Rodney R. Williams

Shrimp Antimicrobial Testing. II. Toxicity Testing and Safety Determination for Twelve Antimicrobials with Penaeid Shrimp Larvae

Abstract The need for federally approved chemotherapeutants for use in domestic shrimp culture in the USA is acute. A summary of toxicity testing of 12 antimicrobials against penaeid shrimp larvae is presented. In addition, the toxicity data are examined in concert with previously reported data on minimum inhibitory concentrations to establish a therapeutic index (a measure of margin of safety) for each compound tested. The 11 prospective antimicrobials were compared with the reference compound, chloramphenicol. The antimicrobials tested were enrofloxacin, erythromycin, florfenicol, oxytetracycline, paromomycin, four experimental fluoroquinolines (PD124816, PD127391, PD131628, PD132133), Romet-30®, and Sarafin®. The top six compounds (in their relative order of safety, from the safest to the least safe) were PD127391, oxytetracycline, chloramphenicol, enrofloxacin, florfenicol, and Romet-30.

Residues of oxytetracycline in cultured juvenile blue shrimp, Penaeus stylirostris (Crustacea: Decapod), fed medicated feed for 14 days

Abstract Juvenile shrimp fed for 14 days on oxytetracycline (OTC) medicated feed with a potency of 1500 mg OTC kg −1 of feed reached a level of 3.3 μg OTC g −1 of shrimp tail muscle within 4 days, as measured by the microbial agar plate diffusion assay method for oxytetracycline in tissues, approved by the Association of Official Analytical Chemists. The concentration of OTC remained between 3.3–5.2 μg OTC g −1 of shrimp tail muscle from Day 4 through Day 14 of the feeding period. These concentrations were greater than the Minimum Inhibitory Concentration for sensitive organisms. By the fifth day following cessation of feeding medicated feed the drug content in shrimp tail muscle was less than the detectable limit for the method, or 0.4 μg of OTC g −1 shrimp tissue.

Bioaccumulation of cyanuric acid in edible tissues of shrimp following experimental feeding

Due to concerns that cyanuric acid (CYA)-contaminated feed had been used in aquaculture and could enter the human food chain, a method to quantify CYA residues in the edible tissues of fish and shrimp was previously developed and validated. This paper provides further data on the deliberate feeding of CYA to shrimp to determine the extent of residue accumulation in edible tissue. Liquid chromatography–tandem mass spectrometry (LC–MS/MS) was employed for the analysis of CYA in shrimp tissue. Edible tissue of shrimp fed 1666 or 3333 mg kg−1 CYA in their diet (approximately 55 and 124 mg kg−1 body weight) contained 0.767 and 0.406 mg kg−1 CYA, respectively. The residue levels are below the World Health Organization (WHO) tolerable daily intake level for CYA and are generally considered unlikely to pose a human health risk.

Evaluation of Difloxacin for Shrimp Aquaculture: In Vitro Minimum Inhibitory Concentrations, Medicated Feed Palatability, and Toxicity to the Shrimp Penaeus vannamei

Abstract Standard in vitro minimum inhibitory concentrations (MICs) were determined for difloxacin and compared with the MICs of several other antimicrobials, against a standardized battery of 13 gram-negative bacterial isolates associated with shrimp disease. The palatability and safety (toxicity) of difloxacin to the shrimp Penaeus vannamei were also evaluated during 15 d of medicated feeding at 1× (100 mg/kg of feed), 2×, and 4× treatment levels to give doses of approximately 5, 10, and 20 mg difloxacin/kg body weight. A significant reduction (P ≤ 0.05) in difloxacin-medicated feed palatability was noted in the 2× and 4× trials. However, differences were still acceptable, because more than 80% of the feeds were consumed in both treatments relative to the control diet. Shrimp mortality rates increased with difloxacin level from 7% for the control treatment to 20% for the 4× treatment. Differences in percent survival were not significant (P > 0.05) by the Williams test; however, analysis of mean survival...

Toxicity and residue studies of cultured blue shrimp treated with the algicide Cutrine-Plus

Abstract Laboratory bioassays on the blue shrimp (Penaeus stylirostris) were conducted with Cutrine-Plus, a chelated copper algicide registered for use in fish hatcheries but not for shrimp culture facilities. The 24- and 96-h LC50s for blue shrimp were found to be 151.3 and 19.5 mg/L copper as Cutrine-Plus, respectively. Cutrine-Plus was found to be safe (i.e., produced no statistical mortality) at a use rate of 1.0 mg/L for a 24-h static exposure. The 24-h EC50 for gill melanization was 0.64 mg/L copper. In residue studies no accumulation of copper in whole-body tissue due to the treatments could be shown.