Proteus infection – a cause of UTIs

Proteus organisms are believed to be responsible for serious infections in humans, being most commonly found in the digestive tract, but also in the urinary tract. People suffering recurrent infections are most at risk, along with those with structural abnormalities of the urinary tract, those who have had instruments inserted into the urethra, and those with hospital-acquired infection. Those with indwelling catheters are at an increased risk of infection of 3-5 per cent per day of catheterisation.

Proteus infection rates are increased in women, those with long catheterisations, anyone with an underlying illness, faulty catheter insertions, lack of antibiotic therapy. The infection occurs due to the migration of bacteria up the catheter or by migration up the catheter from infected urine.

Infections can also appear in urinary tract infections outside of hospitals.

     Who gets Proteus UTIs?

Urinary tract infections are the most common clinical manifestation, with Proteus being responsible for 1-2 per cent of UTIs in healthy women and about five per cent of hospital-acquired UTIs. In those who are catheterised or have what’s known as a ‘complicated UTI’, the incidence is 20-45 per cent. In babies, boys see more Proteus infections than girls due to more anatomical abnormalities found in boys than girls. After age 50, the balance of infection between genders evens out, however UTIs are most common in people aged between 20 and 50.

Women who are sexually active have a greater risk of UTIs. In men, having unprotected anal or vaginal sex and not being circumcised increase risk.

      Symptoms of Proteus urinary tract infection

  • Urethritis – may be mild
  • Painful urination (dysuria)
  • Pus in the urine (cloudy urine, pyuria)
  • More frequent urination
  • Urethral discharge
  • Cystitis – sudden onset
  • Urinary urgency
  • Back pain
  • Concentrated urine
  • Small volumes of urine
  • Blood in the urine
  • Kidney inflammation
  • Prostatitis in men
  • If sepsis, fever, chills, malaise
  • Nausea
  • Vomiting
  • Flank pain

     About Proteus species

Proteus are a gram-negative bacilli found often in certain environments, such as hospitals and long-term care facilities. In hospitals, gram-negative bacilli often infect the skin and mouth of staff and patients alike. Proteus mirabilis causes about 90 per cent of Proteus infections in the community, while Proteus vulgaris and Proteus penneri are most often found in people in hospitals and long-term care facilities.

This bacteria has an extracytoplasmic outer membrane like other gram-negative bacteria. The outer membrane is made of a lipid bilayer, lipoproteins, polysaccharides and lipopolysaccharides. The microbe adheres to its host’s uroepithelial cells, using fimbriae, like other gram-negative bacteria such as E. coli and P. mirabilis. After attachment, Proteus species start a series of events in the cells including secretion of interleukin 6 and interleukin 8. Proteus also cause cell death and loss of epithelial cells (desquamation). The bacteria also produce urease, thought to increase risk of kidney inflammation.

An inflammatory cascade ensues infection, which if allowed to enter the bloodstream can cause death by sepsis.

Proteus’ ability to produce urease and alkalise urine (by hydrolysing urea to ammonia) means it creates its own environment to survive in. The result is struvite stone formation, made of magnesium ammonium phosphate (struvite) and calcium carbonate-apatite. Struvite stone formation can only occur when ammonia production is increase and pH of the urine is elevated to decrease solubility of phosphate – this can only occur when urine is infected with a urease-producing bacteria like Proteus. Urease metabolises into ammonia and carbon dioxide, making urine rich in ammonia and highly alkaline.

Symptoms of struvite stones are not common, with women seeking help with a urinary tract infection, flank pain, blood in the urine and always alkaline urine with a pH of seven or more.

     Outcomes of Proteus infections

In long-term care residents, UTIs are the most common reason for hospital admission second only to pneumonia. UTIs can rapidly turn into sepsis if not treated promptly, with serious repercussions including death. Caught early and treated effectively, Proteus treatment has a good success rate.

     Diagnosis and treatment of Proteus infections

Lab cultures can easily find Proteus strains. Uncomplicated UTIs in women can be treated with oral antibiotics, but anyone with a complicated UTI may need longer and/or alternative treatments. This might include the removal of struvite calculi or other surgery.