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M. Nikolic, S. Kilvington; Evaluation of the Wasp (whitley Automated Spiral Plater) and Protocol Colony Counting System for Antimicrobial Efficacy Testing of Contact Lens Disinfectant Solutions. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6363.
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Contact lens disinfectant efficacy testing is conducted according to ISO 14729. The test solution is challenged with organism and viability determined over time through serial dilutions and plating of samples. This is laborious and prone to error due to the numerous manipulation steps and counting of results. Here, we evaluated the automated WASP and ProtoCol system for assessing contact lens disinfectant efficacy against bacteria and fungi.
MPS-1, a commercial multipurpose solution (1 ppm PHMB), was challenged with test organism and, at timed intervals, aliquots removed, diluted 1:10 in neutraliser broth and processed as follows:
1.Serial 10-fold dilutions (0.5 ml + 4.5 ml PBS-Tween) and 0.1 ml aliquots of each dilution spread over an appropriate agar culture plate. 2.Serial 10-fold dilutions (20 µl + 180 µl) across wells of a microtitre plate and 50 µl aliquots inoculated as 3 discrete drops on one quarter of an agar culture plate (Miles & Misra method). 3. Inoculation of 50 µl over the surface of an agar culture plate using the spiral plater with plate counts made using the ProtoCol system. The methods were also used to determine cell viability of challenge inocula.
The log10 total viable organism counts obtained by the three methods tested in triplicate are shown in the table (n = 3 with SEM 0.01 to ≤0.5).
The WASP and ProtoCol systems enabled the accurate and reproducible evaluation of contact lens disinfectant efficacy, with results comparable to other culture based methods. The system can resolve up to 4 x 10E5 cfu on a single plate and avoids serial dilutions and numerous plating steps. It is rapid to use, requires minimal maintenance and results in a substantial saving in media and technician time.
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