Blood culture useful only in selected patients with urinary tract infections - a literature review

Purpose: The practice of obtaining blood culture in febrile urinary tract infections is controversial, considering that blood cultures rarely provide additional useful information compared to urine cultures alone. Furthermore, whether a longer treatment duration is necessary in bacteremic patients is also controversial. Here, we aim to review to relevant studies. Materials and methods: We searched PubMed and Scopus for studies providing information regarding the discordance between urine and blood cultures. We also searched for clinical trials regarding the treatment duration in bacteremic patients with urinary tract infections. Results: It seems that a higher likelihood of a negative urine culture (e.g. in patients with antibiotic pre-treatment) combined with a higher likelihood of a positive blood culture (e.g. patients with high fever, or patients with complicated urinary tract infections) increases the chance that a blood culture might provide additional useful information. Furthermore, when polymicrobial infection or contamination of the urine specimen is likely (e.g. in patients with indwelling urinary tract catheters or bedridden patients with frequent hospitalizations and catheterizations), blood cultures may help identify the clinically significant pathogen and guide the choice of the antimicrobial regimen. Finally, because bacteremia has been associated with more severe disease and worse outcomes, some authors suggest a longer treatment duration for bacteremic patients. However, whether the presence of bacteremia should alter the duration of treatment remains unclear. Conclusions: Obtaining blood cultures may be useful in selected patients. Randomized controlled trials are needed to clarify the value of bacteremia in guiding the duration of antimicrobial therapy.