School of Optometry, The Hong Kong Polytechnic University, Hong Kong SAR, China.
Ophthalmic Physiol Opt. 2019 Sep;39(5):337-349. doi: 10.1111/opo.12635. Epub 2019 Aug 22.
The presence of biofilm in the lens case has been shown to be a risk factor for contamination of lenses and consequently microbial keratitis. This study aimed to evaluate effectiveness of solutions for rigid contact lenses in prevention and disruption of biofilm in lens cases and methods for biofilm detection.
This study adopted a stepwise approach to evaluate effectiveness of four rigid lens disinfecting solutions against biofilm. These included two polyhexamethylene bigiuanide (PHMB) solutions and a chlorhexidine/PHMB-based solution, as well as a novel povidone-iodine formulation. The presence of biofilm following exposure to the solutions was assessed using both crystal violet (CV) staining and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) viability assay, taking into account the effect of lens case design. Three lens case designs, conventional flat, large bucket type, and cylindrical cases, were investigated for the ability to trap stain and allow biofilm formation.
Considerable differences were noted between solutions in their ability to prevent and disrupt biofilm (p < 0.001). Lens case design greatly influenced optical density (OD) measurements even in negative controls, as cylindrical cases trapped more stain, increasing OD readings. Correcting for this factor reduced variations, but could not differentiate between residues and biofilm. MTT assay revealed that both povidone-iodine and chlorhexidine-containing solutions could effectively kill > 95% of organisms, whilst PHMB-based solutions were less effective with up to 55% of staphylococci and 41% of Pseudomonas surviving at 24 h.
Biofilm can rapidly form in lens cases and may not be killed by disinfecting solutions. Of the solutions tested, none were able to prevent biofilm formation or disrupt established biofilm, but those containing chlorhexidine or povidone iodine were able to penetrate the biofilm and kill organisms. Assessment of biofilm by CV assay may be confounded by lens case design. Whilst CV assay can demonstrate presence of biofilm, this technique should be accompanied by viability assay to determine bactericidal activity.
研究表明，镜片盒内生物膜的存在是镜片污染和随后发生微生物角膜炎的一个危险因素。本研究旨在评估四种硬性隐形眼镜消毒剂在预防和破坏镜片盒内生物膜以及生物膜检测方法方面的效果。
本研究采用逐步方法评估四种硬性隐形眼镜消毒剂对生物膜的效果。这些消毒剂包括两种聚六亚甲基双胍（PHMB）溶液和一种氯己定/PHMB 基溶液，以及一种新的聚维酮碘配方。通过结晶紫（CV）染色和 MTT（3-（4,5-二甲基噻唑-2-基）-2,5-二苯基四氮唑溴化物）活力测定评估暴露于溶液后的生物膜存在情况，同时考虑镜片盒设计的影响。为了研究捕获染色剂和形成生物膜的能力，研究了三种镜片盒设计，包括传统的平片型、大桶型和圆柱形。
在预防和破坏生物膜方面，不同溶液之间的能力存在显著差异（p<0.001）。镜片盒设计极大地影响了光学密度（OD）测量值，即使在阴性对照中也是如此，因为圆柱形盒更容易捕获染色剂，从而增加了 OD 值读数。纠正这一因素虽然减少了差异，但无法区分残留物和生物膜。MTT 检测表明，聚维酮碘和含氯己定的溶液均能有效杀死>95%的生物膜，而 PHMB 基溶液的效果较差，24 小时后，金黄色葡萄球菌的存活率高达 55%，铜绿假单胞菌的存活率高达 41%。
生物膜可在镜片盒内迅速形成，且可能无法被消毒剂杀死。在所测试的溶液中，没有一种能够预防生物膜形成或破坏已建立的生物膜，但含有氯己定或聚维酮碘的溶液能够穿透生物膜并杀死生物。CV 检测法评估生物膜可能会受到镜片盒设计的干扰。虽然 CV 检测法可以证明生物膜的存在，但该技术应辅以活力检测法以确定杀菌活性。
