Virulence phenotype first: a framework for assessing the clinical risk of resistance-hypervirulence convergence in Klebsiella pneumoniae.

Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) marks a pivotal evolutionary shift in which antimicrobial resistance and hypervirulence increasingly co-exist within the same lineages. Evidence supports two dominant convergence routes, hypervirulent backgrounds acquiring resistance modules and carbapenem-resistant classical backbones acquiring virulence modules, followed by diversification into distinct plasmid/genomic architectures. However, current research is constrained by inconsistent definitions of hypervirulence, reliance on imperfect proxy assays such as hypermucoviscosity, heterogeneity across experimental models, and limited integration of genetic markers with clinical outcomes across hosts and infection sites. We argue that the central clinical threat is fundamentally phenotypic. Accordingly, this review proposes a 'virulence phenotype-first' framework that prioritizes the functional expression of virulence over genetic markers for assessing clinical risk. Convergence does not produce uniform hypervirulence. Instead, convergent strains span a spectrum of virulence outcomes that include enhanced, maintained, or adaptively attenuated states. These outcomes are shaped by context-dependent regulation, metabolic cost, and niche-specific selection. When viewed through host behavior, resistance and virulence are integrated as stage- and niche-dependent programs that can reinforce mucosal colonization, support invasive survival under immune and nutrient constraints, and enable persistence under combined antimicrobial and immune pressure. This phenotype-first perspective helps explain genotype-phenotype discordance and why resistance profiles or single phenotypic proxies are insufficient for real-time risk assessment. Finally, we outline phenotype-aware priorities for surveillance and diagnostics, emphasizing rapid and standardized frameworks that integrate molecular routes and architectures with a short panel of clinically informative functional assays.