An improved microbial assay for the detection of chloramphenicol residues in shrimp tissues

An improved microbial assay was developed for the detection of chloramphenicol (CAP) residues in shrimp muscle using Photobacterium leiognathi (L-2 strain) isolated from squid, as test organism, using a pad plate technique. CAP spiked in shrimp muscle tissues at concentrations ranging from 1 to 100 μg/kg was extracted using ethyl acetate and ammonium hydroxide. The assay showed a maximum inhibition zone of 23.0 mm for 100 μg/kg and a minimum inhibition zone of 9.3 mm for 1 μg/kg. The method had a good recovery of 95.63% with a minimum detection limit of 1 μg/kg. It can be performed within 18 h following simple extraction. The method therefore proved to be advantageous over chromatographic procedures as it was inexpensive, quite sensitive and can be adopted for rapid screening of CAP in shrimp tissues.