Abstract
Purpose:
To compare antimicrobial efficacy of multipurpose disinfecting solutions (MPS) against Gram-negative clinical isolates following multiple rechallenge over 14 days storage.
Methods:
The multipurpose disinfecting solutions studied were - MPS-1: polyquaternium (PQ1) + alexidine dihydrochloride (ALX), MPS-2: polyhexamethylene biguanide (PHMB) + poloxamer, MPS-3: PQ1 + myristamidopropyl dimethylamine (ALDOX) + nonanoyl-EDTA, MPS-4: PQ1 + ALDOX,+ polyoxyethylene-polyoxybutylene (EOBO-41), MPS-5: PQ1 + ALDOX and MPS-6: PHMB + PQ1. Test solutions were inoculated with Gram-negative clinical isolates in the test tube according to ISO 14729. Test solution efficacy was evaluated at minimum recommended manufacturer disinfection time of 6 hours, 24 hours, 48 hours, 7 days and 14 days. Rechallenge of test solutions with 103-104 CFU/ml inoculum was performed at 24 hours, 48 hours and 7 days. Clinical isolates tested were: Achromobacter sp. Delftia sp., Serratia marcescens, Achromobacter xylosoxidans, Delftia acidovorans and Ralstonia insidiosa.
Results:
After 6 hours exposure, MPS-1 showed >3 log kill against all clinical isolates. MPS-2 showed >3 log kill against all clinical isolates after 6 hours except Ralstonia insidiosa, at 1.6 log kill. MPS-1 and MPS-2 did not exhibit any regrowth or reduced efficacy following multiple rechallenge over 14 days storage. MPS-3 showed <1 log kill against most of the clinical isolates after 6 hours exposure, and exhibited regrowth of all clinical isolates following multiple rechallenge over 14 days. MPS-4 and MPS-5 exhibited <1 log kill against most of the clinical isolates after 6 hours exposure and showed reduced efficacy following multiple rechallenge over 14 days storage. MPS-6 showed >3 log kill against all clinical isolates after 6 hours except Ralstonia insidiosa, which had 0.8 log kill at 6 hours and reduced efficacy following 24 hours rechallenge.
Conclusions:
MPS-1, MPS-2 and MPS-6 showed high ability to reduce microbial load under repeated exposure to Gram-negative bacteria while MPS-3, MPS-4 and MPS-5 exhibited reduced disinfection efficacy.
Keywords: 477 contact lens