Bioencapsulation of Therapeutic Quantities of the Antibacterial Romet‐30 in Nauplii of the Brine Shrimp Artemia and in the Nematode Panagrellus redivivus

Nauplii of the brine shrimp, Artemia, and cultures of the soil nematode, Panagrellus redivivus, were fed a suspension of the water‐insoluble antibacterial Romet‐30 (sulfadimethoxine plus ormetoprim) to determine if they could be used as a mechanism for delivery of the drug to larval penaeid shrimp. Romet‐30 was added to groups of brine shrimp nauplii and nematodes in 1 L beakers to achieve a concentration of 3 mg of drug per ml of seawater. After a 4 h uptake period, predetermined numbers of organisms were assayed for antibiotic content using the micro‐plate diffusion method and a Romet‐30 sensitive strain of Vibrio alginolyticus as the indicator. The resulting zones of inhibition were compared to that of a standard Kirby‐Bauer sensitivity disc containing 25 μg of the drug that was placed on each plate as standard control. Negative controls consisted of equal numbers of nauplii and nematodes that were not exposed to the antibiotic. Artemia nauplii and nematodes accumulated approximately 0.1 μg of the drug per nauplius and approximately 0.25 μg per nematode. They exhibited no signs of toxicity from exposure to the drug and contained the antibiotic in sufficient quantity to provide a theoretical therapeutic dose of the drug when fed to penaeid larvae. In subsequent tests, normal and diseased larval Penaeus stylirostris readily accepted Romet‐30 enriched Artemia. Diseased larvae fed the drug in this manner exhibited a statistically greater overall survival and a greater survival to the post‐larval stage by Student's t‐test at the 5% significance level.