Since 2000, we have witnessed the worldwide emergence of Gram-negative 'superbugs' such as E. coli ST131 and Klebsiella pneumoniae ST258 which not only encode multiple virulence factors associated with extraintestinal disease, but also Class A enzymes that hydrolyze third-generation cephalosporins and carbapenem antibiotics (CTX-M-15 and KPC, respectively). Dr. Weissman’s lab developed and used PCR- and sequence-based molecular typing techniques to characterize clinical isolate collections gathered through active and passive surveillance by NIH-funded multicenter studies at freestanding children’s hospitals, the NICHD Neonatal Research Network, and by local and state Departments of Health in California, Minnesota, Oregon and Washington. Specifically, his lab developed molecular techniques to characterize the complex spread of plasmid-borne, extended-spectrum beta-lactamase (ESBL) and carbapenemase enzymes among Enterobacteriaceae. These molecular studies have shed light on the regional dynamics of antibiotic resistance, a complex mix of autochthonous (“indigenous”) and imported pathogens that circulate through healthy and vulnerable populations alike, both in community and healthcare settings, and will inform the development of “One Health” surveillance systems that may provide for inference of molecular dynamics from pooled clinical microbiology data. Dr. Weissman currently focuses on leveraging clinical microbiology data to inform antimicrobial stewardship interventions.