Poster Presenter

Resistance Of Balamuthia mandrillaris Cysts To Physical, Chemical And Radiological Conditions And Encystment Mechanisms
Ruqaiyyah Siddiqui and Naveed Ahmed Khan
UK

Balamuthia mandrillaris is a free-living protozoan pathogen that can cause serious human and animal infections. Under harsh conditions, B. mandrillaris trophozoites differentiate into dormant cysts. Given the free-living nature of this organism and its ability to encyst in human tissues establishing latent infections suggests that B. mandrillaris cysts are resistant to a variety of hostile conditions. In the present study, resistance of B. mandrillaris cysts to physical, chemical and radiological conditions was tested. Following various treatments, cysts were cultured on human brain microvascular endothelial cells and excystment of B. mandrillaris trophozoites was observed for up to 14 days. B. mandrillaris cysts were resistant to repeated freeze-thawing (up to 3x) and temperatures of up to 60°C. Cysticidal effects of sodium dodecyl sulfate (SDS) were concentration-dependent. For example, 0.1% SDS had minimal effects and trophozoites emerged within 48 h. However cysts treated with 0.5% SDS excysted on day 10, post-culturing. Moreover, cysts were resistant to chlorine (up to 500 ppm), up to 10µg/ml pentamidine (antiamoebic compound) and 800mJ/cm2 of ultraviolet irradiation. Furthermore we showed that phosphatidylinositol 3-kinase dependent cytoskeletal re-arrangments are critical in B. mandrillaris encystment. Exogenous galactose but not other sugars enhanced B. mandrillaris encystment suggesting a role for galactose binding protein. Overall, these results suggest that B. mandrillaris cysts are highly resistant to harsh conditions and pose a major problem in eradication from the environment as well as for chemotherapeutic treatment. A complete understanding of the pathways involved in encystment will shed light on the potential therapeutic targets.