Gram-negative
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...
,
rod-shaped
A bacillus (), also called a bacilliform bacterium or often just a rod (when the context makes the sense clear), is a rod-shaped bacterium or archaeon. Bacilli are found in many different taxonomic groups of bacteria. However, the name '' Baci ...
bacterium
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were amon ...
widely distributed in nature (e.g. fresh water, salt water, or soil). It may be normally present in
fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...
and
frogs
A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" '' Triadobatrachus'' is ...
; it may be isolated from chronic infectious states, as in the sputum of cystic fibrosis patients. In 1959, American
bacteriologist
A bacteriologist is a microbiologist, or similarly trained professional, in bacteriology -- a subdivision of microbiology that studies bacteria, typically pathogenic ones. Bacteriologists are interested in studying and learning about bacteria, ...
Kingella kingae
''Kingella kingae'' is a species of Gram-negative facultative anaerobic β-hemolytic coccobacilli. First isolated in 1960 by Elizabeth O. King, it was not recognized as a significant cause of infection in young children until the 1990s, when ...
'' in 1960) was studying unclassified bacteria associated with pediatric meningitis at the
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...
in Atlanta, when she isolated an organism (CDC group IIa) that she named ''Flavobacterium meningosepticum'' (''Flavobacterium'' means "the yellow
bacillus
''Bacillus'' (Latin "stick") is a genus of Gram-positive, rod-shaped bacteria, a member of the phylum '' Bacillota'', with 266 named species. The term is also used to describe the shape (rod) of other so-shaped bacteria; and the plural ''Bacill ...
" in
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
; ''meningosepticum'' likewise means "associated with meningitis and
sepsis
Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...
"). In 1994, it was reclassified in the
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
''Chryseobacterium'' and renamed ''Chryseobacterium meningosepticum''(''chryseos'' = "golden" in
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
, so ''Chryseobacterium'' means a golden/yellow rod similar to ''Flavobacterium''). In 2005, a
16S rRNA 16S rRNA may refer to:
* 16S ribosomal RNA
16 S ribosomal RNA (or 16 S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome ( SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure.
The g ...
phylogenetic tree of Chryseobacteria showed that ''C. meningosepticum'' along with ''C. miricola'' (which was reported to have been isolated from Russian space station
Mir
''Mir'' (russian: Мир, ; ) was a space station that operated in low Earth orbit from 1986 to 2001, operated by the Soviet Union and later by Russia. ''Mir'' was the first modular space station and was assembled in orbit from 1986 to&n ...
in 2001 and placed in the genus ''Chryseobacterium'' in 2003) were close to each other but outside the tree of the rest of the Chryseobacteria and were then placed in a new genus '' Elizabethkingia'' named after the original discoverer of ''F. meningosepticum''.
Presence in plants
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. 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''.
Microbiology
Under a microscope, ''E. meningoseptica'' appears as slender, slightly curved rods which are nonmotile and are negative by
Gram stain
In microbiology and bacteriology, Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. The name comes from the Danish b ...
. They do not form spores, and require oxygen to survive. ''E. meningoseptica'' is positive by the
catalase test
Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting t ...
, the
oxidase test
The oxidase test is used to determine if an organism possesses the cytochrome c oxidase enzyme. The test is used as an aid for the differentiation of ''Neisseria'', ''Moraxella'', ''Campylobacter'' and ''Pasteurella'' species (oxidase positive). It ...
chocolate agar
Chocolate agar (CHOC) or chocolate blood agar (CBA), is a nonselective, enriched growth medium used for isolation of pathogenic bacteria. It is a variant of the blood agar plate, containing red blood cells that have been lysed by slowly heating ...
. 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. Often, a greyish discoloration is seen around the colonies on blood agar due to
protease
A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the ...
s and
gelatinase Gelatinases are enzymes capable of degrading gelatin.
Gelatinases are expressed in several bacteria including ''Pseudomonas aeruginosa'' and ''Serratia marcescens''.
In humans, the gelatinases are matrix metalloproteinases
Matrix metalloprot ...
. ''E. meningoseptica'' grows poorly on
MacConkey agar
MacConkey agar is a selective and differential culture medium for bacteria. It is designed to selectively isolate Gram-negative and enteric (normally found in the intestinal tract) bacteria and differentiate them based on lactose fermentation. ...
and is considered a glucose oxidizer. Most strains do not grow on colistin nalidixic acid agar because, although they are resistant to
colistin
Colistin, also known as polymyxin E, is an antibiotic medication used as a last-resort treatment for multidrug-resistant Gram-negative infections including pneumonia. These may involve bacteria such as ''Pseudomonas aeruginosa'', '' Klebsiella ...
, they are susceptible to
quinolones
Quinolone may refer to:
* 2-Quinolone
* 4-Quinolone
4-Quinolone is an organic compound derived from quinoline. It and 2-quinolone are the two most important parent (meaning simplified) quinolones. 4-Quinolone exists in equilibrium with a mino ...
such as
nalidixic acid
Nalidixic acid (tradenames Nevigramon, NegGram, Wintomylon and WIN 18,320) is the first of the synthetic quinolone antibiotics.
In a technical sense, it is a naphthyridone, not a quinolone: its ring structure is a 1,8-naphthyridine nucleus that ...
.
''E. meningoseptica'' may show colistin-resistant and
vancomycin
Vancomycin is a glycopeptide antibiotic medication used to treat a number of bacterial infections. It is recommended intravenously as a treatment for complicated skin infections, bloodstream infections, endocarditis, bone and joint infections, ...
-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
''Aeromonas salmonicida'' is a pathogenic bacterium that severely impacts salmonid populations and other species. It was first discovered in a Bavarian brown trout hatchery by Emmerich and Weibel in 1894. ''Aeromonas salmonicida's'' ability to in ...
''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
Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves. Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or the ...
immunocompromised
Immunodeficiency, also known as immunocompromisation, is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors that a ...
adults. Only recently has it also been found to cause soft-tissue infection and sepsis in the
immunocompetent
In immunology, immunocompetence is the ability of the body to produce a normal immune response following exposure to an antigen. Immunocompetence is the opposite of immunodeficiency (also known as ''immuno-incompetence'' or being ''immuno-compro ...
and in a case of a fatal
necrotizing fasciitis
Necrotizing fasciitis (NF), also known as flesh-eating disease, is a bacterial infection that results in the death of parts of the body's soft tissue. It is a severe disease of sudden onset that spreads rapidly. Symptoms usually include red or p ...
in a diabetic patient.
Some 48 cases of ''Elizabethkingia'' infection resulting in 17 fatalities were reported in Wisconsin over a 5-month period beginning in November 2015.
antibiotics
An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention o ...
typically prescribed for treating Gram-negative bacterial infections, including extended-spectrum beta-lactam agents (due to production by most strains of two betalactamases: one ESBL and one class B carbapenem-hydrolyzing metallolactamase),
aminoglycosides
Aminoglycoside is a medicinal and bacteriologic category of traditional Gram-negative antibacterial medications that inhibit protein synthesis and contain as a portion of the molecule an amino-modified glycoside ( sugar). The term can also refer ...
,
tetracycline
Tetracycline, sold under various brand names, is an oral antibiotic in the tetracyclines family of medications, used to treat a number of infections, including acne, cholera, brucellosis, plague, malaria, and syphilis.
Common side effects in ...
, and chloramphenicol. Though vancomycin has been used in the past, its high
Minimum inhibitory concentration In microbiology, the minimum inhibitory concentration (MIC) is the lowest concentration of a chemical, usually a drug, which prevents visible growth of a bacterium or bacteria. MIC depends on the microorganism, the affected human being (in vivo only ...
(16 µg/ml) has led to a search for alternatives, especially for meningitis. Presently,
ciprofloxacin
Ciprofloxacin is a fluoroquinolone antibiotic used to treat a number of bacterial infections. This includes bone and joint infections, intra abdominal infections, certain types of infectious diarrhea, respiratory tract infections, skin inf ...
,
minocycline
Minocycline, sold under the brand name Minocin among others, is a tetracycline antibiotic medication used to treat a number of bacterial infections such as pneumonia. It is generally less preferred than the tetracycline doxycycline. It is also ...
,
trimethoprim-sulfamethoxazole
Trimethoprim/sulfamethoxazole, sold under the brand name Bactrim among others, is a fixed-dose combination antibiotic medication used to treat a variety of bacterial infections. It consists of one part trimethoprim to five parts sulfamethoxaz ...
,
rifampin
Rifampicin, also known as rifampin, is an ansamycin antibiotic used to treat several types of bacterial infections, including tuberculosis (TB), ''Mycobacterium avium'' complex, leprosy, and Legionnaires’ disease. It is almost always used tog ...
, and novobiocin are considered good alternatives. Most of these are classic drugs for Gram-positive bacteria and not routinely tested on Gram-negative bacteria.
Predictors of poor outcome
Hypoalbuminemia, increased pulse rate at the onset of infection, and central venous line infection were associated with a poor outcome.
Resource persons
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.