Abstract:
Background: Emergence of resistance among Escherichia coli (E.coli) isolates against therapeutic
options for UTIs (Urinary tract infections) has led to renewed interest in older antibiotics like
Fosfomycin. In this study we evaluated diagnostic accuracy of Rapid Fosfomycin NP test based on
glucose metabolism for rapid Fosfomycin susceptibility testing among urinary E.coli isolates.
Methods: In a cross-sectional validation study conducted in the Microbiology Department, Armed
Forces Institute of Pathology, Rawalpindi, Pakistan from 15th March to 15th September 2020, 149
consecutive urine specimens were included as per selection criteria. Rapid Fosfomycin NP test
was performed as per protocol of Nordmann P et al on urinary E.coli isolates for detection of
Fosfomycin resistance and results were compared with reference modified Kirby-Bauer disk
diffusion method. Results: Out of total 149 E.coli isolates from 149 urine specimens, 80 were
classified as Fosfomycin susceptible and 69 as Fosfomycin resistant by reference disk diffusion
method. Sensitivity, specificity, positive predictive value, negative predictive value and diagnostic
accuracy of rapid Fosfomycin NP test was found to be 94.2%, 98.75%, 98.48%, 95.2% and
96.64%, respectively. In our study reliable results were achieved after 2.5 hours of incubation.
Conclusion: The rapid Fosfomycin NP test is valid and user-friendly technique which can be
performed with minimal technical expertise. It is less time consuming than disk diffusion and Etest
strips and easy to perform as compared to agar dilution method. It can be useful as alternative
to agar dilution in urinary E.coli isolates which would help in selecting appropriate therapeutic
option for UTIs.
