Proteus is the name for a type of bacteria. The microorganisms are found in the intestines of humans and animals and can cause disease.
What are proteus bacteria?
The name Proteus is used to describe a gram-negative genus of bacteria. The name Proteus goes back to the ancient Greek sea god Proteus. This was described by the poet Homer in his Odyssey as outwardly extremely versatile. Proteus bacteria are members of the Enterobacteriaceae family. They are equipped with flagella around their cells and are multiform. The term Proteus comes from the German pathologist and bacteriologist Gustav Hauser (1856-1935), who gained fame through the discovery of the bacterial species Proteus mirabilis. Proteus mirabilis is considered the most medically important Proteus species. Other members of this genus include Proteus penneri, Proteus vulgaris, Proteus hauseri and Proteus myxofaciens. In this respect, Proteus myxofaciens differs significantly from the rest of the genus species in its genetics. As a pathogen, this species is the only one of its genus that does not play a role. Although Proteus morganii, Proteus rettgerti, and Proteus inconstans also bear the name Proteus, they are no longer considered to belong to the genus Proteus based on new DNA analyses. Instead, they now belong to the genera Providencia and Morganella.
Occurrence, distribution, and characteristics
Resident Proteus bacteria, which are considered undemanding, are mostly saprophytes in waters and soil containing organic material. This can be the excreta of living organisms or dead biomass. In addition, Proteus bacteria are found in the intestines of humans as well as in those of animals. In nature, the microorganisms are important in putrefaction processes and the aerobic decomposition of proteins. The cells of Proteus bacteria have the shape of rods. They have a diameter between 0.4 and 0.8 µm. The length of the microorganisms is considered variable. Due to their peritrichous flagella, Proteus bacteria are also extremely mobile. The germs do not require oxygen for their metabolism. The energy metabolism of the bacteria is oxidative and fermentative. The partly parasitic microorganisms obtain their energy from chemical reactions of substances from their environment. They mostly use sugar as an energy source. In addition, members of the Proteus genus are catalase-positive and oxidase-negative. Furthermore, they have the property of reducing nitrate to nitrite. There is a greater similarity between the Proteus genus and the bacterial genera Morganella and Providencia. Thus, phenylalanine deaminase is produced by all three species. In addition, all three genera are unable to metabolize malonate or produce arginine decarboxylase. In addition, they cannot produce acid in L-arabinose metabolism, D-sorbitol and dulcitol. Other characteristic properties of the Proteus genus include the formation of hydrogen sulfide from amino acids containing sulfur, liquefaction of gelatin, and cleavage of corn oil fats and urea. Also typical for the Proteus bacteria is their swarming behavior. So-called swarm cells, which are densely flagellated cells, are formed on gel food soils. On the gel surface, they move on a thin liquid layer formed by syneresis. If the bacterial colony is quite narrow at the beginning, it can rapidly spread over the surface of the gel as it progresses. As swarming alternates with local proliferation, the gel surface is eventually covered by an extensive Proteus colony. Due to their swarming behavior, Proteus bacteria are usually easily detectable. In addition, they degrade glucose under the formation of acid. In the case of serological examination, several antigens can be differentiated, allowing the bacteria to be subdivided into serotypes.
Diseases and symptoms
Proteus bacteria are among the opportunistic pathogens. Within the intestine, they have no pathogenic significance and adapt to the intestinal flora. However, if the germ can colonize another organ, there is a risk of infection. Some indole-positive Proteus strains also belong to the hospital germs and cause infections, especially in people with a lowered immune system.The most common diseases caused by Proteus bacteria include urinary tract infections such as cystitis. In contrast, infections of other organs are much rarer, such as peritonitis, infections of the bile ducts, gastroenteritis, inflammation of the prostate gland, inflammation of the renal pelvis, empyema (encapsulated collection of pus) or meningitis. Sometimes severe courses such as blood poisoning (sepsis) are also within the realm of possibility. Treatment of diseases caused by Proteus bacteria usually involves the administration of antibiotics. For example, most Proteus species can be successfully treated with broad-spectrum cephalosporins, which are second- and third-generation antibiotics, and quinolones. If it is an uncomplicated urinary tract infection, cotrimoxazole is also considered helpful. In most cases, the species Proteus mirabilis causes the infectious disease. Against this bacterium, cefazolin and ampicillin are promising. First- and second-generation cephalosporins and aminopenicillins are not considered effective against Proteus vulgaris because the bacterium is resistant to these antibiotics. In contrast, other antibiotics, such as carbapanems or cefotaxime, as well as beta-lactamase inhibitors, have a positive effect. All Proteus species are naturally resistant to antibiotic agents such as tetracyclines, nitrofurantoin, colistin and tigecycline. However, the resistance of Proteus bacteria varies over time as well as from region to region, so obtaining an antibiogram may be useful.
