In a L. vannamei farm located in the town El Cardonal (Hermosillo, Sonora state, Mexico), two groups of ponds geographically separated were selected, during a semi-intensive production cycle of approximately 6 months. After around 70 days, an infectious outbreak affected the production, which was diagnosed as AHPND(+) for one of the ponds studied. Oxytetracycline was applied through feed throughout the farm (5kg/ton), which was carried out in each group according to their culture days. Those sown first and whose desired harvest size was larger (green) received the antibiotic before those who were sown later and whose target harvest size was smaller (yellow). (Fig. 1).
At four times, intestinal samples were collected, which were subjected to analysis of the V3-V4 region of the 16s rRNA gene. The results were as follows: the infection period coincides with the decrease in Proteobacteria and the increase in Tenericutes, being represented mainly by Vibrio and Candidatus Bacilloplasma, respectively. The statistically significant decrease in the latter was possibly due to treatment with Oxytetracycline, while Vibrio had no major changes. The abundance of Fusobacteria increased significantly in the group that was sampled three days after the end of antibiotic treatment, but no genus exceeded 0.5% relative abundance.
With the data obtained in this analysis, the following question arises: will the decrease in Candidatus Bacilloplasma have led to the increase in members of Fusobacteria?