Background: Antistaphylococcal penicillins have historically been regarded as the drugs of choice for methicillin-susceptible Staphylococcus aureus (MSSA) bloodstream infections (BSI). However, recent outcomes data compared to cefazolin treatment are conflicting. Objective: This study compared treatment failure and adverse effects associated with nafcillin and cefazolin for MSSA BSI. Methods: Adult inpatients with MSSA BSI between January 1, 2009 and August 31, 2015 were included in this retrospective cohort study if they received ≥72 h of nafcillin or cefazolin as directed therapy after no more than 72 h of any empiric therapy. The primary composite endpoint was treatment failure defined by clinician documentation, 30-day recurrence of infection, all-cause 30-day in-hospital mortality, or loss to follow-up. Secondary outcomes included antibiotic-related acute kidney injury (AKI), acute interstitial nephritis (AIN), hepatotoxicity, and rash. Results: Among 157 patients, 116 (73.9%) received nafcillin and 41 (26.1%) received cefazolin. The baseline characteristics were similar except cefazolin-treated patients had higher APACHE II scores and more frequent renal dysfunction. No difference in the composite treatment failure outcome (28.4 vs. 31.7%; p = 0.69) was detected between the nafcillin and cefazolin groups, respectively. In a sensitivity analysis excluding patients without known follow-up, there was no significant difference of treatment failure. AKI, AIN, hepatotoxicity, and rash were all numerically more frequent among nafcillin-treated patients. Conclusions: Among nafcillin- or cefazolin-treated patients with MSSA BSI, there was no significant difference in treatment failure. Observing more frequent presumptive adverse effects associated with nafcillin receipt, future prospective studies evaluating cefazolin appear warranted.

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Background Inpatient settings have been the focus of most antimicrobial stewardship (AS) practices; however, the Joint Commission has now published requirements for accredited ambulatory healthcare organizations to implement AS. This analysis aimed to create a urine isolate antibiogram and to evaluate microbiological data and prescribing practices for UTI patients in the ED. Methods This retrospective cohort study included adults admitted to either of two EDs at University of Minnesota Medical Center and diagnosed with a UTI between 1/1/2018 and 12/31/2018. Patients were excluded if subsequently admitted to an inpatient unit or if they had a repeat culture growing the same organism as the index isolate. Diagnosis of cystitis versus pyelonephritis was based on ICD-10 coding. Data including urinalysis and culture results, susceptibilities, empiric antibiotic selection, and readmissions were collected. Results Data from 350 isolates were collected for inclusion in the antibiogram. Patient characteristics corresponding to this isolate collection included 78.9% female, median age of 41 years, and 64.6% diagnosed with pyelonephritis. Escherichia coli was the most common organism (70%), followed by Klebsiella pneumoniae (5.4%) and Proteus mirabilis (4%). Combined susceptibilities of E. coli isolates from both EDs were: 49.4% ampicillin, 55.7% ampicillin/sulbactam, 69.8% sulfamethoxazole/trimethoprim, 83.7% ciprofloxacin (CIP), 85.7% cefazolin, 93.9% ceftriaxone, and 94.3% nitrofurantoin (NIT). The most common discharge antibiotics prescribed for cystitis patients were NIT (29.8%) and cephalexin (25%). Pyelonephritis patients were most frequently prescribed CIP (32.3%) and cefdinir (14.2%). Drug-bug mismatches occurred in 19.1% of patients (10.5% cystitis vs. 23.9% pyelonephritis). The rates of ED readmission within 96-hours and inpatient admission within 30 days, for any reason, were 4.3% and 9.1% respectively. Conclusion Based on the ED-specific urine antibiogram generated, NIT (cystitis) and CIP (pyelonephritis) could be considered first-line agents for empiric treatment of UTI at our institution. Drug-bug mismatches were more common in pyelonephritis patients. These data will be used to develop a treatment algorithm aimed at improving treatment of UTI in the ED. Disclosures Elizabeth B. Hirsch, PharmD, Merck (Grant/Research Support)Nabriva Therapeutics (Advisor or Review Panel member)