Evaluation of reduction of Fraser incubation by 24h in the EN ISO 11290-1 standard on detection and diversity of Listeria species

Besse, Nathalie Gnanou; Favret, Sandra; Desreumaux, Jennifer; Brasseur, Emilie Decourseulles; Kalmokoff, Martin

doi:10.1016/j.ijfoodmicro.2016.02.010

Cited by 14 publications

(3 citation statements)

References 27 publications

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“…For instance, the probability that a strain would become totally undetectable might be higher after the second enrichment step. According to Gnanou Besse et al (33), who proposed a 24-h reduction in the duration specified the ISO protocol, the latter scenario might be related to the production of inhibitory factors (e.g., phages or phage tails, namely, monocins) by competing strains over the last 24 h of the second enrichment cycle. LiCl, a principal selective agent present in Fraser broth and ALOA, has been reported to induce the production of such inhibitory compounds (34).…”

Section: Discussionmentioning

confidence: 99%

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Listeria monocytogenes Strains Underrepresented during Selective Enrichment with an ISO Method Might Dominate during Passage through Simulated Gastric Fluid and In Vitro Infection of Caco-2 Cells

Zilelidou

Karmiri

Ζουμποπούλου

et al. 2016

Appl Environ Microbiol

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Various Listeria monocytogenes strains may contaminate a single food product, potentially resulting in simultaneous exposure of consumers to multiple strains. However, due to bias in strain recovery, L. monocytogenes strains isolated from foods by selective enrichment (SE) might not always represent those that can better survive the immune system of a patient. We investigated the effect of cocultivation in tryptic soy broth with 0.6% yeast extract (TSB-Y) at 10°C for 8 days on (i) the detection of L. monocytogenes strains during SE with the ISO 11290-1:1996/Amd 1:2004 protocol and (ii) the in vitro virulence of strains toward the Caco-2 human colon epithelial cancer cell line following exposure to simulated gastric fluid (SGF; pH 2.0)-HCl (37°C). We determined whether the strains which were favored by SE would be effective competitors under the conditions of challenges related to gastrointestinal passage of the pathogen. Interstrain competition of L. monocytogenes in TSB-Y determined the relative population of each strain at the beginning of SE. This in turn impacted the outcome of SE (i.e., favoring survival of competitors with better fitness) and the levels exposed subsequently to SGF. However, strong growth competitors could be outcompeted after SGF exposure and infection of Caco-2 cells by strains outgrown in TSB-Y and underdetected (or even missed) during enrichment. Our data demonstrate a preferential selection of certain L. monocytogenes strains during enrichments, often not reflecting a selective advantage of strains during infection. These findings highlight a noteworthy scenario associated with the difficulty of matching the source of infection (food) with the L. monocytogenes isolate appearing to be the causative agent during listeriosis outbreak investigations. IMPORTANCEThis report is relevant to understanding the processes involved in selection and prevalence of certain L. monocytogenes strains in different environments (i.e., foods or sites of humans exposed to the pathogen). It highlights the occurrence of multiple strains in the same food as an important aspect contributing to mismatches between clinical isolates and infection sources during listeriosis outbreak investigations. Selective enrichment (SE) for detection of foodborne pathogens has been a fundamental tool in the food industry, critical for hygiene control and safety monitoring (1) while providing crucial information during trace-back investigations of foodborne outbreaks. However, selective culture-based enrichment procedures are associated with inherent bias since the use of selective agents and the presence of competing background microorganisms in food samples sometimes obstruct the isolation of a target pathogen and lead to false-negative results (2, 3).Listeria monocytogenes stands out among the pathogens of major concern for food safety. This Gram-positive bacterium causes the rare but life-threatening disease listeriosis and manifests the interplay between saprophytic lifestyle and virulence (4, 5). Its ubiquity allows...

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Section: Discussionmentioning

confidence: 99%

“…LiCl, a principal selective agent present in Fraser broth and ALOA, has been reported to induce the production of such inhibitory compounds (34). Furthermore, poor recovery after the second enrichment step could be the result of the inability of the strain to remain viable throughout the whole duration of the procedure (33,35).…”

Section: Discussionmentioning

confidence: 99%

Listeria monocytogenes Strains Underrepresented during Selective Enrichment with an ISO Method Might Dominate during Passage through Simulated Gastric Fluid and In Vitro Infection of Caco-2 Cells

Zilelidou

Karmiri

Ζουμποπούλου

et al. 2016

Appl Environ Microbiol

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“…Despite the use of selective agents in these enrichment methods, species-specific growth is not achieved. When more than one species of Listeria is present in the test sample each may respond differently to selective enrichment conditions (Petran and Swanson, 1993; Curiale and Lewus, 1994; Carvalheira et al, 2010; Cornu et al, 2002; Ganou Besse et al, 2005; Keys et al, 2013; Dailey et al, 2015; Ganou Besse et al, 2016). The importance of this observation is that recovery of only L. innocua or any other non-pathogenic Listeria species does not preclude the presence of L. monocytogenes .…”

Section: Introductionmentioning

confidence: 99%

Comparison of Listeria monocytogenes recoveries from spiked mung bean sprouts by the enrichment methods of three regulatory agencies

2017

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Three selective enrichment methods, the United States Food and Drug Administration’s (FDA method), the United States Department of Agriculture Food Safety Inspection Service’s (USDA method), and the EN ISO 11290-1 standard method, were assessed for their suitability for recovery of Listeria monocytogenes from spiked mung bean sprouts. Three parameters were evaluated; the enrichment L. monocytogenes population from singly-spiked sprouts, the enrichment L. monocytogenes population from doubly-spiked (L. monocytogenes and Listeria innocua) sprouts, and the population differential resulting from the enrichment of doubly-spiked sprouts. Considerable L. monocytogenes inter-strain variation was observed. The mean enrichment L. monocytogenes populations for singly-spiked sprouts were 6.1 ± 1.2, 4.9 ± 1.2, and 6.9 ± 2.3 log CFU/mL for the FDA, USDA, and EN ISO 11290-1 methods, respectively. The mean L. monocytogenes populations for doubly-spiked sprouts were 4.7 ± 1.1, 5.5 ± 1.3, and 4.6 ± 1.4 log CFU/mL for the FDA, USDA, and ISO 11290–1 enrichment methods, respectively. The corresponding mean population differentials were 2.8 ± 1.1, 3.3 ± 1.3, and 3.6 ± 1.4 Δlog CFU/mL for the same three enrichment methods, respectively. The presence of L. innocua and resident microorganisms on the sprouts negatively impacted final levels of L. monocytogenes with all three enrichment methods.

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Eating jellyfish: safety, chemical and sensory properties

et al. 2018

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Evaluation of reduction of Fraser incubation by 24h in the EN ISO 11290-1 standard on detection and diversity of Listeria species

Cited by 14 publications

References 27 publications

Listeria monocytogenes Strains Underrepresented during Selective Enrichment with an ISO Method Might Dominate during Passage through Simulated Gastric Fluid and In Vitro Infection of Caco-2 Cells

Listeria monocytogenes Strains Underrepresented during Selective Enrichment with an ISO Method Might Dominate during Passage through Simulated Gastric Fluid and In Vitro Infection of Caco-2 Cells

Comparison of Listeria monocytogenes recoveries from spiked mung bean sprouts by the enrichment methods of three regulatory agencies

Eating jellyfish: safety, chemical and sensory properties

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