CLM - Efficacy of Contact Lens Solutions - PAP Week 1 Flashcards
What are the four main testing criteria for contact lens solutions?
Sterility
Preservative effectiveness
Microbial limits test
Stability
What does a standalone test for contact lens solutions evaluate?
Innate antimicrobial activity of the solution
What does a regimen test for contact lens solutions evaluate?
Efficacy of a contact lens disinfecting solution in a regimen
Describe the stand alone test in terms of what organisms are used to challenge the solution: Gram + cocci Gram - rod Gram - mycobacteria Yeast Fungus
10^5 to 10^6 CFU/mL used Gram + cocci -staph. aureus Gram - rod -serratia marcescens Gram - mycobacteria -pseudomonas aureginosa Yeast -candida albicans Fungus -fusarium solani
What is the minimum recommended disinfectiongtime and describe how this relates to the primary criteria for a standalone test for bacteria.
Extent of viability loss determined at 25%, 50%, 75%, and 100% of the minimum recommended disinfection time
Bacteria - 3 log unit reduction (99.4%) within the MRDT
Describe the primary criteria for a standalone test for moulds and yeasts.
Reduced 1 log unit on average (90%) within the MRDT and no increase over a period x4 the MRDT
What test can be used if the primary criteria fails for a contact lens solution? What does it evaluate? What does it allow for?
Evaluates the antimicrobial efficacy of the entire regimen described in the cleaning instructions insert
Minimal level of anti-microbial activity acceptable for a contact lens solution, allowing for mechanical cleansing of the lens
What is required for a pass on the regimen test for bacteria, moulds, and yeast.
Bacteria - 5 log average reduction with a minimum of a 1 log reduction at MRDT
Moulds and yeasts - stasis over MRDT
List 6 shortcomings of the standalone test.
Limited number of bacteria tested
No acanthamoeba
No viruses
All microorganisms are lab strains, not clinical isolates
Testing methods dont account for organic matter (mucus/debris)
Sterile lab environment - not the real thing
What percentage of contact lenses get contaminated with daily wear, when does it occur, and what is the major source of conamination?
Up to 90% of lenses, occuring on day 1 of CL wear.
Lens handling is the major source of contamination.
When contaminated contact lens cases are cultured, describe what two main organisms grow (in percentages).
71% bacteria
9% acanthamoeba
What percentage of contact lens cases become contaminated?
80%
Do lens care accessories frequently get contaminated or rarely?
Common
What is the most common gram positive and negative (2) bacteria contaminating contact lens cases and solutions?
Positive - Staphylococci
Negative - Pseudomonas ssp. and enterobacteriaceae
What percentage of contamination occurrences do fungi/yeasts account for (case and solutions)? What about acanthamoeba?
Fungi - 20-40%
Acanthamoeba - 9%
What can chlorhexidine result in the prolonged survival of?
S. marcescens
Against what organism do PHMB and polyquaternium-1 have poor activity against?
Acanthamoeba cysts
Are 1-step 3% hydrogen peroxide systems effective against acanthamoeba? Describe why and explain for cysts and spores.
Acanthamoeba can survive 1-step systems because neutralisation is too rapid.
Cysts need a 1-2h soak
Spores need a 3-5h soak
What are the two major organisms in homemade and unpreserved saline?
Acanthamoeba (homemade)
Unpreserved (unpreserved)
What is the best product for straight kills when disinfecting?
Hydrogen peroxide
Describe the effect of the following on CFU. assume a 1m CFU start:
Rinsing
Rubbing and rinsing
Start - 1,000,000 CFU
99% decrease with rinsing - 3,000 CFU
99.9% decrease with rubbing and rinsing - 300 CFU
Is rubbing and rinsing adequately done?
No
What does acanthamoeba feed off when it contaminates contact lens cases/solutions?
Gram negative biofilms