Elizabethkingia meningoseptica

Two species of Elizabethkingia have recently been found to be abundant on the leaf and root surfaces of the tropical tree Gnetum gnemon in Malaysia.[5] Their role in the biology of the plant is unknown. Several other species of tropical trees studied did not have Elizabethkingia present on their leaves or roots, suggesting a host-specific relationship with Gnetum.

Under a microscope, E. meningoseptica appears as slender, slightly curved rods which are nonmotile and are negative by Gram stain. They do not form spores, and require oxygen to survive. E. meningoseptica is positive by the catalase test, the oxidase test, and the indole test. It is negative by the urease test. In general, it is negative by the nitrate reductase test, although some strains are positive.[6]

E. meningoseptica grows well on blood agar and chocolate agar. Colonies are very pale yellow and may not be easily evident at 24 hours. Strains growing better at 40 °C are mostly associated with invasive meningitis.[7] Often, a greyish discoloration is seen around the colonies on blood agar due to proteases and gelatinase. E. meningoseptica grows poorly on MacConkey agar and is considered a glucose oxidizer.[8] Most strains do not grow on colistin nalidixic acid agar because, although they are resistant to colistin, they are susceptible to quinolones such as nalidixic acid.

E. meningoseptica may show colistin-resistant and vancomycin-sensitive growth, which is paradoxic for a Gram-negative bacterium, but resembles Burkholderia cepacia, which is also a nonfermenter and does not grow well on MacConkey agar. These two can be distinguished by the indole test or the Pyr test, both of which should be clearly negative for B. cepacia and positive for E. meningoseptica. Automated bacterial identification system results should be observed with caution, especially when a patient with Gram-negative bacteremia does not improve with broad-spectrum antibiotic therapy, because several bacteria, including Aeromonas salmonicida (mistaken by ID32 GN[6]) and Sphingobacterium spp. (mistaken by Vitek 2[9]), may be confused with this bacterium, especially the atypical ones. However, unlike many other Aeromonas species such as A. hydrophila and A. punctata, A. salmonicida is indole negative, which can help in distinguishing it in doubtful cases. An automated but so far relatively reliable Rapid NF plus system and API Zym systems use an array of biochemical tests for better identification of nonfermenters and other bacteria and can specifically identify E. meningoseptica.

E. meningoseptica predominantly causes outbreaks of meningitis in premature newborns and infants in neonatal intensive care units of underdeveloped countries.

Some of the outbreaks have been linked to sources such as contaminated lipid stock bottles, contaminated venous catheter lines and nutritional solution, and tap water. The bacterium is also a rare cause of nosocomial pneumonia, endocarditis, postoperative bacteremia, and meningitis in immunocompromised adults. Only recently has it also been found to cause soft-tissue infection and sepsis in the immunocompetent[9] and in a case of a fatal necrotizing fasciitis in a diabetic patient.[10]

Some 48 cases of Elizabethkingia infection resulting in 17 fatalities were reported in Wisconsin over a 5-month period beginning in November 2015.[11]

At the 2006 meeting of the International Committee on Systematics of Prokaryotes, the organization's subcommittee on the taxonomy of Flavobacterium and Cytophaga-like bacteria named J.-F. Bernardet and B. Bruun as two key authorities on this bacterium.[14]

• Flavobacterium meningosepticum King, 1959 (Approved Lists, 1980)
• Chryseobacterium meningosepticum (King, 1959) Vandamme et al., 1994
• Elizabethkingia meningoseptica (King, 1959) Kim et al., 2005

• Wisconsin 2016 Elizabethkingia anophelis outbreak

• NBC News
• Type strain of Elizabethkingia meningoseptica at BacDive - the Bacterial Diversity Metadatabase