Investigation of O25b-ST131 Clone Frequency and Presence of Carbapenem and Fosfomycin Resistance Genes in Escherichia coli Isolates: First Detection of fosA3 from Escherichia coli O25b-STf131 Clone from Turkiye

Escherichia coli ST131 clone was first reported in 2008 and defined as a 'high-risk pandemic clone'. This clone plays a critical role in the spread of antimicrobial resistance worldwide. It was reported in many studies that the E.coli ST131 clone is widespread worldwide and can carry virulence and antibiotic resistance genes. E.coli ST131 clone is associated with a fluoroquinolone and broad-spectrum cephalosporin resistance. The agents used in the treatment of infections caused by the E.coli ST131 clone are limited. For this reason, monitoring the resistance status of these limited agents is crucial. In this study, we aimed to investigate the prevalence of the O25b-ST131 clone, and the presence of carbapenem and fosfomycin resistance genes in fluoroquinolone-resistant E.coli isolates isolated from mid-stream urine samples. For the detection of the O25b-ST131 clone in fluoroquinolone-resistant E.coli isolates, amplification was performed with primers O25pabBspe-F and O25pabBspe-R. For the determination of resistance genes, carbapenem resistance genes bla(NDM), bla(VIM), bla(KPC), bla(IMP), and bla(OXA-48) in carbapenem resistant isolates and plasmid-mediated fosfomycin resistance genes fosA3 and fosC2 in fosfomycin resistant isolates were investigated by multiplex PCR method. According to PCR results, the prevalence of E.coli O25b-ST131 isolates was 51.2%. Carbapenem resistance rate was 3.41%, and fosfomycin resistance rate was 3.41% in fluoroquinolone-resistant E.coli isolates. Carbapenem and fosfomycin resistance rates in E.coli O25b-ST131 isolates were determined as 0.83% and 2.5%, respectively. At least one of the carbapenem-resistance genes (bla(NDM) and/or bla(OXA-48)) was detected in six of the eight carbapenem-resistant isolates. Fosfomycin resistance gene fosA3 was seen in four of eight fosfomycin-resistant isolates. fosC2 gene was not detected in any of the isolates. In addition, the plasmid-mediated fosfomycin resistance gene fosA3 was detected in an E.coli O25b-ST131 isolate, and this result was confirmed by sequence analysis. To the best of our knowledge, this is the second report about fosA3 positivity in E.coli ST131 isolates from the world and the first reported from Europe and Turkiye. As a result, approximately half of the fluoroquinolone-resistant E.coli isolates were identified as E.coli ST131 clones. Despite the high rate of this clone, the carbapenem and fosfomycin resistance rates are still relatively low, which is pleasing for the future of treatment. However, it should not be forgotten that resistance rates and the prevalence of resistance genes should be constantly monitored.