Investigation of Fosfomycin Resistance and Plasmid-mediated Fosfomycin Resistance Genes in Enterobacterales Isolates

The study aimed to investigate the fosfomycin resistance in Enterobacterales isolates and the presence of plasmid-mediated fosfomycin resistance genes fosA3 and fosC2 in fosfomycin-resistant Enterobacterales isolates. A total of 2095 Enterobacterales isolates obtained from urine samples were included in the study. Identification of isolates was performed in the Vitek MS. The antimicrobial susceptibility of the isolates and detection of ESBL was determined using the Vitek 2 Compact. In 185 fosfomycin-resistant isolates, fosA3 and fosC2 genes were investigated by PCR. In addition, carbapenemase genes were investigated in carbapenem-resistant isolates. In 2095 Enterobacterales, 65.8% of the isolates were E. coli, and fosfomycin resistance was determined as 22%. ESBL production was defined as 36.5%, 58.1%, and 32.5% in all isolates, K. pneumoniae, and E. coli isolates, respectively. K. pneumoniae (56.2%) were the most frequently isolated bacteria among 185 fosfomycin-resistant Enterobacterales isolates. In these isolates, 66.95% were ESBL-producing Enterobacterales, and 35.7% were carbapenem-resistant isolates. According to the PCR results, two of the 185 Enterobacterales isolates were positive for the fosA3 gene, fosC2 gene was not detected. According to PCR for carbapenemase genes results with these isolates, blaOXA–48 positivity was 66.7%, and blaNDM positivity was 3%. blaKPC and blaVIM positivity could not be detected. In our study, the prevalence of fosA3 was 1.1%. The occurrence of fosA3 gene positivity in Enterobacterales isolates is important for the future treatment of UTIs.