# Geographical distribution of Burkholderia pseudomallei in Taiwanese croplands and the influence of bacterial community interactions on its incubation viability

## TL;DR

The study maps the distribution of a deadly soil bacterium in Taiwan and shows how other bacteria may suppress its survival.

## Contribution

The study reveals regional and vertical patterns of B. pseudomallei DNA in croplands and identifies bacterial interactions affecting its viability.

## Key findings

- Southern Taiwan has the highest B. pseudomallei DNA detection rates and melioidosis incidence.
- B. pseudomallei DNA is more abundant in deeper soil layers but increases at the surface after rain.
- B. multivorans strongly inhibits B. pseudomallei growth through secreted compounds.

## Abstract

Burkholderia pseudomallei is a soil-borne pathogen responsible for melioidosis, a potentially fatal disease. While endemic melioidosis in Taiwan is marked by both clinical cases and environmental detection, a comprehensive environmental survey has been lacking. A nationwide cropland survey using B. pseudomallei-specific orf2-PCR revealed regional positivity rates of 2.1% in northern, 8.2% in central, 15.1% in southern, and 9.8% in eastern Taiwan, with the highest PCR positivity and cumulative melioidosis incidence (12.14 cases per 100,000 people from 2003 to 2024) observed in the south. Vertical profiling showed a higher DNA detection rate at a depth of 60 cm, with increased surface-level detection during rainy periods and a decline after sunny conditions, particularly in the southern area. Identical molecular sequence types across layers suggested upward movement from deeper soil. However, viable bacteria were not consistently recovered from PCR-positive samples, indicating that bacterial dynamics during incubation may influence B. pseudomallei viability. To investigate this, full-length 16S rDNA sequencing and community analysis revealed inverse abundance patterns between B. pseudomallei and B. multivorans, B. cenocepacia, and B. vietnamiensis during incubation. In vitro assays confirmed strong antagonism by B. multivorans filtered supernatants against the growth of B. pseudomallei, while B. cenocepacia and B. vietnamiensis had weaker or no effects. These findings reveal distinct regional and vertical patterns of B. pseudomallei DNA in croplands and highlight the potential influence of bacterial competition on its viability during incubation.

Burkholderia pseudomallei is a soil-dwelling bacterium that causes melioidosis, a potentially fatal infectious disease in humans and animals. Although melioidosis is endemic in Taiwan, nationwide environmental data on the distribution of B. pseudomallei have been limited. We conducted a large-scale cropland survey across Taiwan using a species-specific PCR method to detect B. pseudomallei DNA. The results revealed regional differences, with the highest detection rate and melioidosis incidence in southern Taiwan. DNA was more abundant in deeper soil layers (60 cm), but surface detection increased after rainfall, especially in the south. Notably, viable B. pseudomallei were not always recovered from PCR-positive samples, suggesting that other microbes may affect B. pseudomallei survival during enrichment. Bacterial community analysis identified an inverse relationship between B. pseudomallei and other Burkholderia species, particularly B. multivorans. Laboratory assays showed that B. multivorans strongly inhibited the growth of B. pseudomallei through secreted compounds. These findings provide new insights into the environmental distribution of B. pseudomallei and suggest that bacterial interactions may influence its viability, with potential implications for disease risk assessment and environmental surveillance strategies.