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Protease production by Burkholderia pseudomallei and virulence in mice
Y P Gauthier1, F M Thibault, J C Paucod
1Unité de Microbiologie, Centre de Recherche du Service de Santé des Armées Emile Pardé, La Tronche, France.
Abstract:
The aim of this study was to assess protease production and virulence of various Burkholderia pseudomallei strains. Protease activity was evaluated in filtrates from cultures grown for 50 h in TSB Dialysate by azocasein hydrolysis, and expressed as absorbancy at 405 nm. Virulence was assessed in 8 weeks old SWISS mice, by intraperitoneal injection of 6-6 x 10(5) CFU, and the LD50 was calculated after 30 days by the method of Reed and Muench. The lethal activity was studied for five strains of B. pseudomallei and the type strains of Burkholderia pseudomallei, Burkholderia mallei, and Burkholderia cepacia. The three type strains appeared to be low protease producers (A405 = 0.11, 0.09 and 0.00, respectively) and avirulent. The two more virulent B. pseudomallei strains exhibited significantly different LD50, 3.5 x 10(2) (IPP 6068 VIR) versus 2.1 x 10(5) CFU/mouse (40/97), and protease activities (A405 = 0.046 and 0.79, respectively). Moreover, the avirulent parent of IPP 6068 (AG), was a better protease producer than the 6068 VIR strain, A405 = 0.26 versus 0.046. These results suggest that there is no correlation between virulence and level of exoproteolytic activity, when B. pseudomallei is injected to mice via the intraperitoneal route.
Insights
This study found no direct link between protease production and the virulence of Burkholderia pseudomallei strains in mice. Protease levels varied independently of lethal activity across different strains.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Biochemistry
Background:
- Burkholderia pseudomallei is an opportunistic pathogen causing melioidosis.
- Proteases are key virulence factors in many bacterial infections.
- The relationship between protease production and virulence in B. pseudomallei requires further investigation.
Purpose of the Study:
- To evaluate protease production in various Burkholderia pseudomallei strains.
- To assess the virulence and lethal activity (LD50) of these strains in a murine model.
- To determine any correlation between exoproteolytic activity and virulence.
Main Methods:
- Protease activity was quantified using azocasein hydrolysis (absorbance at 405 nm).
- Virulence was assessed by intraperitoneal injection of bacterial strains into SWISS mice.
- Lethal dose 50 (LD50) was calculated using the Reed and Muench method.
Main Results:
- Type strains of B. pseudomallei, B. mallei, and B. cepacia showed low protease production and were avirulent.
- Two virulent B. pseudomallei strains displayed significantly different LD50 values and protease activities.
- An avirulent B. pseudomallei strain produced more protease than a virulent counterpart.
Conclusions:
- No direct correlation was observed between exoproteolytic activity and virulence in B. pseudomallei following intraperitoneal injection in mice.
- Protease production does not appear to be a sole determinant of B. pseudomallei virulence in this experimental model.
- Further research is needed to elucidate the complex factors governing B. pseudomallei pathogenesis.