Multilocus enzyme electrophoresis typing of New Zealand Listeria monocytogenes isolates

Eighty-five strains of Listeria monocytogenes, comprising 74 strains isolated from the environment, humans, animals and foods in New Zealand; 10 strains from similar sources in Denmark, and one reference strain, were studied using multilocus enzyme electrophoresis (MEE). Fifty-five electrophoretic types (ETs) were identified among the 85 strains, most (71%) of which were represented by only one isolate. The 74 New Zealand isolates produced 45 ETs, most (67%) of which were represented by only one isolate. There was no link between the source of the isolates and ET, as most ETs contained only one isolate. One cluster of ETs, designated cluster 45, contained only environmental isolates. Of the five ETs that contained isolates from more than one source, four contained isolates that were obtained from clinical specimens and foods indicating a possible link between isolates from these two sources. The population of New Zealand isolates of L. monocytogenes studied appears to be genetically diverse when compared with the diversity found in similar studies in other countries.