Epifluorescent micrographs of V. cholerae O1 and O139 detected in environmental samples collected between March and December 2004. Fluorescent monoclonal antibodies (DFA) specific for V. cholerae serovar O1 or O139, obtained from New Horizon Diagnostic, were used, and the stains were visualized (18, 19) using an epifluorescence microscope (Olympus model BX51, BX2 series). Microscopic images were captured digitally (Olympus DP20) and processed by using Adobe Photoshop (version 5). (A and C) Typical single cells of V. cholerae O1 and O139, respectively; (B and D) cell clusters of V. cholerae O1 in water samples collected from Mathbaria and Matlab, respectively, during July 2004.