In a urinary nitrite test, which organism is most likely to yield a positive nitrite result?

In a urinary nitrite test, which organism is most likely to yield a positive nitrite result?

• A. Enterococcus faecalis
• B. Staphylococcus saprophyticus
• C. Proteus mirabilis
• D. Escherichia coli

Answer: (D)

Urinary nitrite testing relies on bacteria in the urine converting nitrates to nitrites using the enzyme nitrate reductase. Escherichia coli is the classic nitrite-producing uropathogen because it commonly has this capability and is a leading cause of urinary tract infections. When nitrate from urine is reduced to nitrite, the dipstick detects it, yielding a positive result. The other organisms listed are less likely to give a positive nitrite result in typical scenarios: Enterococcus faecalis and Staphylococcus saprophyticus are Gram-positive cocci that often lack nitrate reductase activity in urine, and while some Proteus species can reduce nitrate, E. coli remains the most consistently nitrite-positive and commonly encountered in UTIs.

Urinary nitrite testing relies on bacteria in the urine converting nitrates to nitrites using the enzyme nitrate reductase. Escherichia coli is the classic nitrite-producing uropathogen because it commonly has this capability and is a leading cause of urinary tract infections. When nitrate from urine is reduced to nitrite, the dipstick detects it, yielding a positive result. The other organisms listed are less likely to give a positive nitrite result in typical scenarios: Enterococcus faecalis and Staphylococcus saprophyticus are Gram-positive cocci that often lack nitrate reductase activity in urine, and while some Proteus species can reduce nitrate, E. coli remains the most consistently nitrite-positive and commonly encountered in UTIs.