Date of Award

12-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Bioengineering

Advisor

Melinda K. Harman, Ph.D.

Committee Member

Sarah W. Harcum, Ph.D.

Committee Member

Matthew R. Gevaert, Ph.D.

Abstract

Reusable medical devices or reprocessed single-use devices are original medical devices that have been used once and then are cleaned, sterilized, and remanufactured for the purpose of an additional single use on a single patient [4]. Improperly reprocessed devices are a significant contributor to hospital-associated infections [4]. Challenges that hinder reprocessing are related to the complexity of reusable medical device design, the necessary validation of cleaning protocols required by the U.S Food and Drug Administration (FDA), the impact of human factors throughout the reprocessing cycle, as well as economic factors within new business models that are centered on reprocessing. Current methods for detecting biofilm accumulation on medical devices are established; however, these methods lack appropriate consideration of the complex design features of reusable medical devices. A colorimetric assay widely used for quantifying biofilm accumulation is suitable for the complexity of reusable medical devices; however, its application has been limited to biofilms grown in a tissue culture plate, which does not accurately represent the true growth conditions of biofilm. Both material selection and flow conditions are important factors that are known to have an effect on biofilm formation [15, 23]. The broad objective of this thesis was to deliver a simple, cost-efficient method suitable for detecting biofilms on complex reusable medical devices in a high-throughput, industry setting for the purpose of validating cleaning methods required for reprocessing. Specifically, this thesis aimed 1) to grow biofilms under static and dynamic conditions, 2) to develop methods to quantitatively assess biofilm accumulation using a colorimetric assay and confocal laser scanning microscopy (CLSM), and 3) to apply these methods on commonly used medical device materials with application to reusable surgical instruments. Successful completion of these aims demonstrated a modified colorimetric assay using crystal violet stain is a highly sensitivity assay that can detect very low concentrations of crystal violet eluted from adhered biofilm. The high sensitivity of this colorimetric assay makes it ideal for detecting biofilm on reusable medical devices with complex design features fabricated from various materials. Additionally, it was shown that CLSM, in combination with image processing techniques, could yield quantitative data for detecting biofilm accumulation by measuring pixilation intensities of biofilm with fluorescent staining. Comparing intensity ratios and absorbance measurements from the colorimetric assay for a given biofilm could demonstrate a direct relationship between the two detection modalities effectively validating the modified colorimetric assay as a method for detecting biofilm accumulation on reusable medical devices. This correlation would be addressed in future work. The modified colorimetric assay presented in this thesis is a highly sensitive assay for detecting biofilm accumulation. In this regard, it has potential for improving validation methods for cleaning processes required by the FDA for reprocessing medical devices. Moreover, its simplicity and high-throughput potential makes it suitable for industry applications as it relates to human and economic factors. Ultimately, this research work presents a modified colorimetric assay that offers an innovative solution to many of the current challenges associated with medical device reprocessing.

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