High-throughput genome sequencing of two Listeria monocytogenes clinical isolates during a large foodborne outbreak

Abstract

BackgroundA large, multi-province outbreak of listeriosis associated with ready-to-eat meat products contaminated with Listeria monocytogenes serotype 1/2a occurred in Canada in 2008. Subtyping of outbreak-associated isolates using pulsed-field gel electrophoresis (PFGE) revealed two similar but distinct AscI PFGE patterns. High-throughput pyrosequencing of two L. monocytogenes isolates was used to rapidly provide the genome sequence of the primary outbreak strain and to investigate the extent of genetic diversity associated with a change of a single restriction enzyme fragment during PFGE.ResultsThe chromosomes were collinear, but differences included 28 single nucleotide polymorphisms (SNPs) and three indels, including a 33 kbp prophage that accounted for the observed difference in AscI PFGE patterns. The distribution of these traits was assessed within further clinical, environmental and food isolates associated with the outbreak, and this comparison indicated that three distinct, but highly related strains may have been involved in this nationwide outbreak. Notably, these two isolates were found to harbor a 50 kbp putative mobile genomic island encoding translocation and efflux functions that has not been observed in other Listeria genomes.ConclusionsHigh-throughput genome sequencing provided a more detailed real-time assessment of genetic traits characteristic of the outbreak strains than could be achieved with routine subtyping methods. This study confirms that the latest generation of DNA sequencing technologies can be applied during high priority public health events, and laboratories need to prepare for this inevitability and assess how to properly analyze and interpret whole genome sequences in the context of molecular epidemiology.

Presencia de Listeria monocytogenes en alimentos listos para el consumo, procedentes de plazas de mercado y delicatessen de supermercados de cadena, Bogotá, D.C, 2002-2008

“…Listeria monocytogenes es un bacilo Gram positivo, (2,10,12) que crece a temperaturas de 1 a 45 °C, con temperatura óptima de 30 a 37 °C (2,12,27,28); tiene la habilidad de soportar temperaturas de refrigeración (2,9,12,29-31) y es capaz de desarrollarse a pH de 4,4 a 9,6 (2,28,(32)(33)(34). Asimismo, crece en concentraciones altas de cloruro de sodio (15 %) (2,27,33,34).…”

“…Es un microorganismo ambiental que tiene la facultad de adherirse a las superficies, formando biopelículas (20,30,32,35) para protegerse de la acción de los tratamientos antimicrobianos (20,30,35). En el ambiente de fábrica de producción de alimentos, tiene la oportunidad de contaminar en sus diferentes etapas, siendo esta vía la más frecuente para llegar al ser humano (2,5,12,30).…”

“…Listeria monocytogenes es un patógeno, facultativo intracelular y oportunista (1,2,4,5,9,10,24,32,36). Sus manifestaciones clínicas se pueden agrupar en dos categorías: listeriosis invasiva y listeriosis no invasiva (1,16,17,28).…”

“…La listeriosis no invasiva se manifiesta por síntomas de gastroenteritis (1,5,28,43), como diarrea, fiebre, cefalea y mialgias, y su periodo de incubación es corto (1,4,13,15,19,21,28,(43)(44)(45) Los alimentos considerados de alto riesgo para contraer listeriosis son los listos para el consumo (1,5,(9)(10)(11)16,17,28,(30)(31)(32)34,47,50,(63)(64)(65)(66). Ésta es una categoría amplia y heterogénea de alimentos (incluye bebidas) que no van a tener ningún proceso de cocción antes de su consumo, o que aparentemente son aptos para el consumo sin cocción (5,16), y varían de unos países a otros en relación con los hábitos alimentarios, la disponibilidad de la cadena de frío y la temperatura máxima en el punto de venta (1,5).…”

The Use of Pulsed Field Gel Electrophoresis in Listeria monocytogenes Sub-Typing - Harmonization at the European Union Level

“…Several surveillance networks currently work throughout the world using this protocol Pagotto et al, 2006). These networks have proven their efficiency for an early detection and a better understanding of L. monocytogenes outbreaks (CDC, 2010;CDC, 2011;Gilmour et al, 2010).…”