Constipation, a prevalent clinical condition, significantly impacts patients' quality of life, yet relevant clinical trial technical guidelines have yet to be issued domestically. This disease encompasses various classifications based on etiology, pathology, and pathophysiological characteristics. Slow transit constipation (STC), specifically, arises from colonic motility disorders and is recognized as a neuromuscular colonopathy. Currently, limited therapeutic options are available for patients with refractory STC, rendering it a common ailment associated with substantial disease burden and uncertain etiology. Consequently, identifying the cause and developing effective, targeted, and safe treatment strategies is of paramount importance. Our research team has made a groundbreaking international discovery, revealing that STC is caused by infection with a novel Shigella-like bacterium, termed the peristaltic contraction-inhibiting bacterium (PIB), which secretes docosapentaenoic acid (DPA), an unsaturated fatty acid. The pathogenic mechanism involves inhibition of intestinal peristalsis, subsequently slowing colonic transit. Preliminary epidemiological studies confirm the exclusive presence of PIB in feces from patients with intractable constipation, whereas it is virtually absent in healthy individuals. Notably, consumption of high-dose DPA does not affect colonic transit or induce constipation; however, intracolonic administration does. In response to PIB-induced STC, our team screened a range of antibiotics and identified two primary classes with potent antibacterial effects against PIB: fluoroquinolones and carbapenems. Both classes exhibit strong inhibitory activity against PIB, suggesting their potential use in chronic constipation treatment. Levofloxacin, a quinolone antibiotic, possesses broad-spectrum and potent antibacterial properties, effective in treating intestinal and urinary tract infections. Given that PIB has been confirmed as a novel Shigella-like species, and quinolones are established as the first-line antibiotics for Shigella infections, levofloxacin's efficacy against PIB was anticipated. Preliminary studies have validated levofloxacin's ability to inhibit PIB growth, thereby alleviating PIB-induced refractory constipation through sensitivity testing. The primary objective of this study is to utilize levofloxacin to suppress PIB, thereby achieving the relief of chronic functional constipation.