Enterobacter is the name given to a group of bacteria belonging to the, very large number of species, Enterobacteriaceae family. It is a group of Gram-negative, flagellated rod-shaped bacteria that live facultatively anaerobically and are part of the intestinal flora in the gut. A few species are pathogenic and can cause meningitis, respiratory tract infections, and urinary tract infections.
What are enterobacter?
Enterobacter is a Gram-negative species of normally flagellated rod-shaped bacteria in the very large Enterobacteriaceae family. The bacteria are almost ubiquitous and form part of the healthy intestinal flora in the human gut in association with other bacteria. However, their share of the total intestinal flora is only about 1 percent. The bacteria derive most of their energy from organic matter, which they break down and use 2,3-butanediol fermentation to produce energy under anaerobic conditions. Under aerobic conditions, they are able to obtain energy via oxidation of organic matter and its degradation to carbon dioxide and water. A characteristic of all Enterobacter species is that none of its metabolic pathways produce acids such as lactic or acetic acid. A few species of Enterobacter are pathogenic and occur as causative agents of urinary tract and respiratory tract infections. In very rare cases, they can also cause meningitis. The majority of Enterobacter species are either non-pathogenic or facultatively pathogenic if by some circumstance they enter the bloodstream or internal organs directly, or if the immune system is weakened or artificially suppressed (suppressed). In recent years, Enterobacter species have been increasingly identified as contributors to hospital-acquired infections (nosocomial infections).
Occurrence, distribution, and characteristics
Gram-negative Enterobacter from the Enterobacteriaceae family have taken over many habitats where they persist as free-living bacteria. The so-called Gram stain, which goes back to the Danish bacteriologist Hans Christian Gram, is used to classify bacteria into Gram-positive and Gram-negative species. It is a specific staining that provides information under the light microscope as to whether the bacterial wall is composed of a single layer of murein (peptidoglycan) or multiple layers. In the former case, the staining reacts gram-positive and in the latter case gram-negative. Enterobacter are found in food, in plants, in soil and in water. As intestinal bacteria, they usually live in association with many other bacterial species. The rod-shaped bacteria of the species Enterobacter are very small, ranging from 0.6 to 1.0 micrometers in diameter and 1.2 to 3.0 micrometers in length. Their common feature is peritrichous flagellation, which is a flagellation over the entire body that almost all Enterobacter species exhibit. The flagella, also called flagella, consist of thread-like structures with which the bacteria can actively move by means of propeller-like movements. Another feature, which also serves to distinguish individual species, are so-called antigens that Enterobacter present on their flagella. In most cases, these are type H antigens, which consist of thermolabile flagellar proteins and which the bacterium can remodel in order to evade the immune system as far as possible. The antigens provoke an immune response in the form of specific antibodies that can bind to the antigen and trigger further immune responses. Some Enterobacter species can envelop themselves with a capsule of mucilaginous polysaccharides to evade macrophage attack and thus phagocytosis. A distinctive feature of Enterobacter is their metabolism, which allows them to obtain energy via the aerobic respiratory cycle (citrate cycle) or via anaerobic fermentation metabolism. In the latter case, alcohols and butanediol are produced as metabolic products. Enterobacter can use citrate as their sole carbon source. The chemoorganotrophic lifestyle makes Enterobacter appear slightly parasitic to neutral in its capacity as an intestinal bacterium. In particular, the utilization of undigested food residues in the colon justifies the assumption that the bacteria do not cause any harm to human metabolism and also do not parasitically extract food, since any “residue utilization” in the colon cannot be classified as parasitic due to the lack of absorptive capacity of the colon epithelium.Bacteria of the genus Enterobacter, which form part of the intestinal flora, can in principle be classified as nonpathogenic or as facultative pathogenic unless they encounter a weakened or artificially suppressed immune system (immunosuppression) and enter the bloodstream, through which they can infect other organs.
Significance and function
Enterobacter lives in the intestine in association with a wide variety of other bacteria and other microorganisms. Enterobacter is thus part of the healthy intestinal flora. As an overall system, the intestinal flora performs important health-related tasks and functions. Digestion is supported by enzymatic breakdown of certain food components and intestinal peristalsis is stimulated. The supply of the body with vitamins such as thiamine, riboflavin, B12 and other important micronutrients is particularly important for health. In addition, the healthy intestinal flora exerts a modulating influence on the immune system. The immune system is constantly challenged and kept “in exercise”. Allergic reactions and autoimmune reactions tend to be reduced. It is very difficult to determine what proportion of the positive properties of the intestinal flora can be attributed to the account of Enterobacter. It is very likely that the beneficial properties of the nonpathogenic or the only facultatively pathogenic species clearly outweigh the otherwise parasitic lifestyle.
Diseases and ailments
A few subspecies of Enterobacter, such as E. aerogenes, E. cloacae, and Cronobacter sakazakii, may, in rather rare cases, act as causative agents of respiratory or urinary tract infections when favorable conditions for infection are present and the immune system is simultaneously weakened or artificially suppressed. In some cases, Enterobacter have also been identified as the causative agent of meningitis. Nosocomial infections associated with certain types of Enterobacter have been reported in hospitals. Observance of basic hygiene significantly reduces the risks of infection. By basic hygiene is meant especially hand washing after going to the toilet. Hygienic conditions in the bathroom and toilet are also part of basic hygiene. In the case of contaminated food, heating to at least 70 degrees kills Enterobacter and renders the bacteria harmless. Basic control of Enterobacter bacteria is not advisable, since Enterobacter are a normal part of the intestinal flora and it is not sufficiently known whether and, if so, what benefits they have for humans. In particular, the specific effects of nonpathogenic Enterobacter species on intestinal peristalsis, lipid and carbohydrate metabolism, and electrolyte balance have not been thoroughly elucidated.
