PROTEUS

Proteus

Proteus is a genus of gram-negative bacteria, part of the family Enterobacteriaceae. The most clinically significant species are Proteus mirabilis and Proteus vulgaris. These bacteria are commonly associated with urinary tract infections (UTIs), particularly in patients with urinary catheters or structural abnormalities of the urinary tract. Proteus species are also known for their distinctive swarming motility and ability to produce urease.

Microscopic Appearance

• Gram-negative rods.

• Motile, with peritrichous flagella (flagella distributed all over the cell surface).

• Non-encapsulated.

• Often observed in clusters or as individual rods.

• Member of enterobacteriaceae

• Non capsulated

• Non spore forming

• Non lactose fermenting

• Fishy odor

Main Species of Medical Importance

• P.mirabilis causes urinary tract infections (UIT)

• P.vulgaris causes nosocomial infections

Virulence Factors

• Urease: Breaks down urea into ammonia and carbon dioxide, raising the pH of the urine, which can lead to the formation of struvite and apatite crystals, contributing to kidney stone formation.

• Flagella: Provide motility and facilitate the characteristic swarming on solid media, which aids in colonization and infection.

• Fimbriae (Pili): Allow adherence to urinary tract epithelial cells, promoting infection.

• Endotoxin (LPS): Contributes to inflammation and septic shock in cases of bacteremia.

• Biofilm Formation: Helps in persistence and protection from the host immune response and antibiotics.

• Hemolysins: Both HpmA & HlyA are cytotoxic for a wide variety of cell types , together with urease they play an important role in cell invasion & internalization

• Proteinase: Play a role in :

  a) Degrading antibacterial peptides in the innate

  defense system

  b) Generating products like glutamine to induce

  invasive swarm cell

Pathogenesis

• Urinary Tract Infections (UTIs):

  • Proteus species are often introduced into the urinary tract via catheters or instrumentation.

  • Urease activity leads to alkalization of urine, creating an environment conducive to stone formation and bacterial growth.

  • Stones can become colonized by bacteria, forming "staghorn calculi" in severe cases, leading to chronic infections and obstruction.

• Bacteremia:

  • Proteus can enter the bloodstream from the urinary tract or through wounds, particularly in immunocompromised patients or those with invasive devices.

  • Once in the bloodstream, it can cause sepsis, particularly in hospitalized patients.

Clinical Manifestations

• Urinary Tract Infections (UTIs):

  • Symptoms include dysuria, frequency, urgency, hematuria, and sometimes flank pain.

  • Complicated UTIs may involve the kidneys (pyelonephritis), presenting with fever, chills, and costovertebral angle tenderness.

• Kidney Stones (Urolithiasis):

  • Result from the precipitation of struvite and calcium phosphate in the alkaline urine.

  • Symptoms include severe, colicky flank pain, hematuria, and recurrent UTIs.

• Bacteremia and Sepsis:

  • Fever, chills, hypotension, and multi-organ dysfunction in severe cases.

  • Often associated with infections originating from the urinary tract.

Lab Diagnosis

• Culture:

  • Proteus species grow readily on standard media like blood agar and MacConkey agar.

  • Swarming motility is characteristic on non-selective agar, where the bacteria spread in a wave-like pattern across the surface.

  • Proteus species are lactose-negative on MacConkey agar.

• Biochemical Tests:

  • Urease positive (a key distinguishing feature).

  • Indole test: P. mirabilis is indole-negative, while P. vulgaris is indole-positive.

  • Oxidase negative.

  • Phenylalanine deaminase positive.

• Urine pH: Elevated urine pH due to urease activity can be a clue in the diagnosis of Proteus-associated UTIs.

• Imaging: For suspected urolithiasis, imaging studies like ultrasound or CT scan may be used to detect kidney stones.

Treatment

• Uncomplicated UTIs:

  • Antibiotics such as trimethoprim-sulfamethoxazole, nitrofurantoin, or fluoroquinolones can be used, but choice should be guided by sensitivity testing.

• Complicated UTIs:

  • Requires more aggressive therapy, often with intravenous antibiotics like ceftriaxone or ampicillin-sulbactam.

  • Removal of infected stones or drainage of abscesses may be necessary.

• Kidney Stones:

  • Management may involve lithotripsy (breaking stones with sound waves), surgical removal, or stent placement, in addition to antibiotic therapy.

• Bacteremia:

  • Intravenous broad-spectrum antibiotics are required, tailored to sensitivity results once available.

  • Supportive care for sepsis, including fluid resuscitation and vasopressors, may be necessary.

• Preventive Measures:

  • Good catheter care and minimizing unnecessary catheter use can reduce the risk of Proteus infections.

  • In recurrent stone formers, measures to acidify urine or alter diet may help prevent stone formation.