Three swipes are the charm

(Edmonton) Three is the magic number when it comes to getting rid of bacteria on plastic surfaces, suggests research from a U of A study.

Swiping a plastic surface three times will get rid of most bacteria, regardless of whether you’re using a disinfectant wipe or a tissue with saline, a team in the Faculty of Medicine & Dentistry has discovered. But if time is short, a single swipe with a disinfectant wipe is best.

“It was the mechanical removal, not the actual act of the disinfectant that was key,” says Sarah Forgie, a pediatric infectious diseases specialist in the Department of Pediatrics.

Medical student Andrea Berendt, who worked with Forgie on the research, came up with the protocol and conducted all the experiments in a lab over two months. The duo worked with Robert Rennie, a professor in laboratory medicine and pathology; pediatric epidemiologist Donald Spady and technologist LeeAnn Turnbull.

Three types of bacteria—Staphylococcus aureus (MRSA), Enterococci (VRE) and Pseudomonas aeruginosa—were each prepared in a mixture and streaked onto sterile plastic Petri dishes, then allowed to dry. Numerous bacteria-contaminated plates were prepared throughout the summer—all in the same manner—so each type of bacteria could be tested with five different types of wipes and then again with varying amounts of swipes: one swipe, three swipes and five swipes.

Each 10 cm-diameter plate was wiped for one second and in a manner that the entire surface was swiped, using a flat baton. The plates were then allowed to dry for 10 minutes. Afterwards, bacteria samples were put onto special lab plates, incubated for at least 24 hours at 35C and then the bacteria colonies were counted.

Research results demonstrated that bacterial counts dropped significantly the more often a plate was swiped, regardless of the type of wipe used. Swiping the contaminated plates three times decreased the bacterial load by 88 per cent on average, compared to just swiping a plate once. Swiping a plate five times didn’t result in an additionally significant decrease in bacteria. And a simple saline wipe appeared to be just as effective as disinfectant wipes when the plates were swiped three times or more. However, if the plate was swiped just once, disinfectant wipes were better at reducing bacteria than simple saline wipes.

The research was supported in part by a grant from the Women and Children’s Health Research Institute.