Aaron Packman and Jeromy Miceli

Aaron Packman (right) with graduate student Jeromy Miceli

 

Legionnaires' disease

McCormick, Feinberg join the fight

In 2001, 800 people were suspected to have contracted Legionnaires' disease after being exposed to the bacteria Legionella pneumophila near a hospital in Spain. Six people died. Similar outbreaks have occurred near commercial buildings and health-care facilities in Toronto, Philadelphia, Norway, France, and the United Kingdom. After intense investigations of each outbreak, the incidents were found to share one cause: faulty cooling towers.

Aaron Packman, associate professor of civil and environmental engineering, and Nicholas Cianciotto, professor of microbiology and immunology at Northwestern's Feinberg School of Medicine, are combining their expertise to study disinfection practices for cooling systems in the hope of providing tools to prevent future outbreaks of Legionnaires' disease.

Studying pathogens in large industrial systems requires expertise in several areas, providing an ideal opportunity for collaboration between McCormick and Feinberg. "I've studied Legionella pneumophila for over 20 years, but I don't know much about cooling towers and the engineering aspects," Cianciotto says. "I would have never embarked on this myself, but Aaron brings engineering expertise as well as some microbiology experience."

In order to formally study the efficacy of different cleaning techniques, Packman and Cianciotto's teams developed a unique laboratory setup in Tech. "We set up 10 cells to operate like rooftop cooling towers, replicating what you have in a real building," Packman explains.

The setup gives the team the ability to expose multiple cooling systems to the same pathogens and then compare pathogen growth for each disinfection and cleaning protocol side by side.

"Nobody else has equipment like this," Packman adds. "We're doing microbiology experiments on a large laboratory scale, trying to bridge the gap between basic microbiology and engineering applications in real building systems."

Just like in large industrial and commercial buildings, the cooling towers developed in the lab work by using evaporation. Water is pumped through a hot water system, then dripped across a block of material while air is blown across it, cooling the water. This warm, moist environment is unfortunately ideal for the growth of many pathogens, including Legionella pneumophila, which is transmitted through tiny droplets of water. These systems have the potential to expose large numbers of people to the organisms.

To prevent outbreaks of Legionella pneumophila, technicians put cooling towers through a battery of cleaning procedures each year. "There are recommended industrial treatment measures, but they've never been formally evaluated," says Packman. "There's a lot of debate as to exactly how stringent a control measure like a biocide [a chemical capable of killing all biological life] you need to prevent outbreaks."

U.S. standards require continuous low-level chlorine with occasional biocide added, but other countries require stronger measures, including hyperchlorination or even disassembly of the cooling unit to clean the cooling material. These stronger measures, however, have their own set of drawbacks, particularly for those concerned with the maintenance and longevity of these expensive systems. "You have the potential for damage and downtime," Cianciotto explains. "So it comes down to a very practical question: Is there a good reason to disassemble the cooling units?"

To set up the specialized equipment, Packman and Cianciotto benefited from the work experience of graduate student Jeromy Miceli. Before enrolling to study for a master's in environmental engineering, Miceli had responsibility for testing systems for water contaminants for a large water utility company. Using his knowledge of the systems, he set up the miniature test cells and developed protocols for the experiment in Tech.

With the system up and running, the researchers will introduce the organisms that affect real-life systems, including, says Packman, "organisms that form biological coatings, amoebas that prey on these biological coatings, and then Legionella pneumophila to infect the amoeba. All together we will introduce five organisms to make a realistic microbial system that you would find in a building's hot-water loop."

After evaluating current maintenance procedures for cooling towers, Packman and Cianciotto hope to expand their joint research. Future projects may identify even better cleaning procedures to eliminate not just large outbreaks of Legionnaires' disease but also other illnesses. "Now that we've established this partnership and built this unique equipment, we hope to use it for years," Cianciotto says. "This project is just the first step."

Kyle Delaney