Mobley Research Laboratory: Department of Microbiology & Immunology: University of Michigan Medical School

Proteus mirabillis


Our population is aging. In the U.S., the proportion of the population aged >65 years is projected to increase from 12.4% (30 million) in 2000 to 19.6% (71 million) in 2030 [1] . In 1997, the U.S. had the highest health-care spending per person aged >65 years ($12,100) [2] ; nursing home and home health-care expenditures doubled during 1990-2001, reaching approximately $132 billion [3] . The absolute number of persons >65 years old residing in our 18,000 nursing homes is currently estimated at 1.5-1.9 million residents [4] . In these facilities urinary incontinence, a very frequent complication is treated with long term (>30 days) urinary catheterization. Nearly 100% of these patients become bacteriuric [5] , often leading to fever, bacteremia and death [6] . Proteus mirabilis and related species, Providencia stuartii and Morganella morganii account for more than half of these infections [5, 7] .

Proteus mirabilis, a gram-negative enteric bacterium, differentiates between the vegetative swimmer cell and the hyper-flagellated swarmer cell [8] . Individuals suffering urinary tract infections (UTI) caused by P. mirabilis and related urease-positive bacterial species often develop bacteriuria, kidney and bladder stones, catheter obstruction due to stone encrustation, acute pyelonephritis, and fever [7, 9, 10] . P. mirabilis is one of the most common causes of UTIs among individuals with long term indwelling catheters, complicated urinary tract infections, and bacteremia among the elderly [7, 11] . As the aging population continues to expand, more individuals will be at risk for P. mirabilis UTI [5] .