An NUI team has found a way to prevent bacterial infection in catheters. Dick Ahlstrom reports
The risk of infection in patients fitted with long-stay catheters is a serious challenge for healthcare specialists. The catheters are used with many chemotherapy patients but the tubing often becomes the home of bacteriological "films" which can coat the inside of the catheters. A research group at NUI Galway believe they may have found the answer to this problem. Success would mean that patients would not have to undergo painful removal and replacement procedures for deep vein catheters, explains Prof Emer Colleran of Galway's Department of Microbiology.
"Many of these catheters are left in the patients for a long time. If they get infected and the infection is inside the line, it forms a biofilm. They act as a source of bloodstream infection."
Estimates suggest that a quarter of all bloodstream infections in hospital intensive care units are associated with infected deep vein catheter lines. There is an associated mortality in these patients of between 20 and 25 per cent, and treatments for infected patients can be very expensive.
Biofilms occur when the bacterial cells clump together, she explains. "When they grow in this way they are protected and less susceptible to the drugs used to knock them out."
Placing antibiotic solutions in the line in a treatment called "antibiotic lock therapy" is the usual answer, but the films protect the bacteria from the treatment. Bacteria at the biofilm surface are killed off but others survive to cause new infections. Treatment failure often means the catheter has to be replaced, which is "stressful for the patient". Colleran joined with postgraduate student, John Curtain and NUI Galway colleague, Prof Martin Cormican of the Department of Bacteriology to find a way to beat the biofilms.
Curtain developed a model system to test a range of antibiotic solutions at different concentrations against a common drug resistant infecting agent, Staphylococcus epidermidis. He used four US Food and Drug Administration approved antibiotics known to work against multiple drug resistant bacteria. These included the familiar "last resort" antibiotics vancomycin and gentamicin, and a relative newcomer, linezolid, which only received its drug approval here 15 months ago.
Curtain found that the linezolid killed off the staph biofilm after a 24-hour lock therapy treatment. "The most surprising finding is that the linezolid is more effective than existing treatments," says Cormican. It is comparatively simple to trap the antibiotic solution in the catheter during treatment, says Colleran, but the approach does pose problems.
It may be impossible to block the line for the required 24 hours because of ongoing medical treatments. One way around this might be to fit patients with two lines, one being used for medical therapies while the other is being cleared of a biofilm infection.