Two stage enzyme-based assay for detection of L. Monocytogenes in milk
Technology Details:
Two-stage bio-assay has been developed for detection of L.monocytogenes based on the principle of targeting “enzyme substrate reaction for specific marker enzyme (s) to release free chromogen that can be visually detected by color change (Patent Reg. 1357/DEL/2013). The assay can confirm the presence of L. monocytogenes with in real time of 4.30±0.10 h after initial pre-enrichment of food samples in novel selective medium i.e., LSEM for 24h as against 5-7 days protocol following conventional method (ISO: 11290 Part-1: 1996). The color change from yellow to black in Stage-1 indicates the presumptive detection of Listeria spp. in 24±0.3h at 1.2 log CFU levels for 25g / or 22±0.3h per g of the milk sample. The color change from off-white to green in Stage-2 in T-1 indicates the confirmation of L. monocytogenes and yellow color in T-2 indicates Listeria spp. Rapid detection within one working day as against 5-7 days required in the conventional method. Selective inhibition of contaminants other than Listeria spp like Enterococci, B. cereus, S. aureus, Lactobacilli, Salmonella and E. coli etc. Internal/third party Validation of Technology at M/s SGS India Pvt. Ltd, Gurgaon, Certificate no. SGS GG12- 009772.001 dated 09-11-2012. Two stage assay can be used for regulatory compliance of food samples including raw, pasteurized, dried milk and other food products as specified in FSS Act. 2015. Cost effective (Rs 75/- test as against Rs 762/- in conventional method). Animal disease surveillance/risk assessment work in organized dairy farms.