Israel Medical Association Journal

Background: Although indwelling catheters are increasingly used in modern medicine, they can be a source of microbial contamination and hard-to-treat biofilms, which jeopardize patient lives. At times 70% ethanol is used as a catheter-lock solution due to its bactericidal properties. However, high concentrations of ethanol can result in adverse effects and in malfunction of the catheters.

Objective: To determine whether low concentrations of ethanol can prevent and treat biofilms of Pseudomonas aeruginosa.

Methods: Ethanol was tested at a concentration range of 0.625–80% against laboratory and clinical isolates of P. aeruginosa for various time periods (2–48 hours). The following parameters were evaluated following ethanol exposure: prevention of biofilm formation, reduction of biofilm metabolic activity, and inhibition of biofilm regrowth.

Results: Exposing P. aeruginosa to twofold ethanol gradients demonstrated a significant biofilm inhibition at concentrations as low as 2.5%. Treating pre-formed biofilms of P. aeruginosa with 20% ethanol for 4 hours caused a sharp decay in the metabolic activity of both the laboratory and clinical P. aeruginosa isolates. In addition, treating mature biofilms with 20% ethanol prevented the regrowth of bacteria encased within it.

Conclusions: Low ethanol concentrations (2.5%) can prevent in vitro biofilm formation of P. aeruginosa. Treatment of previously formed biofilms can be achieved using 20% ethanol, thereby keeping the catheters intact and avoiding complications that can result from high ethanol concentrations.

The pulmonary microbiology is a dominant element in cystic fibrosis and the main cause of death. Contemporary consensus accords an exclusive role in this to a single microorganism, Pseudomonas aeruginosa. The evidence convincingly shows that the microbiology consists of a multiplicity of species living in perpetual interaction and in a variety of forms – planktonic, sessile, anaerobic – and in organized communities as microcosms, biofilms and ecosystem. This compound microbiology, the essence of the pulmonary disease, is of necessity exposed to constant influence both from without (the air) and within (via the blood), leading to a perpetual state of flux with consequent impact on the clinical course. It is perhaps significant that to date, most or all microbiologic studies were probably conducted, classically, with inert instruments (glass? plastic?), whereas in real life the CF[1] microbiology lives in “test-tubes” of live mucosa with which it maintains a permanent “cross-talk.” The difference to microbial life between these two media may well be very important. It therefore justifies study and may be far-reaching in its effect. There is persuasive argument to strive for a novel holistic view of the totality of the complex microbiology of CF, and to initiate fresh concepts, strategies and methods.

Objectives: To investigate the time relation between the insertion of a new NGT and formation of the biofilm.

Methods: We examined sequential samples on NGTs that were forcibly pulled out by the patients themselves during any of the 7 days after insertion. Scanning electron micrography and confocal laser scanning microscopy were used for biofilm detection.

Results: Biofilm was identified on 60% of the 35 samples of day 1 and on all the samples of the following days, by both microscopic methods.

Conclusions: Biofilms form within a single day on most NGTs inserted for the feeding of elderly patients with dysphagia. Further research should be devoted to prevention of biofilm formation on NGTs.