Mk. Miettinen et al., Characterization of Listeria monocytogenes from an ice cream plant by serotyping and pulsed-field gel electrophoresis, INT J F MIC, 46(3), 1999, pp. 187-192
One dominating strain of serotype 1/2b was found when serotyping and pulsed
-field gel electrophoresis (PFGE) patterns were used for the characterizati
on of 41 Listeria monocytogenes isolates originating from an ice cream plan
t. Samples were taken from the production environment, equipment and ice cr
eam during the years 1990-1997. Serotyping divided the isolates into two se
rovars, 1/2b and 4b. Three rare-cutting enzymes (ApaI, Asci and SmaI) were
used in the creation of PFGE patterns. Asci resulted in the best restrictio
n enzyme digestion patterns (REDPs) for visual comparison. Eight different
Asci REDPs were obtained, whereas ApaI produced six and SmaI seven banding
patterns. When one-band differences are taken into account, 12 different PF
GE types were distinguished based on information obtained with all three en
zymes. The dominant PFGE type was found to have persisted in the ice cream
plant for seven years. Improved and precisely targeted cleaning and disinfe
ction practices combined with structural changes making for easier cleaning
of the packaging machine, resulted in eradication of L. monocytogenes from
this plant. (C) 1999 Elsevier Science B.V. All rights reserved.