Whole-genome characteristics of non-toxigenic Vibrio cholerae O1 isolated from blood and ascites of 1 old patient with infections

OBJECTIVE To analyze the genomic characteristics of non-toxigenic Vibrio cholerae O1 (HL01 and HL02) isolated simultaneously from the blood and abdominal cavity of a patient.

METHODS In Jul. 2024, Vibrio cholerae strains (HL01 and HL02) were isolated from the blood and ascites of an elderly patient in the Infectious Diseases Ward of the First Affiliated Hospital of Nanchang University. The antimicrobial susceptibility of the strains was determined with an automated susceptibility analyzer. The complete genomic sequences of the strains were obtained through next-generation gene sequencing. Online BLAST alignment was performed with comprehensive antibiotic resistance database, resistance gene prediction database Resfinder and other databases to identify the resistance genes and virulence genes carried by the strains. Based on genomic single-nucleotide diversity, a phylogenetic tree was constructed with Jolytree, with the median method used for rooting. FastANI was employed to calculate the genomic similarity by comparing the nucleotides of HL01 and HL02 with those of 146 genomes.

RESULTS Both strains were identified as non-toxigenic Vibrio cholerae O1, with multilocus sequence typing (MLST) classified as ST167. They carried multiple virulence-related genes and exhibited resistance to cefazolin and polymyxin. Based on genomic evolutionary relationships, it was found that the presence of resistance genes and resistance plasmids among the strains showed a certain degree of clustering. The traditional ST type of strains HL01 and HL02 was ST167, and their cgMLST type was a novel type closest to cgMLST-960. The genomes of the two strains were highly homologous. The phylogenetic tree indicated a close relationship between the two Vibrio cholerae strains and those isolated from aquatic environment.

CONCLUSIONS Although HL01 and HL02 do not carry the ctxAB virulence gene, they possess multiple virulence factors that can cause disease. Therefore, continuous monitoring of O1/O139 Vibrio cholerae isolated from extraintestinal sites is necessary, and whole-genome analysis is essential.