The Journal of Biological Physics and Chemistry

Survival of Shigella flexneri cells in laboratory microcosms

Munawar Sultana ¹, Md. Ziaur Rahman ¹, Nils-Kåre Birkeland ² and Siraj. I. Khan ¹

¹ Department of Microbiology, University of Dhaka, Bangladesh
² Department of Biology, University of Bergen, Norway

The survival of Shigella flexneri was studied in laboratory microcosms to assess culturability. Laboratory microcosms were set up using tap, pond and lake water. In each series, three different densities e.g. 10⁶, 10⁷ and 10⁸ cfu/mL, were used. The findings of the present study showed that, survivability of Shigella flexneri increases with the increase of inoculum density. Survival potential of the cells was highest in the case of tap water, followed by pond and lake waters. With the initial inoculum rate of 10⁶ cfu/mL, the strain became non-culturable after 7, 8 and 10 days in lake, pond and tap water respectively. When the initial inoculum was 10⁷ cfu/mL, the culturability of the strain increased to 10 days in lake and pond waters whereas it was 12 days with tap water. However, with the highest inoculum level of 10⁸ cfu/mL, the culturability extended to more than 20 days. In all the cases, the strain became non-culturable after 7 to more than 20 days (dependent on the initial inoculum density and type of water), but remained viable as determined by fluorescence microscopy using DAPI staining and amplification of the Shigella spp. specific ipaH gene by PCR