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Soft contact lens disinfection solution efficacy: clinical Fusarium isolates vs. ATCC 36031
Emma B H Hume1, Judith Flanagan, Simin Masoudi
1Institute for Eye Research, The School of Optometry and Vision Science, The University of New South Wales, Kensington, New South Wales, Australia. e.hume@ier.org.au
Purpose:
To compare the disinfecting efficacy of five soft contact lens multipurpose disinfection solutions (MPDS) against Fusarium solani clinical isolates and the ISO standard ATCC 36031 strain.
Methods:
Three commercially available and two recalled MPDS were tested using the ISO/CD 14,729 stand-alone test for contact lens care products against 10 ocular isolates of F. solani and the ATCC 36031 strain. The effect of filtering the fungal suspension before incubating in MPDS was also tested. An average log reduction in colony forming units at the manufacturer's minimum recommended disinfection time was determined and compared with criteria for stand-alone disinfection products for each MPDS against each strain.
Results:
No difference between filtered and unfiltered fungal suspensions was observed for the ISO standard, whereas in one MPDS the representative clinical isolate showed significantly increased resistance when unfiltered. All but one solution met the stand-alone criteria of 1.0-log reduction of colony forming units against the recommended ISO standard strain ATCC 36031. However, there was wide variation in the ability of MPDS to meet the ISO disinfection criteria when tested against clinical isolates. Among the commercially available MPDS, the two polyquaternium-based solutions showed a higher disinfecting efficacy than the biguanide-based solution. The two recalled solutions showed a lower disinfecting efficacy than the polyquaternium-based solutions. Further, the clinical isolates were significantly more resistant to disinfection than was the recommended ISO strain.
Conclusions:
The effect of filtering the fungal suspension to remove hyphae seems to be relevant in the clinical isolate tested, but not in the ISO strain. Clinical isolates were significantly more resistant to disinfection than the recommended ISO strain in the presence of both the commercially available and the recalled MPDS. The use of clinical isolates in stand-alone disinfection testing is indicated. Because there were significant differences in increased resistance exhibited by clinical isolates and in a mixed (unfiltered) culture the use of a single laboratory strain may be insufficient to provide assurance that the disinfection solution will be effective against clinical isolates.
Insights
Clinical isolates of Fusarium solani showed greater resistance to multipurpose disinfection solutions (MPDS) than the standard strain. Testing MPDS with clinical isolates is crucial for ensuring effective soft contact lens disinfection.
Area of Science:
- Ophthalmology
- Microbiology
- Infectious Diseases
Background:
- Soft contact lens wear is associated with microbial keratitis.
- Multipurpose disinfection solutions (MPDS) are essential for maintaining contact lens hygiene.
- Fusarium solani is a significant ocular pathogen causing keratitis.
Purpose of the Study:
- To evaluate the efficacy of five MPDS against clinical isolates of Fusarium solani.
- To compare the performance of MPDS against clinical isolates versus the standard ATCC 36031 strain.
- To assess the impact of fungal suspension preparation on disinfection efficacy.
Main Methods:
- Three commercial and two recalled MPDS were tested.
- The ISO/CD 14,729 stand-alone test was employed.
- Ten ocular isolates of F. solani and the ATCC 36031 strain were used.
- The effect of filtering fungal suspensions was examined.
Main Results:
- Clinical isolates of F. solani demonstrated significantly higher resistance to MPDS compared to the ATCC 36031 strain.
- Polyquaternium-based MPDS showed greater efficacy than biguanide-based solutions.
- Recalled MPDS exhibited lower efficacy than commercially available polyquaternium-based solutions.
- Filtering fungal suspensions impacted efficacy for one clinical isolate.
Conclusions:
- Clinical isolates of F. solani are more resistant to disinfection than the standard laboratory strain.
- Current disinfection testing using only standard strains may not fully represent real-world efficacy.
- Incorporating clinical isolates into MPDS efficacy testing is recommended for enhanced assurance of disinfection performance.
