Deadly Midwest Outbreak of Elizabethkingia

John McQuiston, PhD


April 01, 2016

A Life-Threatening Outbreak

(Updated April 7, 2016) Elizabethkingia anophelis, the Gram-negative bacteria causing an ongoing and deadly outbreak in Wisconsin and, recently, Michigan, is generally a rare cause of illness in healthy individuals. E anophelis is an environmental microorganism that is not part of the human microflora and was originally isolated from the midgut of anopheline mosquitos.[1] The clinical presentation of E anophelis infection resembles many other more likely etiologies, and therefore it may not be among the top candidates for a potential cause of bloodstream infections. In addition, diagnostic capabilities across many states and clinical labs may not be sufficient to identify this genus, let alone species, quickly, which affects patient treatment. E anophelis is also resistant to many commonly prescribed antibiotics.

The cases in Wisconsin and Michigan represent the first reported outbreak of E anophelis in the United States and the largest known outbreak of Elizabethkingia on record, with 53 confirmed cases and 17 deaths as of March 28.[2]

Background, Diagnosis, and Treatment of Elizabethkingia

Although commonly found in the environment, particularly in soil and water, Elizabethkingia rarely causes disease in otherwise healthy individuals. CDC laboratories receive 5-10 isolates per year in each US state. Following the recognition of this outbreak, CDC asked states to send isolates of all species of Elizabethkingia for further testing to confirm whether the isolate was from the main outbreak cluster or an unrelated case. The recent call for case-finding has shown that some cases of Elizabethkingia infection may be unrecognized.

In this outbreak, the bacteria primarily infect older adults and those who have serious underlying health conditions. The infection typically presents as septicemia and can be deadly if not treated early with appropriate antibiotics. (The fatality rate in the current outbreak is about 30%.) Clinicians who have patients with underlying health issues and bloodstream infections of unknown etiology should consider Elizabethkingia as a possible cause.

Diagnosis and Testing

Diagnosis is made on the basis of results of culture from sterile sites, most often blood. However, owing to its rarity, some clinical laboratories use bacterial detection software that may misidentify Elizabethkingia as other bacteria. Therefore, if results come back as Flavobacterium meningosepticum or Chryseobacterium meningosepticum, CDC advises clinicians to report these results to the state health department for consultation, and to treat presumptively as E anophelis.

State clinical microbiology laboratories can characterize the isolates using pulsed-field gel electrophoresis, a method that can identify the Elizabethkingia genus correctly. Isolates sent to CDC's Special Bacteriology Reference Laboratory are confirmed as the species E anophelis on the basis of the pathogen's protein profile, acquired using the mass spectrometry method MALDI-ToF (matrix-assisted laser desorption/ionization time-of-flight), and optical mapping of the bacterial genome.

Treatment of the Current Outbreak

Even though this bacterium is resistant to many antimicrobials used to treat gram-negative rod bloodstream infections, Wisconsin clinical microbiology laboratories, along with CDC, have identified that the strains responsible for most cases in the current outbreak are susceptible to several antibiotics. These include fluoroquinolones, rifampin, minocycline, and trimethoprim/sulfamethoxazole. If possible, combination treatment is recommended over monotherapy. For best results, treatment should be selected based on antimicrobial susceptibility testing results for each suspected case.

Health departments, hospitals, and clinical laboratories wanting to learn more about Elizabethkingia and other rare pathogens can join MicrobeNet, a CDC-curated virtual reference library that helps laboratorians and clinicians get the information they need to accurately identify causes of disease faster and save lives. MicrobeNet provides laboratorians, at no cost, with unprecedented access to CDC's virtual microbe library of more than 2400 rare and emerging infectious bacteria and fungi. It contains complete information about growing and identifying the bacteria, and, for many pathogens, information on antibiotic resistance.

CDC and the affected states continue to work toward managing the ongoing outbreak. The unexpected number of infections with this unusual pathogen reminds us of the importance of new and emerging technologies, such as advanced molecular detection and MicrobeNet, to quickly detect and track rare and deadly pathogens like Elizabethkingia.

Web Resources

CDC: Elizabethkingia

Wisconsin Department of Health Services: Elizabethkingia

To submit isolates to CDC:
Bacterial Special Pathogens Branch (BSPB)—Special Bacteriology Reference Laboratory (SBRL)