From the Guidelines
A patient with a UTI positive for nitrites and negative for leukocyte esterase should be treated with antibiotics, as the positive nitrite result strongly indicates bacterial presence, despite the negative leukocyte esterase suggesting minimal inflammatory response. According to the most recent and highest quality study 1, the presence of nitrites in the urine is a reliable indicator of a urinary tract infection, and treatment should not be withheld based on the absence of leukocyte esterase. The study recommends treating patients with symptoms such as frequency, incontinence, and urgency, unless the urinalysis shows negative nitrite and negative leukocyte esterase.
In this case, the patient's positive nitrite test suggests a UTI caused by nitrate-reducing bacteria, most commonly Escherichia coli. Treatment typically involves antibiotics such as nitrofurantoin (Macrobid) 100mg twice daily for 5 days, trimethoprim-sulfamethoxazole (Bactrim DS) one tablet twice daily for 3 days, or fosfomycin (Monurol) 3g single dose. Increased fluid intake is also recommended to help flush bacteria from the urinary tract.
Some key points to consider when treating UTIs in older adults include:
- The diagnostic laboratory evaluation of suspected UTI should be reserved for those with acute onset of UTI-associated symptoms and signs 1
- The minimum laboratory evaluation for suspected UTI should include urinalysis for determination of leukocyte esterase and nitrite level by use of a dipstick and a microscopic examination for WBCs 1
- If pyuria (≥ 10 WBCs/high-power field or a positive leukocyte esterase or nitrite test is present on dipstick, only then should a urine culture (with antimicrobial susceptibility testing) be ordered 1
It is essential to note that the presence of nitrites in the urine is a reliable indicator of a UTI, and treatment should not be delayed based on the absence of leukocyte esterase. Patients should complete the full course of antibiotics even if symptoms improve quickly to prevent recurrence. If symptoms persist after treatment, a urine culture may be needed to identify the specific bacteria and its antibiotic sensitivities.
From the Research
UTI Diagnosis and Treatment
- A UTI positive for nitrites and negative for leukocyte esterase (LE) can be challenging to diagnose and treat 2.
- The presence of nitrites in urine is often indicative of a bacterial infection, but the absence of LE does not necessarily rule out an infection 2.
- Studies have shown that urinary nitrite results are not helpful in choosing an initial antibiotic to treat a UTI 2.
- The use of nitrofurantoin or cephalexin for the treatment of cystitis was found to be optimum, and in the presence of negative LE, nitrofurantoin was preferable to cephalexin 2.
Antibiotic Resistance and Treatment Options
- The resistance rate was higher in the nitrite positive group for certain antibiotics, such as TMP/SMX and ampicillin with or without sulbactam 2.
- No significant correlation was found between LE and the resistance patterns in all of the studied antibiotics, except cefazolin 2.
- A study comparing the efficacy of nitrofurantoin and fosfomycin in women with uncomplicated lower urinary tract infections found that nitrofurantoin resulted in a significantly greater likelihood of clinical and microbiologic resolution at 28 days after therapy completion 3.
Diagnostic Methods
- Leukocyte esterase is a useful marker that can be used in establishing a diagnosis of urinary tract infections (UTIs) 4.
- A microfluidic paper-based device has been developed for the sensitive detection of LE, allowing for quantitative determination and early detection of LE in human urine 4.
- The device can detect LE concentrations between 2 to 32 (×5.2 U mL-1), covering the commercial dipstick range of trace, +1 and +2 4.