Susceptibility of Urinary Escherichia coli to Fosfomycin and Nitrofurantoin- Re-Exploration of Old and Forgotten Oral Antibiotics

BACKGROUND Urinary tract infections (UTI) are one of the most common causes for patients to seek medical attention and also for prescription of antibiotics. Escherichia coli is the most common pathogen isolated from both complicated and uncomplicated UTI. Frequent and inappropriate use of antibiotics has led to antimicrobial resistance in the organisms. Multidrug resistance and carbapenem resistance are posing greater challenges to the clinicians. With only few antibiotics expected to be in the pipeline in the continuing five to ten years, the options that we are left with today are prudent use of antibiotics and re-exploration of old and forgotten antibiotics like nitrofurantoin, fosfomycin to help in combating the development of further resistance. METHODS This study was conducted in the Department of Microbiology, of our tertiary care hospital from March 2019 to June 2019. Retrospective analysis of results of urine culture was done. Isolates resistant to one antibiotic in at least three classes were considered as multidrug resistant. Susceptibility to fosfomycin and Nitrofurantoin among the MDR and non-MDR isolates were compared RESULTS Escherichia coli (66.67 %) was the most common Enterobacteriaceae to be isolated, followed by Klebsiella pneumoniae ( 25.49 %). A very high susceptibility was noted to fosfomycin and Nitrofurantoin, with only 2.91 % and 14.04 % of the isolates being resistant to fosfomycin and nitrofurantoin respectively. Highest resistance was noted against ampicillin with 485 (83.05 %) being resistant followed by ciprofloxacin (65.75 %), norfloxacin (62.84 %), cotrimoxazole (47.09 %) and amoxicillin-clavulanic acid (36.99 %). About 49.14 % of the isolates were found to be multi-drug resistant. There was no significant difference in the resistance rates to fosfomycin among the MDR (3.83 %) and non-MDR isolates (2.02 %), while 20.55 % of the MDR isolates and 7.74 % of non-MDR isolates were resistant to nitrofurantoin. CONCLUSIONS Due to emergence of resistance to commonly used oral antibiotics in UTI, among the two older drugs- Nitrofurantoin and Fosfomycin, the latter can be used for treatment of acute cystitis, especially in cases due to MDR Escherichia coli, as Fosfomycin is equally effective against both MDR and non-MDR Escherichia coli isolated from urine samples while nitrofurantoin may be less effective against the MDR strains.