Acanthamoeba: could it be an environmental host of Shigella?
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.
Jeong
Hae Jin
HJ
Department of Parasitology, School of Medicine, Pusan National University, 1-10 Ami-dong, Seo-gu, Busan 602-739, Republic of Korea.
Jang
Eun Seong
ES
Han
Byung In
BI
Lee
Keun Hee
KH
Ock
Mee Sun
MS
Kong
Hyun Hee
HH
Chung
Dong Il
DI
Seol
Sung Yong
SY
Cho
Dong Taek
DT
Yu
Hak Sun
HS
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
D003470:Culture Media