Evaluation of Fosfomycin in-vitro susceptibility among gram negative isolates from urine culture in a tertiary care hospital in Lucknow

Abstract

The rise of bacteria that are Multidrug- resistant or Extended Drug Resistant (MDR or XDR) and the lack of novel antibiotics have wreaked havoc on patient treatment options. Fosfomycin has just recently come to light because of the development of resistance to existing drugs. This study aims to evaluate the Fosfomycin susceptibility of Gram- negative isolates in vitro. A prospective study done in the Department of Microbiology, Integral Institute of Medical Sciences of Research, Lucknow, over a period of six months from April 2023 to September 2023. A total of 1328 urine samples were processed in microbiology lab and after identification of urinary isolates, antibiotic susceptibility testing was performed, and results were interpreted following the Clinical and Laboratory Standards Institute guidelines (CLSI). Fosfomycin sensitivity was tested by the Kirby-Bauer disc diffusion method. 353 of the 1328 processed urine samples showed a growth of pathogens. 184 (52.1%) of the isolates were Gram-negative, while 169 (47.8%) were Gram-positive. Fosfomycin (7%) and Nitrofurantoin (13%) showed lower rates of resistance among these isolates. Relatively higher rates of resistance were observed for Doripenem (17%), Meropenem (17%), Imipenem (18%), Amikacin (18%), Gentamicin (27.9%). Norfloxacin, Aztreonam, Cefepime, Ciprofloxacin and Levofloxacin and Cotrimoxazole showed a high resistance rate of 46.2%, 48.8%, 50%, 60.4%, 61% and 70% respectively. Fosfomycin's low resistance (7%) to the antibiotic indicates that it works well as a urinary antibiotic. Uropathogenic Enterobacteriaceae isolates exhibited an excellent level of in vitro susceptibility to Fosfomycin. These in vitro results highlight the unexplored possibilities of Fosfomycin as a superior therapeutic option for the treatment of UTIs, and it has a good chance of expanding into a safe and effective oral alternative treatment that can be used in inpatient as well as outpatient settings.