Evaluation of immunomagnetic separation in combination with ALOA Listeria chromogenic agar for the isolation and identification of Listeria monocytogenes in ready-to-eat foods.
A study was conducted to evaluate the performance of the ALOA (chromogenic media) in combination with immunomagnetic separation (IMS) for the detection of Listeria monocytogenes in ready-to-eat food products. IMS-ALOA method was found to be equivalent to Health Canada's reference culture method as well as comparable to BAX-PCR method in terms of the sensitivity of the methods for the detection of L. monocytogenes in ready-to-eat foods such as turkey roast, beef roast, mixed vegetable salads, potato and egg salad, soft cheese and smoked salmon. The IMS-ALOA method gave 100% sensitivity in the inclusivity tests with 42 pure L. monocytogenes strains. Exclusivity testing with five other species of Listeria genus and 29 pure non-L. monocytogenes strains from 21 different genera showed 97% specificity. The method was able to detect L. monocytogenes at levels near or below 1cfu/25g regulatory limit in ready-to-eat food matrices after 24h enrichment, with a turnaround time of 3days compared to 7-8days for culture method. IMS-ALOA method is a valuable alternate test method for the screening of L. monocytogenes in a variety of foods especially ready-to-eat foods.
Wadud
Shaila
S
Laboratory Services Division, University of Guelph, 95 Stone Rd. West, Guelph, ON, Canada N1H 8J7.
Leon-Velarde
Carlos G
CG
Larson
Nathan
N
Odumeru
Joseph A
JA
D000362:Agar; D001431:Bacteriological Techniques / Q000379:methods*; D002170:Canada; D003470:Culture Media / Q000737:chemistry*; D005516:Food Microbiology; D018189:Immunomagnetic Separation / Q000379:methods*; D008089:Listeria monocytogenes / Q000145:classification* / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D013997:Time Factors
D003470:Culture Media; D000362:Agar