Novel Mechanistic Insights into Bacterial Fluoroquinolone Resistance.

Advancements in studies on the evolutionary mechanisms underlying bacterial antibiotic resistance are unclear. This study aimed to investigate the evolutionary mechanism underlying bacterial antibiotic resistance using isobaric tags for relative and absolute quantitation-based quantitative proteomics along with functional validation. Quantitative analysis revealed 101, 325, and 428 differentially expressed proteins (DEPs) at three drug resistance levels (low-R, 0.2 μg/mL; medium-R, 5 μg/mL; high-R, 15 μg/mL). Continuous adjustment of metabolic patterns to enhance nucleotide synthesis and energy generation may underlie evolution. Indeed, nucleotide levels were elevated and strengthened ciprofloxacin resistance. Quorum sensing (QS) genes were upregulated in the early growth phase, thus potentially improving survival. Further, a thicker cell wall potentially serves as a stronger barrier and reduces drug permeation. The aforementioned three drug resistance levels displayed continuity and differences; the low-resistant level displayed no prominent mechanism; medium, a more focused change in nucleotide metabolism; and high, a thorough evolution to a complete systematic mechanism with higher adenosine 5'-triphosphate levels, serving as a defense mechanism for reducing drug-induced stress. Thus, gradual increments in nucleotide synthesis, energy synthesis, cell wall synthesis, QS, and biofilm formation may direct the evolution of bacterial resistance.