Xiaoyi Li’s research while affiliated with South China Sea Fisheries Research Institute and other places

Ictalurus punctatus are introduced species and successfully farmed freshwater fish in China. With the intensive farming of Ictalurus punctatus and water quality deterioration, the bacterial diseases have become a great concern of the industry. Nonetheless, data pertaining to molecular immunological responses, which could elucidate critical genetic information pertinent to the control and prevention of Aeromonas hydrophila infections, remain deficient for the species Ictalurus punctatus . In this investigation, we conducted a comparative analysis of transcriptomic alterations within the hepatic, cephalic renal, and splenic tissues of Ictalurus punctatus following exposure to A. hydrophila and phosphate buffer solution (PBS) as a mock infection at the 24-hour post-infection mark. In total, 2043, 2145, 2708 genes were up-regulated and 1797, 1753, 2669 genes were down-regulated in the liver, head kidney and spleen, respectively. GO and KEGG analysis showed that many DEGs were significantly enriched in immune terms, including immune system, immune diseases, signal transduction. 10 DEGs were selected for qRT-PCR analysis to validate the RNA-seq data and confirmed the consistency of the expression levels.This investigation offers an enhanced comprehension of the gene expression profile and the dynamic immunological response of Ictalurus punctatus following infection with A. hydrophila . Such insights will contribute to future research endeavors aimed at developing preventative strategies for Ictalurus punctatus .

Pathogenic Aeromonas spp. are the etiological agents of Motile Aeromonas Septicemia (MAS). This study aimed to identify the pathogen of diseased tadpoles (Quasipaa spinosa) and the antibiotic-resistance characteristics of this bacterium. A Gram-negative bacterium, named strain QST31, was isolated from the ascites of diseased tadpoles and was identified as Aeromonas media based on physiological and biochemical tests, as well as molecular identification. Artificial infection experiments showed that strain QST31 was highly virulent to tadpoles, with an LC50 of 2.56 × 107 CFU/mL. The antimicrobial susceptibility of strain QST31 was evaluated using the disk diffusion method, and the results indicated that strain QST31 was resistant to 28 antibacterial agents. In addition, the whole genome of strain QST31 was sequenced, and the presence of antimicrobial resistance genes, integron, and transposon was investigated. Genes involved in adherence, hemolysis, type II secretion system (T2SS), T6SS, iron uptake system, and quorum sensing were identified in the genome of strain QST31. More than 12 antimicrobial resistance genes were predicted in the genome of strain QST31. Interestingly, a novel Tn7709 transposon harboring sul1, aadA16, catB3, blaOXA-21, aac(6′)-IIa, and tet(A) genes was identified. In conclusion, this is the first report on the isolation and identification of pathogenic A. media with multidrug resistance genes from diseased tadpoles. The results revealed that preventing and controlling aquatic animal diseases caused by multidrug resistance A. media will be a huge challenge in the future.

Objectives A multidrug-resistant bacterium, Stenotrophomonas sp. SXG-1, was isolated from the liver of diseased hybrid sturgeon from Guizhou province, China. Methods Whole-genome sequencing was performed on the Illumina HiSeq 2500-PE125 platform with MPS (massively parallel sequencing) Illumina technology. All good quality paired reads were assembled using the SOAPdenovo into a number of scaffolds. PHI (Pathogen Host Interactions), VFDB (Virulence Factors of Pathogenic Bacteria) and ARDB (Antibiotic Resistance Genes Database) were used to analyses pathogenicity and drug resistance. Results Here we reported the complete genome sequence of Stenotrophomonas sp. SXG-1, which comprised 4534,602 bp in 4077 coding sequences (CDS) with a G + C content of 66.42%. The genome contained 4 gene islands, 72 tRNAs and 13 rRNAs. According to the annotation analysis, strain SXG-1 encoded 22 genes related to the multidrug resistance. In addition to 10 genes conferring resistance to antimicrobial drugs of different classes via altermative mechanisms, 12 genes of efflux pumps were presented, 9 of which were reported for the first time in Stenotrophomonas maltophilia. Conclusion This was the first complete genome sequence of Stenotrophomonas sp. isolated from the sturgeon. The complete genome sequence of Stenotrophomonas sp. strain SXG-1 may provide insights into the mechanism of antimicrobial resistance and prevent disease.