A Pathogenic Providencia rettgeri Isolated and Identified from Pelodiscus sinensis

Area of Science:

• Aquatic animal health
• Bacteriology
• Disease pathology

Background:

• Increasing infectious diseases in farmed Chinese soft-shelled turtles (*Pelodiscus sinensis*) correlate with rising aquaculture production.
• Disease outbreaks present with severe symptoms including hemorrhages, necrosis, and visceral bleeding.

Purpose of the Study:

• To isolate, identify, and characterize the bacterial pathogen responsible for disease in farmed *Pelodiscus sinensis*.
• To confirm the pathogenicity of the isolated bacterium through challenge experiments.
• To investigate potential therapeutic options.

Main Methods:

• Bacterial isolation and identification using morphology, biochemistry, and 16S ribosomal RNA (16S rRNA) sequencing.
• Histopathological examination of infected tissues (spleen, liver, kidneys, intestines).
• Virulence-associated gene screening and antibiotic susceptibility testing.

Main Results:

• *Providencia rettgeri* (*P. rettgeri*) was identified as the causative agent.
• Histopathology revealed significant tissue damage in multiple organs.
• Challenge experiments confirmed *P. rettgeri* causes high morbidity and mortality (up to 91%) in *Pelodiscus sinensis*, with similar clinical signs observed.
• The identified strain possesses key virulence factors, including invasion protein gene and alpha-hemolysin.
• The bacterium showed sensitivity to amikacin and ciprofloxacin.

Conclusions:

• *Providencia rettgeri* is confirmed as the pathogen responsible for a significant disease affecting farmed *Pelodiscus sinensis*.
• Virulence factors contribute to the pathogenicity of *P. rettgeri* in turtles.
• Amikacin and ciprofloxacin represent potential effective treatments for this disease, aiding in prevention and control strategies for *Pelodiscus sinensis* farming.