Development Of Rapid Detection System For Pathogenic Vibrio Harveyi In Sea Bass, Groupers And Shrimps

Several diagnostic techniques have been developed for Vibrio harveyi including the use of biochemical tests, culture of the bacterium on selective medium and the use of polymerase chain reaction (PCR) that are targeting different genes such as 16S ribosomal DNA and toxin gene (toxR). However, these detection techniques have their own limitations. The biochemical characterization is always insufficient to correctly identify heterogeneous bacteria like V. harveyi. Moreover, biochemical methods are time consuming and costly as many tests are required before reliable identification can be achieved. It is no doubt that the existing PCR techniques developed for V. harveyi are rapid but encounter problem relating to specificity and detection limit. The multiplex polymerase chain reaction (multiplex PCR) technique developed in this study has the advantages over the previous methods for its specificity, rapidity, repeatability and detection limit. In addition, the method can also differentiate two strains of V. harveyi. The first strain being virulent to both shrimp and fish while the second strain virulent only to shrimp. Moreover, the method accepts variety of samples from purely grown bacterium, seawater samples to swabs from the affected animal. The detection limit was at 102 CFU/ml which satisfies the requirement for detection of V. harveyi in the culture environment as it normally exists at 10-104 CFU/ml in the seawater. At this limit, the pathogen may not be able to cause vibriosis but the detection method can be used to monitor the level of the pathogen in the culture facility. Such a rapid monitoring can give alarm at which treatment can be initiated as soon as possible, thereby minimizing vibriosis outbreak