ENHANCEMENT OF IN-VITRO CYTOPATHOGENICITY BY ACANTHAMOEBA SPP. FOLLOWING ACQUISITION OF BACTERIAL ENDOSYMBIONTS

Approximately one in five isolates of Acanthamoeba spp. recovered from clinical and environmental sources are found to harbor obligate, uncu ltured bacterial endosymbionts of unknown clinical significance. To in vestigate their possible role in amoebic pathogenesis, four uninfected amoebic strains were exposed to four different endosymbionts, from wh ich 12 stably-infected host-symbiont pairs resulted. Standardized inoc ula of amoebae with and without endosymbionts were placed on fibroblas t monolayers to examine for cytopathic effects (CPEs). Eight to 10 day s were required for monolayer effacement by endosymbiont-free amoebae; 5-8 days for amoebae containing Gram-negative rod endosymbionts; and 3 days for two amoebic isolates infected with a Chlamydia-like endosym biont. All endosymbiont-infected amoebae produced a statistically sign ificant enhancement in CPEs in comparison to uninfected amoebae; endos ymbionts alone on monolayers produced no CPEs, This report provides ev idence that obligate bacterial endosymbionts are able to enhance amoeb ic pathogenic potential in vitro by some as-yet unknown mechanism. (C) 1998 Federation of European Microbiological Societies. Published by E lsevier Science B.V. All rights reserved.