First report of multidrug-resistant and pathogenic Plesiomonas shigelloides from endangered crested ibis (Nipponia nippon).

Plesiomonas shigelloides (P. shigelloides) is a gram-negative, thermotolerant, motile, and pleomorphic microorganism that acts as an opportunistic pathogen, capable of causing abscesses, enteric infections, and even sepsis in humans and other animals, thereby posing a threat to human and animal health worldwide. The crested ibis (Nipponia nippon) is a globally endangered avian species with a limited population and is vulnerable for various infections. To gain a better understanding of the prevalence of P. shigelloides in the endangered crested ibis, fecal samples from the crested ibis at the Xiazhu Lake Crested Ibis Breeding Research Center, China were collected and analyzed. The results confirmed that 45.6% (36/79) of the fecal samples tested positive for P. shigelloides. Antibiotic susceptibility testing showed that 27.8% (10/36) of P. shigelloides isolates were multidrug-resistant, with resistance to ampicillin and amikacin being 100% and 77.8%, respectively. Subsequently, ten representative isolates were subjected to whole genome sequencing, and resistance and virulence genes were analyzed. The evolutionary tree of the genomes show that these strains have different origins, with one strain closely related to a strain from human. Finally, the pathogenicity experiment demonstrated that several strains exhibit pathogenicity in both mice and waterfowl, with two strains displaying lethal pathogenicity in mice. To the best of our knowledge, this is the first report of multidrug-resistant and pathogenic P. shigelloides isolated from the crested ibis, suggesting a potential threat to this endangered species and broader public health implications.