Cornell researchers developing speedy test to find bacteria in beach water

Jul 9, 2018

A group of researchers at Cornell University has developed a new, faster test to determine whether bacteria are present in beach water. The team will be field-testing their system on Lake Erie near Buffalo July 16-18.

Beaches are supposed to close to swimmers when bacteria levels in the water surpass state limits, but the test in use in most of the Great Lakes region takes 24 hours to return results, leaving swimmers at risk in the meantime, said Ruth Richardson, an engineering professor at Cornell University.

The current method of testing water for bacteria has been in use for almost 100 years, Richardson said. “This sort of gold standard that’s outdated in the molecular age is ripe for replacement,” said Richardson, who is leading a team that developed, and is now evaluating, a new testing method that she says “gives an answer on-site within an hour.”

Richardson’s test collects a pint-size sample of water, strains out the bacteria, and collects a sample of bacterial DNA. That DNA is run through a process that isolates particular markers unique to a certain type of bacteria. The results are displayed on an iPhone about an hour later.

On-site results are important, Richardson said, because it means parks officials don’t have to send their samples off to a lab and wait for their results to come back the next day. Officials can make a decision on the spot, before the beach opens for the day, about whether it’s safe to swim.

Without on-the-spot tests, Monroe County Health Department Spokesperson John Ricci said, the department relies on substitute measures, like how murky the water is, or whether algae blooms are in sight, to predict whether the water is safe.

“To actually wait on the lab results, you would always be waiting 24 hours, and that clearly wouldn’t be acceptable. We need to make a decision every day by about 9 or so whether we’re going to allow swimming.”

Ricci and Richardson both say the current method is prone to error—both overestimating and underestimating the danger.

“In a very few number of cases, we actually close the beach, and then a day later learn that be beach actually could have been open,” Ricci said.

“The opposite problem can happen too,” said Richardson. “It looks like a fine day, and you take your sample and invite your guests in, and you find 24 hours later that the indicator levels were actually very elevated, and the water might not have been safe.”

The new form of testing is still under development. Richardson said her team is working on a pitch to the state parks department before submitting the test for eventual federal approval by the Food and Drug Administration and the Environmental Protection Agency.