Exclusión competitiva frente a vibrios en larvas de litopenaeus vannamei mediante aplicación de bacterias benéficas aisladas de oreochromis niloticus

Abstract

At present, the aquaculture field is intensifying greatly and this in turn contracts a series of factors that we must take into account for the correct development of production. One of the key points is the issue of diseases, which tend to manifest in greater proportion when the system begins to intensify; One of the measures that have been used for disease control is the use of antibiotics, which presented a high degree of efficacy at the beginning but then their action has been reduced due to the high resistance that the bacteria in the environment have contracted. to these drugs. However, the productive field has been forced to look for alternatives that work for the control of this problem, among the most used we have organic acids and probiotics. Probiotics are live microorganisms that help to improve the conditions of culture of the production pond and also work within the organism colonizing the intestinal flora of the animal thus allowing better intestinal health and subsequent better performance; The efficiency of these microorganisms will depend strictly on their dosage, as well as on the conditions that these microorganisms have to comply with their replication process and subsequent beneficial action. In this work we proceeded to isolate bacteria from the intestinal tract of Tilapia with a view to developing a probiotic that serves to control Vibrios in larvae and juveniles of Litopenaeus vannamei, of the 13 isolated strains that were obtained only 2 presented an inhibitory effect considerable to deal with the Vibrios, these strains we identify as M6 and M7 belonging to the Marine Agar; It should be noted that the isolated strains were sown in both Marine Agar and MRS Agar. The strains with probiotic potential were tested for safety and viability, resulting in being harmless against larvae of Litopenaeus vannamei as well as having the characteristic of staying in the water after a freezing process; For the challenge test, aquariums with 1 liter of water were used together with 5 post-larvae, constant aeration, feeding 2 times a day, a temperature of 28 to 30 ° C, daily replacement of 10% and deep cleaning. There were 2 treatments and one control with their respective replicas, T1 (treatment 1) corresponds to strain M7 and T2 (treatment 2) corresponds to the mixture of strains M6 and M7; The trial lasted 7 days: on day 1 the treatments were infected with a dose of 10⁶ of Vibrios sp. just as the probiotic strains were added with a dose of 10⁶, on days 2,3 and 4 only the strains with probiotic potential were added with the aforementioned dose, while on day 5 the process of day 1 was repeated, on day 6 nothing was added while on day 7 the plate cultures of the different treatments were carried out to count Vibrios colonies and determine the incidence of the treatments in the concentration of these pathogenic organisms.The results obtained showed that the strains with probiotic potential have a control over the proliferation of Vibrios and establish that if there is competitive exclusion on them, just as T2 proved to have greater survival (86%) compared to T1 (66%).