One Group of Genetically Similar Listeria monocytogenes Strains Frequently Dominates and Persists in Several Fish Slaughter- and Smokehouses

Abstract

Contamination of foods with the human pathogen Listeria monocytogenes may occur during processing, and the purpose of this study was to determine whether genetically similar strains colonize different processing plants or whether specific persistent strains are unique to each processing plant. We hypothesized that specific L. monocytogenes strains may be better adapted to specific environmental niches in the processing environment. L. monocytogenes contamination patterns were identified by the collection of 686 and 267 samples from the processing environments: raw fish and products of four fish smokehouses and four fish slaughterhouses, respectively. Samples were collected both during production and after cleaning and disinfection. Typically, these samplings were separated by 1 to 3 months. Sampling sites were targeted toward areas likely to harbor the bacterium. L. monocytogenes was isolated from 213 samples, and one strain from each positive sample was typed by RAPD (random amplified polymorphic DNA) analysis with four different primers. The 213 strains were divided into 37 RAPD types. One RAPD type was predominant; 86 of 213 strains belonged to this type. This type was found in three smokehouses and two slaughterhouses and was predominant in three of these plants. A subset of 35 strains was also analyzed by amplified fragment length polymorphism typing, which confirmed the genetic similarity of the groups. Moreover, strains of the dominant RAPD type were indistinguishable from strains isolated frequently from smoked fish products 10 years ago. One smokehouse was surveyed for a year and a half, and the dominant RAPD type persisted throughout the survey period and accounted for 94 of 118 isolates. Our study indicates that strains of L. monocytogenes that are genetically very closely related may be especially adapted to colonizing the processing equipment or especially resistant to cleaning and disinfection.

Diverse Geno- and Phenotypes of Persistent Listeria monocytogenes Isolates from Fermented Meat Sausage Production Facilities in Portugal

“…Persistence may indicate deficiencies in sanitation procedures or potential niches in the processing environment where L. monocytogenes is protected from sanitation. While persistence of L. monocytogenes in meat processing plants (15,37,38,61) and in other plants (44,47,73) has previously been reported, identification of different PFGE types (as well as different molecular serotypes and lineages) associated with persistence in different plants (except for one PFGE type associated with persistence in two plants) clearly suggests that many different L. monocytogenes strains have the ability to establish persistent populations in processing plants.…”

Genome Sequencing Identifies Two Nearly Unchanged Strains of Persistent Listeria monocytogenes Isolated at Two Different Fish Processing Plants Sampled 6 Years Apart

“…Although it can be present in raw food materials, the processing plant environment is typically the immediate source of L. monocytogenes contamination of food products (5-8). Even though food processing equipment and facilities are cleaned frequently, some molecular subtypes of L. monocytogenes may persist in the food processing environment for many years (7-9).We have found that one specific molecular subtype of L. monocytogenes strains was dominant and persistent in several fish processing plants (8,10,11). Other subtypes were also isolated several times in the processing plants although not as frequently (8).…”

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

“…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).…”