Piperacillin/tazobactam resistant, cephalosporin susceptible Escherichia coli bloodstream infections driven by multiple independent acquisition events of resistance mechanisms

Routine blood culture surveillance identified the emergence of this phenotype of E. coli in the Royal Liverpool University Hospital, Liverpool, UK, between 2014 and 2017. Our analysis demonstrates that the introduction and subsequent increase of this phenotype in the hospital is not the spread of a single or few clones or resistance mechanisms but was introduced multiple times into phylogenetically distant lineages. This demonstrates that this is a recurring problem with the potential to occur in a wide variety of E. coli lineages and has to be closely monitored to prevent unnecessary over-use of carbapenems on 3GC-sensitive infections.