Proteus vulgaris is a rod-shaped, nitrate-reducing, indole-positive and catalase-positive, hydrogen sulfide-producing, Gram-negative bacterium that inhabits the intestinal tracts of humans and animals.

Over the past two decades, the genus Proteus, and in particular P. vulgaris, has undergone a number of major taxonomic revisions.

Enterobacterales (of which Proteus is a member) and Pseudomonas species are the micro-organisms most commonly responsible for Gram-negative bacteremia and sepsis.

Struvite stone formation can be sustained only when ammonia production is increased and the urine pH is elevated to decrease the solubility of phosphate.

The ammonia/ammonium buffer pair has a pK of 9.0, resulting in the combination of highly alkaline, ammonia-rich urine.

More often, women present with UTI, flank pain, or hematuria, and are found to have a persistently alkaline urine pH (>7.0).