Bacteria of the Legionella genus are a highly relevant example of a poorly understood water-borne pathogen with multiple routes of transmission. Recent epidemiological data suggesting driving automobiles as a risk factor for legionellosis demonstrate the need for research aimed at determining novel routes these bacteria take to come into contact with humans and cause disease. To address this concern, a series of experiments were conducted to determine the potential for automobile windshield washer fluid to serve as a previously unknown source of exposure for Legionella.
To measure the capability for Legionella to survive within washer fluid, a bench scale study was performed in which cultures of Legionella pneumophila were inoculated into a variety of fluids and incubated. Results from culture counts show that Legionella were capable of surviving anywhere from days to months depending on the type of washer fluid, with significantly higher final concentrations seen in one brand of fluid than in sterile water after a period of several months. In a bench scale study performed to determine the capability for Legionella growth in windshield washer fluid reservoirs, reservoirs were filled with tap water inoculated or not with L. pneumophila and incubated at room temperature and 37° C. Concentrations of Legionella increased over time for both inoculated and plain tap water at 37° C, with culturable Legionella populations remaining stable for up to 9 months. Finally, a field study was conducted to monitor washer fluid collected from school bus reservoirs for the presence of Legionella via molecular and culture-based analysis. Culturable Legionella were detected in approximately 75% of buses sampled, with L. pneumophila concentrations observed as high as 8 X 104 CFU/ml. Aerosolized cells were also cultured from windshield wiper spray. By demonstrating the capability for Legionella to survive and grow in wiper fluid reservoirs and documenting the presence of this pathogen in actual reservoirs, this work provides evidence suggesting the potential for this novel source of exposure.