Environmental Monitoring of Listeria Genus Using Enzyme-Linked Fluorescence Assay in the Natural Cheese Factory

Abstract

Listeria infection is caused by consuming food containing L. monocytogenes which is contaminated from environment. Therefore, the cleanliness and hygiene maintained in the factory are the utmost importance in controlling L. monocytogenes. VIDAS UP Listeria is an automated rapid detection kit of Listeria genus in food and environmental samples. In this study, VIDAS UP Listeria and a selective medium, LPT Broth, were evaluated. The maximum growth rate and OD of L. monocytogenes in LPT Broth were compared with those in half Fraser Broth with no added ammonium iron(III) citrate or Fraser Broth with no added ammonium iron(III) citrate. The maximum growth rate of LPT Broth was 3.0 to 6.3 times faster than other medium. The maximum OD of LPT Broth was 2.4 to 2.9 times higher than other medium. In addition, the growth of Gram-negative bacteria such as Acinetobacter and Pseudomonas was inhibited in LPT Broth. The growth of L. monocytogenes was delayed in co-culture with Microbacterium arborescens and P. putida group. Negative correlation was detected between initial counts of these bacteria and the count of L. monocytogenes after co-culture. A long incubation time (26 to 30 hr) was suitable for detection of L. monocytogenes in environment samples. In conclusion, VIDAS UP Listeria was a powerful tool for the rapid detection of Listeria genus in environmental samples.