Structural transition in antimicrobial resistance dynamics of Corynebacterium striatum

Antimicrobial resistance (AMR) is typically interpreted as a process of gradual accumulation of resistance traits. However, resistance systems may instead undergo structural transitions under changing selective pressures. We investigated whether long-term AMR dynamics in Corynebacterium striatum reflect accumulation or reorganization of a constrained phenotypic state space.

Longitudinal resistance data (2013-2025) were analyzed using segmented regression, multinomial modeling, entropy-based diversity metrics, and Markov transition analysis to characterize temporal dynamics, architecture distributions, and system-level behavior.

A significant structural breakpoint was identified around 2020 (Davies' test p < 0.001). The estimated breakpoint location showed limited uncertainty based on model-based confidence interval estimation. Prior to 2020, aminoglycoside-containing resistance architectures were prevalent, whereas after 2020 they collapsed and were replaced by aminoglycoside-negative, fluoroquinolone-associated configurations. Phenotypic diversity declined significantly over time, indicating contraction of the resistance state space. Markov analysis demonstrated convergence toward a stable stationary distribution dominated by two related architectures, with increased dynamical stability after the breakpoint.

AMR dynamics in C. striatum reflect a structural transition and restructuring within the simplified state space rather than progressive accumulation of resistance traits. The system converges toward a low-diversity phenotypic attractor, highlighting the importance of dynamical systems approaches in understanding resistance evolution.