Five-tube most-probable-number method using the Fung-Yu tube for enumeration of Listeria monocytogenes in restructured meat products during refrigerated storage

Environmental Reservoir and Transmission into the Mammalian Host

“…Since many environments can contain multiple Listeria species and/or multiple Listeria strains (Pritchard et al 1995;Ryser et al 1996Ryser et al , 1997 (Sauders and Wiedmann in press). A paucity of quantitative data on L. monocytogenes loads in different environments (Bernagozzi et al 1994) other than in food samples (Yu and Fung 1993) exists due to the labor-and cost-intensive nature of MPN methods.…”

ENUMERATING LISTERIA MONOCYTOGENES IN FOOD: A PROBLEM OF LOW NUMBERS

“…In most cases, L. monocytogenes MPN procedures relies on conventional detection methods, for media, incubation times and isolation protocols, such as for example, FDA, U.S. Department of Agriculture Food Safety and Inspection Service (USDA-FSIS), International Standard Organization (KO) or Netherlands Government Food Inspection Service (NGFIS) protocols. However, in some instances, original enrichment procedures or uses of the MPN principle have been developed: Yu and Fung (1993), developed a MPN method using the Fung-Yu tubes. This system utilizes a U-shaped glass apparatus, combined with unique biochemical and physical properties of Listena spp.…”

“…(1988) proved that the MPN method could estimate high levels of L. monocytogenes (10' CFU g-I) in Brie cheese. Yu and Fung (1993) showed that a five-tube MPN method using the Fung-Yu tubes was effective in enumerating both low and high levels of L. monocytogenes (from 10 to lo6 CFU mL-l) in cooked chopped hams, with a correlation coefficient of 0.99 when compared to direct plate counts. Tortorello er al.…”

“…Using the MPN procedure, sample size can be quite large, which could be important comparing other techniques used to improve sensitivity of counts, such as membrane filtration. Consequently, sensitivity and recovery with the MPN technique is generally significantly better at low populations levels of L. monocytogenes than with the plate count procedure (De Buyser et al 1990; Yu and Fung 1993;Yu et al 1995): for example, isolation efficiencies (expressed as the percentage of positive samples) of the MPN and the direct plate count method were 31 and 17% respectively for enumeration of Listena spp. in natural raw meats (Yu et al 1995), and 98 and 68%, respectively, for enumeration of Listeria spp.…”

“…In most cases L. rnonocytogenes was enumerated using the Most Probable Number (MPN) technique (De Buyser et al 1990;Hayes et al 1992;Jemmi and Keusch 1992;Yu and Fung 1993;Blysick-McKennal and Schaffner 1994;Farber and Daley 1994;Yu et al 1995;Tran and Hitchins 1996;Cortesi et al 1997;Dalgaard and Jorgensen 1998;Jorgensen and Huss 1998;Inout5 et al 2000;Capita and Alonso-Calleja 2003). Several attempts to enumerate L. monocyrogenes with methods based on molecular biology (Wang and Hong 1999;Nogva et al 2000;Hough et al 2002;Choi and Hong 2003) have also been reported.…”