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BMC Microbiol. 2017 Jun 7;17(1):132. doi: 10.1186/s12866-017-1040-4.

An avirulent Burkholderia pseudomallei ∆purM strain with atypical type B LPS: expansion of the toolkit for biosafe studies of melioidosis.

Author information

1
Department of Infectious Diseases and Pathology, College of Veterinary Medicine, Univeristy of Florida, Gainesville, FL, USA.
2
Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.
3
Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL, USA.
4
Department of Infectious Diseases and Pathology, College of Veterinary Medicine, Univeristy of Florida, Gainesville, FL, USA. tuanyok@ufl.edu.
5
Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA. tuanyok@ufl.edu.

Abstract

BACKGROUND:

The work was undertaken to expand the tools available for researching Burkholderia pseudomallei (Bp), the etiological agent of the tropical disease melioidosis. Melioidosis has the potential to pose a severe threat to public health and safety. In the United States, Bp is listed as a Tier-1 select agent by the Centers for Disease Control and Prevention (CDC), thus requiring high levels of regulation and biosafety level 3 (BSL3) facilities for experimental manipulation of live organisms. An avirulent ∆purM derivative of strain 1026b (Bp82) has proven to be a valuable tool for biosafe research as a select-agent excluded strain, but the high level of genetic diversity between Bp strains necessitates an expansion of the biosafe toolset.

RESULTS:

The ∆purM mutation was recapitulated in the Bp 576a strain, a serotype B background. An important difference between strains 1026b and 576a is the lipopolysaccharide (LPS), a major virulence factor and protective antigen. Polyclonal sera from 1026b-challenged non-human primates showed no cross reactivity with strain 576a LPS and low reactivity with whole cell lysate. Strain 576a replicates to higher levels in mouse organs and induces more TNF-α in the lungs of BALB/c mice compared to 1026b. The newly created Bp 576a ∆purM strain, designated 576mn, was auxotrophic for adenine in minimal media, capable of wild-type growth in rich media with addition of adenine, and auxotrophy was abrogated with single-copy complementation. Bp 576mn was unable to replicate in human cells and was avirulent in BALB/c mice following high-dose intranasal inoculation, similar to Bp82. Organ loads indicated a significant reduction in bacterial replication.

CONCLUSIONS:

In this work, the new biosafe strain 576mn with atypical type B LPS was generated. This strain should prove a valuable addition to the toolkit for biosafe studies of Bp and development of therapeutic and preventative strategies aimed at combatting melioidosis. Strain 576mn is an ideal candidate for select-agent exclusion.

PMID:
28592242
PMCID:
PMC5461690
DOI:
10.1186/s12866-017-1040-4
[Indexed for MEDLINE]
Free PMC Article

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