Unusual situations keep public health laboratory work challenging and unpredictable, say two microbiologists who spoke with CAP TODAY recently and presented at the 2015 meeting of the American Society for Microbiology, where they told stories on things as disparate as geoduck and cheese.

Staff at the State Hygienic Laboratory in Ankeny tests for minerals and metals, including arsenic and lead.

When China suddenly banned the import of geoducks – which are large clams – from the U.S. in 2013, it sent shock waves through the shellfish industry, reported William Glover who oversees testing services as director of science and technology at Washington State Public Health Laboratories.

“They’re a high-value export for our area, and China is the largest consumer,” he said, noting the Chinese pay exporters more than $100 per pound for the giant clams. Geoducks (pronounced “gooey ducks”) can grow to 3 kg and live for more than 100 years. “They’re considered a delicacy in Asian countries,” Glover said. “They grow naturally along the shoreline from the low tide level to 100 feet of water, and there are hundreds of rows of geoduck farms here in the Pacific Northwest.”

In a surprise move, the Chinese government informed the National Oceanic and Atmospheric Administration about a new standard for acceptable levels of inorganic arsenic in geoducks, and the information was passed along to exporters and to public health departments in the affected states. Previously, “inorganic arsenic levels didn’t have any standard we knew of,” Glover said. “So our environmental laboratory, along with its federal, state and commercial partners, had to come up with methods to test and certify that all geoduck clams exported to China were below this inorganic arsenic limit.”

The challenge was extracting, separating and measuring organic and inorganic arsenic, the latter being the more toxic of the two and the former being more abundant in the animals.

“It’s not unusual to have to come up with a new test, but the speed with which we had to do this was unusual,” Glover said. “People gave up their Christmas vacations. It was an urgent matter.”

The expertise needed to develop and validate the test was spread throughout different laboratories within the Washington State Public Health Laboratories’ Office of Environmental Laboratory Sciences, which worked in conjunction with federal, state and commercial partners, Glover said.

“The shellfish biotoxin lab knew how to shuck, skin, separate and homogenize the geoducks. The radiation laboratory had expertise in cryo-grinding [freezing and then grinding the sample]. The chemical incident response laboratory had expertise in the extraction of arsenic because they do that in food. And then the biomonitoring group had experience in the arsenic speciation method because they had developed the method for urine, apple juice, and brown rice testing.”

Those groups developed and validated the protocol, then turned the assay over to the shellfish biotoxin laboratory to perform.

“They came up with a test very quickly, the data generated by validation of the study was deemed sufficient by the Chinese government and, ultimately, the ban was lifted. And the people in environmental laboratory sciences who worked on the test got a call from the governor.”

In contrast to the rapid development of the test for inorganic arsenic, the development of a PCR assay for Vibrio parahaemolyticus has been a slower process. “Our assay has evolved over time due to the fact that Vibrio parahaemolyticus serotypes that cause human illnesses in Washington state vary,” Glover said. Vibrio is a halophilic bacterium that occurs naturally in Washington coastal waters, with levels rising during the warmer months. Vibrio parahaemolyticus, in particular, is often the culprit when people become ill after consuming raw oysters.

“When I came on board in 2013, we were getting requests from the Office of Shellfish and Water Protection to provide them with results on a new marker of virulence that had been reported in the literature, a gene called TDH-related hemolysin [trh]. Previously we were detecting only the thermostable direct hemolysin [tdh], a different gene. We have Vibrio strains in Washington that are tdh-negative but trh-positive, so it was important to incorporate that marker into the assay,” Glover said.

As it turned out, “That marker is one of the trickiest targets to develop an assay for because of the sequence variations.” Updating the assay for trh required a year of testing and another year of validation. The Interstate Shellfish Sanitation Conference, which reviews and approves tests for incorporation into state regulatory programs, has granted the assay emergency use authorization.

“We know from our experience here that there are other Vibrio species in the water that can cause human illness. It’s very important that all Vibrio clinical isolates in Washington state are submitted to us, because if we see something new causing illness in people eating shellfish, it may indicate we need to modify our assay.” The series will conclude with part three in the January 2017 Lab Link.

The series will conclude with part three in the January 2017 Lab Link.