From the Guidelines
Nitrite Test in Klebsiella UTI
Yes, nitrites are often positive in Klebsiella UTI. Klebsiella pneumoniae, a common cause of urinary tract infections (UTIs), is a gram-negative bacterium that can reduce nitrates to nitrites, resulting in a positive nitrite test 1, 2. This is because Klebsiella species possess the enzyme nitrate reductase, which enables them to convert nitrates to nitrites.
- The nitrite test has high specificity, with a range of 90-100% 1, but lower sensitivity, ranging from 15-82% 1 and 19-48% 2.
- A positive nitrite test can be a useful indicator of a UTI caused by Klebsiella or other nitrate-reducing bacteria.
- However, negative nitrite test results have little value in ruling out UTI, especially in children who empty their bladders frequently 3.
- The combination of leukocyte esterase and nitrite tests can improve the sensitivity and specificity of UTI diagnosis, with a sensitivity of 88% and a false-positive rate of 7% when either test is positive 4.
- It is essential to consider the limitations and variability of the nitrite test in different patient populations and clinical contexts.
From the Research
Nitrite Test Results in Klebsiella UTI
- The sensitivity of the nitrite test for UTI was found to be 30.8% in a study of infants with UTI, with Klebsiella pneumoniae being one of the most common etiologies 5.
- Another study found that 3% and 5% of urine samples from patients with UTI caused by Enterobacterales species, including Klebsiella pneumoniae, were nitrite-negative by dipstick test but positive for Enterobacterales in urine culture 6.
- A study of adult outpatients with uncomplicated UTI found that 17.6% of gram-positive organisms and 62.5% of gram-negative organisms, including Klebsiella spp, yielded positive nitrite results 7.
- In a study of children with UTI, pyuria was less common in patients with Klebsiella spp and Enterococcus spp, and the absence of pyuria did not exclude UTI in patients with compatible clinical findings 8.
- A retrospective study of patients with UTI found that the resistance rate was higher in the nitrite positive group for certain antibiotics, but no significant correlation was found between urinary nitrite results and the choice of initial antibiotic therapy 9.
Bacterial Resistance and Nitrite Test Results
- A study found that nitrite-positive groups demonstrated higher resistance to certain antibiotics, including ceftriaxone, cefuroxime, and cefotaxime, but not to others 7.
- Another study found that the resistance rate was higher in the nitrite positive group for TMP/SMX and ampicillin with or without sulbactam, but no significant correlation was found with other antibiotics 9.
- The use of nitrofurantoin or cephalexin for the treatment of cystitis was found to be optimum, and in the presence of negative leukoesterase, nitrofurantoin was preferable to cephalexin 9.
Clinical Implications
- The presence of nitrite in urine is highly suggestive of UTI, but has low sensitivity 5.
- Urine culture tests should be performed in children with suspected UTI, even in the absence of pyuria, to avoid delay in diagnosis and treatment 8.
- Physicians should not adjust antibiotic therapy for UTIs based on the presence of nitrite, and urine bacteriology should be ordered 7.