Forty-eight strains of Listeria monocytogenes were genotyped by two rapid m
ethods: random amplification of polymorphic DNA (RAPD) and 16S to 23S rRNA
internal transcribed spacer fragment length polymorphism (ITS), and compare
d to the more time-consuming pulsed-field gel electrophoresis (PFGE). The s
trains originated primarily from either pigs, pork products, or pork produc
t processing environments. With strict standardisation of procedures in two
separate laboratories, we were able to obtain excellent inter- as well as
intralaboratory RAPD typing reproducibility. RAPD typing employing two diff
erent PCR primers divided the strains into 10 RAPD types (index of discrimi
nation of 0.793). ITS typing employing primers designed for conserved eubac
terial rRNA sequences gave only two ITS types. and was therefore not suited
for genotyping of L. monocytogenes. PFGE typing by ApaI-restriction of chr
omosomal DNA gave 15 PFGE types (index of discrimination of 0.910). Combina
tion of RAPD and ITS typing gave an index of discrimination of 0.844. There
was generally good agreement between the relatedness of strains and subgro
ups indicated by the three methods. (C) 2000 Elsevier Science B.V. All righ
ts reserved.