Background: Rising rates of antimicrobial resistance among Enterobacteriaceae
limit the use of reliably active forms of available drugs. The aim of this study was to investigate
the prevalence of fosfomycin (US6794490B2) resistance gene among ESBL producing
isolates in Iran.
Method: We tested 355 isolates of Enterobacteriacea collected from various clinical samples
including urine, wounds, blood and other sources during June 2016 to July 2017. Antibiotic
sensitivity and Extended Spectrum Beta Lactamase (ESBL) production were tested
using agar dilution method according to the Clinical and Laboratory Standards Institute
(CLSI) guidelines. ESBL genes (blaTEM, bla SHV,bla CTX-M), plasmid-encoded fosfomycin resistance
genes (fosA, fosB, fosA3 and fosC2) and chromosomal mutations (murA, glpT,
uhpT) were detected by Polymerase Chain Reaction (PCR).
Results: In this study, 151 of the 355 isolates were ESBL-positive. blaCTX-M (77%) was the
most common gene followed by blaSHV (70%) and blaTEM (58%), either alone or in combination.
Eighty nine percent (132/151) of the ESBL-positive isolates were MDR. Antimicrobial
susceptibility rates were higher for fosfomycin (92.8%) and imipenem (35.5%) among
ESBL-positive isolates. None of the ESBL- positive isolates harbored any mutations or
plasmid-mediated fosfomycin resistance determinants.
Conclusion: In conclusion, fosfomycin showed good antimicrobial activity against
multidrug resistance ESBL- positive Enterobacteriaceae.