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Burkholderia pseudomallei JW270 Is Lethal in the Madagascar Hissing Cockroach Infection Model and Can Be Utilized at
Jennifer Chua1, Ethan Nguyenkhoa1, Sherry Mou1
1Bacteriology Division, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, USA.
Abstract:
Burkholderia pseudomallei, the causative agent of melioidosis, is classified by the CDC as a tier 1 select agent, and work involving it must be performed in a biosafety level 3 (BSL-3) laboratory. Three BSL-2 surrogate strains derived from B. pseudomallei 1026b, a virulent clinical isolate, have been removed from the CDC select agent list. These strains, Bp82, B0011, and JW270, are highly attenuated in rodent models of melioidosis and cannot be utilized to identify virulence determinants because of their high 50% lethal dose (LD50). We previously demonstrated that the Madagascar hissing cockroach (MHC) is a tractable surrogate host to study the innate immune response against Burkholderia. In this study, we found that JW270 maintains its virulence in MHCs. This surprising result indicates that it may be possible to identify potential virulence genes in JW270 by using MHCs at BSL-2. We tested this hypothesis by constructing JW270 mutations in genes that are required (hcp1) or dispensable (hcp2) for B. pseudomallei virulence in rodents. JW270 Δhcp1 was avirulent in MHCs and JW270 Δhcp2 was virulent, suggesting that MHCs can be used at BSL-2 for the discovery of important virulence factors. JW270 ΔBPSS2185, a strain harboring a mutation in a type IV pilin locus (TFP8) required for full virulence in BALB/c mice, was also found to be attenuated in MHCs. Finally, we demonstrate that the hmqA-G locus, which encodes the production of a family of secondary metabolites called 4-hydroxy-3-methyl-2-alkylquinolines, is important for JW270 virulence in MHCs and may represent a novel virulence determinant.
Insights
Madagascar hissing cockroaches can identify Burkholderia virulence factors in a BSL-2 lab. This insect model reveals novel determinants like the hmqA-G locus, aiding melioidosis research.
Area of Science:
- Microbiology
- Infectious Diseases
- Pathogen Research
Background:
- Burkholderia pseudomallei causes melioidosis and is a CDC Tier 1 select agent requiring Biosafety Level 3 (BSL-3) containment.
- Attenuated BSL-2 surrogate strains (Bp82, B0011, JW270) lack virulence in rodent models, hindering virulence factor discovery.
- Madagascar hissing cockroaches (MHCs) serve as a tractable surrogate host for studying Burkholderia innate immune responses.
Purpose of the Study:
- To evaluate the Madagascar hissing cockroach (MHC) as a surrogate host for identifying virulence factors of the attenuated BSL-2 strain JW270.
- To determine if MHCs can facilitate virulence gene discovery for B. pseudomallei at Biosafety Level 2 (BSL-2).
Main Methods:
- JW270 strain mutations were constructed in genes previously associated with B. pseudomallei virulence in rodents (hcp1, hcp2, BPSS2185).
- Virulence of wild-type JW270 and its mutant derivatives was assessed in MHCs.
- The role of the hmqA-G locus in JW270 virulence within MHCs was investigated.
Main Results:
- JW270 maintained virulence in MHCs, unlike its attenuated phenotype in rodent models.
- Mutations in hcp1 and BPSS2185 attenuated JW270 in MHCs, while hcp2 mutation did not affect virulence.
- The hmqA-G locus, responsible for producing 4-hydroxy-3-methyl-2-alkylquinolines, was identified as important for JW270 virulence in MHCs.
Conclusions:
- Madagascar hissing cockroaches (MHCs) are a viable BSL-2 surrogate model for identifying B. pseudomallei virulence factors using attenuated strains like JW270.
- The study successfully identified key virulence genes (hcp1, BPSS2185) and a novel determinant (hmqA-G locus) in the JW270 strain using MHCs.
- This approach offers a safer and more accessible method for melioidosis research and virulence factor discovery.
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