Protease production by Burkholderia pseudomallei and virulence in mice

The aim of this study was to assess protease production and virulence of va rious Burkholderia pseudomallei strains. Protease activity was evaluated in filtrates from cultures grown for 50 h in TSB Dialysate by azocasein hydro lysis, and expressed as absorbancy at 405 nm. Virulence was assessed in 8 w eeks old SWISS mice, by intraperitoneal injection of 6-6 x 10(5) CFU, and t he 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 typ e strains of Burkholderia pseudomallei, Burkholderia mallei, and Burkholder ia cepacia. The three type strains appeared to be low protease producers (A (405) = 0.11, 0.09 and 0.00, respectively) and avirulent. The two more viru lent 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 act ivities (A(405) = 0.046 and 0.79, respectively). Moreover, the avirulent pa rent of IPP 6068 (AG), was a better protease producer than the 6068 VIR str ain, A(405) = 0.26 versus 0.046. These results suggest that there is no cor relation between virulence and level of exoproteolytic activity, when B. ps eudomallei is injected to mice via the intraperitoneal route. (C) 2000 Publ ished by Elsevier Science B.V. All rights reserved.