Nitrates are naturally occurring chemical compounds found widely in the environment, including in many foods we eat. These compounds are present in vegetables like leafy greens, celery, and cabbage, and are also used as preservatives in some processed foods. Healthy urine typically contains nitrates, and their presence alone is not a cause for concern.
Nitrate and Nitrite: Understanding the Difference
While nitrates are common and generally harmless in urine, nitrites are different compounds with distinct implications. Both nitrates and nitrites are forms of nitrogen, but they differ in their chemical structure: nitrates have three oxygen atoms, while nitrites have two. Nitrites are produced when specific types of bacteria, often those associated with urinary tract infections (UTIs), convert nitrates into nitrites. This conversion process makes nitrites a notable indicator in urine analysis, whereas nitrates are normal constituents.
Nitrite as a Marker for Urinary Tract Infections
The presence of nitrites in urine is medically significant because it often signals bacterial activity in the urinary tract. Certain bacteria, particularly Gram-negative bacteria like Escherichia coli (E. coli), which is a common cause of uncomplicated UTIs, possess an enzyme called nitrate reductase. This enzyme converts dietary nitrates, normally present in urine, into nitrites. The detection of nitrites in a urine sample therefore indicates the presence of these nitrate-reducing bacteria, suggesting a urinary tract infection. Other Gram-negative organisms such as Klebsiella, Proteus, and Citrobacter can also produce nitrites.
Interpreting Urine Test Results for Nitrite
A positive nitrite test in urine typically indicates a urinary tract infection. However, a negative nitrite result does not definitively rule out an infection. False negatives can occur if urine has not remained in the bladder for at least four hours, which is necessary for sufficient bacterial conversion of nitrate to nitrite, or due to factors like a low nitrate diet, high vitamin C concentrations, or an acidic urine pH. Additionally, some UTI-causing bacteria, such as Enterococcus faecalis or Pseudomonas, do not produce nitrites, leading to a negative result despite active infection. False positives are less common but can happen if the urine sample is contaminated during collection or if the test strip is improperly stored.
Next Steps After Nitrite Detection
If nitrites are detected in a urine sample, consulting a healthcare professional is important for proper diagnosis and treatment. A positive nitrite test typically prompts further diagnostic evaluation, such as a full urinalysis and a urine culture. A urine culture identifies the specific type of bacteria causing the infection and helps determine which antibiotics will be most effective. Treating a confirmed urinary tract infection usually involves a course of antibiotics. Complete the entire course of prescribed antibiotics, even if symptoms improve, to ensure the infection is fully eradicated and prevent antibiotic resistance.