''Klebsiella aerogenes'', previously known as ''Enterobacter aerogenes'', is a
Gram-negative
Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists ...
,
oxidase
In biochemistry, an oxidase is an oxidoreductase (any enzyme that catalyzes a redox reaction) that uses dioxygen (O2) as the electron acceptor. In reactions involving donation of a hydrogen atom, oxygen is reduced to water (H2O) or hydrogen peroxid ...
-negative,
catalase
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 ...
-positive,
citrate
Citric acid is an organic compound with the formula . It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry
Biochemistry, or biological chemistry, is the study of chemical processes within and relati ...
-positive,
indole
Indole is an organic compound with the formula . Indole is classified as an aromatic heterocycle. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered pyrrole ring. Indoles are derivatives of indole ...
-negative,
rod-shaped
Bacterial cellular morphologies are the shapes that are characteristic of various types of bacteria and often key to their identification. Their direct examination under a light microscope enables the classification of these bacteria (and archae ...
bacterium
Bacteria (; : 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 among the ...
. Capable of motility via peritrichous flagella, it is approximately one to three microns in length.
''Klebsiella aerogenes'' is a
nosocomial
A hospital-acquired infection, also known as a nosocomial infection (from the Greek , meaning "hospital"), is an infection that is acquired in a hospital or other healthcare facility. To emphasize both hospital and nonhospital settings, it is s ...
,
pathogenic bacterium
Pathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and many are beneficial but others can cause infectious diseases. The number of t ...
that causes
opportunistic infection
An opportunistic infection is an infection that occurs most commonly in individuals with an immunodeficiency disorder and acts more severe on those with a weakened immune system. These types of infections are considered serious and can be caused b ...
s of most types. Infections are generally sensitive to antibiotics designed for this bacteria class, though complicated by inducible resistance mechanisms, particularly
lactamase
Beta-lactamases (β-lactamases) are enzymes () produced by bacteria that provide multi-resistance to beta-lactam antibiotics such as penicillins, cephalosporins, cephamycins, monobactams and carbapenems (ertapenem), although carbapenems ...
; infections accordingly become quickly resistant to standard antibiotics during treatment, necessitating a change in antibiotic to avoid worsening of the
sepsis
Sepsis is a potentially life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs.
This initial stage of sepsis is followed by suppression of the immune system. Common signs and s ...
.
Some infections caused by ''K. aerogenes'' result from specific
antibiotic
An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...
treatments,
venous catheter
In medicine, a peripheral venous catheter, peripheral venous line, peripheral venous access catheter, or peripheral intravenous catheter, is a catheter (small, flexible tube) placed into a peripheral vein for venous access to administer intrave ...
insertions, and/or surgical procedures. It is generally found in the human
gastrointestinal tract
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the Digestion, digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascula ...
and does not generally cause disease in healthy individuals. It has been found to live in various wastes, hygiene chemicals, and soil. It also has some commercial significance; experiments using
molasses
Molasses () is a viscous byproduct, principally obtained from the refining of sugarcane or sugar beet juice into sugar. Molasses varies in the amount of sugar, the method of extraction, and the age of the plant. Sugarcane molasses is usuall ...
as the substrate have produced hydrogen gas.
''K. aerogenes'' is an outstanding hydrogen producer. It is an
anaerobic facultative and
mesophilic
A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, with an optimum growth range from . The optimum growth temperature for these organisms is 37 °C (about 99 °F). The term is mainly applied ...
bacterium that can consume different sugars, and—unlike the cultivation of strict anaerobes—there is no requirement to remove all oxygen from the fermenter. Along with a short doubling time, it has a high hydrogen productivity and evolution rate. Furthermore, its hydrogen production is not inhibited at high hydrogen partial pressures. Its hydrogen yield is lower than that of such strict anaerobes as ''Clostridia'': strictly anaerobic bacteria produce a theoretical maximum of 4 mol H
2/mol glucose, while such facultative anaerobic bacteria as ''K. aerogenes'' theoretically yield a maximum of 2 mol H
2/mol glucose.
''K. aerogenes'' may spoil maple sap and syrup.
Owing to diverse metabolites—acids and alcohols—produced by such a strain in conjunction with its ability to utilize different sugars, the metabolism and growth of ''K. aerogenes'' can vary significantly with the conditions.
Biochemical identification test results
References
External links
*
*
Type strain of ''Klebsiella aerogenes'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q644487
Enterobacteriaceae
Pathogenic bacteria
Bacteria described in 1960