From 2007.igem.org

Revision as of 17:10, 21 October 2007

• Home
  • Site Map
  • Meet the Team
  • Fun with iGEM
  • IcGEMs@OpenWetware
  • Acknowledgements
• Infector Detector
  • Introduction
  • Specification
  • Design
  • Modelling
  • Implementation
  • Testing/Validation
  • F2620 Comparison
  • Conclusion
• Cell by Date
  • Introduction
  • Specification
  • Design
  • Modelling
  • Implementation
  • Testing/Validation
  • Conclusion
• Cell-Free
  • What is Cell-Free?
  • Cell-Free Vs. Cell
  • Our Contributions
  • Characterisation
  • Applications
• Wet Lab
  • Lab Notebook
  • Protocols & Results
  • DNA Constructs
• Dry Lab
  • Modelling
  • Data Analysis
  • Software

Infector Detector: Introduction

Project Summary

In this project, we have decided to find a solution to the ongoing problem of catheter-associated urinary tract infections (CAUTI). To do this, we targeted the biofilms formed by the pathogens on the catheter, and designed a system which would be able to detect these biofilms. To do this, we identified the signaling molecule AHL, which is produced by these bacteria in response to biofilm formation. We picked the LuxR and lux promoter as components to detect the presence of AHL in the surroundings. We also implemented the cell free system, or the in vitro chassis. This is to reduce the possible inherent sources of contamination of our device. Through this, we have created an AHL detector, which is able to differentiate between different concentrations of AHL. Our device can also visibly report the presence of AHL after a specific threshold of 5nM.

Motivations

Why urinary catheters?

Urinary catheters are used commonly in all hospitals - their primary purpose is to drain the bladder of patients who are unable to do so themselves. Patients who are either confined to bed or undergoing surgery often need to be catheterized. However, the application of a urinary cathether can lead to urinary tract infection, the most common nosocomial infection in the hospital.

So what are the risks of obtaining a catheter-associated urinary tract infection? Patients who receive one brief catheterization have a 1% chance of getting a urinary tract infection. With approximately 4-5 catheterizations per day, the chance of infection can reach a total of 5% daily. Mishandling of the catheter, or application by unspecialized staff can further increase the risk to around 20% (1.Kunin,1996).

Treatment of a urinary tract infection with antibiotics generally cost only US$1,000 (2.Maki,2001). However, if further complications arise, the cost of treatment increases dramatically. Also, considering the high risk of obtaining such an infection and the large number of people who undergo catheterization every year (over 5 million in the US), the treatment costs total up to a phenominal number. Furthermore, further antibiotic treatment can result in the development of stronger resistant bacteria, making urinary tract infections harder to treat in the future.

What causes urinary tract infections?

There are a large variety of bacteria that can be involved in urinary tract infection. Most common ones include Escherichia coli, Enterococcus and Enterobacter, all of which are gram-negative bacteria. These pathogens are generally opportunistic, and are not highly pathogenic. Occasionally, more pathogenic species, such as Staphylococcus aureus (which is responsible for MRSA), might also cause such infections.

One important feature found in all these species of bacteria is their ability to form a thick bacteria biofilms. Biofilms consists of a complex of polysaccharides, excreted proteins and the bacteria glycocalyx. These mixture of molecules not only allow the bacteria to adhere together, but can also protect the bacteria from various foreign materials, most importantly antibiotics or anti-microbial agents. Some research groups have also shown that cleaning a cathether does not significantly reduce the risk of infection, possibly due to the resistance of bacteria to these foreign agents.

There are several modes of entry for the bacteria into the urinary tract. The most common mode of infection is by the migration of bacteria on the tube into the urinary tract. Bacteria can contaminte the collection bag or the catheter tube by exogenous sources (such as the non-sterile gloves), or endogenous sources, such as the urine or other waste products of the patients. The process of the extension of the bacteria biofilm along the urinary tract cannot be determined by current medical procedures, since the infection has not begun, and the patient will not exhibit any symptoms.

How can we reduce the risk?

In our project, we have decided that the best way to prevent a patient from contracting catheter-associated urinary tract infection is to have a way to assay for the presence of this bacteria. Our device would detect for the presence of biofilm, which is an indicator of the bacteria. If the bacteria is shown to be present on the catheter, it can be changed immediately to reduce the risk of the bacteria from migrating into the urinary tract. So how would we achieve this? Take a look at the specifications of our device!

Achievements

References