Proteus mirabilis in urine is a sign of a urinary tract infection that can occur in patients who are catheterized for long periods, have structural or functional abnormalities, or are elderly, according to Infection and Immunity. The bacterium causes fever, acute pyelonephritis, or severe kidney infections, and bladder and kidney stones that obstruct catheters. Proteus mirabilis has motile and adhesive qualities that enable it to swim counter to urine flow and ascend through the urethra to the bladder.
Flowing urine typically stops low doses of infectious bacteria from invading the body's tissues, explains Infection and Immunity. However, P. mirabilis enters the body in the area surrounding the urethra, migrates up to the bladder to the kidneys, and can enter the bloodstream. Among the reasons why the bacterial infection is difficult to treat is the organism's ability to encase itself, create urinary stones, and encrust patients' catheters.
P. mirabilis is a gram-negative bacterium that lives in water, soil and the human intestinal tract, according to University of Michigan Medical School. The bacteria causes kidney stones and kidney infections, and the urinary stones that it forms block urine flow.
P. mirabilis resists treatment with tetracycline and nitrofurantoin, but as of 2016, trimethoprim-sulfamethoxazole and fluoroquinolones are among the antibiotics doctors use to cure infections that the bacteria cause, according to the American Society for Microbiology. However, reports of the bacteria's ability to resist drugs are increasing.