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Applied and Environmental Microbiology, March 2006, p. 2185-2190, Vol. 72, No. 3
0099-2240/06/$08.00+0 doi:10.1128/AEM.72.3.2185-2190.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
International Center for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh,1 Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, Maryland,2 Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland,3 University of Maryland Institute for Advanced Computer Studies, College Park, Maryland4
Received 18 July 2005/ Accepted 31 December 2005
It has long been assumed that prolonged holding of environmental samples at the ambient air temperature prior to bacteriological analysis is detrimental to isolation and detection of Vibrio cholerae, the causative agent of pandemic cholera. The present study was aimed at understanding the effect of transporting environmental samples at the ambient air temperature on isolation and enumeration of V. cholerae. For water and plankton samples held at ambient temperatures ranging from 31°C to 35°C for 20 h, the total counts did not increase significantly but the number of culturable V. cholerae increased significantly compared to samples processed within 1 h of collection, as measured by culture, acridine orange direct count, direct fluorescent-antibody-direct viable count (DFA-DVC), and multiplex PCR analyses. For total coliform counts, total bacterial counts, and DFA-DVC counts, the numbers did not increase significantly, but the culturable plate counts for V. cholerae increased significantly after samples were held at the ambient temperature during transport to the laboratory for analysis. An increase in the recovery of V. cholerae O1 and improved detection of V. cholerae O1 rfb and ctxA also occurred when samples were enriched after they were kept for 20 h at the ambient temperature during transport. Improved detection and isolation of toxigenic V. cholerae from freshwater ecosystems can be achieved by holding samples at the ambient temperature, an observation that has significant implications for tracking this pathogen in diverse aquatic environments.
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