Epidemiological investigation and ß-lactam antibiotic resistance of Riemerella anatipestifer isolates with waterfowl origination in Anhui Province, China.

Riemerella anatipestifer (R. anatipestifer) is a highly pathogenic and complex serotypes waterfowl pathogen with inherent resistance to multiple antibiotics. This study was aimed to investigate the antibiotic resistance characteristics and genomic features of R. anatipestifer isolates in Anhui Province, China in 2023. A total of 287 cases were analysed from duck farms and goose farms, and the R. anatipestifer isolates were subjected to drug resistance tests for 30 antimicrobials. Whole genome sequencing (WGS) and bioinformatics analysis were performed on the bacterial genomes, targeting the ß-lactam resistance genes. The results showed that a total of 74 isolates of R. anatipestifer were isolated from 287 cases, with a prevalence of 25.8%. The antimicrobial susceptibility testing (AST) revealed that all the 74 isolates were resistant to multiple drugs, ranging from 13 to 26 kinds of drugs. Notably, these isolates showed significant resistance to aminoglycosides and macrolides, which are also commonly used in clinical practices. Data revealed the presence of several ß-lactamase-related genes among the isolates, including a novel blaRASA-1 variant (16.2%), the class A extended-spectrum ß-lactamase blaRAA-1 (12.2%), and a blaOXA-209 variant (98.6%). Functional analysis of the variants blaRASA-1 and blaOXA-209 showed that the blaRASA-1 variant exhibited activity against various ß-lactam antibiotics while their occurrence in R. anatipestifer were not common. The blaOXA-209 variant, on the other hand, did not perform any ß-lactam antibiotic resistance. Furthermore, we observed that blaRAA-1 could undergo horizontal transmission among different bacteria via the insertion sequence IS982. In conclusion, this study delves into the high prevalence of R. anatipestifer infection in waterfowl in Anhui, China. The isolated strains exhibit severe drug resistance issues, closely associated with the prevalence of antibiotic resistance genes (ARG). Additionally, our research investigates the ß-lactam antibiotic resistance mechanism in R. anatipestifer.

Prevalence and conservation of ebp genes in Enterococcus faecalis originated from animals.

AIMS: The study aimed to investigate the prevalence and conservation of endocarditis and biofilm-associated pili (ebp) genes in Enterococcus faecalis originated from animals and the potential of developing Ebp into serological diagnostic and vaccine targets. METHODS AND RESULTS: In this work, we investigated the prevalence and conservation of ebp genes in 116 strains of E. faecalis originated from animals by using PCR and sequencing methods. The results demonstrated the presence of ebp genes (ebpA, ebpB and ebpC) in all 116 strains of E. faecalis, and their amino acid homology ranges from 96.6% to 100.0%. Moreover, the phylogenetic analysis of ebp genes in all 164 E. faecalis strains (including 48 reference strains) revealed that ebp genes show no significant correlation with species origins and regions of E. faecalis, indicating that ebp genes are conserved features in E. faecalis, even though it evolved under environmental pressures from various regions and origins. Given that EbpA1 as a part of the adhesion protein EbpA has immunogenicity, we further determined whether amino acid mutations have effects on the function and 3D structure of EbpA1. The results showed that two of the 26 mutations, at amino acids positions 178 and 387, had deleterious effects on the biological function of EbpA1 protein, while all mutations had no effect on the 3D structure or binding pockets of EbpA1 protein. CONCLUSIONS: This study suggests that ebp genes are prevalent and conserved in E. faecalis originated from diverse animal origins and regions. EbpA1 could be a potential target for serological diagnosis and vaccine development to prevent E. faecalis infection. SIGNIFICANCE AND IMPACT OF STUDY: The current study provides data to support further research on Ebp as a serological diagnostic and vaccine target against E. faecalis infection.