Beneficial impact of acquired AmpC β-lactamases on bacterial fitness and pathogenicity: a new paradigm

Isogenic Escherichia coli MG1655 strains carrying empty vector (p0) or plasmids encoding CMY-2, CMY-42, or CMY-145 β-lactamase variants were grown to mid-log phase in minimal M9 medium with kanamycin. Total RNA was extracted in three biological replicates, ribosomal RNA was depleted, and strand-specific libraries were sequenced.

Reads were mapped to the E. coli K-12 reference genome and differential expression analysis was performed. Comparative transcriptomics revealed large gene expression changes associated with AmpC variant production, including consistent deregulation of genes involved in flagellar biosynthesis, motility, and additional metabolic functions. These RNA-seq data provide a transcriptomic framework to understand how distinct AmpC variants differentially reshape bacterial regulatory networks beyond β-lactam resistance.