A survey of Vibrio cholerae O1 and O139 in estuarine waters and sediments of Beira, Mozambique

Abstract

This study determined whether the estuarine and freshwater environment in Beira, Mozambique, serves as a reservoir of Vibrio cholerae O1 and O139. Ninety-nine estuarine water samples were collected at 6 sites in Beira. An additional 54 samples were collected from rural areas around Beira which included 3 freshwater lake samples, 15 river, 5 pond, and 4 estuarine water samples, and an equivalent number of sediment samples, collected from the same sites as the water samples. In addition, fish scales from 5 ocean fish and 1 deep sea water sample were also collected. The samples were analysed for the presence of V. cholerae O1 and O139 using culture methods, the direct fluorescent antibody (DFA) method and polymerase chain reaction (PCR) using a single-primer pair for the ompW gene and a semi-nested PCR selecting for the ctxA
gene, encoding subunit A of cholera toxin. DFA results showed 37 V. cholerae O1- and 6 O139-positive samples. Vibrio cholerae O1 and O139 were observed on the scales of 4 of the 5 fish. The findings of the study provided in situ evidence for V. cholerae O1 and O139, predominantly as viable but non-culturable cells in the aquatic environment of Beira. This is the first record of the presence of V. cholerae O139 in the estuarine environment on the coast of Africa.

Keywords: Vibrio cholerae O1, Vibrio choleare O139, water quality, estuary, PCR, DFA