Fosfomycin Susceptibility Among Multidrug-Resistant Extended-Spectrum β-Lactamase and Metallo-β-Lactamase–Producing Uropathogens in a Tertiary Care Hospital

Urinary tract infections (UTIs) affect an estimated 150 million people each year worldwide involving women more than men. Because of unrestricted use of antimicrobials and accelerating antimicrobial resistance, therapeutic options for treatment of UTIs are becoming limited. Fosfomycin, a broad-spectrum, rapidly absorbable, antimicrobial agent with good bioavailability and substantial activity against multidrug-resistant (MDR) isolates has antimicrobial activity against a substantial percentage of these MDR isolates. A cross-sectional study over a period of 20 months on urine samples of all patients of all age groups clinically suspected of UTI was conducted in a tertiary care center of southern Rajasthan. Samples were processed immediately as per standard microbiological techniques, followed by culture by a semiquantitative method and antimicrobial susceptibility testing using the Kirby-Bauer disk diffusion method. All gram-negative pathogens were screened for extended-spectrum β-lactamase and further metallo-β-lactamase production using standard disk diffusion tests. Of the 1858 positive samples isolated, the most common uropathogen was Escherichia coli (59.96%), with 8.97% confirmed extended-spectrum β-lactamase–producing isolates. Fosfomycin had susceptibility of 96.69%, with its sensitivity and specificity being 98.15% and 6.98% more than nitrofurantoin, respectively. Among the metallo-β-lactamase producers, fosfomycin had susceptibility of 78.58%, with sensitivity and specificity being 91.67% and 25% more than nitrofurantoin, respectively. With an increasing threat due to MDR uropathogens in both hospitals and in the community, fosfomycin, with its unique mechanism of action, appears to be a better oral, effective, and safe therapeutic option and a viable potential alternative over other drugs for treatment of UTIs.