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Enterobacteriaceae
Citrobacter freundii, one member of the family
Scientific classification
Domain: Bacteria
Phylum: Proteobacteria
Class: Gammaproteobacteria
Order: Enterobacteriales
Family: Enterobacteriaceae
Rahn, 1937

The Enterobacteriaceae is a large family of Gram-negative bacteria that includes, along with many harmless symbionts, many of the more familiar pathogens, such as Salmonella, Escherichia coli, Yersinia pestis, Klebsiella and Shigella. Other disease-causing bacteria in this family include Proteus, Enterobacter, Serratia, and Citrobacter. This family is the only representative in the order Enterobacteriales of the class Gammaproteobacteria in the phylum Proteobacteria.[1] Phylogenetically, in the Enterobacteriales, several peptidoglycan-less insect endosymbionts[citation needed] form a sister clade to the Enterobacteriaceae, but as they are not validly described, this group is not officially a taxon; examples of these species are Sodalis, Buchnera, Wigglesworthia, Baumannia cicadellinicola and Blochmannia, but not former Rickettsias.[2] Members of the Enterobacteriaceae can be trivially referred to as enterobacteria, as several members live in the intestines of animals. In fact, the etymology of the family is enterobacterium with the suffix to designate a family (aceae) — not after the genus Enterobacter (which would be "Enterobacteraceae")— and the type genus is Escherichia.

Characteristics[edit]

Members of the Enterobacteriaceae are rod-shaped, and are typically 1-5 μm in length. They appear as small grey colonies on blood agar. Like other proteobacteria, enterobacteria have Gram-negative stains,[3] and they are facultative anaerobes, fermenting sugars to produce lactic acid and various other end products. Most also reduce nitrate to nitrite, although exceptions exist (e.g. Photorhabdus). Unlike most similar bacteria, enterobacteria generally lack cytochrome C oxidase, although there are exceptions (e.g. Plesiomonas shigelloides). Most have many flagella used to move about, but a few genera are nonmotile. They are not spore-forming. Catalase reactions vary among Enterobacteriaceae.

Many members of this family are a normal part of the gut flora found in the intestines of humans and other animals, while others are found in water or soil, or are parasites on a variety of different animals and plants. Escherichia coli is one of the most important model organisms, and its genetics and biochemistry have been closely studied.

Most members of Enterobacteriaceae have peritrichous, type I fimbriae involved in the adhesion of the bacterial cells to their hosts. Some enterobacteria produce endotoxins. Endotoxins reside in the cell cytoplasm and are released when the cell dies and the cell wall disintegrates. Some members of the Enterobacteriaeceae produce endotoxins that, when released into the bloodstream following cell lysis, cause a systemic inflammatory and vasodilatory response. The most severe form of this is known as endotoxic shock, which can be rapidly fatal.

Identification[edit]

To identify different genera of Enterobacteriaceae, a microbiologist may run a series of tests in the lab. These include:[4]

  • Phenol red
  • Tryptone broth
  • Phenylalanine agar for detection of production of deaminase, which converts phenylalanine to phenylpyruvic acid
  • Methyl red or Voges-Proskauer tests depend on the digestion of glucose. The methyl red tests for acid endproducts. The Voges Proskauer tests for the production of acetylmethylcarbinol.
  • Catalase test on nutrient agar tests for the production of catalase enzyme, which splits hydrogen peroxide and releases oxygen gas.
  • Oxidase test on nutrient agar tests for the production of the enzyme oxidase, which reacts with an aromatic amine to produce a purple color.
  • Nutrient gelatin tests to detect activity of the enzyme gelatinase.

In a clinical setting, three species make up 80 to 95% of all isolates identified. These are Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis.

Antibiotic resistance[edit]

Several Enterobacteriacea strains have been isolated which are resistant to antibiotics including carbapenem, which are often claimed as "the last line of antibiotic defense" against resistant organisms. For instance, some Klebsiella pneumonia strains are carbapenem resistant.[5]

Examples/classification[edit]

The following inexhaustive list details bacterial genera classified as members of Enterobacteriaceae.

Genera[edit]

References[edit]

  1. ^ Don J. Brenner, Noel R. Krieg, James T. Staley (July 26, 2005) [1984 (Williams & Wilkins)]. George M. Garrity, ed. The Gammaproteobacteria. Bergey's Manual of Systematic Bacteriology 2B (2nd ed.). New York: Springer. p. 1108. ISBN 978-0-387-24144-9. British Library no. GBA561951. 
  2. ^ Williams, K. P.; Gillespie, J. J.; Sobral, B. W. S.; Nordberg, E. K.; Snyder, E. E.; Shallom, J. M.; Dickerman, A. W. (2010). "Phylogeny of Gammaproteobacteria". Journal of Bacteriology 192 (9): 2305–2314. doi:10.1128/JB.01480-09. PMC 2863478. PMID 20207755.  edit
  3. ^ "Dorlands Medical Dictionary:Enterobacteriaceae". 
  4. ^ MacFaddin, Jean F. Biochemical Tests for Identification of Medical Bacteria. Williams & Wilkins, 1980, p 441.
  5. ^ Centers for Disease Control and Prevention - Klebsiella Quotation: "Increasingly, Klebsiella bacteria have developed antimicrobial resistance, most recently to the class of antibiotics known as carbapenems."

External links[edit]

  • Enterobacteriaceae genomes and related information at PATRIC, a Bioinformatics Resource Center funded by NIAID
  • Evaluation of new computer-enhanced identification program for microorganisms: adaptation of BioBASE for identification of members of the family Enterobacteriaceae [1]
  • Brown, A.E. (2009). Benson's microbiological applications: laboratory manual in general microbiology. New York: McGraw- Hill.

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Enterobacteriaceae — Please support Wikipedia.
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80 news items

 
7thSpace Interactive (press release)
Wed, 09 Apr 2014 07:26:15 -0700

On April 2, our hospital confirmed from his urine specimen that he had carbapenem-resistant Enterobacteriaceae (CRE) with OXA-carbapenemase, an imported infected case. The hospital later confirmed that two more patients (a male and a female, aged 79 ...
 
7thSpace Interactive (press release)
Thu, 17 Apr 2014 02:45:00 -0700

Update on case of carbapenem-resistant Enterobacteriaceae with OXA and NDM carbapenemase in Queen Elizabeth Hospital. Hong Kong (HKSAR) - The following is issued on behalf of the Hospital Authority: The spokesperson for Queen Elizabeth Hospital ...
 
The Herald | HeraldOnline.com (press release)
Mon, 21 Apr 2014 05:22:30 -0700

The addition of tazobactam broadens coverage to include most Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (E. coli), Klebsiella pneumoniae, and other Enterobacteriaceae. Ceftolozane/tazobactam is being developed for the potential ...

Medscape

Medscape
Tue, 15 Apr 2014 10:11:57 -0700

CAPE TOWN, South Africa — A biochemical test that can rapidly identify extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae in a blood culture is 100% accurate on all fronts, new research shows. It could soon be ready for clinical use.
 
Sioux City Journal
Wed, 16 Apr 2014 11:55:47 -0700

Lethal carbapenem-resistant Enterobacteriaceae (CRE) outbreaks began on the East Coast and have stricken hospitals and long-term care facilities across the country. So far, Lamptey said Mercy hasn't had a case of CRE. “Those are very bad organisms.

Food Safety Magazine

Food Safety Magazine
Tue, 15 Apr 2014 10:43:05 -0700

In addition to these three, there are a number of other microorganisms, or groups of microorganisms potentially associated with food on the list, including Enterococcus, Streptococcus, Staphylococcus and the Enterobacteriaceae. The CDC list also ...

Guardian Liberty Voice

Guardian Liberty Voice
Mon, 14 Apr 2014 00:07:30 -0700

The samples were examined to determine if any ESBL-producing Enterobacteriaceae, a gram-negative bacteria family that includes Salmonella, E. coli and Klebsiella, was present. The researchers found that 6.5 percent of the hospital kitchen cutting ...
 
Science Codex
Tue, 08 Apr 2014 07:09:02 -0700

These samples were tested for the presence of ESBL-producing Enterobacteriaceae, a family of gram-negative bacteria that includes Salmonella, E. coli and Klebsiella. In testing the cutting boards, researchers found that 6.5 percent of hospital cutting ...
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