Legionella pneumophila bacteria
A form of bacteria responsible for respiratory illness, including the deadly pneumonia known as Legionnaires’ disease, may be able to grow in windshield washer fluid and was isolated from nearly 75% of school buses tested in one district in Arizona, according to research presented this week at the annual meeting of the American Society for Microbiology.
“Washer fluid spray can release potentially dangerous numbers of these bacteria into the air. These results suggest that automobiles may serve as a source of transmission for Legionella infections,” says Otto Schwake, a doctoral student at Arizona State University, who presented the research.
The Legionella bacterium causes a type of pneumonia that got its name after the 1976 outbreak at an American Legion convention in Philadelphia. There are no vaccines that can prevent Legionnaires’ disease.
Legionella are found naturally in the environment, usually in water. They are commonly associated with the cooling towers found in large-scale air conditioners and hot tubs. They are not spread from person to person but instead are transmitted via mist or vapor containing the bacteria.
The study results come from a series of experiments conducted in the summer of 2012. Schwake and his colleagues attempted to grow Legionella bacteria in a variety of different washer fluid preparations. They found that the bacterial concentrations increased over time and they were able to maintain stable populations for up to 14 months. In the second study, they tested the washer fluid from school buses in central Arizona and found culturable Legionella in approximately 75% of the samples.
Although windshield washer fluid is not normally associated with spreading disease, Schwake says this project was begun after a series of epidemiological studies found motor vehicle use to be associated with increased risk for Legionnaires’ disease. One such study attributed nearly 20 percent of Legionnaires’ disease cases in the United Kingdom not associated with hospitals or outbreaks to automobile windshield washer fluid.
“This study is the first to detect high levels of Legionella in automobiles or aerosolized by washer fluid spray,” says Schwake. “While potential transmission of a deadly respiratory disease from a source as common as automobile windshield washing systems is significant, the study also points to the fact people can be exposed to pathogens – particularly those occurring naturally in the environment – in previously unknown and unusual ways.”
According to the Centers for Disease Control, each year 8,000 – 18,000 people are hospitalized with Legionnaires’ disease in the U.S., but many infections are not diagnosed or reported, so this number may be higher. More illness is usually found in the summer and early fall, but it can happen any time of year. The bacteria can also cause Pontiac fever, a milder illness resembling the flu.
Image: Under a moderately-high magnification of 5356X, this colorized scanning electron micrograph (SEM) depicted a grouping of Gram-negative Legionella pneumophila bacteria. You’ll note that a number of these bacteria seem to display an elongated-rod morphology. L. pneumophila are known to most frequently exhibit this configuration when grown in broth, however, they can also elongate when plate-grown cells age, as it was in this case, especially when they’ve been refrigerated. The usual L. pneumophila morphology consists of stout, “fat” bacilli. Credit: Janice Haney Carr/CDC