CDC: Source of E. anophelis outbreak still unknown

BOSTON — The CDC is still trying to determine why dozens of patients in the Midwest were recently sickened by a rare bloodstream infection caused by Elizabethkingia anophelis bacteria.

“We are still looking for the missing piece,” Maroya S. Walters, PhD, ScM, epidemiologist at the CDC, said at ASM Microbe.

Figure 1. Gram-negative Elizabethkingia anophelis bacteria isolated from specimens obtained during a recent outbreak in Wisconsin.

Source: CDC

In the largest identified Elizabethkingia outbreak in history, 66 patients in Wisconsin, Michigan and Illinois — most of them older adults — have been infected with the same strain of E. anophelis. Sixty-three of these cases occurred in Wisconsin, where the outbreak began last November and peaked in February. Under increased surveillance, isolates in 11 other states have tested positive for Elizabethkingia — half of them for E. anophelis — but none have matched the outbreak strain, Walters said.

Elizabethkingia bacteria — named for Elizabeth O. King, the CDC bacteriologist who discovered it — are commonly found in the environment in soil, river water and reservoirs. They do not typically cause illness in humans, though Walters said the outbreak investigation revealed that infection is more common than previously thought.

All but one of the patients infected during the outbreak had a serious underlying medical condition, and 32% (n = 21) have died. The median age of the patients was 72 years, 47% (n = 31) were female and 97% (n = 64) were white. The outbreak occurred mostly in a community setting, with 66% (n = 40) of the patients living in a private residence at the time of their initial specimen collection. The most common symptoms were weakness and shortness of breath, Walters said.

Walters said the CDC has not found a source of contamination in health care products, hospitals, food, personal care products, or in patients’ homes, nor has the agency discovered evidence of patient-to-patient transmission. She said the CDC is continuing its search by conducting focus groups among patients who have closely related isolates, who live in the same town or who share the same occupation, but that the investigation might soon end.

“We’re likely coming to the end of the active component of our investigation,” Walters told Infectious Disease News. “We’re doing focus groups to see if we can identify another likely hypothesis because we’d like to find the source of this outbreak, but also because we don’t know if this will come back, and if it does, we’d like to have more hypotheses to test. But once we feel like we are at baseline and we’ve been at baseline for several weeks, it will be the Wisconsin Department of Health Services’ decision whether or not to call off the active part of the investigation.” – by Gerard Gallagher

Reference:

Walters MS, et al. Elizabethkingia outbreak. Presented at: ASM Microbe; June 16-20, 2016; Boston.

Disclosures: Walters reports no relevant financial disclosures.