearothermophilus Plasma (Sterrad): G. stearothermophilus Ontario guidelines: Steam: monitor daily, every load with implantables ETO: monitor every load Biological Monitors

  10. Clean items Package items Load sterilizer Monitor Physical (time/temp/pressure) Chemical Biological Storage post-sterilization Documentation Sterilization process

  11. Problems with sterility • Lack of understanding of risk/process • physicians introducing new products (borrowed, samples) • Multidose vials • What is sterile vs not • Lack of understanding of components of process • MDs, technologists have less training than nurses (anaesthesiology, imaging, urology)

  12. Unwrapped objects, 132°C, 3mins, 27-28lbs pressure in gravity Acceptable for processing items that cannot be sterilized and stored before use Flash Sterilization

  13. Bryce E; ICHE 1997;18(9):654-6

  14. High risk patient Known/suspected CJD or other TSEs Rapidly progressive dementia Family history of CJD or other TSE History of dura mater transplant, cadaver-derived pituitary hormone injection High risk tissue Brain, spinal cord, eyes High risk device Critical or semi-critical Reprocessing for Prions

  15. Steam sterilization with NaOH Alkaline cleaner (pH 2.2, 1 hr 23°C) Copper plus peracetic acid Vapourized hydrogen peroxide (Sterrad NX) Inactivation of Prions Yan ICHE 2004;25:280, Fichet Lancet 2004;384:251, Baier JHI 2004;57:80, Lemmer J Gen Virol 2004;85:3805; Roger-Kreuz, ICHE 2009;30(8):769-77 Lehman Hosp Infect. 2009;72(4):342-50;

  16. Semi-critical items • Endoscopes/bronchoscopes • Laryngoscopes • Respiratory therapy and anaesthesia equipment • Tonometers • Endocavitary probes • Vaginal specula, diaphram fitting rings

  17. Problems with semi-critical items • Complex and delicate pieces of equipment • Expensive equipment used frequently • Centralizing process difficult • Time an important factor • Absence of regulation/guidance for design • Narrow margin of safety

  18. Endocavitary probes • Prostate & vaginal ultrasounds, TEE • Trans-rectal biopsies • Transvaginal probes for IVF • Infrared coagulation for hemmorhoids

  19. Laryngoscopes - blades are semi-critical - handles are non-critical (but still need to be disinfected) Biopsy forceps, endoscopy Applanation tonometers

  20. Disinfection of tonometers Rutala AAC 2006;50:1419

  21. Recent Toronto problems • Badly designed connectors (Steris) • Inadequate manufacturer’s instructions (trans-rectal biopsies) • Belief that a freeze thaw cycle for cryotherapy probe will kill microbes • Both reservoirs in endoscopy washer/disinfector filled with detergent • 2% hydrogen peroxide for high level disinfection • Vaginal ultrasound probes • Breast pump kits • Sterilizer failures

  22. Solutions • Centralization of disinfection & sterilization wherever possible • Standards: PIDAC, CSA • Processes, monitoring, training • New technology • Endoscopes that can be steam sterilized • Better sterilization technology • Elimination of high-level disinfection

  23. Outbreaks (1999-2007 • Failure to clean/disinfect/sterilize adequately • Manual balloons for ventilation (B. cereus) • Pasteurizer failure (x2) • Thermometers (E. cloacae, NICU) – x3 • Temperature sensors for ventilators (S. maltophilia) x 2 • Ophthalmology equipment (adenovirus) • Endoscopes (TB x3, P.aeruginosa x2, pseudo outbreaks x5) • OR sterilization/high-level disinfection failure • Forceps in cystoscopy (P. aeruginosa) • Rigid laryngoscopes in NICU (P. aeruginosa, M. tuberculosis) • Transrectal prostate needle biopsies (P. aeruginosa x2) • Transesophageal echocardiography probes (E. cloace) • Bite blocks (P. aeruginosa, Group A streptococci) • Laparoscopy ports (Mycobacterium chelonae)

  24. Outbreaks (2) • Contaminated disinfectants. • Non-antimicrobial soap x2 • Benzalkonium chloride and other quaternary ammonium compounds • 0.5% chlorhexidine • Chlorhexidine without alcohol • Improperly diluted disinfectants (disinfectant spray, environmental cleaning solutions) • Open containers with soaked cotton balls • S. marcescens, P. aeruginosa, M. abscessus, R. picketii, A. xylosoxidans, K. oxytoca,

  25. Outbreaks (3) • Other • Incompetent waste drain ports on hemodialysis machines x2 • Inadequately maintained endoscopy washer/disinfector • Incorrect hook-up for endoscopes to sterilizer • Environmental contamination with Acinetobacter

  26. Outbreaks (4)Adverse effects • Anterior segment syndrome post cataract surgery due to residual glutaraldehyde • Toxic endothelial cell destruction (TECD) syndrome after ophthalmologic surgery due to brass degradation by plasma gas sterilization

  27. Non-critical items

  28. Factors necessary for environmental transmission • The organism must survive in the environment • Environmental contamination must occur frequently • The organism must maintain its virulence • The organism must be transported from the environment to (new) patients

  29. Epidemiology of streptococcal infectionsTransmission of epidemic and non-epidemic streptococci in military barracks Wannamaker, Chap 12 in McCarty, Streptococcal Infections, 1954

  30. MRSA and environmental transmission • 20 month retrospective study in 8 ICUs where patients were screened weekly • Assessed odds of acquiring MRSA among patients admitted to rooms just vacated by MRSA + and + patients • MRSA acquired by: 2.9% of those admitted to MRSA- pt room 3.9% of those admitted to MRSA + pt room Huang SS, Arch Int Med 2006;166:1945

  31. Effect of improved environmental cleaning on VRE transmission Hayden MK, Clin Infect Dis 2006:42:1552

  32. Can environmental cleaning reduce MRSA transmission? • Setting: ward with endemic MRSA, and widespread environmental contamination • Before-after study • Cleaning time increased by 57 hours per week • Responsibility for routine cleaning of shared equipment delineated • In 6 months post-intervention, number of MRSA acquisitions decreased fro 30 to 3 per 6 months Rampling A JHI 2001;49:109

  33. Contaminated Surfaces Carling PC, et al. Am J Infect Control. 2006 Oct;34(8):513-9.

  34. Contamination of objects/areas exclusively touched by staff • Supply cabinets, ICU telephones, keyboards 33.3% MRSA 36.6% VRE Speck et al., Abstract, (2007) SHEA 17th Annual Scientific Meeting, Baltimore, MD

  35. Problems • How important is environmental transmission overall? • What do we mean by “environment”? • What is the right standard for “clean”? • How do we measure adherence?

  36. Improving non-critical item/environment disinfection • Audit and feedback

  37. PROPORTION OF OBJECTS CLEANED 15 ACUTE CARE HOSPITALS 100 80 % Objects Cleaned 60 40 20 0 Sink Tray Table Hand hold Side rails Toilet door Call box BR light Toilet seat Toilet handle Bedpan cleaner Chair Room door Telephone

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