Researchers Explore How Climate Affects Legionella Presence in Car Washer Fluid


Otto Schwake, PhD, discusses how he and his team sought to validate their hypothesis regarding climate and Legionella presence in car washer fluid.

Otto Schwake, PhD, Department of Civil and Environmental Engineering at Virginia Tech, discusses how he and his team sought to validate their hypothesis regarding climate and Legionella presence in car washer fluid.

Interview Transcript (slightly modified for readability).

“For this current study, we did two sets of experiments; one was a field study where we went out to 7 sites in America (2 schools, 3 military bases, and 2 transportation departments), and collected washer fluid samples and tried to cultivate those samples to look for Legionella. We purposely picked sites in different parts of the country with different climates.

Our main hypothesis going in was [taking into account our] previous work in Arizona, [where we] found a lot of Legionella in [the] washer fluid. Based on what we know about Legionella, they like warm temperatures, and what we know about washer fluid, the colder climate washer fluid is rated for the more methanol is has by volume. Based on those two ideas, we [had] a simple prediction: the warmer it is, the more Legionella we’ll see. In the colder areas with 40%+ methanol by volume in their washer fluid, we might not see anything. Methanol is kind of toxic—keep that in mind.

For this study, we gathered washer fluid samples. We actually took an interesting approach; we figured it would be difficult to get onto military bases to kind of mess with their vehicles, so, we used citizen science, where we made an arrangement with personnel at their bases with their different vehicle departments, and had them collect their samples for us and ship them to us. But, regardless of how we got the samples back in our lab, we tested a few measurements. We looked at how warm the washer fluid was; we looked at the pH of the washer fluid. The main thing that we did was try to grow Legionella from them. Unfortunately, we did not do any molecular detection, which we’re really kicking ourselves because the other experiment really kind of hinted that that would have been a good idea.

The other set of experiments we ran for this project, was a bench-scale study, to corroborate and add support to our findings that Legionella were more present in warm weather areas in the washer fluid we sampled, and much, much less common the colder it got. We decided to set up bioreactors, but basically test tubes full of washer fluid and water filled with different concentrations of methanol, and incubating those at different times, inoculating those with Legionella and seeing how they lived or died over time. We measured those, along with methanol to see if there’s any changes in the methanol, and, for this study, because it was a little simpler to control in the lab, we didn’t just grow the Legionella, we also looked for their DNA, and we performed microscopy on them to see if they were there and if they were alive.”

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