CONTACT LENS DISINFECTION EFFICACY TEST METHODS

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CONTACT LENS DISINFECTION EFFICACY TEST METHODS
CONTACT LENS DISINFECTION EFFICACY TEST METHODS

• Mary F. Mowrey-McKee, Ph.D.

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I. Current Status Contact Lens Disinfecting
Methodology Worldwide

• ISO 14729
• 1. Stand Alone Test
• measures the intrinsic antimicrobial activity of
  a contact lens disinfecting solution (CLDS) in a
  compatible test tube over regimen soak time.
• 2. Regimen Test
• measures recovery of organisms on inoculated
  contact lenses subjected to a cleaning/disinfectin
  g regimen according to product labeling and/or
  patient instructions
• Both tests require use of three lots of product.

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Challenge Organisms

• Staphylococcus aureus ATCC 6538
• Pseudomonas aeruginosa ATCC 9027
• Serratia marcescens ATCC 13880
• Candida albicans ATCC 10231
• Fusarium solani ATCC 36031
• Inoculum Concentration
• 1 x 105 1 x 106 cfu/mL (Stand Alone Test) or 2
  x 105 2 x 106 cfu/lens (Regimen Test)

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Stand Alone Criteria

• Primary Criteria regimen test not required if
  met
• Bacteria gt 3 log reduction at regimen soaking
  time
• Fungi gt 1 log reduction at regimen soaking
  time
• Secondary Criteria regimen test required if
  fails primary criteria but passes secondary
  criteria
• Bacteria gt 1 log reduction at regimen soaking
  time for each bacterial species and sum of
  average log reductions for the three bacterial
  species equals 5 or more
• Fungi stasis at regimen soaking time 0.5
  log

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Regimen Test Criteria

• Qualification of one lens type 120 lenses total
• 24 lenses per challenge organism (8 lenses/ lot
  of product)
• Qualification for all hydrophilic lenses 120
  lenses total
• 12 group I lens type per challenge organism
• 12 group IV lens type per challenge organism
• Each lens is cultured in agar sandwich and entire
  contents of each lens case well filtered and
  filter placed on agar.
• Determine survivors per lens case well (i.e., sum
  of lens solution filter).
• Criteria For each microbial species, the
  average regimen recovery count (for all lots
  tested) shall be no more than 10 cfu for each
  lens type/storage solution combination

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II. Current Status Contact Lens Disinfecting
Methodology USA

• ANSI Z80.18-2003 Contact Lens Care Products
  Vocabulary, Performance Specifications, and Test
  Methodology
• For regimen consisting of a rub, rinse and soak,
  methodology same as ISO 14729.
• Elimination of the traditional rubbing and/or
  rinsing steps requires
• passing the secondary criteria of the Stand Alone
  Test in the presence of organic soil
• additionally passing the Regimen Test using
  organic soil.
• No Rub regimens must meet a much more rigorous
  challenge than a regimen including a rub, rinse
  and soak in the USA according to this standard.

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III. Development of New Methodology to Take Into
Consideration The Effect of Lenses And Lens Cases
On Disinfection Efficacy

• Methodology in development by Contact Lens
  Institute with input from FDA
• Scope
• Provides a process for evaluating compatibility
  of solutions used for disinfection with contact
  lenses and lens cases using an antimicrobial
  efficacy endpoint.
• Microbiological effect of the antimicrobial
  agent(s) while in the presence of the lens cases
  and/or lenses evaluated as described in the soak
  step of the label instructions.
• Applies only to lens cases with side-to-side
  horizontal wells.
• Status methodology currently being evaluated
  for reproducibility.

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New Methodology continued

• Materials
• Same 5 challenge organisms as ISO 14729 but
  prepared in organic soil
• Manufacturers recommended lens case
• Lenses
• Group I
• Group IV
• Representative silicone hydrogel lenses
• Contact lens disinfecting solution
• Neutralizing Broth
• TSA and SDA plates

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New Methodology continued

• Process
• Inoculation
• Sterile lens placed in lens case well
• Use lens case well without lens as control
• All samples tested in triplicate
• Inoculum (1 x 105 1 x 106 cfu/lens) placed in
  cup of lens and in empty well of control lens
  case
• Wait 3 10 minutes then dispense lens care
  product into well minimum of 2 mL per well.
• Hold inoculated cases at 20 - 25º C for regimen
  soak time, 24 hours, 7 days and maximum labeled
  storage of CLDS in lens case

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New Methodology continued

• Process
• Sampling
• Vortex inoculated well of lens case on high speed
• Aseptically pick up lens with sterile tweezers
  and shake off surface liquid
• Place lens in 2 mL neutralizing broth, allow
  sufficient soak time to neutralize antimicrobial
  agent(s), vortex, dispense aliquots of
  neutralizing broth for pour plates and plate lens
  in agar sandwich
• Prepare decimal serial dilutions of the CLDS in
  neutralizing broth and dispense for pour plates
• Incubate plates

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New Methodology continued

• Process
• Counting plates and calculations
• Per lens case well
• 1 Calculate total cfu/well in solution cfu on
  lens total cfu in lens extract (neutralizing
  broth)
• 2 Calculate total cfu/well of inoculum
• 3 Log reduction per lens case well
• log (inoculum) 2 log (cfu solution
  cfu lens cfu lens extract)1
• Average log reduction for unique sample (triplet
  replicates)
• (log red. well 1 log red. well 2 log
  red. well 3)/3

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New MethodologyInitial Ring Test

• Simple solution formulated to provide moderate
  antimicrobial efficacy used for ring test
  chlorhexidine active agent
• Two organisms evaluated initially by five
  laboratories
• Residual chlorhexidine in wells measured by HPLC
• Data to date indicate the need for refinement
• Modifications have been made to the method with
  the intention of improving the consistency and
  reproducibility
• Repeat of initial test, phase 1a, in progress

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Residual Chlorhexidine Gluconate in Lens Case
Solution by Lens Type - Preliminary Data
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Preliminary Results for Staph. aureusby Lens
Type for All Labs - Log Reductions
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New MethodologyInitial Ring TestResults

• The presence of lenses may affect the kinetics of
  antimicrobial activity of a contact lens
  disinfecting solution
• Antimicrobial activity may vary by lens material
• Uptake by lenses may affect the concentration of
  the antimicrobial agent(s) in a CLDS in the lens
  case during storage
• Lens cases have the potential to uptake active
  agents, however, this was not observed in the
  study

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New MethodologyConclusion

• Ring test, phase 1a, to be completed and data
  analyzed to determine whether modifications have
  increased reproducibility
• If reproducibility is acceptable, will complete
  phase 2 of the ring test with additional
  organisms
• Consultation with ANSI and ISO will determine
  pathway forward for continuing development of a
  standard