Antimicrobial Susceptibility of Clostridium difficile (C. diff) to Semeltec and VTT003

Background: C. diff colitis ranks among the most common infection acquired by patients in healthcare facilities.  While C. diff colitis is the result of antibiotic use in patients, the organism is transmitted by contact.  Use of garments made with antimicrobial textiles may reduce such contact acquisition and transmission.  VTT003 is an early generation, cotton-based fabric embedded with the antimicrobial Semeltec and a hydrophobic nanoparticle barrier (Vestagen Technical Textiles, Orlando, FL).

Objective: To evaluate the susceptibility of C. diff to Semeltec and, subsequently, VTT003.

Methods: Time Kill Assays (TKAs) were performed to determine the antimicrobial effects of Semeltec against C. diff.  In brief, C. diff was exposed to three dilutions of Semeltec for 5, 10, and 15 minutes.  The organism (consisting of spores and germinated spores) and Semeltec mixture was then diluted in growth medium to achieve a test article concentration lower than the minimal inhibitory concentration (MIC; 1:1,024) and placed in triplicate wells on a 96-well plate.  Organism diluted in growth media to an equivalent concentration was used as the positive control and growth media only was used as the negative control.  The plate was incubated anaerobically for 48hrs at 37°C and the optical density read at 620nm on a Thermo Multiskan Plus microplate reader.

Swatches of VTT003 (treated with Semeltec and the hydrophobic barrier) and untreated control were cut into 1.0g squares and autoclaved in individual pill packs.  Each square was then placed into a 250mL baffled flask containing pre-reduced growth medium.  Flasks were then reduced overnight to remove any oxygen retained in the cloth squares.  The next day, freshly thawed C. diff was added to each flask.  All flasks were then anaerobically incubated overnight at 37°C.  2mL samples were then collected from each flask and their optical densities (620nm) recorded. 

Results: The TKA showed that all dilutions of Semeltec (above and below the MIC) were effective at killing ≥90% of organism within 5min.  Further, VTT003 swatches reduced the OD₆₂₀ from 0.734 (organism alone) to 0.000 overnight.  Untreated control fabric had an OD₆₂₀ of 0.710.

Conclusions: The antimicrobial agent, Semeltec, is highly effective in killing C. diff organism within 5min.  Further, VTT003 fabric, embedded with Semeltec and a hydrophobic barrier, maintains this killing effect after overnight incubation.  These data suggest that VTT003 may represent a novel antimicrobial fabric for use as an anti-infective barrier, specifically against C. diff, in healthcare institutions.