Screening for Type III Secretion System Inhibitors

Screening for Type III Secretion System Inhibitors

Commonly used antibiotics are becoming less effective since overuse creates a selective pressure forbacteria to become resistant, leading to the formation of “super bugs”. Some of these pathogenicbacteria include E. coli, Salmonella, Chlamydia and Yersinia species. These species utilize a type III secretion system (T3SS), which are needle-like structures on their surface used to inject host cells with toxins to evade our immune system and cause infection. The goal of this research was to screen for antimicrobials produced by soil bacteria that may target T3SSs. Many species of bacteria found in soil produce antimicrobials to compete for nutrients and space. Serial dilution plating was used to isolate soil bacteria and each isolate was patched onto MOX agar plates pre-inoculated with Y. pestis. After incubation, the areas around each soil isolate were analyzed for the Y. pestis growth characteristics associated with blocked T3S or growth inhibition. The soil bacteria that exhibited positive results were tested against ESKAPE pathogen alternatives and identified using 16S rDNA sequencing. Bacillus cereus strain JEM-2, Bacillus amyloliquefaciens strain SSH100-3 and Pseudomonas aeruginosa strain NBAII AFP-7 were soil isolates identified to have antibacterial activity against Y. pestis and at least one ESKAPE pathogen. Compounds from these organisms will be extracted using ethyl acetate and further characterized.