Enterobacter is a genus of common Gram-negative, facultatively anaerobic, rod-shaped, non-spore-forming bacteria of the family Enterobacteriaceae. Cultures are found in soil, water, sewage, feces and gut environments. It is the type genus of the order Enterobacterales.
One clinically important species from this genus is E. cloacae.
Researchers in 2018 reported, after detecting the presence on the International Space Station (ISS) of five Enterobacter bugandensis bacterial strains, none pathogenic to humans, that on ISS should be carefully monitored to continue assuring a medically healthy environment for the astronauts.
Biochemical characteristics
The genus
Enterobacter ferments lactose with gas production during a 48-hour incubation at 35-37 °C in the presence of bile salts and detergents. It is
Oxidase test-negative,
Indole test-negative, and
urease-variable.
[Russo Thomas A, Johnson James R, "Chapter 143. Diseases Caused by Gram-Negative Enteric Bacilli" (Chapter). Fauci AS, Braunwald E, Kasper DL, Hauser SL, Longo DL, Jameson JL, Loscalzo J: Harrison's Principles of Internal Medicine, 17e: [1]]
Virulent characteristics
For Enterobacter species, the flagella is used for adhesion,
biofilm formation, and protein export as well as motility. Between the strains, the microbial genus produces endotoxins unique to the species.
As a gram negative bacterium, the lipopolysaccharide capsule helps to avoid phagocytosis and can initiate inflammatory response.
Symptoms
In patients, pathogenic strains were found in the sputum, blood, wounds, and stool. Enterobacter is associated with common nosocomial infections including respiratory, endocarditis, bacteremia, urinary tract infections, osteomyelitis, among others.
Enterobacter bacteremia presents as fever but can progress to SIRS and shock.
For Enterobacter pneumonia, symptoms include coughing and shortness of breath.
Treatment
Treatment is dependent on local trends of antibiotic resistance.
Enterobacter huaxiensis and
Enterobacter chuandaensis are two recently discovered species that exhibit especially antibiotic resistant characteristics.
Cefepime, a fourth-generation cephalosporin from the β-Lactam antibiotic class. Imipenem (a carbapenem) is often the antibiotic of choice. such as amikacin have been found to be very effective, as well.
Linked to obesity
A 2012 study has shown that the presence of
Enterobacter cloacae B29 in the gut of a morbidly obese individual may have contributed to the patient's
obesity. Reduction of the bacterial load within the patient's gut, from 35%
E. cloacae B29 to non-detectable levels, was associated with a parallel reduction in
endotoxin load in the patient and a concomitant, significant reduction in weight.
Furthermore, the same bacterial strain, isolated from the patient, induced
obesity and insulin resistance in germfree C57BL/6J mice that were being fed a high-fat diet. The study concludes that
E. cloacae B29 may contribute to
obesity in its human hosts through an
endotoxin-induced,
inflammation-mediated mechanism.
Davin-Regli, A., Lavigne, J. P., & Pagès, J. M. (2019). Enterobacter spp.: Update on Taxonomy, Clinical Aspects, and Emerging Antimicrobial Resistance. Clinical microbiology reviews, 32(4), e00002-19. https://doi.org/10.1128/CMR.00002-19
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