Objective To understand the epidemiological characteristics of a recent anthrax outbreak and the genetic characteristics of the isolated Bacillus anthracis strains in Jingbian county, Shaanxi province, and provide references for the prevention and control of anthrax.

Methods From August 2 to 21, 2024, an anthrax outbreak occurred in Jingbian. Biological and environmental samples were collected from the affected area for nucleic acid identification and pathogen isolation. Drug susceptibility test and whole-genome sequencing were conducted for the isolated strains. Analyses on virulence genes and antibiotic resistance genes were performed, and core genome multi-locus sequence typing (cgMLST) and core genome single nucleotide polymorphism (cgSNP) analyses were carried out.

Results A total of 3 cases of cutaneous anthrax were reported in this outbreak. Three strains of Bacillus anthracis were isolated, with an isolation rate of 12.00% (3/25). The isolated strains were sensitive to the firstly used drugs, penicillin, tetracycline, and ciprofloxacin. Whole-genome analysis revealed the presence of virulence genes capA, capB, capC, dep/capD, capE, cya, inhA, lef, and pagA. Antibiotic resistance genes for β-lactams (bla), carbapenems (bla2), fosfomycin (fosB2), and streptothricin (satA) were also identified. cgMLST and cgSNP analyses showed that the three strains clustered together and had close genetic distance to the isolates from Huyi district of Xi'an in 2018, Pucheng county of Weinan in 2021, Linwei district of Weinan in 2020, and Chengcheng county of Weinan in 2020, but had far genetical distance from those isolated Huayin in 2021 and Ganquan county of Yan'an in 2015.

Conclusion This anthrax outbreak was caused by the same infection source, but there was no significant association with historical isolates in Shaanxi. Because anthrax outbreak was rare in its history, Jingbian was identified as a new epidemic focus, providing a basis for long-term surveillance, prevention and control of anthrax in the future.