Typing Listeria monocytogenes isolates from fish products and human listeriosis cases

Abstract

Seventy-two Listeria monocytogenes isolates originating from 10 different fish products of 12 producers and 47 isolates from human listeriosis cases were typed by serotyping and multilocus enzyme electrophoresis. Seventy-five of these isolates were further subtyped by restriction analysis of genomic DNA with the enzyme XhoI and by pulsed-field gel electrophoresis using the enzymes ApaI and SmaI. The results show that several L. monocytogenes clones identified by multilocus enzyme electrophoresis are frequently found in fish products of different origins. One of these clones is the same as another previously shown to be frequently associated with meat and meat products. The epidemic-associated electrophoretic type 1 was only rarely found in fish products. No association was found between any type of fish product and a particular lineage of L. monocytogenes. Both long-term persistence of a strain and simultaneous presence of several clearly distinct strains in the products of single producers were observed. The comparison of L. monocytogenes isolates from human clinical listeriosis cases in Switzerland and those from imported fish products by use of multilocus enzyme electrophoresis showed that they do not form two clearly distinct lineages but nevertheless belong to two separate populations. None of the 48 subtypes distinguished by the combination of all four typing methods could be found in both populations of human origin and those of fish origin.

The characterization of Listeria spp. isolated from food products and the food-processing environment

“…Previous studies have found that serotype 1 ⁄ 2a was the predominate serotype of L. monocytogenes food and environmental isolates. (Boerlin et al 1997;Corcoran et al 2006;Gilbreth et al 2005;Gudbjornsdottir et al, 2004;Lukinmaa et al 2003). One explanation could be the ability of this specific serotype to survive better in certain foods.…”

Gravad (Gravlax) and cold‐smoked salmon, still a potential source of listeriosis

“…Re-circulating brine is another source for contamination of the products as L. monocytogenes could grow in NaCl solutions up to 10%. As L. monocytogenes has the ability to attach to surfaces and produce biofilms (Bansal 1996;Blackman & Frank 1996), it can colonize, multiply and persist in the foodprocessing environment (Boerlin et al 1997;Vogel et al 2001;Medrala et al 2003). For example, Unnerstad et al (1996) reported the survival of the same type of L. monocytogenes in a dairy for at least 7 years.…”

Listeria y listeriosis: un desafío de los nuevos tiempos

“…La listeriosis es considerada como una enfermedad infecciosa de origen alimentario con una tasa de mortalidad de 30%. Estudios muestran que el origen de casos esporádicos y epidémicos de listeriosis en humanos es principalmente de origen alimentario 2 .…”