Isolation and characterization of biofilm-mediated vibriosis-causing bacteria from Macrobrachium rosenbergiii-aquaculture

Abstract

Vibriosis is one of the major problems in prawn aquaculture leading to a significant loss in yield. The objective of the study was to isolate and identify the etiological agent of vibriosis from the giant freshwater prawn (Macrobrachium rosenbergiii) aquaculture. The study was conducted by isolating the bacteria using selective media of thiosulfate-citrate-bile salts-sucrose (TCBS) agar followed by the morphological and biochemical characterizations, i.e., indole, methyl-red (MR), Voges-Proskauer (VP), citrate, urease, NaCl 0%, gelatinase and lysine decarboxylase tests. The isolated bacteria were further assayed for their standard growth-curve as well as the ability to form a biofilm on Congo-red agar (CRA). The results showed that the bacteria showed a yellow color in colony appearance and had negative Gram staining. On the biochemical assays, the isolates showed positive reactions on the indole, MR, VP, gelatine, and lysine decarboxylase; but had negative reactions on the citrate, urea, and NaCl 0% tests. The isolates were then identified as Vibrio alginolyticus and after further characterization, the isolates showed the ability to form a biofilm. This result signifies the urgency to overcome V-. alginolyticus as the causing agent of vibriosis that was able to form a biofilm on the giant river prawn aquaculture.