Re: Proteus Mirabilis
Roseanne Devon
Proteus mirabilis is a Gram-negative, facultatively anaerobic, rod-shaped bacterium. It shows swarming motility and urease activity. P. mirabilis causes 90% of all Proteus infections in humans. It is widely distributed in soil and water.[1] Proteus mirabilis can migrate across the surface of solid media or devices using a type of cooperative group motility called swarming. Proteus mirabilis is most frequently associated with infections of the urinary tract, especially in complicated or catheter-associated urinary tract infections.[2]
An alkaline urine sample is a possible sign of P. mirabilis. It can be diagnosed in the lab due to characteristic swarming motility, and inability to metabolize lactose (on a MacConkey agar plate, for example). Also P. mirabilis produces a very distinct fishy odor.
This rod-shaped bacterium has the ability to produce high levels of urease, which hydrolyzes urea to ammonia (NH3), so makes the urine more alkaline. Prolonged increased alkalinity can lead to the formation of crystals of struvite, calcium carbonate, and/or apatite, which can result in struvite kidney stones. Delayed or suboptimal treatment often allows these kidney stones to act as a nidus for P. mirabilis growth causing recurrent infections despite antibiotic treatment. If the stones grow large enough they can cause obstruction and kidney failure. Proteus species can also cause wound infections, sepsis, and pneumonia, mostly in hospitalized patients.[3]
P. mirabilis can use urea.[6] It can produce hydrogen sulfide gas, and forms clear films on growth media. It is motile, possessing peritrichous flagella, and is known for its swarming ability. It is commonly found in the human digestive system. P. mirabilis is not pathogenic in guinea pigs or chickens [citation needed]. This species' ability to inhibit growth of unrelated strains had been a topic for scientific curiosity, which then resulted in the discovery a macroscopically visible line of reduced bacterial growth where two swarming strains intersect. This line is named the Dienes line after its discoverer Louis Dienes.[7]
Swarming is a specialized form of motility that groups of multicellular, flagellated bacteria can undergo to expand their populations to new locations.[8] The swarming capability of Proteus mirabilis is important because it is implicated in the pathogenesis of the bacteria and the swarming capability is associated with the bacteria's ability to express virulence factors[9] Proteus mirabilis has a very characteristic bulls-eye appearance on an agar plate due to the regular periodic cycling between the vegetative and swarming state of the cells.[10]
In liquid culture, Proteus mirabilis exists as a vegetative cell that is approximately 2 μm long and has four to ten peritrichous flagella. In the vegetative cell the flagella are used to propel the bacterium forward. Swarming cells are only formed when the bacteria are grown on solid surfaces so the ability to detect these solid surfaces is a required feature. It has been proposed that Proteus mirabilis senses a solid surface by the inhibition of its flagellum rotation, and it is this lack of freely rotating flagella that let the bacteria know it is on a solid surface. When Proteus mirabilis encounters a solid surface, and other necessary conditions have been met, the cell will undergo the differentiation process into a swarmer cell. This differentiation process includes the elongation of the cell 20 to 50 times longer than the vegetative cell, multinucleation, and more than a 50-fold greater surface density of flagella.[8]
The swarming process continues as periodic cycles of cell differentiation, population migration, and consolidation as the bacteria undergo these changes in response to environmental stimulants. The repetition of this cycle is what gives Proteus mirabilis its distinctive bulls-eye pattern when growing on solid media. This pattern can be used to distinguish Proteus mirabilis from other species of swarming bacteria. Each ring is formed when the bacteria is in the consolidation stage and the bacteria is increasing in population.[9]
SYNONYM OR CROSS REFERENCE: Sometimes referred as members of the Proteeae tribe Footnote 1. Former species of genus Proteus now homotypic synonyms with other species: P. inconstans with Providencia alcalifaciens, P. morganii with Morganella morganii, and P. rettgeri with Providencia rettgeri Footnote 2.
CHARACTERISTICS: Proteus spp. consist of Gram-negative, motile, aerobic rod-shaped bacilli belonging to the family Enterobacteriaceae Footnote 3Footnote 4. Members of the Enterobacteriaceae family generally range from 0.3 to 1.0 mm in width and 0.6 to 6.0 mm in length Footnote 3. They are urease positive and form swarmer cells which allow for swarming motility on solid media. They are part of normal flora of human gastrointestinal tract.
PATHOGENICITY/TOXICITY: Proteus spp. are commonly associated with complicated urinary tract infections (UTIs) Footnote 1Footnote 3-Footnote 5. They generally affect the upper urinary tract (common site of infection), causing infections such as urolithiasis (stone formation in kidney or bladder) Footnote 3Footnote 4, cystitis Footnote 4, and acute pyelonephritis. Rare cases of bacteraemia, associated with UTIs, with Proteus spp. have also been reported Footnote 1. Other infections include septicaemia and wound infections. After attachment and colonization within the urinary tract, Proteus spp. release urease, which catalyzes the conversion of urea into ammonia and CO2 Footnote 3Footnote 5. This causes a decrease in the urine pH and may eventually lead to the formation of kidney or bladder stones. P. mirabilis causes the most infections among all Proteus spp.
EPIDEMIOLOGY: Proteus spp. infections occur worldwide and Proteus spp. are part of the human intestinal floraFootnote 1Footnote 3-Footnote 5. They are also widespread in the environment, including animals, soil, and polluted water. They are important causative agents in community-acquired and nosocomial UTIs; within Europe and North America, 4 to 6% of Proteus infections are community-acquired and 3 to 6% are nosocomialFootnote 3. Proteus spp. are generally considered pathogenic for young individuals and opportunistic pathogens for the elderlyFootnote 4. The rate of infection is highest among the elderly, particularly those with indwelling catheters (long-term catheterization) or under frequent antibiotic therapyFootnote 1Footnote 4Footnote 5. Other target groups include prepubescent males and females, with higher rate of infection reported among uncircumcised malesFootnote 4. Individuals with long-term catheterization or structural abnormalities of the urinary tract are more susceptible to infection with Proteus spp.Footnote 1Footnote 4Footnote 5. Nosocomial outbreaks with antibiotic-resistant Proteus spp. have been reportedFootnote 4.
MODE OF TRANSMISSION: Proteus spp. are part of the human intestinal flora Footnote 1Footnote 3-Footnote 5 and can cause infection upon leaving this location. They may also be transmitted through contaminated catheters (particularly urinary catheters) Footnote 1Footnote 4Footnote 5 or by accidental parenteral inoculation. The specific mode of transmission, however, has not been identified.
RESERVOIR: Humans Footnote 1Footnote 3Footnote 4, animals, birds Footnote 3, and fish. Proteus spp. are widespread within the environment, including soil, water, and sewerage Footnote 1Footnote 4.
DRUG SUSCEPTIBILITY: Proteus spp. are generally susceptible to broad-spectrum cephalosporins, aminoglycosides, and imipenem Footnote 3. P. mirabilis is also susceptible to trimethoprim-sulfamethoxazole, ampicillin, amoxicillin, and piperacillin. P. vulgaris and P. penneri are also susceptible to cefoxitin, cefepime, and aztreonam. P. mirabilis is resistant to nitrofurantoin. Resistance to ciprofloxacin may develop with unrestricted use. P. vulgaris and P. penneri are resistant to piperacillin, amoxicillin, ampicillin, cefoperazone, cefuroxime, and cefazolin. P. penneri is more resistant to penicillin than P. vulgaris. Resistance to β-lactamases among Proteus spp. is emerging Footnote 4. Carbapenem resistance, including pan-resistant isolates, have been described in India Footnote 6.
SURVIVAL OUTSIDE HOST: Proteus spp. survive only for a few days on inanimate surfaces; and only 1 to 2 days in the case of P. vulgarisFootnote 9 . They also survive well within the environment in soil, water, and sewageFootnote 3 .
SURVEILLANCE: Monitor for symptoms. Proteus spp. can be diagnosed by isolation and differentiation with chromogenic media (i.e. by means of cultured organisms from urine and bloods samples) Footnote 3.
PRIMARY HAZARDS: Use of contaminated catheters (particularly urinary catheters) in medical procedures Footnote 1Footnote 4Footnote 5, and accidental parenteral inoculation and/or ingestion of contaminated material.
RISK GROUP CLASSIFICATION: Risk Group 2 Footnote 10. The risk group associated with "Proteus spp." reflects the genus as a whole, but does not necessarily reflect the risk group classification of every species within the genus.
CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures Footnote 11. These containment requirements apply to the genus as a whole, and may not apply to each species within the genus.
PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. Eye protection must be used where there is a known or potential risk to splashes Footnote 10.
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