Discussion

In our large cross-sectional study among adult patients, we found an overall prevalence of gram+ UTI of 6.2%, most of which were caused by e. faecalis (Table 1). However, gram-positive infections accounted for only 10.8% of nitrite-negative urine dipstick tests.

Strikingly, the presence of urinary nitrites did not exclude the presence of a gram-positive uropathogen, yielding a positive result in 12.2% of gram-positive UTIs.

UTIs are common and are usually diagnosed based on history, physical examination, and urinary dipstick test. ^{Reference Gupta, Hooton and Naber1} Because most UTI treatment is empirical this is of special importance in the outpatient setting where urine cultures are not routinely obtained, or at the emergency department where the choice of antibiotic regiment is done quickly, and time to appropriate antibiotic treatment is closely associated with critically ill patients’ outcomes. ^{Reference Weinberger, Rhee and Klompas8}

Notably, inappropriate empiric antibiotic therapy was recently shown to result in increased risk for UTI-related hospitalization and re-consultation. ^{Reference Aryee, Rockenschaub and Robson9}

Given the importance of appropriate empirical antibiotic therapy, previous studies addressed predictive factors for e. faecalis UTI. ^{Reference Madrazo, Esparcia and Alberola6} Consistent with our findings, the e. faecalis group had a higher proportion of men, older age, and more comorbidities. Disappointingly, the presence or absence of urinary nitrites lacks specificity and sensitivity for guiding empiric therapy.

Not only that relying on the absence of nitrites would lead to adding coverage for e. faecalis in ∼50% of gram-negative UTI cases, but we also show that nitrites may be present in cases caused by gram-positive organisms. Thus, the clinical presentation and patient characteristics, rather than the urinary dipstick test, should guide the choice of empiric antibiotic coverage.

There are several limitations to our study. First, it is limited by its retrospective design. Second, due to the locality of the cohort patient characteristics may largely vary in other places. Third, the case definition is complex and represents and inherent limitation. ^{Reference Bilsen, Jongeneel and Schneeberger10} Due to the nature of retrospective cohort formation, the inclusion criterion were patients who presented to the ER in whom both a urine dipstick and a urine culture were performed. Although usually it is performed after a clinical decision by an ER physician or a nurse suggesting UTI was suspected, sometimes it is done as a workup of fever or sepsis without specific urinary complaints or when a patient is unable to pinpoint specific etiologies for their condition, affecting the rate of UTIs and asymptomatic bacteriuria in this large cohort. However, urinary colonization with bacteria, either in asymptomatic bacteriuria or urinary tract infections, that has nitrate reductase should still produce positive nitrites. Meaning that the production of nitrates and leukocyte esterase presence should be independent of symptoms and thus does not affect the validity of our conclusions.

In conclusion, nitrites or the lack of them are not necessarily correlated with infections and the pathogens causing them, and dipstick testing alone is not suitable for guiding empirical antibiotic coverage for suspected UTI.