Piscirickettsia salmonis is the causal agent of piscirickettsiosis, a disease that causes severe losses in Chile’s marine salmonid farms. This has encouraged the search for new alternatives to mitigate the adverse effects of this pathogen. On the other hand, it has been described that mannobiose hydrolyzed copra meal (MCM), which contains varying chain-length disaccharides with ß-1,4-mannobiose as the primary active ingredient, has binding affinity for Gram-negative bacteria, which infers that blocking adhesion and preventing colonization during exposure to a high Salmonella spp. load may be the mode of action of MCM. This study evaluated MCM’s binding capacity against the pathogen P. salmonis.
For this purpose, the protocol consists of 3 stages: 1) Adherence of MCM to the surface of the wells of a microplate; 2) Inoculation of the wells with the pathogen, and 3) Incubation of the plate with Austral-SRS broth and reading. The agglutination capacity of P. salmonis to MCM substrate was studied in 3 groups: BSA (control group), MCM, and MCM + bovine serum albumin (BSA).The results showed that P. salmonis presents a shorter growth time in the presence of MCM than in the control culture (P. salmonis + BSA). The time (hours) of growth that P. salmonis took to reach an OD630nm of 0.5 was 28 hours for the control, 12 hours for MCM, and 17.5 hours for MCM + BSA. The MCM group showed a shorter time in reaching an OD=0.5, which can be interpreted as a greater binding capacity, since it could bind to more bacteria. While the MCM + BSA group achieved an OD in less time than the control group, it took longer for the MCM group (Figure 1). We determined significant differences between the groups studied (p-value < 0.05) (Figure 2), concluding that a shorter time to reach OD630nm cutoff indicated a greater adherence of P. salmonis to MCM. We concluded that MCM exhibits binding capacity against P. salmonis under in vitro conditions.