RT Journal Article SR Electronic T1 β-lactamase Amplification and Porin Loss Drive Progressive β-lactam Resistance in Recurrent ESBL Enterobacteriaceae Bacteremia JF bioRxiv FD Cold Spring Harbor Laboratory SP 616961 DO 10.1101/616961 A1 William C. Shropshire A1 Samuel L. Aitken A1 Reed Pifer A1 Jiwoong Kim A1 Micah M. Bhatti A1 Xiqi Li A1 Awdhesh Kalia A1 Jessica Galloway-Peña A1 Pranoti Sahasrabhojane A1 Cesar A. Arias A1 David E. Greenberg A1 Blake M. Hanson A1 Samuel A. Shelburne YR 2019 UL http://biorxiv.org/content/early/2019/04/23/616961.abstract AB Carbapenem resistant Enterobacteriaceae (CRE) are a critical public health issue. Recent studies indicate many CRE lack carbapenemases, but contain extended spectrum β-lactamases (ESBLs). We investigated 16 longitudinal, recurrent cases of extended spectrum B-lactamase (ESBL)-positive Enterobacteriaceae bacteremia to gain insights into mechanisms underlying the emergence of non-carbapenemase producing CRE (non-CP-CRE). Using a combination of short- and long-read sequencing technologies, we identified that non-CP-CRE emerges from an ESBL background through a combination of insertion sequence mediated β-lactamase translocation, subsequent amplification of β-lactamase encoding genes such as blaOXA-1 and blaCTX-M, and porin inactivation. Interestingly, the β-lactamase gene amplification occurred both on plasmids and on the chromosome, including in the middle of porin-encoding genes. Additionally, overexpression of blaOXA-1 increased resistance to the broad-spectrum β-lactam, piperacillin-tazobactam. This analysis shows mechanisms underlying non-CP-CRE emergence and demonstrates that copy number of β-lactamase genes needs to be considered to fully understand antimicrobial resistance amongst key human pathogens.One Sentence Summary Amplification of β-lactam genes with porin loss was associated with development of β-lactam resistance in serial Enterobacteriaceae clinical isolates.