Virulence and Antibiotics Resistance Characteristics of Non-O1/O139 Vibrio cholerae in the Sewage Environment of Xuhui District, Shanghai, 2024-2025

Objective To investigate the antibiotic resistance profile, its genetic basis, and virulence gene carriage of non-O1/O139 Vibrio cholerae in the sewage environment of Xuhui District, Shanghai.Methods Sewage samples were collected from five communities in Xuhui District, Shanghai, between April 2024 and September 2025 for isolation and culture. The isolates were identified biochemically and serologically. Virulence genes in the isolates were detected by quantitative real-time PCR. Antibiotic susceptibility was analyzed using a broth dilution test. Whole-genome sequencing of the isolates was conducted to predict antibiotic resistance genes and virulence genes.Results 57 strains of non-O1/O139 Vibrio cholerae were isolated from 345 sewage samples, accounting for 16.52%. Antimicrobial susceptibility testing showed high resistance rates to β-lactam antibiotics: the highest was to cefazolin (70.18%), and the lowest were to cefotaxime and cefuroxime (21.05% each); resistance to ampicillin was 59.64%. Resistance rates to the other 7 tested antibiotics ranged between 22.81% and 35.09%. The lowest resistance rates were observed for tetracycline (0%) and the macrolide azithromycin (0%). Resistance to the sulfonamide compound trimethoprim-sulfamethoxazole was 14.04%. Resistance rates to the aminoglycosides gentamicin and amikacin were 1.75% and 43.86%, respectively. The resistance rate to quinolones (ciprofloxacin) was 21.05%, and to acetaminophen (chloramphenicol) was 3.51%. A total of 20 resistance genes, belonging to 6 classes, were detected among the 57 isolates. The carriage rate of β-lactam resistance genes was the highest (42.11%), while no macrolide resistance genes were detected. Four types of virulence-associated genes, totaling 29 genes, were identified in the 57 non-O1/O139 V. cholerae strains. These included 2 hemolysin genes (hlyA and tlh), 4 RTX toxin genes (rtxA, rtxB, rtxC and rtxD), and genes for 2 types of secretion systems (T2SS and T6SS). Conclusion The 57 non-O1/O139 V. cholerae strains isolated in this study showed no significant differences in temporal and spatial distribution. They exhibited good susceptibility to tetracycline, azithromycin, and chloramphenicol. However, they carried a wide variety of resistance genes and virulence genes that can cover the entire pathogenic mechanism chain, warranting further investigation.