This study aimed to determine the optimal concentration of Moringa oleifera leaf extract as an antibacterial agent on Litopenaeus vannamei larvae that are infected by Vibrio sp.. It was conducted in 15 March - 15 April 2019 at PT. Global Gain Superior Seeds, Pantai Cermin, North Sumatera. The research used a completely randomized design (CRD) method with five treatments and four replications. The shrimps infected by Vibrio sp. were immersed into M. oleifera leaf extract in various concentration of (A) 0 ppm, (B) 400 ppm, (C) 600 ppm, (D) 800 ppm, and (E) 1000 ppm for ±15 minutes. The size of shrimp used was post-larvae 8 (length of 3.5-5 mm/ind). The best performance results of vannamei shrimps were obtained in treatment E (1000 ppm), namely length growth of 16.75 ± 1.16 cm, weight growth of 0.92 ± 0.89 g and survival rate of 91±7.87%.Keywords:Moringa oleiferaVibrio sp.Immersion

Indonesia is famously known for its rich plant biodiversity with medicinal properties. Guava (Psidium guajava Linn.) is one of medicinal plants which can be used as alternative for treating diseases. Guava leaf contains flavonoids, saponins, and tannins, that can act as inhibitors against bacteria, antioxidants, and antibacterial. Numerous dental and oral diseases are caused by bacteria, one of which is dental caries. Principally, dental caries can be prevented by maintaining the oral cavity hygiene, chemically or mechanically, using antiseptics possessing antibacterial activities. The aim of this study was to investigate the effectiveness of guava leaves steep water against S. Mutans bacterium using microdilution method. The aim also included the investigation of inhibition concentration of guava leaves steep water. This research was experimental in nature, by using the guava leaves steep water as the sample with various concentrations (0.753%, 1.563%, 3.125%, 6.25%, 12.5%, 25%, 50%, 100%). S. Mutans was obtained from the laboratory of veterinary Universitas Syiah Kuala (Unsyiah). The results of this research revealed that the guava leaves steep water was effective in inhibiting S. Mutans with Minimum Inhibitory Concentration (MIC) of 6.25% In conclusion, we would like to investigate the guava leaves steep water as a mouthwash in our research with a preclinical trial.