Acanthamoeba castellanii an environmental host for Shigella dysenteriae and Shigella sonnei
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S H O R T CO M MU N I C A T I O N
Acanthamoeba castellanii an environmental host for Shigella dysenteriae and Shigella sonnei Amir Saeed · Hadi Abd · Benjamin Edvinsson · Gunnar Sandström
Received: 19 March 2008 / Revised: 2 July 2008 / Accepted: 23 July 2008 / Published online: 20 August 2008 © Springer-Verlag 2008
Abstract The interaction between Shigella dysenteriae or Shigella sonnei and Acanthamoeba castellanii was studied by viable counts, gentamicin assay and electron microscopy. The result showed that Shigella dysenteriae or Shigella sonnei grew and survived in the presence of amoebae for more than 3 weeks. Gentamicin assay showed that the Shigella were viable inside the Acanthamoeba castellanii which was conWrmed by electron microscopy that showed the Shigella localized in the cytoplasm of the Acanthamoeba castellanii. In conclusion, the relationship between Shigella dysenteriae and Shigella sonnei with Acanthamoeba castellanii is symbiotic, and accordingly free-living amoebae may serve as a transmission reservoir for Shigella in water. Keywords A. castellanii · Shigella · Environmental reservoir
Introduction The World Health Organization (WHO) has estimated that about 1.1 billion people worldwide drink unsafe water (Kindhauser 2003) The organization has also concluded Communicated by Jörg Overmann. A. Saeed · G. Sandström (&) Department of Laboratory Medicine, Division of Clinical Microbiology, Karolinska Institute, 141 86 Stockholm, Sweden e-mail: [email protected] A. Saeed · H. Abd · B. Edvinsson · G. Sandström Centre for Microbiological Preparedness, Swedish Institute for Infectious Disease Control, 171 82 Solna, Sweden
that most diarrheal diseases in the world are due to unsafe water, poor sanitation or poor hygiene (Who 2003; Niyogi 2005). Most of the diseases that are transmitted via drinking water are caused by enteric pathogens (Hunter et al. 2002), of which Shigella is the genus that has the greatest economic impact in the developing world. Shigella is a gram-negative, facultative intracellular bacterium that causes shigellosis or bacillary dysentery in man. Approximately, 164.7 million cases occur annually worldwide, 163.2 million of them are in developing countries. The infection results in 1.1 million deaths each year, 60% of which are children aged less than 5 years (Niyogi 2005). Shigella is transmitted via the fecal–oral route. Most Shigella infections occur in young children, in crowded living conditions, and in locations of poor hygiene (Faruque et al. 2002). Shigella is a highly infectious bacterium, and as few as ten microorganisms acquired orally are enough to cause shigellosis in man (Du Pont et al. 1989; Sansonetti et al. 1999). The only known host of Shigella is man; it is not known that which factors determine the emergence and decline of epidemic shigellosis. Contaminated food and water are the main sources of the epidemic spread of Shigella, while it is unclear whether the bacterium is present in environmental water and if so, whether it can spread through this route (Fa
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