Proteus Infections Clinical Presentation

Updated: Feb 21, 2023
  • Author: Shirin A Mazumder, MD, FIDSA; Chief Editor: Michael Stuart Bronze, MD  more...
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Approximately 95% of UTIs occur when bacteria ascend through the urethra and the bladder.

Complicated UTIs occur with instrumentation (including Foley catheters), obstruction, calculi, or neurogenic bladder. These carry a higher risk for complications such as hospitalization and sepsis.

Sexually active women are at greater risk for UTIs. The same is true for men, although to a lesser degree.

Other predisposing factors for UTIs are men who have unprotected anal intercourse, an uncircumcised penis, unprotected vaginal intercourse, and/or CD4 count less than 200/µL.

Although infrequent, chronic prostatitis should be considered in males with a history of recurrent UTIs. Obstructive symptoms are transient but may progress to infect the bladder because of poor bladder emptying.

Frequent and unexplained incidents of renal calculi may be indicative of a chronic Proteus infection. Multiple magnesium ammonium phosphate crystals are present in the urine sediment along with radio dense renal calculus. (This calculus is less radio dense than calcium oxalate.) This results in formation and precipitation of struvite crystals, a predominant component of urinary calculi and encrustations on urinary catheters.

Proteus are common among the gram-negative causes of bacteremia, with most cases secondary to UTI and often associated with urinary catheters. Community-acquired Proteus UTI in the presence of hydronephrosis or urolithiasis increases the risk for bacteremia. Proteus can persist in the urinary tract despite antibiotics and catheter exchange, potentially because of immune evasion and the protective reservoir that urinary stones may provide.



Patients may present with urethritis, cystitis, prostatitis, or pyelonephritis. Chronic, recurring stones may be an indication of chronic infection.


Symptoms of urethritis usually are mild and may be dismissed by the patient.

Women present with dysuria, pyuria, and increased frequency of urination.

Presenting symptoms in males usually are mild and may include urethral discharge.


Signs and symptoms of cystitis tend to be more prominent compared to those of urethritis.

In both men and women, symptoms are of sudden onset.

They include dysuria, increased frequency, urgency, suprapubic pain, back pain, small volumes, concentrated appearance, and hematuria. If the patient is febrile, this could be a sign of bacteremia and impending sepsis. These symptoms may not be present if the patient has an indwelling catheter. Physical examination findings may include abdominal or pelvic pain and/or costovertebral angle tenderness.


Prostatitis is obviously limited to men and occurs more acutely than cystitis. This becomes more common as men age.

In addition to symptoms of cystitis, patients with prostatitis may present with fever and chills.

Perianal pain and various symptoms of urinary tract obstruction may be present. The prostate may be tender and diffusely swollen.


Pyelonephritis can be considered a progression of disease, and symptoms are therefore more profound. Sepsis can develop quickly, especially in elderly patients or those with a compromised immune system.

Symptoms of urethritis and cystitis may or may not be present.

Defining symptoms of pyelonephritis include flank pain, nausea and vomiting, costovertebral angle tenderness, fever, and, rarely, a palpable and tender kidney. Hematuria and pyuria are frequently encountered.



Hospital-acquired infections usually are caused by interruption of the closed sterile system by hospital personnel.

Proteus species also cause sepsis neonatorum and bacteremia with fever and neutropenia.

Proteus species are also involved in synergistic nonclostridial anaerobic myonecrosis, which may involve subcutaneous tissue, fascia, and muscle. This condition is caused by combinations of other aerobic gram-negative bacilli (E coli or Klebsiella or Enterobacter species) and anaerobes. Surgical evaluation and intervention is critical to successful treatment.