A Nationwide Screen of Carbapenem-Resistant Klebsiella pneumoniae Reveals an Isolate with Enhanced Virulence and Clinically Undetected Colistin Heteroresistance

The convergence of hypervirulence and multidrug resistance in is a significant concern. Here, we report the first screen for hypermucoviscosity, a trait associated with increased virulence, using a U.S. surveillance collection of carbapenem-resistant (CR) isolates. We identified one hypermucoviscous isolate, which carried a gene encoding the KPC-3 carbapenemase, among numerous resistance genes. The strain further exhibited colistin heteroresistance undetected by diagnostics. This convergence of diverse resistance mechanisms and increased virulence underscores the need for enhanced surveillance.