Background Ceftolozane/tazobactam (C/T) is a novel cephalosporin/β-lactamase inhibitor currently dosed by 8-hour intervals to treat complicated and multidrug-resistant Pseudomonas aeruginosa infections in inpatients. This dosing strategy limits the ability to transition patients to outpatient antimicrobial therapy. There are limited data in the literature to support continuous infusion (CI) dosing. Methods This study is a retrospective chart review of patients who received CI C/T at an infusion center part of a community health system. Patients were evaluated from August 2016 through January 2018. Patients were included in the study if they were ≥18 years old and received their entire course of C/T as a CI in the outpatient setting. Patients were excluded if they received any part of their therapy as an inpatient. Results The primary outcome evaluated was symptom resolution. Secondary outcomes evaluated were microbiologic resolution as well as patient satisfaction. Seven patients received either 4.5 or 9 grams of continuous infusion C/T every 24 hours in the outpatient setting over the study period. For the primary outcome, 6 of 7 patients had symptom resolution. For the secondary outcomes, 3 of 3 patients had microbiologic resolution, and patient satisfaction scores were overall positive among respondents. Conclusions Ceftolozane/tazobactam delivered as a continuous infusion may be a safe, effective, and convenient way to treat infections caused by P aeruginosa. This novel treatment regimen can be an option for patients to avoid hospital admission or discharge to complete therapy as an outpatient.

BackgroundCeftolozane/tazobactam (C/T) is indicated for complicated intra-abdominal infections and complicated urinary tract infections (cUTI). Its spectrum of activity extends to most Gram-negative bacteria including multidrug-resistant (MDR) Pseudomonas aeruginosa and extended-spectrum β-lactamase-producing enterobacteriaceae. Current dosing requires 8-hour intervals in order to meet appropriate concentrations above the MIC, making outpatient delivery logistically difficult. C/T is stable up to 24 hours at room temperature, allowing for potential continuous infusion. This study evaluated patients who received this novel dosing regimen at an outpatient infusion center.MethodsThis study was a nonrandomized, retrospective chart review of adult patients who received C/T August 2016–January 2018 for any indication, including off-label, in the outpatient setting as a continuous infusion. Primary outcome evaluated was symptom resolution at the end of therapy documented in outpatient records. Secondary outcomes were microbiologic resolution at the end of therapy, if available, and patient satisfaction via a modified patient satisfaction survey assessed from follow-up phone call to patient.ResultsSeven patients received C/T in the outpatient setting and were included in the study. Infections treated varied and included pneumonia (three), cUTI (two), skin and soft tissue (one), and bacteremia (one). Most patients received 4.5 g (with one receiving 9 g) C/T over 24 hours mixed with normal saline via an ambulatory infusion pump refilled each day at an outpatient infusion center. All seven patients were infected with P. aeruginosa (four being MDR) with one patient co-infected with E. coli. Susceptibility testing was performed on three P. aeruginosa isolates (two susceptible and one intermediate). Six of seven patients reported symptom resolution at the end of therapy. Three patients were microbiologically evaluable at the end of therapy and all three demonstrated microbiologic resolution. Three of seven patients completed the satisfaction survey with all three reporting overall satisfaction. No adverse events were documented from any patients.ConclusionCeftolozane/tazobactam administered as a continuous infusion in the outpatient setting is a safe, effective, and convenient way to treat complicated P. aeruginosa infections.Disclosures B. M. Jones, Merck: Grant Investigator, Grant recipient. C. Bland, Merck: Grant Investigator and Speaker’s Bureau, Grant recipient and Speaker honorarium.