Tongchai Chalermchaikit, Surasuk Dilokkiat, Songsuk Srisagha, and Naphaporn Lertworapreecha

pp. 283 - 290

Abstract

Medicated feed had been given to white shrimp (Penaeus vannamei) for 7 days. Shrimp samples,
collected at day-1 to day-7 after withdrawal time, were tested for antimicrobial residues by microbial inhibition disk assay (MIDA) and “SAM-Test”. The results from “SAM-Test” indicated much higher numbers of
positive (antimicrobial detectable) samples than MIDA. Percentages of positive samples from oxytetracycline, sulfamethoxazole+trimethoprim and enrofloxacin treatment groups were decreased on day-3 or day-4
after drug withdrawal but increased on day-5 or day-6. In one of shrimp samples from sulfamethoxazole
treatment groups, residues could not be detected on day-4 to day-6 after drug withdrawal but they were
detectable again on day-7. These phenomena might indicate that eating behavior of shrimp had retaken
antimicrobial residues that were bound on their faeces. Therefore, it is impractical to determine the antibiotic
withdrawal period in white shrimp by using withdrawal time of other aquatic animals. Further data of pharmacokinetics is critically important for determining the withdrawal time of antibiotic use in white shrimp
farming.