The effects of competition from non-pathogenic foodborne bacteria during the selective enrichment of Listeria monocytogenes using buffered Listeria enrichment broth

Dailey, Rachel C.; Martin, Keely; Smiley, R. Derike

doi:10.1016/j.fm.2014.05.004

Cited by 27 publications

(34 citation statements)

References 11 publications

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“…But, the presence of some microorganisms in food at high counts is able to inhibit the growth of other microorganisms. For example, the presence of E. coli in high counts inhibits the growth of L. monocytogenes in food (DAILEY et al, 2014). In our study, the presence of high counts of mesophilic aerobic bacteria, coliforms and Staphylococcus sp.…”

Section: Lotsupporting

confidence: 49%

Microbial contamination in industrial tofu

Ribeiro

Costa

2017

Cienc. Rural

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This study aimed to evaluate the microbiological quality of tofu sold in supermarkets in Porto Alegre/Brazil. Bacteria counts were performed for Bacillus cereus , mesophilic, coliforms and Staphylococcus coagulase positive and negative. The presence of Listeria sp. was also evaluated. Two different brands of tofu (A and B) were collected, one lot per month, for six months. Five samples from each lot were analyzed. All lots presented mesophilic aerobic counts above 4.3x105CFU g-1. Four of the six lots from brand A and all lots from brand B showed E. coli and/or Staphylococcus coagulase positive counts above the Brazilian law accepted limits. The Staphylococcus coagulase negative counts were higher than those of coagulase positive in all lots. In all lots where Staphylococcus coagulase positive counts were above the legal limit, there were counts of coagulase negative above 104CFU g-1. B. cereus and Listeria sp. were not found in either brand. The majority of lots of brand A and all lots of brand B were unsuitable for human consumption. Our results showed that there are problems in tofu manufacturing in both industries analyzed. There is a need of improvement on its microbial quality to avoid problems of food-borne illness, and finally the need of a better control by the Brazilian inspection services.

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Section: Lotsupporting

confidence: 49%

Microbial contamination in industrial tofu

Ribeiro

Costa

2017

Cienc. Rural

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“…The use of 16S rDNA sequence analysis was used to confirm the species of all isolates (Hellberg et al, 2013). Bacterial cultures were prepared and maintained as previously described Dailey et al, 2014). Commercial bacterial identification kits (Vidas Listeria, bioMerieux; API Listeria, bioMerieux; MicroSeq Listeria monocytogenes, ABI) were used following manufacturer's instructions.…”

Section: Listeria Strainsmentioning

confidence: 99%

“…The generation times and populations following growth in buffered Listeria enrichment broth (BLEB) for 48 h at 30 °C were determined as previously described Dailey et al, 2014). Briefly, growth was measured in 2.5 mL volumes of BLEB at 30 °C using a Synergy HT microplate reader (BioTek, Inc., Winooski, VT).…”

Section: Generation Times and Selective Enrichment Populationsmentioning

confidence: 99%

“…Commonly used selective enrichment formulations do not display absolute species level specificity resulting in competition between L. monocytogenes and non-target background microorganisms (Dailey et al, 2014;Dallas et al, 1991;Tran et al, 1990) and between L. monocytogenes and the non-pathogenic species, Listeria innocua (Besse et al, 2005;Carvalheira et al, 2010;Curiale and Lewus, 1994;Keys et al, 2013;Petran and Swanson, 1993). Competition results in limited growth and ultimately a reduced final population of L. monocytogenes which lowers the overall sensitivity of subsequent detection platforms and hinders recovery.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Listeria seeligeri or Listeria welshimeri on Listeria monocytogenes detection in and recovery from buffered Listeria enrichment broth

et al. 2015

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The presence of multiple species of Listeria in regulated food products is not uncommon and can complicate the recovery of Listeria monocytogenes particularly on a non-differentiating medium. The potential complications of Listeria seeligeri and Listeria welshimeri on the recovery of L. monocytogenes from inoculated food test samples using the U.S. Food and Drug Administration's (FDA) selective enrichment procedure was investigated. Post-enrichment enumeration, in the absence of food product, indicates that some L. seeligeri and L. monocytogenes pairings may have population differentials as great as 2.7 ± 0.1 logs with L. seeligeri being the predominant species. A similar observation was noted for L. welshimeri and L. monocytogenes pairings which resulted in population differentials as large as 3.7 ± 0.2 logs with L. welshimeri being the predominant species. Select strain pairings were used to inoculate guacamole, crab meat, broccoli, and cheese with subsequent recovery by the FDA Bacteriological Analytical Manual (BAM) method with 10 colonies per sample selected for confirmation. The presence of L. seeligeri had little effect on the recovery of L. monocytogenes. The presence of L. welshimeri resulted in the failure to recover L. monocytogenes in three out of the four food matrices. This work extends the observation that nonpathogenic species of Listeria can complicate the recovery of L. monocytogenes and that competition during selective enrichment is not limited to the presence of just Listeria innocua. Keywords

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“…Nonetheless, the bias associated with enrichment protocols introduces recovery limitations and compromises the isolation of the pathogen. The interference of background food microflora (9,10) or other Listeria spp. (particularly L. innocua) may mask the presence and diminish the detectability of L. monocytogenes (11)(12)(13)(14)(15)(16)(17).…”

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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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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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The effects of competition from non-pathogenic foodborne bacteria during the selective enrichment of Listeria monocytogenes using buffered Listeria enrichment broth

Cited by 27 publications

References 11 publications

Microbial contamination in industrial tofu

Microbial contamination in industrial tofu

Effect of Listeria seeligeri or Listeria welshimeri on Listeria monocytogenes detection in and recovery from buffered Listeria enrichment broth

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

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