3.25 Proteus Species

Microbiology review for the USMLE Step 1 exam

• Proteus species are gram-negative rods that cause hospital acquired urinary tract infections
• They have swarming motility and can move quickly in a coordinated fashion across surfaces due to their numerous flagella
• They can self-elongate and secrete a sticky polysaccharide when in contact with solid surfaces, allowing for attachment and easy motility
• Proteus mirabilis and Proteus vulgaris are the two main species that cause infections in humans
• Proteus mirabilis tends to cause hospital acquired UTIs and can cling to medical devices such as catheters, where it can infect the epithelium of the urinary tract and ascend up to the kidneys
• Proteus mirabilis expresses urease, converting urea to ammonia, which can cause the formation of struvite kidney stones
• Proteus vulgaris is less common than Proteus mirabilis and tends to be more difficult to treat due to drug-resistance plasmids
• Treatment for Proteus mirabilis infection depends on the type of infection, and for uncomplicated UTIs, patients can be given bactrim, while fluoroquinolones are given for pyelonephritis.