title: Listeria monocytogenes isolates from invasive infections: variation of sero- and genotypes during an 11-year period in Finland.
abstract: Listeria monocytogenes strains that were isolated from 314 human listeriosis cases in Finland during an 11-year period were analyzed by O:H serotyping and pulsed-field gel electrophoresis (PFGE). Serotyping divided the isolates into five serotypes, the most common being 1/2a (53%) and 4b (27%). During the study period, the number of cases caused by serotype 1/2a increased from 22% in 1990 to 67% in 2001, and those caused by serotype 4b decreased from 61 to 27%, respectively. PFGE with restriction enzyme AscI divided the strains into 81 PFGE genotypes; among strains of serotypes 1/2a and 4b, 49 and 18 PFGE types were seen, respectively. PFGE type 1 (serotype 1/2a) was the most prevalent single type (37 strains). Together with six other, closely related PFGE types, PFGE type 1 formed a group of 71 strains, representing 23% of all 314 strains. Strains of PFGE type 1 have also been isolated from cold smoked fish, suggesting a source of human infections caused by this type. Moreover, PFGE type 24 (serotype 1/2c) was significantly associated with gender: 5% of 180 male subjects but none of 132 female subjects (P = 0.012). An electronic database library was created from the PFGE profiles to make possible the prompt detection of new emerging profiles and the tracing of potential infection clusters in the future.
authors.affiliation: Laboratory of Enteric Pathogens, National Public Health Institute, FIN-00300 Helsinki, Finland.
authors.forename: Susanna
authors.initials: S
authors.lastname: Lukinmaa
authors.forename: Maria
authors.initials: M
authors.lastname: Miettinen
authors.forename: Ulla-Maija
authors.initials: UM
authors.lastname: Nakari
authors.forename: Hannu
authors.initials: H
authors.lastname: Korkeala
authors.forename: Anja
authors.initials: A
authors.lastname: Siitonen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015373:Bacterial Typing Techniques; D002648:Child; D002675:Child, Preschool; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D005387:Finland / Q000453:epidemiology; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008089:Listeria monocytogenes / Q000145:classification* / Q000235:genetics; D008088:Listeriosis / Q000453:epidemiology* / Q000382:microbiology*; D008297:Male; D008875:Middle Aged; D012703:Serotyping