Characterization of ESBL/pAmpC-producing Escherichia coli isolates from long-term recurrent bloodstream infections.

Abstract The aim of the study was to investigate recurrent infections within individual patients caused by Extended-spectrum beta-lactamase and plasmid-AmpC-producing Escherichia coli (ESBL/pAmpC Ec) isolates, with more than one year interval. The national collection of ESBL/pAmpC Ec isolates collected from January 2014 through June 2017, where screened for patients with multiple isolates with more than one year between the episodes. The isolates were whole genome sequenced and analysed for resistance genes, virulence genes and MLST. The isolates were sub-typed by cgMLST and CH-typing. From a total of 970 patients, 15 unrelated patients experienced recurrent infections with ESBL/pAmpC Ec. Ten of those 15 patients (67%) were found to be infected a second or a third time with a genetically identical or similar strain. The resistance and virulence properties of the strains were similar within individual patients, however quite diverse when comparing between patients. Recurrent ESBL/pAmpC Ec bloodstream infections of genetically related strains, occurring with more than 12 month intervals, might be related to the previous episode and to less extend be caused by reinfection. With more than 1.000 days between first and second episode of genetically similar strains (4 allele differences), the recurrent infection is likely due to long-term host colonisation of ESBL/pAmpC Ec. From our analysis, strains able to cause such recurrent infection were relatively diverse between patients. Knowledge about host and strain factors influencing such recurring infections is needed to implement preventive measures.