Elizabethkingia strain possibly became more virulent during Wisconsin outbreak, study suggests

A new genetic analysis published in the journal Nature revealed that the Elizabethkingia anophelis strain responsible for the 2016 Wisconsin outbreak mutated as infections spread.


Between November 2015 and May 2016, the typically innocuous bacteria Elizabethkingia infected more than 60 people in the state of Wisconsin, and potentially contributed to the deaths of 18 people who officials confirmed to have been infected with the bacteria, according to the Wisconsin Department of Health Services.

In addition to the 63 patients in Wisconsin, two Illinois individuals and one individual from Michigan were also infected. The source of the outbreak was never identified. Officials also could not determine if the infection was the direct cause of death among the infected individuals because a majority of them were 65 years old or older and had suffered from multiple comorbidities. CDC officials categorized the outbreak as the largest of its kind the agency has ever investigated.

For the study, researchers conducted a comparative phylogenetic analysis between 69 Elizabethkingia isolates extracted from 59 of infected patients from Wisconsin and 45 other strains from outside sources. The analysis revealed that while the outbreak was caused by a single ancestral strain, the bacteria underwent a torrent of genetic mutations as the outbreak continued.

"We were seeing 40, 50, even 100 [genetic] differences between some of [the isolates]," said John McQuiston, PhD, the team leader for the CDC's Special Bacteriology Reference Laboratory and one the study's authors, according to The Atlantic.

The research team identified a missing chunk of DNA in the bacteria, which hindered the microbe's ability to perform DNA repairs, which subsequently resulted in a wealth of mutations. The study's authors suggested one or more of these mutations may have made the bacteria more virulent to humans.

"We, therefore, urge healthcare and public health systems to establish a laboratory based surveillance for Elizabethkingia infections, and to be particularly vigilant for a possible re-emergence of the unique E. anophelis strain that caused the Wisconsin outbreak," concluded to the study's authors.

To read the full study, click here.

To read The Atlantic's article on the study, click here.

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