Proteus vulgaris is a bacterium that resides in the natural environment and as part of the normal microorganisms in the human gut. It is an opportunistic pathogen, causing infections in people with vulnerabilities like a weakened immune system or other health conditions. It causes illness when it moves from the gut to other areas of the body.
Characteristics and Habitat
Proteus vulgaris is a rod-shaped, Gram-negative bacterium. “Gram-negative” is a classification where bacteria have a thin cell wall that does not retain a specific laboratory stain, a property linked to antibiotic resistance. One notable behavior of P. vulgaris is its swarming motility, where the bacteria use their flagella—whip-like appendages—to move rapidly across a surface like an agar plate.
This organism is widespread in nature and is frequently found in soil, polluted water, and sewage. It is also a common inhabitant of the gastrointestinal tracts of humans and various animals. Its ability to survive in diverse environments contributes to its presence in both community and healthcare settings.
Associated Human Infections
The most frequent infection caused by Proteus vulgaris is a urinary tract infection (UTI). This occurs when the bacteria colonize the urethra and travel into the bladder, a process aided by its vigorous motility. A factor in these infections is the enzyme urease, which P. vulgaris produces.
Urease breaks down urea in urine into ammonia, which increases the urine’s pH and makes it more alkaline. This alkaline environment promotes the formation of struvite stones. These stones can grow large, obstructing urine flow and serving as a reservoir for bacteria, leading to recurrent infections.
Beyond UTIs, P. vulgaris is a known cause of wound infections, contaminating injuries or surgical sites and leading to pain, swelling, and pus. In hospital environments, it can cause more severe conditions among vulnerable patients. These serious infections include bacteremia, a bloodstream infection, and respiratory tract infections.
Diagnosis and Treatment
Diagnosing a Proteus vulgaris infection requires laboratory analysis of a clinical sample, such as urine, blood, or a wound swab. In the lab, samples are cultured to grow the bacteria for identification. The characteristic swarming growth of Proteus on an agar plate helps microbiologists identify the genus.
Treatment is centered on antibiotics, but P. vulgaris is resistant to multiple common ones. It is naturally resistant to drugs like tetracycline and can produce enzymes that inactivate others, like ampicillin. For this reason, healthcare providers perform antibiotic susceptibility testing on the cultured bacteria. This testing determines which antibiotics will be effective against the specific strain causing the infection.
Prevention and Risk Factors
People at higher risk for a P. vulgaris infection include the elderly, patients in long-term care facilities, and those with a compromised immune system. A primary risk factor is the use of a long-term urinary catheter, which provides a direct pathway for bacteria to enter the bladder. People with structural abnormalities in their urinary tract are also more susceptible.
Preventive strategies focus on minimizing these risks. Good personal hygiene helps prevent the transfer of bacteria from the gut to the urinary tract. In healthcare settings, using sterile techniques for urinary catheters is important for preventing UTIs. Proper wound care also helps prevent contamination and infection.