Dissemination of Ceftriaxone-Resistant Enteritidis Harboring Plasmids Encoding or Gene in China.

Enteritidis was the primary foodborne pathogen responsible for acute gastroenteritis. The growing ceftriaxone resistance poses a significant threat to public health. Infection with Enteritidis has emerged as a major public health concern, particularly in developing countries. However, research on ceftriaxone-resistant Enteritidis (CRO-RSE) remains limited, particularly concerning its resistance mechanism, plasmid structure, and transmission characteristics. This study aims to address these gaps comprehensively. We collected 235 Enteritidis isolates from Hangzhou First People's Hospital between 2010 and 2020. Among these, 8.51% (20/235) exhibited resistance to ceftriaxone. Whole-genome analysis revealed that 20 CRO-RSE isolates harbored or on the plasmid. Moreover, the dissemination of the gene was associated with IS and IS. Plasmid fusion entailing the integration of the p1 plasmid with antibiotic resistance genes and the p2 (pSEV) virulence plasmid was observed in certain CRO-RSE. Additionally, the structural analysis of the plasmids unveiled two types carrying the gene: type A with multiple replicons and type B with IncI1 (Alpha) replicon. Type B plasmids exhibited superior adaptability and stability compared to type A plasmids within . Interestingly, although the type B (S808-p1) plasmid displayed the potential to spread to , it failed to maintain stability in this species.