Last reviewed by Editorial Team on August 13th, 2018.
Proteus mirabilis is a Gram-negative and anaerobic bacterium, which upon laboratory analysis demonstrates swarming motility (coordinated translocation of the bacterial population across solid surfaces) and urease activity. It is known that over 90% of the Proteus infections are caused by this particular bacterium (community-acquired infection). Proteus mirabilis is part of the Enterobacteriaceae family. The infection with these bacteria depends on the defense mechanism of the host, meaning the immune system.
The urine of the patients who suffer from infections with Proteus mirabilis becomes alkaline, as the bacterium produces urease in increased quantities. Urease is known to transform the urea into ammonia, hence the alkalinity of the urine. If the infection is not treated, the alkalinity will increase to very high levels and crystals are going to form, which are going to eventually become kidney stones. Even if the person is treated with antibiotics for the infection, the bacteria that is found on the kidney stones can lead to the reactivation of the infection. The kidney stones can reach impressive dimensions, leading to obstruction at the level of the renal system and even to renal failure.
In case of chronically-ill patients or in those who stay in the hospital for prolonged periods of time, Proteus mirabilis can also lead to the appearance of the following health problems: pneumonia of the lungs, septicemia (generalized infection of the blood) and infection at the level of existent wounds.
Where is Proteus mirabilis found?
Proteus mirabilis is commonly encountered in water and soil. In humans, it is generally found at the level of the intestinal tract, being part of the normal human intestinal flora. The bacterium is also found in hospitals and in clinics that provide treatment on a long-term basis. As it was already mentioned, in hospitals, the bacteria will quickly colonize the skin of patients, and also the oral mucosa. In many cases, the medical staff is also affected by this bacterium. Despite the increased risk for infection, this is not the most encountered nosocomial infections. The most common site of the disease is the genitourinary tract.
Proteus mirabilis has the following characteristics:
- The bacteria use the urea
- Has a characteristic fishy odor, due to the production of hydrogen sulfide gas
- If bacterium is cultivated for lab testing, it forms a clear film on the media used for growth
- Characteristic swarming motility
- Can lead to the formation of struvite stones
The infection with Proteus mirabilis can be diagnosed by taking a urine sample. If the sample is alkaline, this might suggest the infection with Proteus mirabilis. In the laboratory, the diagnosis of the infection with Proteus mirabilis is made based on the above-mentioned swarming motility. Apart from that, it seems that Proteus mirabilis is unable to metabolize lactose and it has a very distinct odor (fishy smell).
If the patient does not respond to the antibiotic treatment, the doctor will most likely suggest ultrasonography or a CT scan. This will allow for a better visualization of the kidneys and the surrounding structures. It will also allow to exclude other possible health problems, mimicking the symptoms of a bacterial infection.
Proteus mirabilis Infection
These are some of the most common symptoms that are caused by the infection with Proteus mirabilis:
- Urinary tract infection
- Flank pain
- Hematuria (blood in the urine)
- Increased urination frequency
- Urethral discharge (in men)
- Suprapubic pain
- Urgency to urinate
- Back pain
- The urine has a concentrated appearance
- Systemic symptoms can also be present, being suggestive of a severe bacterial infection and possible sepsis (high-running fever) – more common in patients who have been catheterized for prolonged periods of time
- Fever and chills might be present in men who are suffering from the chronic inflammation of the prostate
- Perianal pain is also a symptom encountered in men diagnosed with the above-mentioned problem
- Nausea and vomiting might be present in patients who suffer from pyelonephritis, caused by the infection with Proteus mirabilis; other symptoms suggestive of this infection include: fever, tenderness in the respective flank and hematuria (blood in the urine)
These are some of the most common causes that lead to the infection with Proteus mirabilis:
- Recurrent infections (especially UTI)
- Structural abnormalities at the level of the urinary tract
- Urethral instrumentation
- Hospital-acquired infection (especially due to prolonged stay/ reduced immunity)
- Multiple antibiotic treatments
- Urinary tract obstruction
- Urinary catheter (especially when used for prolonged periods of time)
- Neurogenic bladder
- Sexual activity (increased risk for women, especially if no methods of protection were used)
- Other risk factors include – unprotected anal intercourse and uncircumcised penises
- Chronic inflammation of the prostate (recurrent UTIs)
Patients who have been infected with Proteus mirabilis can be treated with antibiotics. However, it should be noted that the bacterium has developed resistance to certain antibiotics, such as tetracycline and nitrofurantoin. More recent studies have shown that the bacterium has developed resistance to other antibiotics as well, including to ampicillins and cephalosporin antibiotics (10-20% of the cases). Intravenous antibiotics are administered in the bacterial infections that are severe. Patients who present big kidney stones, causing the obstruction of the urinary tract, will have to undergo surgical intervention. If an abscess has formed because of the infection, surgical removal will be the most recommended approach. In case the infection was so severe that it has caused tissue necrosis, amputation is going to be indicated. In patients who suffer from other pre-existing conditions or those who have a compromised immunity, the mortality rate remains at a high level.
Some patients might present anaphylactic reactions to the administration of antibiotics, so this risk has to be taken into consideration. In case of a severe allergic reaction, adrenaline remains the only course of treatment. Immediate medical intervention is necessary before the symptoms become life-threatening and the patient dies from suffocation. It is also important to note that the antibiotics should be taken for as long as they are prescribed, otherwise the bacteria will develop resistance to the treatment. Apart from that, for the duration of the antibiotic treatment, it is recommended that probiotics are administered as well (so as to protect the healthy intestinal flora).