Subtyping Listeria monocytogenes isolates genetically related to the Swiss epidemic clone

Abstract

Macrorestriction analysis by pulsed-field gel electrophoresis was used to assess the diversity of strains within the epidemic-associated electrophoretic type 1 (ET1) clone of Listeria monocytogenes. For this purpose, a total of 144 isolates from Switzerland shown by multilocus enzyme electrophoresis to belong to the ET1 were examined. These isolates were subtyped by macrorestriction analysis using the enzymes ApaI and SmaI and field inversion gel electrophoresis. Among these 144 isolates, 45 were isolated in human listeriosis cases of the postepidemic period of 1988 to 1993 and 44 were isolated in animal listeriosis cases of the same period. Forty-seven isolates were from the epidemic period of 1983 to 1987, and eight additional isolates were from cattle from two different farms. Twenty-nine different subtypes could be identified among the 144 isolates tested. Five major subtypes were found more frequently than the others during the postepidemic period, both in humans and in animals. Two of these subtypes had been previously implicated in outbreaks of listeriosis, thus suggesting that particular pulsed-field gel electrophoresis subtypes may be frequently associated with disease in humans and animals. Two of these frequent subtypes were also suspected to be related to small clusters of listeriosis cases during the postepidemic period. The results obtained by typing epidemiologically related isolates from different animals within the same farms and from different body sites of a given patient confirmed the potential of macrorestriction analysis for epidemiological studies restricted to short periods of time and to small number of isolates. The analysis of 47 isolates related to the Swiss listeriosis epidemic period of 1983 to 1987 and the use of Southern blotting and hybridization experiments show that the interpretation of relatedness between isolates presenting slightly different macrorestriction patterns may be more complex than commonly accepted. In such cases, careful interpretation of the potential molecular mechanisms leading to the differences observed between patterns is necessary.

Typing Listeria monocytogenes isolates from fish products and human listeriosis cases

“…Some of them, like serotyping, are not very powerful in terms of discrimination (4) and usually only perform a first, broad differentiation of strains. Other methods, such as PFGE, are very efficient in distinguishing strains of L. monocytogenes but may be more prone than other techniques to some instability of the characteristics used for typing (1,3). MEE and REA take an intermediate position in this classification (4).…”

“…Description of L. monocytogenes isolates from fish products and isolation procedure. Seventy-two L. monocytogenes isolates originating from 10 different imported fish products (salmon terrine, salmon gravad, smoked salmon, smoked trout, smoked buckling, smoked halibut, smoked mackerel, smoked herring, schillerlocken, and tarama) of 12 producers (in Denmark [2], France [3], Germany [1], Great Britain [4], Norway [1], and New Zealand [1]) were examined. Sixty-five isolates were recovered during routine microbiological testing of imported food in Switzerland between January 1993 and December 1994.…”

Epidemiological studies on Listeriosis in sheep

“…The incidence of listeriosis in ruminants has markedly increased over the last few decades and feeding of poor-quality silage seems to be a key factor in disease transmission (Boerlin et al, 1996) Among farm animals, sheep appear to be particularly susceptible to listeriosis. The organism is spread world-wide in nature (decaying herbage, soil, feces, and sewage) and occurs usually in low numbers (Fenlon, 1988).…”

Ocorrência e caracterização sorológica e genotípica de Listeria monocytogenes em indústrias de queijo do Estado de São Paulo.

“…A ocorrência de perfis com baixa similaridade sugere a existência de diversas fontes de contaminação como matéria prima contaminada e/ou persistência de diferentes linhagens (THÉVENOT et al, 2006) Se, por um lado, os trabalhos de Boerling et al (1996) e de Leite et al (2006) revelam graus consideráveis de diversidade em populações de L. monocytogenes, por outro, AUTIO et al (2002) sugerem uma ampla distribuição geográfica e temporal de algumas linhagens de L. monocytogenes, uma vez que isolaram os mesmos pulsotipos da bactéria em produtos diversos de diferentes países.…”

“…A suspeita inicial era que os pulsotipos encontrados no queijo fossem os mesmos da salmoura e essa fosse a fonte de contaminação óbvia dos queijos, porém, os pulsotipos do queijo (P27) eram distintos dos Uma interpretação similar foi apresentada porTham et al (2007) que, analisando o sangue de duas pessoas com listeriose, encontraram, em amostras únicas de sangue, dois perfis distintos de PFGE, e consideraram a possibilidade de instabilidade genética de uma única linhagem de L. monocytogenes ou ocorrência de infecção com uma população mista do microrganismo.Quanto à diversidade da espécie L. monocytogenes, diferentes resultados são encontradas na literatura, dependendo da fonte e origem geográfica. De acordo comBoerling et al (1996) existe um grau considerável de diversidade de perfis de PFGE em populações de L. monocytogenes, o que também foi observado nessa pesquisa Filiousis et al (2009). compararam perfis de PFGE de L. monocytogenes isoladas de diferentes tipos de alimentos na Grécia e consideraram baixa a diversidade entre isolados de diferentes fontes, com base no número de pulsotipos López et al (2008),.…”