The Role of Urinary Nitrite in Predicting Bacterial Resistance in Urine Culture Analysis Among Patients With Uncomplicated Urinary Tract Infection

Abstract

Objective This study aims to determine the relationship between the presence of urinary nitrite and bacterial resistance to antimicrobial therapy in patients with uncomplicated urinary tract infections. Methods During a six-month time period (April-October, 2020), we reviewed the urine samples of 59 adult outpatients from the Urology Department of Tbilisi State Medical University the First University Clinic with the diagnosis of urinary tract infection. The infecting microorganisms and the presence of urine nitrite were recorded. Resistance rates to the antibiotics were compared between the positive and negative nitrite groups. Chi-squared test was used to perform the statistical analysis using Prism software version 9.3.1 (GraphPad Software, Inc., San Diego, California). Results We examined the correlation between the nitrite-positive and -negative groups with the resistance pattern to ceftriaxone, trimethoprim/sulfamethoxazole (TMP-SMX), ampicillin-sulbactam, fosfomycin, amikacin, doxycycline, cefuroxime, cefotaxime, ceftazidime, and nitrofurantoin. A total of 59 outpatients with a mean age of 37 years met the inclusion criteria between April and October 2020. In the positive and negative nitrite groups, there were 23 and 36 patients, respectively. Three (17.6%) of the 17 gram-positive organisms and 20 (62.5%) of the 42 gram-negative organisms yielded positive nitrite results. In nitrite-positive group, resistance rates to ceftriaxone, TMP-SMX, ampicillin-sulbactam, fosfomycin, amikacin, doxycycline, cefuroxime, cefotaxime, ceftazidime, and nitrofurantoin were 52.2%, 70.8%, 63.5%, 67.7%, 25.8%, 31.9%, 29.6%, 32.5%, 22.5% and 83.8%, respectively. These values in the nitrite-negative group were 6.5%, 41.3%, 60.7%, 72.9%, 49%, 3%, 2.3%, 3.3%, 4.3% and 81.9%, respectively. Highest relative resistance rate was recorded against cefuroxime (12.9), followed by doxycycline (10.6), cefotaxime (9.8), ceftriaxone (8.03), ceftazidime (5.2), TMP-SMX (1.71), ampicillin-sulbactam (1.05), nitrofurantoin (1.02), fosfomycin (0.93), and amikacin (0.53). The most commonly isolated pathogen was Escherichia coli, which was detected in 35 (71%) isolates. Other bacteria commonly found were Proteus spp in five (12%) isolates, Klebsiella spp in two (5%) isolates, and Enterococcus in five (12%) isolates. Conclusion The findings revealed that out of 10 antibiotics, nitrite-positive groups demonstrated higher resistance only against ceftriaxone, cefuroxime, cefotaxime, and doxycycline. Other antibiotics showed no statistically significant differences in resistance. Furthermore, the highest relative resistance rate was recorded against cefuroxime, whereas amikacin revealed the lowest. Therefore, we suggest physicians to not adjust antibiotic therapy for urinary tract infections (UTIs) based on the presence of nitrite. Urine bacteriology should be ordered.

Keywords: anti-bacterial agents; antibiotic resistance; dysuria; escherichia coli; nitrite; urinary tract infection.

Figure 1. Gram stain and nitrite test pattern for isolated pathogens

Figure 2. Comparison of resistance rates between the nitrite-positive and nitrite-negative groups

TMP-SMX: Trimethoprim-sulfamethoxazole.