Genomic Characterization of Listeria monocytogenes Strains Involved in a Multistate Listeriosis Outbreak Associated with Cantaloupe in US

Listeriosis is a disease that causes significant economic losses at the farm level because of high morbidity and mortality in ruminants. This study was performed to investigate the role of ruminants in the epidemiology of listeriosis in northern Italy and the possible association of animal-adapted strains of Listeria monocytogenes with strains associated with human disease. Twenty ruminant rhombencephalitis isolates previously confirmed as L. monocytogenes by bacteriology and PCR were characterized by serotyping, pulsed-field gel electrophoresis, multi-virulence-locus sequence typing (MVLST), and multiplex single nucleotide polymorphism (mSNP) typing for the detection of epidemic clones. Subtyping results were subsequently compared with those obtained from human, food, and environmental isolates of L. monocytogenes, including 311 isolates from the University of Turin, Grugliasco, Italy, and 165 isolates representing major human listeriosis outbreaks worldwide, in addition to other unrelated isolates. Both mSNP typing and MVLST showed that 60% of the isolates analyzed belonged to epidemic clone I (ECI), which has been epidemiologically linked to several human outbreaks of listeriosis. In particular, the 1981 Canada outbreak was linked to the use of sheep manure and the 1985 California outbreak was linked to the use of raw cow's milk. In our study, ECI isolates were collected from different ruminant species on geographically and temporally distinct occasions for the last 13 years. Our results support the hypothesis that ruminants represent possible natural reservoirs of L. monocytogenes strains capable of causing epidemics of listeriosis in humans.

mentioning

confidence: 99%

Ruminant Rhombencephalitis-Associated Listeria monocytogenes Strains Constitute a Genetically Homogeneous Group Related to Human Outbreak Strains

Rocha

Lomonaco

Bottero

et al. 2013

“…Presence of the following prophages: Different studies have demonstrated the importance of bacteriophages in the evolution of closely related strains of L. monocytogenes (20,(30)(31)(32). WGS analysis can reveal prophage regions that explain differences between phylogenetically similar populations with different PFGE types (33).…”

Section: Bacmentioning

confidence: 99%

“…It can be used to characterize foodborne pathogen isolates, providing new insights into foodborne pathogen biology and transmission (28,29). Regarding L. monocytogenes, subtyping by the highly discriminatory pulsed-field gel electrophoresis (PFGE) method has been critical in detecting and investigating outbreaks of foodborne listeriosis (30)(31)(32). Genome sequencing will likely replace PFGE, allowing the in-depth characterization of L. monocytogenes isolates in food safety laboratories (29,31).…”

mentioning

confidence: 99%

The Connection between Persistent, Disinfectant-Resistant Listeria monocytogenes Strains from Two Geographically Separate Iberian Pork Processing Plants: Evidence from Comparative Genome Analysis

Ortiz

López-Alonso

Rodríguez³

et al. 2016

100

The aim of this study was to investigate the basis of the putative persistence of Listeria monocytogenes in a new industrial facility dedicated to the processing of ready-to-eat (RTE) Iberian pork products. Quaternary ammonium compounds, which included benzalkonium chloride (BAC), were repeatedly used as surface disinfectants in the processing plant. Clean and disinfected surfaces were sampled to evaluate if resistance to disinfectants was associated with persistence. Of the 14 isolates obtained from product contact and non-product contact surfaces, only five different pulsed-field gel electrophoresis (PFGE) types were identified during the 27-month study period. Two of these PFGE types (S1 and S10-1) were previously identified to be persistent and BAC-resistant (BAC r ) strains in a geographically separate slaughterhouse belonging to the same company. The remaining three PFGE types, which were first identified in this study, were also BAC r . Whole-genome sequencing and in silico multilocus sequence typing (MLST) analysis of five BAC r isolates of the different PFGE types identified in this study showed that the isolate of the S1 PFGE type belonged to MLST sequence type 31 (ST31), a low-virulence type characterized by mutations in the inlA and prfA genes. The isolates of the remaining four PFGE types were found to belong to MLST ST121, a persistent type that has been isolated in several countries. The ST121 strains contained the BAC resistance transposon Tn6188. The disinfection-resistant L. monocytogenes population in this RTE pork product plant comprised two distinct genotypes with different multidrug resistance phenotypes. This work offers insight into the L. monocytogenes subtypes associated with persistence in food processing environments. Listeria monocytogenes is a Gram-positive bacterium of the phylum Firmicutes. Often found in raw foods, L. monocytogenes bacteria can cause the life-threatening disease listeriosis. Most cases of human listeriosis appear to be caused by ready-to-eat (RTE) foods, and the risk of illness increases with the number of cells ingested and with RTE foods that support the growth of L. monocytogenes (1). Processed foods can be contaminated by contact with equipment, by the handling of raw products by staff, or from postprocessing environmental niches in which L. monocytogenes can survive despite the routine use of thorough disinfection procedures (2, 3). Mechanisms that facilitate the survival of L. monocytogenes in food processing environments include biofilm formation (4, 5), acquisition of antimicrobial resistance (6-10), and stress resistance mechanisms (11,12).L. monocytogenes is capable of colonizing food production plants with certain subtypes that are found only in specific sections of the plants (13, 14). Furthermore, some of these subtypes may persist in food processing environments for years (15-17). Persistent strains have been identified to be major postprocessing contaminants of RTE foods, and in many cases, listeriosis outbreaks have been associated with cases of p...

“…isteria monocytogenes can cause sporadic cases and outbreaks of severe disease among humans by exposure through contaminated foodstuffs (1,2). Increasingly definitive molecular subtyping is linking sporadic cases and identifying outbreaks often dispersed over wide geographical areas (2).…”

mentioning

confidence: 99%

“…Increasingly definitive molecular subtyping is linking sporadic cases and identifying outbreaks often dispersed over wide geographical areas (2). The pathogen presents a major public health problem in vulnerable groups (2,3). This places a large responsibility on food business operators (FBOs) to ensure the production of safe food that is free from L. monocytogenes.…”

mentioning

confidence: 99%

Phylogenetic Profiles of In-House Microflora in Drains at a Food Production Facility: Comparison and Biocontrol Implications of Listeria-Positive and -Negative Bacterial Populations

Fox

Solomon

Moore

et al. 2014

g Listeria species experience complex interactions with other microorganisms, which may promote growth and colonization of the organism in local environments or negatively affect them. This study investigated the microbial community at a food production facility, examining interactions between Listeria and the associated microbiome. Listeria species can be transferred between zones in the production environment by individuals or equipment, and drains may act as a reservoir for the organism, reflecting the microbial flora potentially in the production environment. Drains that were colonized by Listeria species and those determined to be free of Listeria were examined. In each case, 16S rRNA gene analysis was performed using the PhyloChip platform. Some general similarities in bacterial population structure were observed when Listeria-negative and -positive drain communities were compared, with some distinct differences also noted. These included increased populations of the genera Prevotella and Janthinobacterium associated with the absence of Listeria species, whereas Enterococcus and Rhodococcus were in higher abundance in drains colonized by Listeria species. Based on these results, a selection of bacterial species were grown in coculture biofilm with a Listeria monocytogenes strain identified as having colonized a drain at the facility. Mixed-species biofilm experiments showed that Janthinobacterium inhibited attachment and subsequent biofilm formation of L. monocytogenes; however, Enterococcus gallinarum significantly increased it. The results of this study suggest the microbial community in food processing facilities can impact the colonization of Listeria species and that influencing the microbiome in favor of antilisterial species may reduce the colonization of Listeria species and limit the likelihood of product/process contamination.