During this period, diagnostic research coalesced around molecular and protein-based strategies that linked virulence determinants to detection and typing. Plasmid-borne virulence genes and toxin-based assays drove the development of molecular typing and rapid antigen detection, while immunodetection enabled more rapid differentiation of strains for infection control and epidemiology. Cross-species comparisons of toxin and virulence traits clarified shared mechanisms and informed interpretation of diagnostic cross-reactivity, even as epidemiology and surveillance contexts shaped method choice to map disease burden and transmission. Influential Works: Landmark breakthroughs included the demonstration that genetic exchange could blur species boundaries, foreshadowing hybridization-based diagnostic strategies. Protein-focused techniques then transformed typing and virulence detection, with slab gel electrophoresis enabling rapid pattern analysis across strains. Supplementary methods, including isoelectric focusing for beta-lactamases and immune electron microscopy for viral particles, laid the groundwork for visual and enzymatic diagnostics that informed surveillance and outbreak response.