Elizabethkingia is a Gram-negative bacterium in the Flavobacteria family. The bacterium, like the multitude of other species of Flavobacteria, is almost ubiquitous in soils and in water bodies. Occasionally, the species Elizabethkingia meningoseptica occurs as a causative agent of meningitis in premature infants, babies and young children. Since November 2015, a mysterious wave of infection caused by the bacterium Elizabethkingia anophelis has been observed in Wisconsin, USA, and has so far sickened more than 50 people by mid-March 2016.
What is Elizabethkingia?
Elizabethkingia is a Gram-negative, rod-shaped, slightly curved, immobile bacterium in the Flavobacteriaceae family. The bacterium, discovered in 1960 by U.S. bacteriologist Elizabeth O. King, was temporarily given the name Flavobacterium meningosepticum, indicating that the bacterium may be associated with meningitis and sepsis. It was not until 2005 that it was determined that the bacterium, along with another species, established a distinct species of Flavobacteria and was subsequently named Elizabethkingia in honor of its discoverer. At least two subspecies, Elizabethkingia meningoseptica and Elizabethkingia anophelis, are known. The assignment of the bacterium to the Flavobacteria means that they have a yellowish coloration like the other members of the family. The yellowish coloration, caused by the pigment flexirubin, is readily seen in larger colonies of Flavobacteria. Some strains of Flavobacteria live aerobically and others anaerobically. Elizabethkingia is an obligate aerobic bacterium that depends on oxygenation for energy and is nearly ubiquitous in nature, soil, and water.
Occurrence, distribution, and characteristics
As stated above, the microbe Elizabethkingia is found almost ubiquitously in the environment, especially in arable soils and in freshwater or saltwater lakes, as well as in almost all standing waters. It does not differ fundamentally in its occurrence from other members of the large Flavobacteria family. Only in rare cases does the bacterium have facultative pathological effects. Elizabethkingia reproduces exclusively by sprouting, since the bacterium cannot form spores. In established bacterial cultures, the reactions in appropriate detection tests are positive with respect to the enzymes catalase, indole and oxidase, while the reaction to the enzyme urease is negative. This means that colonies of Elizabethkingia have the enzymes tested as positive by self-synthesis, while the enzyme urease is not produced as a result of negative testing. The subspecies Elizabethkingia meningoseptica also occasionally occurs as a nosocomial germ, that is, a hospital-specific germ that is resistant to some of the known antibiotics. The bacterium has the ability to synthesize enzymes such as beta-lactamases and extended beta-lactamases (ESBL), which allow them to deactivate certain antibiotics. Premature infants, babies and young children whose immune systems have been weakened or artificially suppressed are at increased risk of infection. Dialysis patients also carry an increased risk of infection. Typical clinical pictures that can be caused by the germ are meningitis, pneumonia and inflammation of the inner lining of the heart (endocarditis). Sepsis, a systemic spreading inflammation, can also be caused by Elizabethkingia meningoseptica. Hospital equipment, tap water, and contaminated venous catheters can be considered the main routes of infection. There is no direct risk of human-to-human infection.
Significance and function
The flavobacterium Elizabethkingia is as ubiquitous as most other members of the flavobacteria family. That they appear as pathogens is relatively rare. However, no studies have been reported to date that demonstrate association of the bacterium with other bacteria that colonize skin or mucous membranes or are part of the healthy intestinal flora. It is very likely that the obligate aerobic microbes have no immediate and special significance for the body and health of humans.
Diseases and ailments
Despite their near ubiquity, Flavobacteria and also Elizabethkingia are not normally pathogenic with the exception of the bacterium Elizabethkingia meningoseptica, which can cause problems in part as a nosocomial germ, as described above. Since November 2015, a specific germ called Elizabethkingia anophelis has been emerging in Wisconsin, USA. During the period November 1, 2015, to March 16, 2016, 54 individuals over the age of 65 have been confirmed to have contracted the germ in Wisconsin. All of the ill individuals were suffering from another illness at the same time, so it is also highly likely that a weakened or severely compromised immune system facilitated infection in this case. Common symptoms of infection with Elizabethkingia anophelis typically include fever, dyspnea, and chills. Pneumonia presents in most patients. Of the 54 people infected, 15 patients have already died, although the cause of death in each case may be due to another illness also present. Authorities in the U.S. continue to search for the causes of infection. Apparently, Elizabethkingia anophelis responds to certain antibiotics, so efficient treatment options are available. Some circumstantial evidence suggests that the pathogen is transmitted by mosquitoes. A similarly explosive case of a series of infections with Elizabethkingia was delivered a few years ago by a London hospital, in whose intensive care unit 30 of a total of 900 patients were infected with the germ. After a long search, certain taps were identified as the source of infection. Unlike the series of infections in London, which occurred exclusively in a hospital’s intensive care unit, people outside hospitals have also become infected in Wisconsin, complicating the search for the source or sources of infection.
