Proteus mirabilis is a bacterium commonly found in natural environments like soil and water, and it also inhabits the gastrointestinal tract of humans and animals. While usually part of the normal microbial community, it can act as an opportunistic pathogen, causing infections under certain conditions.
Key Biological Characteristics
Proteus mirabilis is a Gram-negative, rod-shaped bacterium. A key characteristic is its high “swarming motility,” which allows it to move rapidly and spread across surfaces, including medical devices and host tissues, facilitated by numerous flagella.
Another important feature is its production of the enzyme urease. Urease breaks down urea in urine into ammonia and carbon dioxide, significantly increasing the urine’s pH and making it alkaline. This alkaline environment can lead to the precipitation of minerals like struvite and calcium carbonate-apatite, which then form kidney stones.
Common Infections Caused
Proteus mirabilis is most frequently associated with urinary tract infections (UTIs). While it causes about 1-2% of UTIs in healthy women, this rises to 5% in hospital-acquired UTIs and can be as high as 20-45% in complicated cases, especially those involving catheterization. The bacterium’s urease production contributes to struvite kidney stone formation, which can act as protected sites for bacteria, leading to persistent or recurrent infections and potentially obstructing urine flow.
Beyond UTIs, Proteus mirabilis can cause other, less common infections. It has been isolated from wound infections, particularly in hospitalized patients or those with compromised skin barriers. It can also lead to pneumonia, especially in individuals with chronic lung disease or weakened immune systems. If the infection enters the bloodstream, it can cause bacteremia, a serious condition that may result in sepsis.
Identification and Treatment
Identifying Proteus mirabilis infections typically involves laboratory tests, with culture being the definitive method. For suspected UTIs, a urine sample is collected and cultured to identify the specific bacteria. Diagnosis often relies on the bacterium’s characteristic swarming motility and urease activity. Additional biochemical tests confirm its identity, distinguishing it from other bacteria.
Treatment primarily involves antibiotic therapy, guided by susceptibility testing. This testing determines which antibiotics are effective against the particular strain, as resistance patterns can vary. Common antibiotics include fluoroquinolones, trimethoprim/sulfamethoxazole, and certain cephalosporins, though resistance is increasing. For infections complicated by kidney stones, antibiotic treatment alone may not suffice; surgical intervention might be necessary to remove stones that harbor bacteria and lead to recurrent infections.
Preventing Proteus mirabilis Infections
Preventing Proteus mirabilis infections involves several key practices. Maintaining good personal hygiene, including proper handwashing, helps reduce bacterial spread. For individuals with indwelling urinary catheters, meticulous catheter care is important to minimize infection risk, including keeping the system closed and practicing good hygiene around the insertion site.
Minimizing catheterization duration is also a significant preventive factor. Prompt treatment of underlying medical conditions that increase infection susceptibility can further reduce risk. Promoting a healthy immune system through balanced nutrition and lifestyle choices also supports the body’s natural defenses.