A DNA dot hybridization model for assessment of bacterial bioburden in orthokeratology lens storage cases

PURPOSE. The aim of this study was to evaluate a DNA dot hybridization assay (DHA) for assessing bacterial bioburden in orthokeratology lens (OK) storage cases. METHODS. Forty-one OK wearers participated in this study. The dot hybridization assay was used to assess the bacterial bioburden of OK after removal and 6-hour soaking in a storage case. Signals of the DHA were standardized after gray image transformation. The correlations between the hybridization intensities of three universal bacteria probes (BP1, BP2, and BP3) and bacterial bioburden determined by culture (colony forming units per milliliter) was analyzed by Pearson’s correlation coefficient and receiver operating characteristic plots. In addition, three genus-specific probes for Pseudomonas, Acinetobacter, and Klebsiella were used to detect potentially hazardous bacterial contamination regardless of bacterial viability status. RESULTS. Among the three universal probes, there were good correlations between probe BP2 (r² ¼ 0.31, P ¼ 9.5 3 10^-5) and probe BP3 (r² ¼ 0.35, P ¼ 3.1 3 10^-5) with bacterial bioburden, but no correlation was found between probe BP1 and bacterial bioburden (r² ¼ 0.04, P ¼ 0.11). In 41 samples, one was Pseudomonas-positive by both DHA and culture, while 10 were Pseudomonas-positive by DHA but negative by culture. Furthermore, nine samples tested positive for Acinetobacter (n ¼ 7) and Klebsiella (n ¼ 2) by DHA only. CONCLUSIONS. The dot hybridization assay provides a novel way to assess the bacterial bioburden of OK storage cases. Lens care quality can be assessed with universal bacteria probes, while potentially hazardous bacterial contamination can be traced with genus-specific probes.