Antibacterial Mechanism of Chitosan-Gentamicin and Its Effect on the Intestinal Flora of Litopenaeus vannamei Infected with Vibrio parahaemolyticus

To explore the application of chitosan-gentamicin conjugate (CS-GT) in inhibiting Vibrio parahaemolyticus (V. parahaemolyticus), which is an important pathogen in aquatic animals worldwide, the antimicrobial activity of CS-GT and the effects of a CS-GT dose on the intestine histopathology and intestinal flora of V. parahaemolyticus-infected shrimps were explored. The results showed that CS-GT possessed broad-spectrum antibacterial activity, with minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and half inhibitory concentration (IC50) of 20.00 +/- 0.01, 75.00 +/- 0.02 and 18.72 +/- 3.17 mu g/mL for V. parahaemolyticus, respectively. Further scanning electron microscope and cell membrane damage analyses displayed that the electrostatic interaction of CS-GT with cell membrane strengthened after CS grafted GT, resulting in leakage of nucleic acid and electrolytes of V. parahaemolyticus. On the other hand, histopathology investigation indicated that high (100 mg/kg) and medium (50 mg/kg) doses of CS-GT could alleviate the injury of a shrimp's intestine caused by V. parahaemolyticus. Further 16S rRNA gene sequencing analysis found high and medium dose of CS-GT could effectively inhabit V. parahaemolyticus invasion and reduce intestinal dysfunction. In conclusion, CS-GT possesses good antibacterial activity and could protect shrimps from pathogenic bacteria infection.

Automated summary

The chitosan-gentamicin conjugate (CS-GT) showed broad-spectrum antibacterial activity against Vibrio parahaemolyticus. High and medium doses of CS-GT alleviated the intestinal injury caused by V. parahaemolyticus in shrimps and effectively inhibited its invasion and reduced intestinal dysfunction.