Re: ‘Treatment duration for Escherichia coli bloodstream infection and outcomes’ by Giannella et al.
Authors: S. Karakonstantis
Journal: Clinical Microbiology and Infection (2018)

I read with great interest the recently published article by Giannella et al. [[1]Giannella M. Pascale R. Toschi A. Ferraro G. Graziano E. Furii F. et al.Treatment duration for Escherichia coli bloodstream infection and outcomes: retrospective single-centre study.Clin Microbiol Infect. 2018; 24: 1077-1083Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar] evaluating the impact of the duration of antimicrobial therapy on mortality and relapse in patients with Escherichia coli bacteraemia. Urinary tract infections (UTIs) were the most common source of bacteraemia in this study (about half of the patients in both treatment groups). The lack of association of treatment duration with outcomes in bacteraemic UTI patients is in agreement with most [[2]Karakonstantis S. Kalemaki D. Blood culture useful only in selected patients with urinary tract infections—a literature review.Infect Dis (Lond). 2018; 50: 584-592Crossref PubMed Scopus (11) Google Scholar], but not all [[3]Nelson A.N. Justo J.A. Bookstaver P.B. Kohn J. Albrecht H. Al-Hasan M.N. Optimal duration of antimicrobial therapy for uncomplicated Gram-negative bloodstream infections.Infection. 2017; 45: 613-620Crossref PubMed Scopus (48) Google Scholar], similar studies. When assessing treatment duration in patients with bacteraemic UTI, many factors should be considered. For example, in a recent multicentre randomized controlled trial comparing 7 days to 14 days of treatment, shorter duration was associated with higher treatment failure among male UTI patients [[4]van Nieuwkoop C. van der Starre W.E. Stalenhoef J.E. van Aartrijk A.M. van der Reijden T.J. Vollaard A.M. et al.Treatment duration of febrile urinary tract infection: a pragmatic randomized, double-blind, placebo-controlled non-inferiority trial in men and women.BMC Med. 2017; 15: 70Crossref PubMed Scopus (45) Google Scholar]. Similarly, in a retrospective study, the association of shorter duration (7–10 vs. >10 days) with treatment failure among patients with bacteraemic UTIs was statistically significant in male but not female subjects [[5]Al-Hasan M.N. Nelson A.N. Justo J.A. Albrecht H. Kohn J. Brandon Bookstaver P. Reply to comments: duration of antimicrobial therapy for Gram-negative bacteremia secondary to urinary source of infection.Infection. 2018; 46: 283-284Crossref PubMed Scopus (2) Google Scholar]. Furthermore, the regimen used for definitive therapy (e.g. fluoroquinolones vs. β-lactams, or intravenous vs. oral therapy) is another important factor to consider when assessing treatment duration. In studies that failed to find a benefit from longer treatment duration, a fluoroquinolone was used for the short treatment course [[2]Karakonstantis S. Kalemaki D. Blood culture useful only in selected patients with urinary tract infections—a literature review.Infect Dis (Lond). 2018; 50: 584-592Crossref PubMed Scopus (11) Google Scholar]. Moreover, in the above-mentioned retrospective study, definitive therapy with intravenous regimens or oral fluoroquinolones was associated with a lower risk of treatment failure [[5]Al-Hasan M.N. Nelson A.N. Justo J.A. Albrecht H. Kohn J. Brandon Bookstaver P. Reply to comments: duration of antimicrobial therapy for Gram-negative bacteremia secondary to urinary source of infection.Infection. 2018; 46: 283-284Crossref PubMed Scopus (2) Google Scholar]. Therefore, a subgroup analysis considering only patients with E. coli bacteraemia resulting from UTI, including a separate analysis in male and female patients, would be interesting. Furthermore, an analysis taking into account the antibiotic regimen would also provide useful information. For example, what was the impact of treatment duration for bacteraemic UTIs when nonfluoroquinolone antibiotics were used for definitive therapy compared to definitive therapy with fluoroquinolones? In conclusion, the appropriate treatment duration for Gram-negative bacteraemia remains unclear [[1]Giannella M. Pascale R. Toschi A. Ferraro G. Graziano E. Furii F. et al.Treatment duration for Escherichia coli bloodstream infection and outcomes: retrospective single-centre study.Clin Microbiol Infect. 2018; 24: 1077-1083Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar]. Retrospective analyses have significant limitations. Ongoing randomized controlled trials (e.g. ClinicalTrial.gov NCT03005145, NCT03101072, NCT01737320, NCT02400268) will provide important information regarding the optimal duration of antimicrobial therapy for Gram-negative bloodstream infections. The author reports no conflicts of interest relevant to this letter. Treatment duration for Escherichia coli bloodstream infection and outcomes: retrospective single-centre studyClinical Microbiology and InfectionVol. 24Issue 10PreviewTo investigate the impact of treatment duration on mortality and on relapse in patients with Escherichia coli bloodstream infection (BSI). Full-Text PDF Open Archive‘Treatment duration for Escherichia coli bloodstream infection and outcomes’ – Author's replyClinical Microbiology and InfectionVol. 25Issue 5PreviewWe are very grateful to Stamatis Karakonstantis for his comments on our study [1]. According to his suggestions [2], we have analysed the impact of treatment duration on outcome among subgroups of our study population (data shown in Table 1). It should be highlighted that, as expected for Escherichia coli bloodstream infection (BSI), the number of outcome events (i.e. all-cause 30-day mortality and 90-day relapse) was low; as a result, the study is not deemed to have reasonable power for these subgroup analyses. Full-Text PDF Open Archive