Biology:Morganella morganii

Short description: Species of bacterium

Morganella morganii
Scientific classification
Domain:	Bacteria
Phylum:	Pseudomonadota
Class:	Gammaproteobacteria
Order:	Enterobacterales
Family:	Morganellaceae
Genus:	Morganella Fulton, 1943
Species:	M. morganii
Binomial name
Morganella morganii Winslow et al., 1919 Fulton, 1943 Brenner et al., 1978
Subspecies
M. m. morganii M. m. sibonii
Synonyms
Proteus morganii Winslow et al., 1919 Yale, 1939

Morganella morganii is a species of Gram-negative bacteria. 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. In 1943, Fulton attempted to define a subspecies, 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

M. morganii grown on blood agar

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 30 °C (86 °F).

M. morganii is split into two subspecies: M. morganii subsp. morganii and M. morganii subsp. sibonii. M. morganii subsp. sibonii is able to ferment trehalose, whereas subsp. morganii cannot, and this is the primary phenotype used to differentiate them.

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. M. morganii also produces urease, allowing it to break down urea. Methyl red tests positive in M. morganii, an indicator dye that turns red due to the bacterium's acid production during fermentation. Similar bacteria from the closely related Proteus and Providencia genera, M. morganii is able to deaminate tryptophan through the production of tryptophan deaminase (TDA).

Role of bacteria

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. 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.

Further reading

• De, A; Raj, HJ; Maiti, PK (2016). "Biofilm in osteomyelitis caused by a rare pathogen, Morganella morganii: A case report". Journal of Clinical and Diagnostic Research 10 (6): DD06–DD08. doi:10.7860/JCDR/2016/18666.7990. PMID 27504288. 
• Emborg, J; Dalgaard, P (2008). "Growth, inactivation and histamine formation of Morganella psychrotolerans and Morganella morganii - development and evaluation of predictive models". International Journal of Food Microbiology 128 (2): 234–243. doi:10.1016/j.ijfoodmicro.2008.08.015. PMID 18845350. 
• Hu, LT; Nicholson, EB; Jones, BD; Lynch, MJ; Mobley, HLT (1990). "Morganella morganii urease: Purification, characterization, and isolation of gene sequences". Journal of Bacteriology 172 (6): 3073–3080. doi:10.1128/jb.172.6.3073-3080.1990. PMID 2345135. 
• Lee, IK; Liu, JW (2006). "Clinical characteristics and risk factors for mortality in Morganella morganii bacteremia". Journal of Microbiology, Immunology, and Infection 39 (4): 328–334. PMID 16926980. 
• Liu, H; Zhu, J; Hu, Q; Rao, X (2016). "Clinical characteristics and risk factors for mortality in Morganella morganii bacteremia". International Journal of Infectious Diseases 50: 10–17. doi:10.1016/j.ijid.2016.07.006. PMID 27421818. 
• Özoğul, F (2004). "Production of biogenic amines by Morganella morganii, Klebsíella pneumoniae and Hafnia alvei using a rapid HPLC method". European Food Research and Technology 219 (5): 465–469. doi:10.1007/s00217-004-0988-0. 
• Parikh, RY; Ramanathan, R; Coloe, PJ; Bhargava, SK; Patole, MS; Shouche, YS; Bansal, V (2011). "Genus-wide physicochemical evidence of extracellular crystalline silver nanoparticles biosynthesis by morganella spp". PLoS ONE 6 (6): e21401. doi:10.1371/journal.pone.0021401. PMID 21713008. Bibcode: 2011PLoSO...621401P. 
• Rojas, L; Vinuesa, T; Tubau, F; Truchero, C; Benz, R; Viñas, M (2006). "Integron presence in a multiresistant Morganella morganii isolate". International Journal of Antimicrobial Agents 27 (6): 502–512. doi:10.1016/j.ijantimicag.2006.01.006. PMID 16690260. </ref>Stock, I; Wiedemann, B (1998). "Identification and natural antibiotic susceptibility of Morganella morganii". Diagnostic Microbiology and Infectious Disease 30 (3): 153–165. doi:10.1016/S0732-8893(97)00243-5. PMID 9572021. 

External links

• Type strain of Morganella morganii at BacDive - the Bacterial Diversity Metadatabase

Wikidata ☰ Q2696880 entry