Document Type

Thesis

Date of Degree

Spring 2015

Degree Name

MS (Master of Science)

Degree In

Chemical and Biochemical Engineering

First Advisor

Eric Nuxoll

Abstract

Bacterial biofilm infection is a common (~ 2 to 4%) complication for recipients of surgically implanted medical devices. Due to the tremendous increase in antibiotic resistance when these bacteria enter the biofilm phenotype, present treatment requires explantation and replacement of the device, often with multiple surgeries and always with much longer patient recovery time. The specific objective of this study was to quantify the degree of biofilm deactivation from exposure to thermal shock for varying temperature and time durations. While extreme temperature (>150˚C) is routinely used to sterilize (e.g. autoclaves), such temperatures have a severe cost within the body. Despite extensive studies on thermal deactivation of bacteria in the planktonic phenotype over a wide range of temperatures (e.g., pasteurization protocols), surprisingly little is known about the thermal deactivation of biofilms except under extreme conditions. Here, the deactivation of Pseudomonas aeruginosa biofilms is reported. These biofilms were cultured at 37°C for 24 hours in a drip-flow reactor and subjected to heat shocks on the range of 50°C to 80°C for durations of 1 to 30 minutes. Heat shocks were delivered by immersion in thermostatted media for the prescribed time and the resulting concentration of colony forming units (CFU/mL) were quantified using direct enumeration. Up to 6.6 orders of magnitude reduction in CFU concentration was observed, indicating that thermal deactivation is a reasonable approach to biofilm mitigation. Integrating this approach with a magnetic nanoparticle implant coating will result in an innovative treatment for implant infections in situ without explantation or device replacement.

Public Abstract

Bacterial biofilm infection is a common (~ 2 to 4%) complication for recipients of surgically implanted medical devices. Due to the tremendous increase in antibiotic resistance when these bacteria enter the biofilm phenotype, present treatment requires explantation and replacement of the device, often with multiple surgeries and always with much longer patient recovery time. The specific objective of this study was to quantify the degree of biofilm deactivation from exposure to thermal shock for varying temperature and time durations. While extreme temperature (>150˚C) is routinely used to sterilize (e.g. autoclaves), such temperatures have a severe cost within the body. Despite extensive studies on thermal deactivation of bacteria in the planktonic phenotype over a wide range of temperatures (e.g., pasteurization protocols), surprisingly little is known about the thermal deactivation of biofilms except under extreme conditions. Here, the deactivation of Pseudomonas aeruginosa biofilms is reported. These biofilms were cultured at 37°C for 24 hours in a drip-flow reactor and subjected to heat shocks on the range of 50°C to 80°C for durations of 1 to 30 minutes. Heat shocks were delivered by immersion in thermostatted media for the prescribed time and the resulting concentration of colony forming units (CFU/cm2) were quantified using direct enumeration. Up to 6.6 orders of magnitude reduction in CFU concentration was observed, indicating that thermal deactivation is a reasonable approach to biofilm mitigation. Integrating this approach with a magnetic nanoparticle implant coating will result in an innovative treatment for implant infections in situ without explantation or device replacement.

Keywords

publicabstract, Biofilm, Pseudomonas aeruginosa, Thermal deactivation

Pages

vii, 37 pages

Bibliography

Includes bibliographical references (pages 34-37).

Copyright

Copyright 2015 Ann O'Toole

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