Adhesion and colonization of potential probiont Pseudomonas aeruginosa FARP72 in the intestine of yellowtail catfish, Pangasius pangasius

Adhesion is recognized as the first important step of a probiont for intestinal colonization. This study assessed the ability of an antagonistic Pseudomonas aeruginosa FARP₇₂ to adhere and colonize the intestine of yellowtail catfish, Pangasius pangasius both in vitro and in vivo. For the in vitro assay, the whole intestines of each of two starved P. pangasius were introduced separately into tubes containing bluish-green pigment-producing P. aeruginosa FARP₇₂ at 8.00 log₁₀ CFU/mL and physiological saline (0.85% sodium chloride) and incubated for 1 h at 30 ± 1 °C. The homogenate mucus solutions from the intestine samples were serially diluted and plated onto Pseudomonas isolation agar to determine the counts of bluish-green pigment-producing P. aeruginosa (BPPAC). The difference between the numbers of BPPAC and presumptive Pseudomonas counts (PPC) in the treated and control intestines was attributed to the adherence of P. aeruginosa FARP₇₂. The levels of BPPAC and PPC in the treated intestines were 6.09 ± 0.59 log₁₀ CFU/g. Similarly, following 30 days of feeding P. pangasius with P. aeruginosa FARP₇₂ supplemented diet, the intestine of catfish recorded the BPPAC of 5.83 ± 0.64 log CFU/g. In control samples, the BPPACs were recorded as < 3.00 log₁₀ CFU/g. The scanning electron micrograph of the intestines of P. pangasius following the in vitro and in vivo adhesion assays confirmed the ability of this bacterium to strongly adhere to the intestine, thus making it most suitable candidate probiont for use in freshwater catfish aquaculture.