P-1331. Efficacy of Levofloxacin for Levofloxacin-Susceptible, Ciprofloxacin-Nonsusceptible Enterobacterales

TL;DR

This study examines how well levofloxacin works against certain bacteria that are resistant to ciprofloxacin but still susceptible to levofloxacin.

Contribution

This is the first study to evaluate clinical outcomes for fluoroquinolone-treated patients with discordant fluoroquinolone sensitivities.

Findings

Microbiologic failure occurred in 29.2% of patients treated with levofloxacin.

Lower fluoroquinolone dose may be a risk factor for treatment failure.

90-day all-cause mortality was 14.6% in the studied cohort.

Abstract

Fluoroquinolones (FQ) are critical Gram-negative agents due to their oral availability and stability against beta-lactamases such as ESBL and AmpC. Resistant organisms frequently co-harbor FQ resistance genes. There are copious resistance mechanisms and no widely available genotypic analysis, yet in vitro studies suggest a higher resistance risk for discordant susceptibilities. Discordance is documented in a subset of Enterobacterales isolates; there is a paucity of literature describing FQ efficacy in this population. We aim to evaluate microbiologic and clinical success of patients receiving levofloxacin LVX-Susceptible (LVX-S), Ciprofloxacin-nonsusceptible (CIP-NS) Enterobacterales.Table 1.Published Microbiologic Success in Similar Populations

Published Microbiologic Success in Similar Populations

This is a single-arm, retrospective, descriptive analysis of patients aged 18-89 treated for LVX-S, CIP-NS Enterobacterales who received LVX. Susceptibility testing was performed via Phoenix BMD with the exception of Serratia (Kirby Bauer). Primary outcome was 90d microbiologic failure, defined as growth of the same organism within 90d of index culture. Secondary outcomes were growth of LVX-R isolates, 90d treatment failure defined as retreatment regardless of cultures, receipt of salvage therapy, and 90d all-cause mortality.

Preliminary reporting identified 73 patients; 48 were included. Median age was 60.0 and patients were predominantly female (66.7%). Most common organism was K. pneumoniae (41.7%). The majority (85.4%) were ceftriaxone-R. Microbiologic failure occurred in 14 (29.2%) of patients. LVX-R isolates grew in 4 patients. Treatment failure occurred in 11 (22.9%) patients. 90d all-cause mortality was 14.6%. Post hoc analysis of risk factors for composite failure was not significant, including receipt of high-dose LVX (OR = 0.2; 95% CI: 0.1-1.1).

In this cohort of LVX-treated patients with LVX-S, CIP-NS isolates showed 90d microbiologic failure in 29.2% of patients, which is higher than published literature. Lower FQ dose may be a risk factor for failure. This study has significant limitations including its design and small sample size. To our knowledge, this is the first study of clinical outcomes for FQ-treated patients with discordant FQ sensitivities. Results should be confirmed with larger analyses.

All Authors: No reported disclosures

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