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Microbiology

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Gram Negative Bacilli

Question
41 out of 81
 

A urinary tract infection as a result of Proteus mirabilis facilitates the formation of kidney stones because the organism:



A Destroys blood vessels in the kidney

B Exhibits "swarming" motility

C Ferments many sugars

D Produces a potent urease

Ans. D Produces a potent urease

a. Most Proteus infections arise from the urinary tract. P. mirabilis causes only 1–2% of cases of UTI in healthy women, and Proteus species collectively cause only 5% of cases of hospital-acquired UTI.

b. However, Proteus is responsible for 10–15% of cases of complicated UTI, primarily those associated with catheterization; in the setting of long-term catheterization, the prevalence of Proteus UTI is 20–45%.

c. This high prevalence is due in part to bacterial production of urease, which hydrolyzes urea to ammonia and results in alkalization of the urine.

d. Alkalization of urine, in turn, leads to precipitation of organic and inorganic compounds, with the formation of struvite and carbonate-apatite crystals, the formation of biofilms on catheters, and/or the development of calculi.

i. Proteus becomes associated with the stones and biofilms; thereafter, it usually can be eradicated only by the removal of the stones or the catheter. Over time, staghorn calculi may form and lead to obstruction and renal failure.

ii. Thus, urine samples with unexplained alkalinity should be cultured for Proteus, and identification of a Proteus species should prompt an evaluation for urolithiasis.

Gram Negative Bacilli Flashcard List

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