2株公园湖水源非O1/O139群霍乱弧菌的分离鉴定和致病性分析OA北大核心

In recent years,infections caused by non-O1/O139 Vibrio cholerae(NOVC)in humans and animals have been reported.From March 2021 to April 2022,water samples from Yuanmingyuan Park Lake were continuously collected for bacterial isolation and culture.The isolated strains were identified through 16S rRNA sequence analysis and hemolytic testing.The pathogenicity of the isolated strains was evaluated through cytotoxicity assays and mouse infection experiments.PCR was employed to detect virulence-related genes ctxA,ctxB,tcpA,hlyA,rtxA,rtxC,and chxA in the isolated strains.The complete length of the chxA gene in the isolated strains was analyzed using phylogenetic evolutionary analysis.Drug sensitivity testing was performed to evaluate the drug susceptibility of the isolated strains.The results showed that two NOVC strains were isolated and identified,exhibiting clear hemolytic activity on blood agar culture medium.The filtered bacterial culture supernatant displayed cytolytic effects and strong toxicity to Vero cells in vitro,causing cell shrinkage and detachment.Both the bacterial culture and culture supernatant were lethal when administered intraperitoneally to mice,with a median lethal dose(LD50)of 107 23CFU.PCR results indicated positive presence of hlyA,rtxA,rtxC,and chxA genes in the isolated strains,suggesting that the pathogenicity of the bacteria may be associated with the expression of virulence factors.Analysis of the complete length of the chxA gene revealed that both isolated strains could encode type Ⅱ ChxA toxins,with the catalytic domain highly homologous to type Ⅰ toxins but lacking a segment of five amino acids(619 AIAKE623)in the corresponding region.Drug sensitivity testing showed that both isolated strains were sensitive to ciprofloxacin,enrofloxacin and amikacin,while resistant to sulfamethoxazole.These findings indicate that waterborne NOVC strains from the park carry multiple virulence-related genes,produce hemolysins and other cytotoxins,can cause fatal infections in mice,exhibit multidrug resistance,and pose a potential threat to public health in aquatic animals and the environment.