Sterilization

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Sterilization Disinfection

• Allison McGeer, MSc, MD, FRCPC

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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)

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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

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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

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Spaulding Classification
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Types of microorganisms and levels of disinfection

• sterilization
• high level disinf
• low level disinf

• Bacterial endospores
• Mycobacteria (tuberculosis)
• Non-lipid (small) viruses (polio)
• Fungi
• Vegetative bacteria (Salmonella)
• Lipid viruses (Herpes, HepB, HIV)

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Sterilization

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

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Sterilization process

• Clean items
• Package items
• Load sterilizer
• Monitor
• Physical (time/temp/pressure)
• Chemical
• Biological

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Biological Monitors

• 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

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Sterilization process

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

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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)

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Flash Sterilization

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

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Bryce E ICHE 199718(9)654-6
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Reprocessing for Prions

• 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

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Inactivation of Prions

• Steam sterilization with NaOH
• Alkaline cleaner (pH 2.2, 1 hr 23C)
• Copper plus peracetic acid
• Vapourized hydrogen peroxide (Sterrad NX)

Yan ICHE 200425280, Fichet Lancet 2004384251,
Baier JHI 20045780, Lemmer J Gen Virol
2004853805 Roger-Kreuz, ICHE 200930(8)769-77
Lehman Hosp Infect. 200972(4)342-50
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Semi-critical items

• Endoscopes/bronchoscopes
• Laryngoscopes
• Respiratory therapy and anaesthesia equipment
• Tonometers
• Endocavitary probes
• Vaginal specula, diaphram fitting rings

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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

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Endocavitary probes

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

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Laryngoscopes - blades are semi-critical -
handles are non-critical (but still need to
be disinfected)
Biopsy forceps, endoscopy
Applanation tonometers
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Disinfection of tonometers
Rutala AAC 2006501419
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Recent Toronto problems

• Badly designed connectors (Steris)
• Inadequate manufacturers 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

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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

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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)

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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,

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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

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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

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Non-critical items
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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

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Epidemiology of streptococcal infectionsTransmiss
ion of epidemic and non-epidemic streptococci in
military barracks
Wannamaker, Chap 12 in McCarty, Streptococcal
Infections, 1954
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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 20061661945
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Effect of improved environmental cleaning on VRE
transmission
Hayden MK, Clin Infect Dis 2006421552
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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 200149109
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Contaminated Surfaces
VRE MRSA C. difficile
Bed Rails
Bed Table -
Door Knobs
Doors -
Call Button
Chair
Tray Table -
Toilet Surface -
Sink Surface
Bedpan Cleaner - -
Carling PC, et al. Am J Infect Control. 2006
Oct34(8)513-9.
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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
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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?

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Improving non-critical item/environment
disinfection

• Audit and feedback

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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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Carling Crit Care Med Jan 2010 epub
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Improving non-critical item/environment
disinfection

• Audit and feedback
• New technology
• Hydrogen peroxide vapour/gas
• UV room decontaminaion
• ?antibacterial surface coatings?

Otter ICHE 200930(6)574-7
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• Seymour S. Block Disinfection, sterilization and
  preservation
• Williams Wilkins (ISBN 0812113640)
• PIDAC best practices for cleaning, sterilization
  and disinfection http//www.health.gov.on.ca/engl
  ish/providers/program/infectious/diseases/best_pra
  c/bp_cds_2.pdf
• PIDAC best practices for environmental cleaning
• http//www.health.gov.on.ca/english/providers/pro
  gram/infectious/diseases/best_prac/bp_enviro_clean
  .pdf
• CDC guideline for disinfection and sterilization
  in healthcare facilities http//www.cdc.gov/hicpac
  /pdf/guidelines/Disinfection_Nov_2008.pdf
• Bryce EA et al. When the biological indicator is
  positive investigating autoclave failures Infect
  Control Hosp Epi 199718654-6
• Rutala WA, Weber DJ. How to assess risk of
  disease transmission to patients when there is a
  failure to follow recommended disinfection and
  sterilization guidelines Infect Control Hosp
  Epidemiol. 200728(2)146-55