Comparative study between probiotic bacterium Arthrobacter XE-7 and chloramphenicol on protection of Penaeus chinensis post-larvae from pathogenic vibrios

A strain of Arthrobacter XE-7, isolated from Penaeus chinensis was evaluated for potential use as a probiotic for shrimp post-larvae. In vitro studies demonstrated antagonism against Vibrio parahaemolyticus, Vibrio anguillarum and Vibrio nereis. During the 14-day challenge experiment, the shrimp post-larvae aged 10 days were reared in water with addition of either Arthrobacter XE-7 (10⁶ CFU/ml), chloramphenicol (2 mg/l) or the three pathogenic vibrios (10⁶ CFU/ml): Controls, (V) pathogenic vibrios alone, (A) Arthrobacter XE-7 alone, (C) chloramphenicol alone, (AV) pathogenic vibrios in combination with Arthrobacter XE-7, and (CV) pathogenic vibrios in combination with chloramphenicol. The surface growth rate of nitrogen and the attenuation rate of bacterium in culture water were detected for the first 7 days, and the cumulative mortality was recorded for the whole challenge experiment. Treatment A had no significant higher survival than the Control. However, Treatment AV produced significantly higher survival than Treatment V (p < 0.05); Furthermore, it was not significantly lower than those of Treatment CV. Comparable attenuation rate of vibrios was observed in Treatment AV and CV, and it was significantly lower than that in Treatment V (p < 0.05). In addition, results of the surface growth rate of nitrogen show that the Arthrobacter XE-7 has the nitrification ability to oxidize ammonium to nitrite. Both chloramphenicol and Arthrobacter XE-7 are able to comparably protect the shrimp post-larvae from the pathogenic vibrios. Then, Arthrobacter XE-7 can be regarded as a probiotic bacterium for the culture of shrimp larvae.