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Burkholderia Pseudomallei is genetically diverse in agricultural land in Northeast Thailand.

Wuthiekanun V, Limmathurotsakul D, Chantratita N, Feil EJ, Day NP, Peacock SJ - PLoS Negl Trop Dis (2009)

Bottom Line: Two sampling points contained mixed B. pseudomallei genotypes, each with a numerically dominant genotype and one or more additional genotypes present as minority populations.Genetic diversity and structuring of B. pseudomallei exists despite the effects of flooding and the physical and chemical processes associated with farming.These findings form an important baseline for future studies of environmental B. pseudomallei.

View Article: PubMed Central - PubMed

Affiliation: Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.

ABSTRACT

Background: The soil-dwelling Gram-negative bacterium Burkholderia pseudomallei is the cause of melioidosis. Extreme structuring of genotype and genotypic frequency has been demonstrated for B. pseudomallei in uncultivated land, but its distribution and genetic diversity in agricultural land where most human infections are probably acquired is not well defined.

Methods: Fixed-interval soil sampling was performed in a rice paddy in northeast Thailand in which 100 grams of soil was sampled at a depth of 30 cm from 10x10 sampling points each measuring 2.5 m by 2.5 m. Soil was cultured for the presence of B. pseudomallei and genotyping of colonies present on primary culture plates was performed using a combination of pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST).

Principal findings: B. pseudomallei was cultured from 28/100 samples. Genotyping of 630 primary colonies drawn from 11 sampling points demonstrated 10 PFGE banding pattern types, which on MLST were resolved into 7 sequence types (ST). Overlap of genotypes was observed more often between sampling points that were closely positioned. Two sampling points contained mixed B. pseudomallei genotypes, each with a numerically dominant genotype and one or more additional genotypes present as minority populations.

Conclusions: Genetic diversity and structuring of B. pseudomallei exists despite the effects of flooding and the physical and chemical processes associated with farming. These findings form an important baseline for future studies of environmental B. pseudomallei.

No MeSH data available.


Related in: MedlinePlus

Splits decomposition based on the concatenated sequences of the seven STs identified from 11 sampling points.This was carried out using SplitsTree 4 (splitstree.org) using the default settings. The analysis suggests that the STs are approximately equidistant from each other, and the high level of reticulation is consistent with free recombination.
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pntd-0000496-g002: Splits decomposition based on the concatenated sequences of the seven STs identified from 11 sampling points.This was carried out using SplitsTree 4 (splitstree.org) using the default settings. The analysis suggests that the STs are approximately equidistant from each other, and the high level of reticulation is consistent with free recombination.

Mentions: The genetic relationships between B. pseudomallei STs isolated from the paddy was considered in relation to allelic profiles and concatenated sequences. The average number of allelic differences between pairs of STs was 3.28. In terms of allelic profile, ST185 was marginally the most diverged genotype, differing on average by 4 alleles from the other 6 STs, although this was similar to the equivalent figures for the other STs (2.83–3.66). Therefore, no STs are highly divergent from all the others, and no pairs or clusters of highly related STs are apparent. Such a pattern is consistent with previous studies demonstrating high rates of recombination and low levels of linkage within the Burkholderia population [6],[13]. Given this, we would not expect to find a strong phylogenetic signal in these data, and this is supported by splits decomposition analysis which reveals extensive reticulation reflecting conflicts in the data consistent with recombination (Figure 2).


Burkholderia Pseudomallei is genetically diverse in agricultural land in Northeast Thailand.

Wuthiekanun V, Limmathurotsakul D, Chantratita N, Feil EJ, Day NP, Peacock SJ - PLoS Negl Trop Dis (2009)

Splits decomposition based on the concatenated sequences of the seven STs identified from 11 sampling points.This was carried out using SplitsTree 4 (splitstree.org) using the default settings. The analysis suggests that the STs are approximately equidistant from each other, and the high level of reticulation is consistent with free recombination.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2713400&req=5

pntd-0000496-g002: Splits decomposition based on the concatenated sequences of the seven STs identified from 11 sampling points.This was carried out using SplitsTree 4 (splitstree.org) using the default settings. The analysis suggests that the STs are approximately equidistant from each other, and the high level of reticulation is consistent with free recombination.
Mentions: The genetic relationships between B. pseudomallei STs isolated from the paddy was considered in relation to allelic profiles and concatenated sequences. The average number of allelic differences between pairs of STs was 3.28. In terms of allelic profile, ST185 was marginally the most diverged genotype, differing on average by 4 alleles from the other 6 STs, although this was similar to the equivalent figures for the other STs (2.83–3.66). Therefore, no STs are highly divergent from all the others, and no pairs or clusters of highly related STs are apparent. Such a pattern is consistent with previous studies demonstrating high rates of recombination and low levels of linkage within the Burkholderia population [6],[13]. Given this, we would not expect to find a strong phylogenetic signal in these data, and this is supported by splits decomposition analysis which reveals extensive reticulation reflecting conflicts in the data consistent with recombination (Figure 2).

Bottom Line: Two sampling points contained mixed B. pseudomallei genotypes, each with a numerically dominant genotype and one or more additional genotypes present as minority populations.Genetic diversity and structuring of B. pseudomallei exists despite the effects of flooding and the physical and chemical processes associated with farming.These findings form an important baseline for future studies of environmental B. pseudomallei.

View Article: PubMed Central - PubMed

Affiliation: Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.

ABSTRACT

Background: The soil-dwelling Gram-negative bacterium Burkholderia pseudomallei is the cause of melioidosis. Extreme structuring of genotype and genotypic frequency has been demonstrated for B. pseudomallei in uncultivated land, but its distribution and genetic diversity in agricultural land where most human infections are probably acquired is not well defined.

Methods: Fixed-interval soil sampling was performed in a rice paddy in northeast Thailand in which 100 grams of soil was sampled at a depth of 30 cm from 10x10 sampling points each measuring 2.5 m by 2.5 m. Soil was cultured for the presence of B. pseudomallei and genotyping of colonies present on primary culture plates was performed using a combination of pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST).

Principal findings: B. pseudomallei was cultured from 28/100 samples. Genotyping of 630 primary colonies drawn from 11 sampling points demonstrated 10 PFGE banding pattern types, which on MLST were resolved into 7 sequence types (ST). Overlap of genotypes was observed more often between sampling points that were closely positioned. Two sampling points contained mixed B. pseudomallei genotypes, each with a numerically dominant genotype and one or more additional genotypes present as minority populations.

Conclusions: Genetic diversity and structuring of B. pseudomallei exists despite the effects of flooding and the physical and chemical processes associated with farming. These findings form an important baseline for future studies of environmental B. pseudomallei.

No MeSH data available.


Related in: MedlinePlus