Incomplete recovery of the fecal flora of hematological patients with neutropenia and repeated fluoroquinolone prophylaxis

BACKGROUND: Routine fluoroquinolone prophylaxis in neutropenic patients with hematological malignancies is still controversial, because of antibiotic resistance concerns. The recovery of the fecal microbiota to the initial composition in patients receiving multiple courses of quinolone prophylaxis and repeated chemotherapy has not been evaluated. METHODS: We prospectively examined the changes in the fecal bacterial composition before and after levofloxacin prophylaxis. A sequential observation of bacterial resistance in patients receiving multiple prophylactic courses was also conducted. RESULTS: In this trial, 68 cases, including (35 with the first course and 33 with the second and subsequent courses) were registered. The disappearance of quinolone-susceptible (QS) Entero-bacteriaceae and dominant emergence of quinolone-resistant (QR) coagulase negative staphylococci (CNS) and QR Enterococci were observed after the first prophylaxis. The detection of QS Enterobacteriaceae was recovered before the second and subsequent courses to a level of the initial composition (28/35 samples, 80.0% before the first course vs 23/33 samples, 69.7% before the second and subsequent courses, P=0.41). In contrast, the detection rate of QR CNS and Enterococci significantly increased at the second and subsequent courses, even before prophylaxis (8/35 samples, 22.9% before the first course vs 20/33 samples, 60.6% before the second and subsequent courses, P=0.003). The incomplete recovery of the initial bacterial composition was associated with a prophylactic interval of within 30 days. Of the patients receiving multiple prophylactic courses, six had QR Escherichia coli, including extended-spectrum β-lactamase (ESBL) producers, at the first course, and four (66.3%) of the six patients had persistent detection of QR E. coli at the second course. CONCLUSION: In patients receiving multiple courses of prophylactic quinolone, along with a common chemotherapy schedule, newly emergent resistant bacteria could be frequently persistent in their fecal flora.