Pulsed-field gel electrophoresis (PFGE) typing of Listeria strains isolated from a meat processing plant over a 2-year period

As part of a hygiene monitoring program in a meat processing plant a total of 131 Listeria isolates were detected by sampling different processing are as and meat products within a 2-year period. The isolates were differentiat ed by means of phenotypic characteristics. Furthermore, the genomic ApaI an d SmaI fragment patterns of all isolates were examined by pulsed-field gel electrophoresis (PFGE). PFGE using SmaI and ApaI yielded 15 (Listeria monoc ytogenes), 20 (Listeria innocua) and six (Listeria welshimeri) pulsotypes. Of the environmental Listeria monocytogenes isolates the predominating PFGE -type B was clearly associated with processing area A whereas PFGE-type E p redominated in the meat products. Moreover, the study showed the persistenc e of closely related Listeria strains over a 2-year period in the environme nt of this meat processing plant. (C) 2000 Elsevier Science B.V. All rights reserved.