B. mallei does not kill rodents as quickly as B. pseudomallei and it is more fastidious than B. pseudomallei and B. thailandensis, so it may not be too surprising that it took longer to kill MH cockroaches [4]. These experiments demonstrate that B. mallei

and B. thailandensis are both virulent in the MH cockroach and suggest that the MH cockroach might serve as a surrogate host for these bacterial species. Figure 4 B. mallei and B. thailandensis are virulent for the MH cockroach and their T6SS-1 mutants are attenuated. (A) 101 cfu. (B) 102 cfu. (C) 103 cfu. Bm, SR1; Bm Δhcp1, DDA0742; Bt, DW503; Bt Δhcp1, DDII0868. As mentioned above, B. thailandensis is considered to be avirulent in humans selleck products and exhibits a higher LD50 in mammalian models of infection than B. mallei and B. pseudomallei. Mammals,

unlike MH cockroaches, possess both an innate and an acquired immune system. The fact that B. thailandensis is highly virulent in the MH cockroach may suggest that the acquired immune system plays an important role in defence against B. thailandensis. B. mallei and B. pseudomallei, on the other hand, may have developed mechanisms to subvert the acquired immune Bleomycin supplier response in mammalian species. T6SS-1 is a critical virulence determinant for B. mallei in the hamster model of infection [25] and for B. thailandensis in the C57BL/6 mouse model of infection [27]. We challenged MH cockroaches with B. mallei and B. thailandensis hcp1 mutants and found that they were highly attenuated in this surrogate host Buspirone HCl (Table 1 and Figure 4). The LD50s for B. mallei Δhcp1 and B. thailandensis hcp1 – were > 103 bacteria on day 5, which was at least 100 times higher than their respective parental strains (Table 1 and Figure 4). The B. mallei results were indistinguishable from what was previously described for SR1 and Δhcp1 using the hamster model of infection [25]. While the B. thailandensis

strains used in this study have not been tested in hamsters, a B. thailandensis T6SS-1 mutant was recently shown to be avirulent in C57BL/6 mice by the aerosol route of infection [27]. Interestingly, MyD88−/− mice were susceptible to the B. thailandensis T6SS-1 mutant, which suggests that T6SS-1 plays a role in evading the innate immune response [27]. The fact that B. thailandensis hcp1 – was attenuated in an insect host, which lacks an adaptive immune response, further supports the notion that the function of the T6SS-1 is to evade the learn more eukaryotic innate immune system. B. pseudomallei replicates inside MH cockroach hemocytes Hemocytes are a key component of the MH cockroach innate immune system and we next examined if B. pseudomallei might be exploiting these phagocytic cells to gain an upper hand in the host-pathogen interaction. A group of eight MH cockroaches were infected with ~ 103 B. pseudomallei K96243 and closely monitored for 48 h.