A comparison of Listeria monocytogenes serovar 4b isolates of clinical and food origin in Japan by pulsed-field gel electrophoresis

Pulsed-field gel electrophoresis (PFGE) patterns of 102 L. monocytogenes serovar 4b isolates from patients and foods examined in Japan were compared with 16 isolates from foodborne listeriosis episodes which occurred in North America or Europe. Using a combination of PFGE patterns with the restriction enzymes SmaI, ApaI, AscI and Sse8387I, 82 clinical isolates from Japan were categorized into 45 PFGE types: the largest group of 17 isolates (20.7%) were of the same PFGE type as cultures from the large foodborne outbreaks which occurred in California (1985) and Switzerland (1983–1987). Twenty cultures from foods on retail sale in Japan were classified into 12 PFGE types: four isolates were of three PFGE types also recognized among isolates of clinical origin from Japan, including the predominant clinical type.