Wash-In Silver Nanoparticle Laundry Additive Was Not Effective in Reducing Bacterial Load on Wrestling Apparel.

Context: The best practice for cleaning wrestling mats is using a residual disinfectant with continued antibacterial action. Recently available wash-in silver additives claim to confer a residual effect to fabric.

Objective: To test the efficacy of laundering with a wash-in silver additive in reducing athletes' exposure to potentially infectious microbes on apparel.

Design: A 4-part controlled laboratory study/parallel group comparison study. (1) To test whether fabrics in athletic clothing would be affected differently, we applied bacteria to control fabrics washed in detergent alone and test counterparts washed in detergent plus wash-in silver additive. Bacteria were applied to fabrics, extracted, plated, incubated, and counted. (2) To see if wash-in silver affected various bacteria differently, we washed cotton t-shirts with detergent alone or with detergent plus wash-in silver. We applied 4 bacterial species commonly found in the wrestling environment. Bacteria were extracted, plated, incubated, and counted. (3) To see if wash-in silver was effective in reducing bacterial contamination during practice, 32 collegiate wrestlers paired off with one wearing a test silver-treated t-shirt and their partner wearing a control shirt. Wrestler rotations exposed shirts to 2, 4, or 8 wrestlers. Identical swatches of fabric were cut from the t-shirts. Bacteria were extracted, plated, incubated, and counted. (4) We simulated prolonged/repeated bacterial exposure as occurs during tournaments by applying bacteria directly to silver-treated and untreated singlet material repeatedly over time. Test samples were taken at regular intervals to see if bacterial growth was inhibited by the presence of the silver nanoparticles. Bacteria were extracted, plated, incubated, and counted.

Setting: Laboratory and practice.

Participants: Collegiate Division III wrestling team.

Main outcome measure(s): Wash-in silver would be considered effective if a statistically significant reduction in bacterial count was observed at 95% confidence.

Results: Wash-in silver reduced bacterial growth at low levels of contamination but did not significantly reduce bacterial growth at levels seen during contact sport competitions. This was true for all bacterial species and all fabrics tested.

Conclusions: The environmental and potential health risks in using a wash-in silver nanoparticle laundry additive in the wash cycle for clothing worn by wrestlers outweigh any potential infection control benefits to these athletes. We do not currently recommend adopting wash-in silver treatment as part of the laundering regimen for wrestling programs until further testing of alternate methods of silver impregnation into sports fabrics has been investigated.