556. Evaluation of Antimicrobial Susceptibility Patterns Following Implementation of Levofloxacin Prophylaxis in those with Cancer and Blood Disorders

Abstract Background Prophylaxis with levofloxacin to prevent bacteremia in certain high-risk oncologic populations has been standard of care since the 2018 publication from the Children’s Oncology Group (JAMA 2018; 320(10)). This study only had susceptibility data for a minority of isolates and did not assess unit-wide impact on development of resistance, an important outcome given fluoroquinolones (FLQs) lead to resistance not only to FLQs but other drug classes, and not only for patients receiving fluoroquinolones rather unit wide. Our objective was to evaluate the development of resistance unit wide after implementing FLQ prophylaxis in our high-risk oncology patients, in addition to evaluating the overall impact on bacteremia. Methods A 6-year (1/2016-12/2021) single-center, retrospective review rates of bacteremia and susceptibility data from the Children’s Hospital Colorado Center for Cancer and Blood Disorders, encompassing the FLQ prophylaxis initiation date of 11/2018. All positive blood cultures were extracted from Meditech® or EPIC Beaker®, and susceptibility data from Microscan® or Sensititer®, with Institutional review board approval. Repeat cultures were not included. All data was analyzed using descriptive statistics performed in Excel®. Results Within the defined study period, there were 199 total blood cultures. These data were normalized per 1000 central line days, and analysis suggests there has been no significant change in bacteremia rates after implementing levofloxacin prophylaxis. Organisms reported nonsusceptible to levofloxacin or ciprofloxacin rose from over 11% in 2016 to almost 46% in 2021. Comparison of trends before and after the 2018 change reveals a significant difference in percent nonsusceptibility for those antibiotics (p = 0.02). Ceftriaxone or cefotaxime and cefepime were also analyzed and while not statistically significant there was a trend toward increasing resistance for ceftriaxone or cefotaxime (Figures). Conclusion Bacteremia on the oncology unit did not decrease after the implementation FLQ prophylaxis in November 2018. Additionally, resistance to FLQ and other antimicrobial classes is increasing, calling into question the benefit of this practice. Disclosures All Authors: No reported disclosures.