Spore based chromogenic assay for detection of β-lactam antibiotic in milk
2013
Kumar, S | Raghu, H | Kumar, N | Singh, N. A. | Malik, R.K.
Dormant spores of B. cereus 13061 used as a indicator strain for real time detection of β-lactam antibiotic residues based on β-lactamase enzyme using nitrocefin as chromogenic substrate. Spore production of indicator strain was significantly improved by modifying the sporulation medium with an increase of 47. 86 % sporulation fold compared to conventional method. A spore based chromogenic assay, where enzyme induction was optimized at 1.0 mL of milk sample, 500 µL of spores suspension and 50 µL of nitrocefin after 20 min of incubation. The efficiency of the chromogenic assay was evaluated through surveillance study on 94 samples of raw, pasteurized and dried milks samples in comparison with AOAC approved Charm 6602 system and spore based assay. The presence of β-lactam antibiotic was 8.51% at Codex MRL with false positive result only in 1.06 % of the samples. The assay can detect specific β-lactam group of antibiotic within 15-20 min at regulatory codex limits with negligible sensitivity towards non β-lactam groups. Output of the present study suggest that developed assay can be a viable option for dairy industry as a routine test for screening of β-lactam groups in milk received at collection point, chilling centre, manufacturing unit, independent testing and R & D centre etc.
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