title: Acanthamoeba: could it be an environmental host of Shigella?
abstract: Shigellosis is a serious public health problem in Korea, because large outbreaks of Shigella sonnei infections were recorded in many parts of the country during the period 1998-2000. However, the epidemiological features of shigellosis are not well known. In this study, we devised conditions suitable for the growth and replication of Shigella in an amoebic intracellular environment, and investigate whether medium conditions affect the survival and replication of Shigella within Acanthamoeba. We evaluated the uptake rates of invasive and non invasive S. sonnei strains by three Acanthamoeba species, namely, A. castellanii Neff, A. astronyxis Ray & Hayes, and A. healyi OC-3A. When A. castellanii Neff was infected with S. sonnei 99OBS1 or 80DH248, shigellae was maintained for a longer time in cytoplasms than in other Acanthamoeba species. S. sonnei 99OBS1 strain (a virulent strain) was recovered in higher numbers than the non-virulent S. sonnei 80DH248 strain in all experiments. Moreover, S. sonnei was more easily engulfed by Acanthamoeba at 18 degrees C. The shigellae uptake rates of Neff strain, which was cultured in free-media (less nutrition), were higher (>10-fold) than those observed in original amoeba culture media (PYG medium) in all time points. S. sonnei 99OBS1 was localized, with an intact membrane, to the vacuoles of Acanthamoeba. We conclude that free-living amoebae more likely act as environmental hosts for shigellae, and thus, may have contributed to outbreaks of shigellosis in Korea.
authors.affiliation: Department of Parasitology, School of Medicine, Pusan National University, 1-10 Ami-dong, Seo-gu, Busan 602-739, Republic of Korea.
authors.forename: Hae Jin
authors.initials: HJ
authors.lastname: Jeong
authors.forename: Eun Seong
authors.initials: ES
authors.lastname: Jang
authors.forename: Byung In
authors.initials: BI
authors.lastname: Han
authors.forename: Keun Hee
authors.initials: KH
authors.lastname: Lee
authors.forename: Mee Sun
authors.initials: MS
authors.lastname: Ock
authors.forename: Hyun Hee
authors.initials: HH
authors.lastname: Kong
authors.forename: Dong Il
authors.initials: DI
authors.lastname: Chung
authors.forename: Sung Yong
authors.initials: SY
authors.lastname: Seol
authors.forename: Dong Taek
authors.initials: DT
authors.lastname: Cho
authors.forename: Hak Sun
authors.initials: HS
authors.lastname: Yu
mesh_terms: D000048:Acanthamoeba / Q000382:microbiology* / Q000648:ultrastructure; D048248:Acanthamoeba castellanii / Q000382:microbiology / Q000648:ultrastructure; D000818:Animals; D003470:Culture Media; D004405:Dysentery, Bacillary / Q000635:transmission; D006367:HeLa Cells; D006801:Humans; D046529:Microscopy, Electron, Transmission; D012764:Shigella sonnei / Q000254:growth & development* / Q000472:pathogenicity / Q000648:ultrastructure; D013045:Species Specificity; D013696:Temperature; D014617:Vacuoles / Q000382:microbiology; D010948:Viral Plaque Assay; D014774:Virulence
chemical_list: D003470:Culture Media