1581. Impact of Colonization with Fluoroquinolone-Resistant Enterobacteriaceae on the Risk of Gram-Negative Bacteremia in Hematopoietic Stem Cell Transplant Recipients Who Receive Prophylactic Levofloxacin

BACKGROUND: Fluoroquinolone (FQ) prophylaxis is widely used to prevent bloodstream infections (BSIs) in neutropenic patients undergoing hematopoietic stem cell transplantation (HCT). In order to assess whether increasing FQ resistance threatens the effectiveness of FQ prophylaxis, we screened HCT recipients for colonization with FQ-resistant Enterobacteriaceae (FQRE) and assessed the impact of colonization on the risk of BSI. METHODS: We collected stool samples on admission for HCT and weekly until neutrophil engraftment from patients at NewYork-Presbyterian Hospital/Weill Cornell Medical Center from November 2016 to March 2018. Patients received FQ prophylaxis during neutropenia. Perianal swabs were used when stool was unavailable. Stool and swab samples were plated onto MacConkey agar with 1 μg/mL ciprofloxacin, and colonies were identified and underwent antimicrobial susceptibility testing. We determined the prevalence of colonization with FQRE on admission for HCT, the risk of acquiring FQRE, and compared the risk of BSI during the transplant admission in colonized and noncolonized patients. RESULTS: We evaluated 178 HCT recipients and found that 35 (20%) had pre-transplant FQRE colonization (allogeneic: 20/89, 22%; autologous: 15/89, 17%). Thirty FQRE (86%) were Escherichia coli, 5 (14%) were Klebsiella pneumoniae, and 13 (37%) were extended-spectrum β-lactamase producers. Five (14%) of the 35 patients with pre-transplant FQRE colonization developed BSI due to an Enterobacteriaceae, and all bloodstream isolates had identical susceptibility profiles to the colonizing FQRE. In contrast, only one (1%) of 143 patients without pre-transplant FQRE colonization developed Enterobacteriaceae BSI (P = 0.001). Patients with pre-transplant FQRE colonization also had higher rates of any Gram-negative BSI (20% vs. 1%, P < 0.001), but did not have increased risk of Gram-positive BSI (6% vs. 11%, P = 0.5). Of 123 patients without initial FQRE colonization who had follow-up samples collected, 10 (8%) acquired FQRE during post-HCT neutropenia. CONCLUSION: FQRE colonization is common on admission for HCT and is associated with decreased effectiveness of levofloxacin prophylaxis in preventing Gram-negative BSI during post-transplant neutropenia. DISCLOSURES: M. J. Satlin, Hardy Diagnostics: Grant Investigator, Research support; Allergan: Grant Investigator, Grant recipient; Merck: Grant Investigator, Grant recipient; Biomerieux: Grant Investigator, Grant recipient; Achaogen: Consultant, Consulting fee. R. Malherbe, Hardy Diagnostics: Employee, Salary. S. G. Jenkins, Merck: Grant Investigator, Grant recipient. L. F. Westblade, Accelerate Diagnostics: Grant Investigator, Grant recipient; Biomerieux: Grant Investigator, Grant recipient; Allergan: Grant Investigator, Grant recipient; Merck: Grant Investigator, Grant recipient. T. J. Walsh, Merck: Grant Investigator, Research grant; Atellas: Consultant, Grant Investigator and Scientific Advisor, Consulting fee and Research grant; Gilead: Scientific Advisor, Consulting fee; Allergan: Grant Investigator and Scientific Advisor, Consulting fee and Research grant; Scynexis: Grant Investigator, Research grant; Amplyx: Grant Investigator, Research grant; Shionogi: Scientific Advisor, Consulting fee.