Morganella morganii NM-11 of snake origin: drug resistance profile, pathogenic potential, and impact on host gut microbiota.

To date, cases of snake infection caused by Morganella morganii and its effects on the intestinal microecology of snakes remain poorly documented. A pathogenic strain, designated NM-11, was isolated from diseased and dead snakes collected from a snake farm in China. In this study, strain NM-11 was identified as Morganella morganii through morphological observation, physiological and biochemical characterization, 16S rRNA gene sequencing, as well as genome-based average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) analyses. Subsequently, artificial challenge assays were performed to evaluate its pathogenicity. The whole genome of the strain was sequenced using PacBio long-read technology, and antimicrobial susceptibility tests were conducted to characterize its antibiotic resistance profile. Furthermore, high-throughput sequencing was applied to explore the alterations in intestinal microbial diversity of Ptyas mucosus upon infection with strain NM-11. Pathogenicity assays revealed that strain NM-11 exhibited strong virulence. After experimental infection, Ptyas mucosus displayed typical clinical signs including depression, lethargy and diarrhea. Gross pathological examination revealed extensive hemorrhage in the abdominal cavity, lungs and gastrointestinal tract, and histopathological observation confirmed severe lesions in multiple organs. Antimicrobial susceptibility tests confirmed the strain was multidrug-resistant (MDR). It had high resistance to many antibiotics. These drugs include polymyxin B, tetracycline, cefuroxime, cephalexin, erythromycin, vancomycin and streptomycin. Intestinal microbiota analysis indicated that infection with NM-11 remarkably reshaped the intestinal microbial community structure of Ptyas mucosus and increased the overall microbial diversity, accompanied by a significant rise in the relative abundance of Morganella morganii. This is the first report of Morganella morganii isolated and identified from diseased snakes in China. Our findings clarify the pathogenic characteristics and antibiotic resistance profile of this resistant strain against Ptyas mucosus. The results provide fundamental scientific evidence for the clinical diagnosis and antimicrobial prevention and treatment of Morganella morganii infection in snakes, and also offer valuable insights for reptile medicine and public health risk prevention and control.