Background: The members of Enterobacteriaceae are considered significant agents in human infections. The emergence of drug resistance is important for physicians. The aims of this study were investigating of fosfomycin resistance and the distribution rate of resistance genes among Enterobacteriaceae in Tabriz Hospitals. Materials and Methods: To determine the susceptibility patterns in 250 isolates, the disk diffusion method was performed. The minimum inhibitory concentration (MIC) of fosfomycin was determined by the agar dilution. The distribution rate of fosfomycin resistance genes (fosA, fosA3, fosB, fosB2, fosC, fosC2, and fosX) was done by the PCR. Results: The resistance rate to fosfomycin was in a value of 15 (6%) and 24 (9.6%) isolates by the disk diffusion and MIC methods, respectively. The MIC50 and MIC90 were 8 µg/mL and 16 µg/mL, respectively. The frequency of fosfomycin resistance genes was 1.6%, 1.6%, 1.6% and 0.8% for fosA, fosC, fosX and fosA3. The fosB, fosB2, and fosC2 was not detected. Conclusion: Fosfomycin is a dramatically useful antibiotic against Enterobacteriaceae-caused infections. A trivial resistance rate is observed to fosfomycin in some isolates, and all detected resistance-genes are plasmid mediate agents. Resistance to other therapeutic options is much more than fosfomycin, which is an alarming point.
