DIRECT FLUORESCENT ANTIBODY-DIRECT VIABLE COUNT AND POLYMERASE CHAIN REACTION DETECTION LIMIT FOR THE IDENTIFICATION OF VIBRIO CHOLERAE O1 IN MUSSELS (MYTILUS EDULIS)

ABSTRACT

Vibrio cholerae O1 is natural to the aquatic environment and can cause gastrointestinal infections when it is consumed from contaminated bivalves. Under unfavorable conditions, this bacterium enters into a viable but nonculturable state. Immunofluorescence and polymerase chain reaction (PCR) methods were a useful alternative for detecting this microorganism without a pre-enrichment step. We investigated the detection limit of the direct fluorescent antibody (DFA)-direct viable count (DVC) and PCR techniques for the identification of V. cholerae O1 in mussel (Mytilus edulis) samples. When 10³ cfu/mL V. cholerae O1 were inoculated in samples, 10²–10³ bacteria mL⁻¹ were determined by immunofluorescence tests and 67% of the samples were positive by PCR assay. No significant difference (T statistic value = 6.5, P = 0.2049) between DFA and DFA-DVC procedures was observed. No presence of endogenous V. cholerae O1 was detected.

PRACTICAL APPLICATIONS

Vibrios are considered the major cause of identifiable illness and death from shellfish consumption. In Argentina, the viable but nonculturable (VBNC) forms of Vibrio cholerae O1 were identified in samples of water and plankton. Because of these facts, it is relevant to research the presence of V. cholerae O1 in aquatic bivalves. Immunofluorescence and polymerase chain reaction methods are a useful alternative to traditional enrichment testing for detecting both culturable and VBNC forms of V. cholerae O1. In this work, it was demonstrated that these methods were sensitive and efficient for detecting V. cholerae O1 in mussels without a pre-enrichment step. Moreover, they can be a useful tool for the rapid detection of this pathogen in the seafood industry.