Novel model for the in vivo study of central nervous system infection due to Acanthamoeba spp. (T4 genotype)

Abstract

In this study it was shown for what is believed to be the first time that the African migratory locust can be used as a model for the study of Acanthamoeba pathogenesis. Mature adult locusts were injected intra-abdominally with 10 μl suspension of 106 Acanthamoeba (a clinical isolate of the T4 genotype) in culture medium, or with the same volume of sterile culture medium. Locusts injected with Acanthamoeba showed significant weight loss and reduced production of faeces compared with control locusts. Furthermore, injection of amoebae killed all of the locusts within 17 days at room temperature, although the speed of kill was temperature and dose dependent. When samples of faecal pellets and various tissues of infected locusts were cultured on non-nutrient agar plates containing bacterial lawns, live amoebae were recovered from haemolymph, flight muscle and fat body samples, but not from faeces. When brains dissected from locusts were incubated with an anti-amoebic drug (100 μM chlorhexidine) to kill extracellular amoebae, and then washed, homogenized and cultured on bacteria-seeded non-nutrient agar plates, only lysates from amoebae-infected locusts were positive for Acanthamoeba. This strongly suggests that amoebae invade the locust brain and, indeed, trophozoites of Acanthamoeba could be identified within the brain in histological sections of brains from infected locusts, but not from uninfected locusts. These findings support the view that locusts can be used as a model for the study of Acanthamoeba pathogenesis in vivo.