Efficacy of trypsin in enhancing assessment of bacterial colonisation of vascular catheters

Facile Modification of Medical-Grade Silicone for Antimicrobial Effectiveness and Biocompatibility: A Potential Therapeutic Strategy against Bacterial Biofilms

A one-step modification of biomedical silicone tubing with N,N-dimethyltetradecylamine, C14, results in a composition designated WinGard-1 (WG-1, 1.1 wt % C14). A surface-active silicon-amine phase (SAP) is proposed to account for increased wettability and increased surface charge. To understand the mechanism of antimicrobial effectiveness, several procedures were employed to detect whether C14 leaching occurred. An immersion-growth (IG) test was developed that required knowing the bacterial Minimum Inhibitory Concentrations (MICs) and Minimum Biocidal Concentrations (MBCs). The C14 MIC and MBC for Gm- uropathogenic E. coli (UPEC), commonly associated with catheter-associated urinary tract infections (CAUTI), were 10 and 20 μg/mL, respectively. After prior immersion of WG-1 silicone segments in a growth medium from 1 to 28 d, the IG test for the medium showed normal growth for UPEC over 24 h, indicating that the concentration of C14 must be less than the MIC, 10 μg/mL. GC-MS and studies of the medium inside and outside a dialysis bag containing WG-1 silicone segments supported de minimis leaching. Consequently, a 5 log UPEC reduction (99.999% kill) in 24 h using the shake flask test (ASTM E2149) cannot be due to leaching and is ascribed to contact kill. Interestingly, although the MBC was greater than 100 μg/mL for Pseudomonas aeruginosa, WG-1 silicone affected an 80% reduction via a 24 h shake flask test. For other bacteria and Candida albicans, greater than 99.9% shake flask kill may be understood by proposing increased wettability and concentration of charge illustrated in the TOC. De minimis leaching places WG-1 silicone at an advantage over conventional anti-infectives that rely on leaching of an antibiotic or heavy metals such as silver. The facile process for preparation of WG-1 silicone combined with biocidal effectiveness comprises progress toward the goals of device designation from the FDA for WG-1 and clearance.

Rapid Assay to Assess Bacterial Adhesion on Textiles

Textiles are frequently colonized by microorganisms leading to undesired consequences like hygienic problems. Biocidal coatings often raise environmental and health concerns, thus sustainable, biocide-free coatings are of interest. To develop novel anti-adhesive textile coatings, a rapid, reliable, and quantitative high-throughput method to study microbial attachment to fabrics is required, however currently not available. Here, a fast and reliable 96-well plate-based screening method is developed. The quantification of bacterial adhesion is based on nucleic acid staining by SYTO9, with Pseudomonas aeruginosa and Staphylococcus aureus as the model microorganisms. Subsequently, 38 commercially available and novel coatings were evaluated for their anti-bacterial adhesion properties. A poly(l-lysine)-g-poly(ethylene glycol) coating on polyester textile substratum revealed an 80% reduction of bacterial adhesion. Both the coating itself and the anti-adhesive property were stable after 20 washing cycles, confirmed by X-ray analysis. The assay provides an efficient tool to rapidly screen for non-biocidal coatings reducing bacterial attachment.