Direct detection of Vibrio cholerae and ctxA in Peruvian coastal water and plankton by PCR.

Seawater and plankton samples were collected over a period of 17 months from November 1998 to March 2000 along the coast of Peru. Total DNA was extracted from water and from plankton grouped by size into two fractions (64 micro m to 202 micro m and >202 micro m). All samples were assayed for Vibrio cholerae, V. cholerae O1, V. cholerae O139, and ctxA by PCR. Of 50 samples collected and tested, 33 (66.0%) were positive for V. cholerae in at least one of the three fractions. Of these, 62.5% (n = 32) contained V. cholerae O1; ctxA was detected in 25% (n = 20) of the V. cholerae O1-positive samples. None were positive for V. cholerae O139. Thus, PCR was successfully employed in detecting toxigenic V. cholerae directly in seawater and plankton samples and provides evidence for an environmental reservoir for this pathogen in Peruvian coastal waters.