Susceptibility Profile and Clinical Response of Fosfomycin and Other Antibiotics against Multidrug Resistant Gram Negative Urinary Isolates: A Cross-sectional Study

Introduction: Irrational use of antibiotics to treat Urinary Tract Infections (UTI) has led to the development of Multidrug Resistant (MDR) bacteria in both community as well as the hospital settings. Fosfomycin has emerged as a novel therapeutic option to treat these UTI patients along with empirically used routine antibiotics.

Aim: To assess the sensitivity, molecular resistance mechanisms and clinical response of fosfomycin along with other urinary antibiotics like nitrofurantoin, colistin, and imipenem.

Materials and Methods: It was a cross-sectional observational study conducted from July 2018 to June 2019 in SGPGIMS, Lucknow, India. Stream urine samples of 24,782 patients were collected with clinical suspicion of UTI. The antibiotics were tested by disc diffusion and Minimum Inhibitory Concentration (MIC) methods. Genotypic analysis was done for testing resistance mechanisms in fosfomycin resistant isolates. Statistical tests were performed using Statistical Package for the Social Sciences (SPSS) software for Windows version 14.0.

Results: Out of the 24,782 urine samples, 2,776 (11.2%) showed significant growth of pathogens with 334 drug resistant isolates among them. Gram negative bacilli 1846 (66.50%) was the most predominantly isolated pathogen in the cultures. Among the 334 drug resistant specimens, Escherichia coli {124 (37.13%)} were maximum in number. Total 79.6% (266/334) of the isolates were sensitive to fosfomycin including 88.7% (110/124) of E. coli, and 91.3% (105/115) of K. pneumoniae isolates. Colistin showed sensitivity in 87.1% (108/124) of the E. coli isolates; followed by Imipenem in 49.2% (61/124) and nitrofurantoin in 37.1% (46/124) of the isolates. Fos A genes were found to be the most prevalent in Fosfomycin resistant. About 41% of the patients showed favourable outcome and were cured with initiation of treatment as per sensitivity pattern.

Conclusion: Fosfomycin has emerged as a safer option in MDR urinary isolates as compared to other urinary antibiotics including colistin. The drug needs to be more widely studied for its possible pharmacokinetics and dynamics as well as it’s possible implications in healthcare settings and patient management.