LAUSR

The characterization of virulent and drug-resistant Escherichia coli strains helps to control and provide more accurate information regarding infection and eradication. The aim of this study was to determine the relationship between antibiotic susceptibility, phylogroups and virulence factors of E. coli isolates from children with septicaemia. One hundred dereplicated E. coli isolates were collected from paediatric patients with septicaemia in five hospitals in Tehran (May 2015 to May 2018). The antibiotic susceptibility of isolates was performed as per the 2016 guidelines of the Clinical and Laboratory Standards Institute. Extended-spectrum β-lactamases and carbapenemase genes, phylogroups, serogroups and virulence encoding genes were detected by PCR. Phylogroup B2 was dominant (40%) among strains, followed by phylogroups D (30%), A (8%) and B1 (7%). CTX-M1 was significantly higher in the B2 group (n = 21, p 0.001). Furthermore, the virulence genes iutA (n = 27, p 0.002), csgA (n = 39, p <0.001), kpsMII (n = 39, p 0.002), ibeA (n = 4, p 0.004), vat (n = 5, p 0.003), traT (n = 24, p <0.001), sat (n = 12, p 0.001) and hlyA (n = 33, p <0.001) showed significantly higher rates in phylogroup B2. Three O25/CTXM1/OXA-48 and cnf, iutA, csgA and traT positive isolates belonged to phylogroup B2. Pulsed-field gel electrophoresis analysis showed 85% similarity among 25% of isolates. More than half of the isolates were multidrug-resistant E. coli. A significant relation was observed among iutA, csgA, kpsMII, ibeA, vat, traT, sat and hlyA genes and phylogroup B2. The characterization of virulent and drug-resistant strains helps control and properly eliminate infections. There was no genetic relation among strains in the pulsed-field gel electrophoresis pattern.