An epidemiological survey of human listeriosis in France during 1987, using serotyping and phage typing.

During 1987 the French National Reference Center for Listeria received, from this country, 384 Listeria monocytogenes strains isolated from human listeriosis cases. A constant exchange of information and strains between the Reference Center and the Bacterial Ecology Unit of the Institute Pasteur of Paris allowed complete characterization of these isolates, using serotyping and phage typing. Among the strains studied 22%, 13% and 63%, respectively belonged to serovars 1/2a, 1/2b, and 4b, but this distribution can vary according to place, and time of isolation. Only 58% of strains were phage-typeable (1/2a: 29%), (1/2b: 66%) and (4b: 40%). Phage typing allows to consider that French human cases, in 1987, were mainly sporadic. However, a small number of cases corresponding to similar phage types could be clustered according to place and/or time.