Novel porous surface anti-infective catheter

Novel porous surface anti-infective catheter

The idea of the new functional principle for an anti-infective catheter system is one of the award winners of the innovation competition 2004 in the field of medical engineering. It is awarded and funded by the Bundesministerium für Bildung und Forschung (German Federal Ministry of Education and Research).
Grant Number: 01EZ0412
See press release BMBF: homepage and PDF-file (60 KB)

Numerous efforts are made to prevent the progress of spreading multi-resistant bacteria. The problem with catheters using bioactive substances is that they may lead to the development of antibiotic resistance. This makes them effective for only a short period of time.
However, catheters are an essential part of many therapies and provide an access to the body. The central venous catheter is especially widely used. Since it offers an access to the cardiovascular system for infusions, it unfortunately also often acts as a pathway for bacteria, which cause infections. They deposit on the surface of a foreign material (here the catheter) and secrete a protective layer of polysaccharides, the biofilm . Under this layer the bacteria thrive and detach from time to time causing bacteraemia and possibly even blood poisoning (sepsis). The area directly surrounding the catheter is therefore prone to become infected because of the biofilm.

These nosocomial infections inflict additional suffering on the patient and often result in death. There are more than 40,000 infection cases per year in the U.S. alone. Nosocomial blood-stream infections account for 3.5 million additional hospital days and US$3.5 billion in costs solely in the United States. Therefore creative approaches in this field are required to fight steadily increasing costs in today's health care systems worldwide.

Nature has found a way to fight against the depositing of bacteria. For example, amphibians live in a humid environment and have permanently moist skin, the ideal breeding ground for these bacteria. However the bacteria have a weakness. On the side where they attach to the surface, they cannot excrete a protective layer. Amphibians utilize this and excrete substances (e.g. antimicrobial peptides) through their skin that counteract the attachment of the bacteria.

The objective of this study is to examine the feasibility of a new concept (German patent no. 101 00 069), which involves the excretion of substances from the microporous surfaces of an indwelling catheter, thus preventing the infections by avoiding the development of biofilms.

A principle sketch of the catheter system

Preliminary studies were conducted using a microporous lipophilic Polypropylene tube with a 0.2 µm pore diameter. Garden mould was used for the inoculation of the tube surfaces. Flow of mineral oil perfusate with rates of 15 and 150 µl/min were achieved by closing the distal tube end and attaching the proximal end to a roller pump. This was compared with two additional experiments using either tap-water perfusate or no perfusate. The development of the biofilms was assessed with alcian blue staining, which stains polysaccharides. Five-day experiments showed a superior performance of the oil-perfused tubes. No biofilm was observed on their surface. Tap-water perfusion showed only minimal biofilm reduction in comparison with non-perfused tube surfaces.

It is assumed that oil-perfusion through the surface produces an oil film which firmly adheres to the catheter and forms an impenetrable barrier against microbes. Future studies will include a hydrophilic surface perfused with a water based substance, which could contain antibiotics. This would be applicable to a central venous catheter system. Increased susceptibility and detachment of previously surface-attached bacteria are expected. An accompanying evaluation will be done concerning the potential of this concept to suppress specific biofilm maturation stages, for instance initial adhesion, colony-forming and polysaccharide-matrix generation.

Links and publications about the catheter system (partly in German):

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