CDC Publishes Additional Findings Regarding 2016 Elizabethkingia Outbreak

Last year, a previously misdiagnosed bacteria was found to be the cause of more than 20 deaths across three states. Upon investigation, the Centers for Disease Control and Prevention (CDC) identified the pathogen to be Elizabethkingia anophelis, a “water-based” bacteria that is seldom the cause for severe illness in humans. Now, the CDC believes that there may have been more than one source for the multi-state outbreak.

Although Elizabethkingia is not usually harmful, some individuals may be more susceptible to infection than others; this includes those with diabetes mellitus, alcohol dependence, chronic renal disease, immunocompromising illnesses, those receiving immunosuppressive treatment, and more. This particular outbreak started in Wisconsin in early 2016, and the state’s Department of Health Services notified neighboring states of the ongoing identification of cases in February of that year.

Following this, healthcare providers and laboratories in Illinois were charged with gathering all E. anophelis isolates from the past two years and sending them to the Illinois Department of Public Health. Of those that were collected, 12 were sent to the CDC for testing, 11 (from 10 patients) of the isolates tested positive for the bacteria. An article published in Morbidity and Mortality Weekly Report in early December noted that these isolates belonged to a “genetic cluster… distinct from the Wisconsin outbreak strain… based on pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS).” According to the report, “Cases were defined as the culture of [E. anophelis] from sterile sites or the respiratory tract of Illinois patients from January 1, 2014 onward, and at least one specimen that was <60 SNPs distance by WGS to the cluster pattern identified by CDC. Eight patients had positive blood cultures and two had positive respiratory specimens.” According to the MMWR article, “The case fatality rate was high: seven of the 10 patients died before June 2, including six who died within 30 days of positive [E. anophelis] specimen collection.” Although E. anophelis may have been a contributing factor to case mortality, the MMWR notes that almost all patients had underlying comorbidities.

Of those individuals who tested positive, seven were male, and the overall average age was 68 years. According to previously collected data, between January 2012 and May 2016, 77 patients in 15 Illinois facilities were reported to have tested positive for E. anophelis, which totals out to an average of around 17 infections per year, and about 5 per facility. This shows that although only 10 individuals were identified to have acquired infection with E. anophelis, this number is notably higher than average; CDC officials previously believed this to be the largest Elizabethkingia outbreak to date.

However, this has not been the first Elizabethkingia outbreak to hit Illinois. According to the CDC, healthcare facilities across Illinois reported three previous outbreaks (between 2008 and 2013) that were caused by a different strain of the pathogen, Elizabethkingia meningoseptica. After sending isolates from these outbreaks to the CDC for further testing, it was found that the pathogens behind these outbreaks were actually, in fact, of the anophelis species.

According to the CDC, due to a “lack of common facility exposure among patients,” previous allegations that this outbreak was the cause of one source and that the number of cases is higher than that identified in previous years is untrue, according to the new findings published in MMWR. The article concludes, “Instead, this more likely represents ongoing sporadic infection among critically ill patients. Of note, after the investigation was completed, additional genetic analysis conducted by CDC indicated that one of the isolates initially identified as part of the cluster had a distinct PFGE pattern and by WGS, differed from the cluster genomes by 160—170 SNPs.”