Morganella morganii

''Morganella morganii'' is a species of Gram-negative bacteria.eMedicine
Morganella infections
/ref> It 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 bacterium from stools of infants who were noted to have had "summer diarrhea". Later in 1919, Winslow'' et al.'' named Morgan's bacillus, ''Bacillus morganii''. In 1936, though, 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. ''M. morganii'' has two subspecies – ''M. m. morganii'' and ''M. m. columbensis''. However, in 1962, a review article by Ewing reported that ''M. columbensis'' had been re-identified as ''Escherichia coli'', thereby removing that organism from the genus ''Morganella''.

Microbiology

''Morganella morganii'' is facultatively anaerobic and oxidase-negative. Its colonies appear off-white and opaque in color, when grown on agar plates. ''M. morganii'' cells 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 .

''M. morganii'' can produce the enzyme catalase, so it is able to convert hydrogen peroxide to water and oxygen. This is a common enzyme found in most living organisms. In addition, it is indole test-positive, meaning that this organism can split tryptophan to indole, pyruvate, and ammonia. Methyl red tests positive in ''M. morganii'', an indicator dye that turns red due to the bacterium's acid production during fermentation. Although a rare human pathogen, ''M. morganii'' has been reported as a cause of urinary tract infections, nosocomial surgical wound infections, peritonitis, central nervous system 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

''M. morganii'' consists of two species: ''M. morganii'' and ''M. sibonii''. ''M. morganii'' has been regarded as a normally harmless opportunistic pathogen, but some strains carry "antibiotic-resistant plasmids" and have been associated with nosocomial outbreaks of infections. Several reports indicate ''M. morganii'' causes sepsis, ecthyma, endophthalmitis, and chorioamnionitis, and more commonly urinary tract infections, soft tissue infections, septic arthritis, meningitis, and bacteremia, in the latter 2 cases with frequent fatal consequences.

In a rare case published in 2003, a patient presented 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:
* Ticarcillin
* Piperacillin
* Ciprofloxacin
* 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, some ''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; these can be cured through use of the aforementioned antibiotics.

References

Further reading

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External links

Type strain of ''Morganella morganii'' at Bac''Dive'' - the Bacterial Diversity Metadatabase

{{portal bar, Biology

Gram-negative bacteria
Antibiotic-resistant bacteria
Healthcare-associated infections
Bacteria described in 1919