Morganella morganii is a gram negative, rod-shaped bacteria that is naturally occurring in the human gut. It is a motile, aerobic, facultative anaerobic, and a member of the Enterobactiaceae. This bacteria is usually grouped within the genus Proteus as these two genera do share many common characteristics. However, there are some very different traits in these two genera. One of the biggest differences is that swarming in Morganella does not occur, unlike that of Proteus. As stated above, this bacteria is a common inhabitant in the human gut, specifically the colon, but it is also present in water and soil. Morganella is the common culprit for many different diseases including, urinary tract infections, summer diarrhea and nosocomial infectionss (O'Hara et al., 2000). Morganella is an opportunistic invader and will take advantage of a compromised immune system. Accordingly, Morganella infection is prevalent in hospital settings after a surgery, or throughout the healing of a serious wound (Kim et al., 2007).
Morganella is a gram negative bacteria that are shaped as straight rods. These rods are usually between 0.6 and 0.7 um in diameter and 1.0 to 1.8 um in length. Morganella is both motile and non-motile depending on the environmental temperature at which it is present. Most bacteria of this genera form flagella at temperatures below 30 degrees Celsius, allowing for rapid movement. In environments above 30 degrees Celsius, Morganella usually will not form the flagella. Unlike some of its close ancestors this bacteria does not swarm (O'Hara et al., 2000).
M. morganii is present in the human gut, specifically in the colon. It does have the ability to enter the urethra, which is where it can cause urinary tract infections but this is mostly seen in women. Morganella is also present in soil and water and has been seen in other mammals, such as dogs and cats. Additionally, Morganella has been known to cause the death of chickens. When the host’s immune system is suppressed, M. morganii will rapidly invade the host and also cause specific IgA responses and as well as cause an the increase in the volume of Peyer’s patches. M. morganii is isolated much like the other Enterobacteriaceae. It is cultured from fecal specimen and is often enriched using tetrathioate and selenite that are added to nutrient broth. It is differentiable from Proteus in that its is urease and indole positive, does not swarm, and is negative for most of the biochemical reactions that are seen with the Proteus species (O'Hara et al., 2000).
Morganella is naturally occurring in the flora of the gut and is not antagonistic until a traumatic event of the host. Due to its highly mobile state, Morganella is able to rapidly colonize the gut. Coupled with enlargement of the Peyer’s patches in the gut and specific IgA responses, it is able to change the environment of the host very quickly. This bacterium is also known to invade the urinary tract. Since the bacteria is urease positive, it can hydrolyze urea in the urine to form ammonia - leading to a rise in the pH of the urine. This can have many adverse effects including the formation of stones causing renal damage, and it can also lead to a urinary tract infection (Manos & Belas, 2006).
Diseases and Parasites
As an opportunistic secondary invader that takes advantage of a compromised immune system, Morganella can be a causative agent of many nosocomial infections, including urinary tract infections and wound and blood infections. As a result, there are many unique Morganella cases and it is difficult to predict when a Morganella infection will occur (O'Hara et al., 2000). This bacteria has many virulence factors. M. morganii contains ureases which have a high affinity for urea. It is able to survive in acidic conditions and its ureases are activated within the gut by the presence of low pH levels. Morganella is also able to synthesize extracellular hemolysin much like E. coli. The hemolysin in M. morganii is very different then those produced by some other bacteria in that it is extracellular which could be accounted for by the presence of the secretory gene hlyD in M. morganii (Manos & Belas, 2006). This bacteria also has the ability to hydrolyze and modify antibiotics through the presence of adhesins and other enzymes.
Life History and Behavior
M. morganii is motile via the use of a flagella. In some cases, it reacts to changes in the pH of the gut as well as to changes in the state of the immune system. Since it is an opportunistic pathogen, it takes advantage of a compromised immune system and that it why it is mostly seen in hospitals after a serious injury or surgery.
Evolution and Systematics
The first isolation of this bacteria was done by a man named Castellani in 1905, and he named it Bacterium columbensea. In 1906 when Morgan came across this bacteria while studying summer infantaile diarrhea, he was unaware that it was indeed the same bacteria that was found by Castellani. Morgan described this as a non-lactose fermenting bacteria - different from the other Bacillus type bacteriia. He named this Morgan's Bacillus and it was later named, in 1919, Bacillus morganii by Winslow. Years later, Rauss performed further evaluation of the bacteria and realized it was very similar to the Proteus group and although there were marked differences, he renamed the bacteria Proteus morganii. Finally in 1943, Fulton made the connection that the bacteria Proteus morganii was in fact the same bacteria discovered by Castellani in 1905 and he proposed a new genus name of Morganella. The species would be called M. morganii and Castellani's species would be called M. columbensis. M. morganii was unable to ferment lactose or sucrose but was able to produce indole. In 1962, Ewing found the M. columbensis was actually E. coli, which left M. morganii as the only species in the genus. This led Ewing to disregard the genus and relate moganii to the Proteus genus. Finally in 1976, morganii was put in its rightful place in the genus of Morganella. The differentiation between the two genera was finally made by Brenner using DNA-DNA hybridization, which showed less then 20% homology between P. morganii and Proteus. The differences were further backed by the ability for trehalose fermentation (O'Hara et al., 2000). Morganella is also distinguishable from the genus Proteus by the lysine iron agar test and by the ability of the genus Proteus to differentiate in to swarmer cells when colonizing a new habitat (Manos & Belas, 2006).
Physiology and Cell Biology
Morganella has been classified as both aerobic and facultatively anaerobic.It is able to ferment sugar and is glucose positive. It is also catalase and phenylalanine positive. Morganella exhibits both a respiratory and fermentative type of metabolism (O'Hara et al., 2000). M. morganii is naturally resistant to drugs like penicillin, ampicillin, oxacillin, and erythromycin (Manos & Belas, 2006).
Molecular Biology and Genetics
Morganella is a motile bacterium via the use of a flagella. This bacteria can be non-motile if the temperature drops below 30 degrees Celsius where the flagella is incapable of forming (O'Hara et al., 2000). The Morganella morganii genome is 3.83 Mb and has a GC content of 51.1 %. (NCBI). Under certain conditions, Morganella has been shown to produce histamine, which can lead to toxic conditions if the temperature is correct. At a temperature of 25 degrees Celsius, the Morganella bacterium will produce 5,253 ppm and this will lead to toxic conditions in the host (Kim et al., 2000). Further research is being done on additional Morganella species, especially the proposed subspecies M. morgnaii sibonii (O'Hara et al., 2000).
Relevance to Humans and Ecosystems
Currently there is no information about the applications for this bacterium other then maintaining certain levels in your gut to keep everything in equilibrium. This is done naturally in a healthy body.
Morganella morganii is a species of Gram-negative bacteria. M. morganii has a commensal relationship within the intestinal tracts of humans, mammals, and reptiles as normal flora. Although M. morganii has a wide distribution, it is considered an uncommon cause of community-acquired infection and it is most often encountered in postoperative and other nosocomial infections such as urinary tract infections.
Historical identification and systematics
Morganella morganii was first described by a British bacteriologist H. de R. Morgan in 1906 as Morgan's bacillus. Morgan isolated the bacteria from stools of infants who were noted to have had "summer diarrhea". Later in 1919 Winslow et al., named Morgan's bacillus, Bacillus morganii. However in 1936, Rauss renamed B. morganii as Proteus morganii. Fulton in 1943, showed that B. columbensis and P. morganii were the same and defined the genus Morganella, due to the DNA-DNA hybridization. Genus Morganella has two species M. morganii and M.columbensis. However in 1962, a review article by Ewing reported that M. columbensis had been reidentified as Escherichia coli, therefore removing that organism from the genus Morganella.
Morganella morganii is facultative anaerobic and oxidase-negative. M.morganii are colonies, that appear off-white and opaque in color, when grown on agar plate M. morganii are straight rods, about 0.6-0.7 µm in diameter and 1.0-1.7 µm in length. This organism moves by way of peritrichous flagella, but some strains do not form flagella at 30 °C.
M. morganii is catalase-positive (meaning it can produce the enzyme catalase), meaning it is able to convert hydrogen peroxide (H2O2) to water and oxygen. This is a common enzyme found in most living organisms. In addition M. morganii, is indole test-positive representing this organism can split tryptophan to indole, pyruvate and ammonium. Methyl red tests positive in M.morganii, indicator dye that turns red in acidic solutions. Although a rare human pathogen, M. morganii has been reported as a cause of urinary tract infections, nosocomial surgical wound infections, peritonitis, CNS infection, endophthalmitis, pneumonia, chorioamnionitis, neonatal sepsis, pyomyositis, necrotizing fasciitis, and arthritis. Numerous cases of nosocomial infection have been described, usually as postsurgical wound infections or urinary tract infections. Patients in whom bacteremia develops are typically immunocompromised, diabetic, or elderly or have at least one serious underlying disease.
Role of bacteria
Morganella morganii, is a member of the tribe Proteeae (normal fecal flora that often causes infection in patients whose normal flora have been disturbed by antibiotic therapy) of the family Enterobacteriaceae, with two subspecies: M. morganii and M. sibonii. Morganella morganii has been regarded as a harmless opportunistic pathogen, however there are strains that carry "antibiotic-resistant plasmids" and have been associated with nosocomial outbreaks of infections. There have been several reports that M. morganii causes sepsis, ecthyma, endophthalmitis, chorioamnionitis, however more commonly urinary tract infections, soft tissue infections, septic arthritis, meningitis and bacteremia often with fatal consequences.
In a rare case published in 2003, a patient present with bilateral necrosis of both upper and lower eyelids. Upon microbial analysis the areas were shown to have heavy growth of M. morganii.
Treatment and antibiotic resistance
Treatment of M. morganii infections may include:
- Third-generation and Fourth-generation cephalosporins
A study conducted at the University Hospital at Heraklion, Crete, Greece showed a 92% success rate in the use of these antibiotics.
However, there are M. morganii strains are resistant to penicillin, ampicillin/sulbactam, oxacillin, first-generation and second-generation cephalosporins, macrolides, lincosamides, fosfomycin, colistin, and polymyxin B. The emergence of highly resistant strains of M. morganii have been associated with use of third-generation cephalosporins.
Polymicrobial infections are most abundantly caused by this microbe which additionally damages the skin, soft tissues, and urogenital tract can be cured through use of the aforementioned antibiotics.
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