Proteus mirabilis is a gram-negative bacterium frequently found in the human intestinal tract and the environment. It commonly causes various human infections, particularly complicated urinary tract infections (UTIs). Its unique characteristics, such as rapid swarming motility and the production of a specific enzyme, contribute to persistent and challenging infections.
Common Infections and Diagnosis
Proteus mirabilis commonly causes urinary tract infections (UTIs), affecting both the lower (cystitis) and upper (pyelonephritis) urinary tract. Individuals with long-term catheterization are particularly susceptible. Symptoms often include painful or frequent urination, cloudy urine, and flank pain. More severe infections, such as wound infections, may show pus discharge, redness, and swelling. Systemic infections, like septicemia, can present with fever, chills, and low blood pressure.
Diagnosis of a Proteus mirabilis infection begins with urinalysis, revealing white blood cells (pyuria) and leukocyte esterase, indicating bacterial infection. Definitive diagnosis relies on a urine culture, where bacteria are grown and identified. This culturing process includes antibiotic susceptibility testing, which determines effective antibiotics against the specific bacterial strain. This step is crucial for guiding treatment decisions.
Primary Antibiotic Regimens
Treatment for Proteus mirabilis infections primarily involves antibiotics, with the specific choice depending on the infection’s severity and susceptibility testing results. For uncomplicated UTIs, a short course of oral antibiotics, such as trimethoprim-sulfamethoxazole or an oral fluoroquinolone like ciprofloxacin, is often prescribed for three days. These medications are typically managed on an outpatient basis.
For acute pyelonephritis, treatment involves a longer course of fluoroquinolones, lasting 7 to 14 days. If fluoroquinolones are not suitable, a single dose of ceftriaxone or gentamicin may be administered, followed by a 7 to 14-day course of other oral antibiotics. For severe conditions or inpatient care, intravenous (IV) antibiotics such as ceftriaxone, gentamicin, or a fluoroquinolone are initiated until fever subsides. Patients may then transition to oral therapy for up to 14 additional days.
Treatment Challenges and Complications
Treating Proteus mirabilis infections is complex due to the bacterium’s specific biological properties. One challenge is its ability to produce the enzyme urease. Urease breaks down urea in urine into ammonia and carbon dioxide, which raises the urine’s pH, making it more alkaline. This alkaline environment promotes the precipitation of magnesium ammonium phosphate, leading to the formation of struvite stones, also known as infection stones.
These struvite kidney stones pose a challenge because they can harbor bacteria within their matrix, creating a protected environment where antibiotics may not effectively reach the pathogens. This shielding effect results in recurrent infections even after antibiotic treatment. Proteus mirabilis also forms biofilms, which are structured communities of bacteria that adhere to surfaces, such as catheters, and are inherently more resistant to antibiotics than free-floating bacteria. The increasing rates of antibiotic resistance, including the emergence of multidrug-resistant strains, further complicate treatment.
Advanced and Surgical Treatment Options
When antibiotic therapy alone is insufficient, additional interventions become necessary. For infections associated with indwelling medical devices, such as urinary catheters, removal or replacement of the infected catheter is required to eliminate the bacterial reservoir. This action helps to clear the infection source, especially where biofilms prevent full antibiotic efficacy.
When infection-related kidney stones have formed, medical or surgical procedures manage and remove them. Procedures like percutaneous nephrolithotomy (PCNL) involve a small incision to directly remove larger stones. Shock wave lithotripsy (SWL) uses shock waves to break stones into smaller fragments for natural passage. If abscesses develop, drainage procedures may be performed to remove pus and facilitate healing.