Extended-Spectrum β-Lactamase-Producing Escherichia coli Refractory to Nitrofurantoin and Fosfomycin Treatment: A Case Report Associated with Nephrolithiasis

Abstract

Urinary tract infections (UTIs) are highly prevalent, with Escherichia coli being the main etiological agent. Therefore, this study aims to report a case of UTI complicated by nephrolithiasis, caused by ESBL-producing E. coli and refractory to treatment, highlighting clinical aspects, the resistance profile, and management. This study is descriptive (case report) with clinical and laboratory follow-up. Diagnosis and susceptibility profiling were based on urinalysis, urine cultures, and an automated system following BrCAST guidelines, combined with ultrasound examinations and assessment of therapeutic response. The female patient had a history of recurrent UTIs, persistent bacteriuria caused by ESBL-producing E. coli, and bilateral nephrolithiasis. Despite in vitro susceptibility to nitrofurantoin and fosfomycin and hospitalization for intravenous antibiotic therapy (piperacillin/tazobactam), the condition evolved with early recurrences and successive therapeutic failures. Refractoriness resulted from a dual mechanism: pharmacokinetic limitations and physical protection of the stones by a probable bacterial biofilm, demonstrating the ineffectiveness of purely conservative therapies in the presence of obstructive barriers. Definitive management of UTIs complicated by nephrolithiasis necessarily requires source control through surgical intervention for complete clearance, eliminating the bacterial reservoir and interrupting the infectious cycle.