TOPLINE:

Among allogeneic haematopoietic cell transplant (allo-HCT) recipients, ciprofloxacin prophylaxis was associated with fewer bloodstream infections (BSIs) as well as higher rates of antimicrobial resistance and greater overall antibiotic use; the reduction in BSIs did not clearly correspond to lower mortality or fewer ICU admissions.

METHODOLOGY:

• Researchers compared clinical and microbiologic outcomes in 343 patients (median age, 50 years; 59.2% men) who underwent their first allo-HCT for haematological malignancies at two transplant centres in London, each of which used a different ciprofloxacin prophylaxis strategy.
• At one centre, patients received oral ciprofloxacin (500 mg twice daily) during neutropenia (n = 150); at the other centre, no antibacterial prophylaxis was given (n = 193).
• Data on BSIs, antimicrobial resistance, antibiotic consumption, and other transplant outcomes were extracted from electronic medical records.
• A BSI was recorded when a bacterial pathogen was isolated from non-contaminated blood cultures; antibiotic use was measured as days of therapy­­ (defined as the administration of one antibiotic on a given day, regardless of dose number or strength).
• The primary outcome was in-hospital all-cause mortality, and secondary outcomes were ICU admission; length of hospital stay; BSIs from the onset of neutropenia until engraftment, discharge, or death; antimicrobial susceptibility of BSI isolates; and antibiotic use.

TAKEAWAY:

• Overall, BSIs occurred in 28.7% of patients at the ciprofloxacin centre vs 44.0% of those at the no-prophylaxis centre, a difference driven mainly by fewer BSIs caused by gram-negative bacteria (15.3% vs 31.6%; P < .001 for both).
• After adjusting for covariates, patients who did not receive prophylaxis had higher odds of developing BSIs (adjusted odds ratio [aOR], 4.06; 95% CI, 2.04-8.09) and BSIs caused by gram-negative bacteria (aOR, 3.43; 95% CI, 1.69-6.95) than those who received ciprofloxacin prophylaxis; however, the rates of in-hospital mortality and ICU admission were similar between centres.
• Enterobacterales isolates from BSIs in patients at the ciprofloxacin centre showed higher antimicrobial resistance to ciprofloxacin (73.7% vs 18.5%), piperacillin-tazobactam (63.2% vs 16.7%), ceftriaxone (68.4% vs 18.5%), meropenem (15.8% vs 0%), and amikacin (21.1% vs 1.9%).
• The overall days of therapy were substantially higher at the ciprofloxacin centre, including more frequent use of carbapenems.

IN PRACTICE:

"The combination of the latest evidence leads us to believe that, in settings with prompt access to treatment antimicrobials and organ support when signs and symptoms of infection develop, cessation of universal fluoroquinolone prophylaxis may be clinically safe… Accordingly, our findings prompt the re-valuation of the place of fluoroquinolone prophylaxis during allo-HCT," the authors wrote.

SOURCE:

The study was led by Ioannis Baltas, University College London, London, England. It was published online on March 29, 2026, in International Journal of Infectious Diseases.

LIMITATIONS:

Variations in procedures and protocols of allo-HCT and patient populations between the two centres may have introduced unmeasured confounders, particularly affecting comparisons of antimicrobial resistance rates, as baseline colonisation rates for resistant pathogens were not assessed and likely differed by centre. Moreover, the retrospective nature of the data prevented reliable identification of the source of bacteraemia in all patients.

DISCLOSURES:

The study was funded by the National Institute for Health and Care Research, the Digital Health Hub for Antimicrobial Resistance funded by The Engineering and Physical Sciences Research Council, the Wellcome Trust, the National Institute of Allergy and Infectious Diseases, and other sources. One author disclosed receiving investigator-initiated funding and honoraria and serving on advisory boards for various pharmaceutical companies.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.