Fosfomycin resistance in extended-spectrum beta-lactamase producing Escherichia coli isolated from urinary tract-infected patients in a tertiary care hospital

Abstract

Introduction. Urinary tract infections (UTIs) are a significant global health concern, with Escherichia coli being the predominant pathogen responsible for uncomplicated and complicated cases. Fosfomycin has emerged as a promising oral treatment option for multidrug-resistant UTIs, particularly those caused by extended-spectrum β-lactamase (ESBL)-producing E. coli. However, fosfomycin resistance has been paralleled by its irrational use and the emergence of enzymes that modify fosfomycin in ESBL-producing Enterobacteriaceae, especially in Asia.Hypothesis/Gap Statement. There is limited data on the prevalence of fosfomycin resistance among UTI patients in Northern Haryana, India. We hypothesize that demographic factors such as age, gender and patient type (inpatient vs. outpatient) may influence the prevalence of fosfomycin resistance and also provide insights into the effectiveness of fosfomycin in combating ESBL-producing E. coli infections in a tertiary care setting.Aim. This study aimed to investigate the prevalence of fosfomycin resistance among ESBL-producing E. coli among UTI patients in a tertiary care hospital.Methodology. Between March 2023 and February 2024, 7,348 urine samples were received from patients suspected of UTIs. The samples were subjected to screening using wet film examination and standard microbiological methods. Antibiotic susceptibility testing was done by VITEK-2 Compact (using an N-235 card), and ESBL production was confirmed using the combination disc diffusion test.Results. Out of 7,348 urine samples, 1,176 (16%) were culture-positive, with E. coli accounting for 57% of the isolates. Among the 385 E. coli isolates, 224 (58%) were ESBL producers. Fosfomycin demonstrated high efficacy, with 95% susceptibility among ESBL-producing E. coli and 96% among non-ESBL producers. However, 5% of ESBL-producing E. coli isolates were resistant to fosfomycin. Resistance to other antibiotics, such as nalidixic acid (98%) and ampicillin (93%), was notably high. No significant associations were found between ESBL production and demographic factors such as age, gender or patient type (outpatient vs. inpatient).Conclusion. Fosfomycin remains a highly effective treatment option for ESBL-producing E. coli UTIs in Northern Haryana, India, with low resistance rates observed. However, the emergence of fosfomycin resistance, albeit minimal, highlights the need for continuous surveillance and rational use of antibiotics to combat the growing threat of antimicrobial resistance.

Keywords: Escherichia coli; extended-spectrum beta-lactamases; fosfomycin resistance; urinary tract infections.

Fig. 1.. Microscopy of urine (wet mount of urine).

Fig. 2.. Fosfomycin resistance among E. coli isolated from inpatient and outpatient groups.