Nathan edited We_previously_determined_that_the__.tex  over 8 years ago

Commit id: 4b96dcbe69ef69217e4f9682bacefad54ae080ba

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We previously determined that the Madagascar hissing (MH) cockroach (\textit{Gromphadorhina laevigata}) met the above noted criteria and was a suitable surrogate host for the facultative intracellular pathogens \textit{Burkholderia mallei}, \textit{B. pseudomallei}, and \textit{B. thailandensis} \cite{22892068}. Here, we sought to determine if tropical cockroach species can serve as experimental hosts for another important bacterial pathogen, namely \textit{F. tularensis}. The Orange Spotted (OS) cockroach (\textbf{Figure 1C}, \textit{Blaptica dubia} Serville 1839) also meets the above criteria as an ideal insect host for pathogenesis studies but is more readily available from commercial suppliers and is more docile compared to the MH cockroach. The OS cockroach does not vocalize like the MH cockroach and it usually remains in an immobile defensive position when placed on its back. Of interest to researchers who desire to rear their own host animals, the OS cockroach does not climb vertical glass or plastic surfaces, which aids in containment of the cockroaches in their rearing containers. The body size and sclerotised cuticle of OS cockroach enables intrahemocoel inoculation using either a standard needle and syringe combination or a sharpened pipette tip (\textbf{Figure 1D}), which improves laboratory safety and decreases costs. We found the OS cockroach to be a permissive host for \textit{F. tularensis} LVS. Lethality depended upon the dose of bacteria given, the temperature of incubation, and, interestingly, the developmental stage and gender of the cockroach. Intracellular and extracellular bacterial titers increased throughout the course of infection and several mutant strains lacking factors known to be involved in \textit{Francisella} pathogenesis were attenuated. Infection could be rescued by systemic or peroral delivery of antibiotics, with protection by the peroral route correlating with known oral absorption profiles in mammals. These results extend our previous findings \cite{22892068} and  demonstrate that tropical cockroaches are a favorable alternative to mammals and other insect species for the study of multiple bacterial pathogens.