Abstract
Purpose:
To compare antimicrobial efficacy of commercially available multipurpose disinfecting solutions (MPS) against Gram-negative clinical isolates following prolonged storage in lens case in the presence of a lens.
Methods:
The multipurpose disinfecting solutions studied were - MPS-1: polyquaternium (PQ1) + alexidine dihydrochloride (ALX), MPS-2: PQ1 + polyhexamethylene biguanide (PHMB), MPS-3: PQ1 + myristamidopropyl dimethylamine (ALDOX) and MPS-4: PQ1 + ALDOX + nonanoyl ethylenediaminetriacetic acid (EDTA). Test solutions were inoculated with Gram-negative clinical isolates in the appropriate lens case, in the presence of Acuvue2 (etafilcon A) lens. Test solution efficacy was evaluated at minimum recommended manufacturer disinfection time of 6 hours and following prolonged storage. Test solutions were also inoculated with Gram-negative clinical isolates in the test tube and tested according to ISO 14729.
Results:
After 6 hours exposure, MPS-1 and MPS-2 showed >3 log kill against clinical isolates in a test tube, while MPS-3 and MPS-4 failed stand-alone criteria. MPS-1 and MPS-2 maintained efficacy in the lens case in the presence of Acuvue2 lens and achieved >2.5 log kill. MPS-3 and MPS-4 showed <1 log kill or organism regrowth at 6 hours exposure. Following 7 days storage in a lens case, MPS-1 achieved >3 log kill for all organisms tested. MPS-2 and MPS-3 failed to achieve 3 log kill for one organism tested. MPS-4 failed to achieve 3 log kill for two organisms tested. Following 30 days storage in a lens case, MPS-1, MPS-2 and MPS-3 achieved >3 log kill for all organisms tested, while MPS-4 failed to achieve 3 log kill for two organisms tested.
Conclusions:
Gram-negative clinical isolates are resistant to MPS-3 and MPS-4. MPS-1 and MPS-2 showed ability to reduce microbial load under worst case conditions, tested in a lens case with Acuvue2 lens present.
Keywords: 477 contact lens