|Porto, Anna - FORMER EMPLOYEE|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 12, 2003
Publication Date: June 30, 2002
Citation: Porto, A., Wonderling, L.D., Call, J.E., Luchansky, J.B. 2002. Use of pfge to determine the persistence of a five-strain mixture of listeria monocytogenes during chilled storage of vacuum-sealed packages of frankfurters. International Association of Food Protection. Abstract #P172, p. 103. Technical Abstract: Listeria monocytogenes can survive and often grow under conditions of high osmolarity, low pH, and low temperature such as found in some ready-to-eat meats. In a previous study, we monitored the viability of the following five-strain mixture of L. monocytogenes during refrigerated storage of frankfurters prepared with and without 3 percent potassium lactate (Klac): :Scott A (serotype 4b), LM-101M (serotype 4b), F6854 (serotype 1/2a), H7776 (serotype 4b), and MFS-2 (serotype 1/2c). Throughout a 90-day period, the initial inoculum level of 20 CFU/ml remained relatively constant in the presence of Klac, but there was about a 2-log-10 increase of the pathogen in the absence of Klac. To determine which of the 5 strains persisted under these conditions, randomly-selected colonies obtained after 28 and 90 days of refrigerated storage were analyzed by PFGE with the restriction enzyme SmaI to generate distinct banding patterns for each of these 5 strains. In nthe absence of Klac, 43 percent of the 58 isolates from day 28 were identified as Scott A, 12 percent as LM-101M, 22 percent as F6854, 10 percent as H7776, and 12 percent as MFS-2; however, by day 90, the majority (83 percent) of the 60 isolates were identified as MFS-2. In packages containing frankfurters prepared with Klac, all 5 strains were present (5- 36 percent) among the 19 isolates tested from day 28; however, by day 90, MFS-2 comprised the majority (63 percent) of the 27 isolates tested. These results indicate that strain MFS-2 was more persistent in packages of frankfurters prepared with or without Klac than strains Scott A, LM-101M, F6854, and H7776 during refrigerated storage.