Expanding the molecular epidemiology of melioidosis in North Central Vietnam.

Cases of melioidosis have been recorded for many years in Vietnam though it is still not a nationally reportable disease in Vietnam. More research is needed to understand the disease ecology and public health impacts of melioidosis in the country. To this aim, broadening the knowledge base of strains and epidemiology of infections in relation to genotypes present in the soil reservoir can tell us about the propensity of Burkholderia pseudomallei genotypes to transmit from soil to humans. Thirty-five clinical B. pseudomallei isolates, ten from soil, one from swine, and one from a bear were collected by the Institute of Microbiology and Biotechnology, Vietnam National University and sequenced at the National Institute of Hygiene and Epidemiology in Hanoi. The clinical strains were isolated from melioidosis patients from Ha Tinh in each month of 2020 (except July). There were 15 STs identified and four of the clinical isolates were new sequence types (ST) as determined by traditional seven marker multi-locus sequence typing (MLST) analysis. Twenty of the thirty-five (57%) clinical strains isolated in this study were ST 41, with ST 41 isolates obtained throughout the year and across Ha Tinh province with core genome (cg) MLST identifying finer scale differences. ST 41 was recovered from one soil sample approximately 1 year after the clinical isolates. cgMLST analysis and whole genome SNP analysis revealed nucleotide differences among strains in Ha Tinh historically contextualizing them in Vietnam and globally. As melioidosis moves towards a reportable disease in Vietnam, molecular epidemiological methods can connect human, veterinary, and environmental genotypes of concern.