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MICROBIOLOGY LEGEND
CYCLE 34 ORGANISM 5
Proteus mirabilis
Proteus mirabilis was first discovered by a German pathologist named Gustav Hauser (Williams and Schwarzhoff, 1978). Hauser named this genus Proteus, after the character in Homer’s The Odyssey that was good at changing shape and evading being questioned (Williams and Schwarzhoff, 1978), a name that seems apt given this organism’s uncanny ability to avoid the host’s immune system.
This organism is not usually a pathogen, but does become a problem when it comes into contact with urea in the urinary tract. From there, infection can spread to other parts of the body. It is one of the species within the Proteus genus responsible for causing urinary tract infections in thousands of people each year in hospitals.
P. mirabilis accounts for most of the urinary tract infections that occur in hospital settings and for ninety percent of Proteus infections (Gonzalez, 2006). Its genome codes for at least 10 adhesion factors making this organism extremely sticky and motile. P. mirabilis tests indole- positive and it can be easily identifiable in a blood agar plate by the formation of concentric rings of its swarming movement (Lund et al., 1975).
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.
P. mirabilis on an XLD agar plate Gram-negative bacilli
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P.O. Box 131375, Bryanston, 2074
Ground Floor, Block 5 Bryanston Gate, 170 Curzon Road Bryanston, Johannesburg, South Africa
804 Flatrock, Buiten Street, Cape Town, 8001
www.thistle.co.za Tel: +27 (011) 463 3260 Fax: +27 (011) 463 3036 Fax to Email: + 27 (0) 86-557-2232 e-mail : [email protected]
Proteus mirabilis Swarm Colony Development
Epidemiology Infections caused by P. mirabilis are seen most often in nursing home patients. These infections are commonly caused by infected medical equipment including catheters, nebulizers (responsible for inhalation), and examination gloves (responsible for wound infections). The length of catherization is directly related to incidence of infection. Each day of catherization gives an infection rate of 3-5%.
Urinary tract infections caused by P. mirabilis also occur commonly in sexually active women and men, especially those engaging in unprotected intercourse. Younger women are at greater risk than younger men; however, older men are at greater risk than older women due to the occurrence of prostate disease.
Diagnosis An alkaline urine sample is a possible sign of P. mirabilis. P. mirabilis can be diagnosed in the lab due to characteristic swarming motility, and inability to metabolize lactose on a MacConkey agar plate. Also P. mirabilis produces a very distinct fishy odour.
Disease
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P.O. Box 131375, Bryanston, 2074
Ground Floor, Block 5 Bryanston Gate, 170 Curzon Road Bryanston, Johannesburg, South Africa
804 Flatrock, Buiten Street, Cape Town, 8001
www.thistle.co.za Tel: +27 (011) 463 3260 Fax: +27 (011) 463 3036 Fax to Email: + 27 (0) 86-557-2232 e-mail : [email protected] This rod shaped bacterium has the ability to produce high levels of urease. Urease hydrolyzes
urea to ammonia (NH3) and thus makes the urine more alkaline. If left untreated, the increased alkalinity can lead to the formation of crystals of struvite, calcium carbonate, and/or apatite. The bacteria can be found throughout the stones, and these bacteria lurking in the kidney stones can reinitiate infection after antibiotic treatment. Once the stones develop, over time they may grow large enough to cause obstruction and renal failure. Proteus can also cause wound infections, septicemia, and pneumonias, mostly in hospitalized patients.
Treatment and Prevention Proteus mirabilis infections can be treated with broad-spectrum penicillin’s or cephalosporin’s except in severe cases. It is not susceptible to nitrofurantoin or tetracycline and has experienced increasing drug resistance of ampicillin, trimethoprim, and ciprofloxin. In cases with severe stone formation, surgery is necessary to remove the blockage.
Proteus mirabilis is part of the normal flora of the gastrointestinal tract, and as a result the bacteria enter the urinary tract or infect medical equipment by the faecal route. Consequently, prevention includes good sanitation and hygiene, including proper sterilization of medical equipment. It is also suggested that patients not requiring catherization should not receive catherization, despite its convenience for the caretaker.
References 1. http://microbewiki.kenyon.edu/index.php/Proteus_mirabilis 2. http://www.biomedhtc.org.uk/ProteusMirabilis.htm
Questions 1. Discuss the morphological characteristics of Proteus mirabilis. 2. Discuss the role of Proteus mirabilis in disease. 3. Discuss the lab diagnosis of Proteus mirabilis.
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