In vitro activity of fosfomycin against carbapenem resistant Enterobacteriaceae isolated from urine

Abstract

BACKGROUND: With the increased detection of multidrug-resistant (MDR) pathogens from urine, an attempt is made to search for safe and effective antibiotics. Recently, fosfomycin has been tried as an alternative to treat urinary tract infections (UTIs).

OBJECTIVE: To see and assess in vitro sensitivity pattern of carbapenem resistant Enterobacteriaceae (CRE) to fosfomycin.

STUDY DESIGN: Cross Sectional Study

PARTICIPANTS: Urinary samples (Enterobacteriaceae) resistant to carbapenems.

METHODS: All urinary isolates which were carbapenem resistant by disk diffusion method were included in the study. Susceptibility testing for fosfomycin was done using disk diffusion, E-Test and agar dilution methods.

RESULTS: A total of 200 carbapenem resistant Enterobacteriaceae (CRE) urinary isolates were collected. Escherichia coli (75%) was the most common isolate recovered followed by Klebsiella spp (22%) , Enterobacter spp (1%); Proteus spp (1%); Serratia and Citrobacter spp (0.5% each).

By disk diffusion, E-test and agar dilution methods 98.0%, 97.3%, 98.6% Escherichia coli and 88.6% , 86.3% , 90.9%  Klebsiella spp were susceptible to fosfomycin respectively.

CONCLUSION: We observed that fosfomycin is active against common UTI causing pathogens especially ESBL’s and CRE’s. The same was confirmed by three methods of antimicrobial sensitivity testing (AST). Agar dilution and E-test being quite laborious, time consuming, expensive and requiring expertise. Thus, disk diffusion can be used as alternative to agar dilution method for routine AST.

IMPLICATIONS: Our study proved that there is still hope against the ESBL and CRE urinary pathogens. Single dose fosfomycin for uncomplicated cystitis makes it a more attractive alternative. However, our study awaits clinical trials in our setup to further see the role of fosfomycin against CRE. Moreover, a continuous effort is needed to study the dynamics of drug resistance against fosfomycin in coming years.