Pre-growth conditions and strain diversity affect nisin treatment efficacy against Listeria monocytogenes on cold-smoked salmon

Chen, Ruixi; Skeens, Jordan; Orsi, Renato H.; Wiedmann, Martin; Guariglia-Oropeza, Veronica

doi:10.1016/j.ijfoodmicro.2020.108793

Cited by 15 publications

(23 citation statements)

References 64 publications

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“…The efficacy of nisin treatments against L. monocytogenes on cold-smoked salmon, either by itself or in synergy with other treatments, has been extensively studied at various antimicrobial concentrations and storage temperatures. Several studies were consistent in showing that when challenged with up to 50 ppm nisin on cold-smoked salmon, L. monocytogenes experienced an initial decrease in level, followed by a potential regrowth of the population to higher levels ( Tang et al, 2013 ; Kang et al, 2014 ; Chen et al, 2020 ). Furthermore, the susceptibility of L. monocytogenes to nisin treatments has been reported to be affected by pre-growth condition in growth media ( Kang et al, 2015 ) and by both pre-growth condition and strain diversity on cold-smoked salmon ( Chen et al, 2020 ).…”

Section: Introductionmentioning

confidence: 77%

The efficacy of nisin against Listeria monocytogenes on cold-smoked salmon at natural contamination levels is concentration-dependent and varies by serotype

2022

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Cold-smoked salmon is a ready-to-eat food product capable of supporting Listeria monocytogenes growth at refrigeration temperatures. While the FDA-approved antimicrobial nisin can be used to mitigate L. monocytogenes contamination, stresses associated with cold-smoked salmon and the associated processing environments may reduce nisin efficacy. A previous study in our laboratory showed that, at high inoculation levels, pre-exposure of L. monocytogenes to sublethal concentrations of quaternary ammonium compounds had an overall detrimental effect on nisin efficacy. The objective of this study was to investigate the impact of nisin concentration and storage temperature on nisin efficacy against L. monocytogenes inoculated on salmon at natural contamination levels. Three L. monocytogenes strains were pre-grown in the presence of sublethal levels of benzalkonium chloride prior to inoculation at ~102 CFU/g on salmon slices that were pre-treated with either 0, 25, or 250 ppm nisin, followed by vacuum-packing and incubation at 4 or 7°C for up to 30 days. L. monocytogenes was enumerated on days 1, 15, and 30 using direct plating and/or most probable number methods. A hurdle model was constructed to describe the odds of complete elimination of L. monocytogenes on salmon and the level of L. monocytogenes when complete elimination was not achieved. Our data showed that (i) nisin efficacy (defined as L. monocytogenes reduction relative to the untreated control) was concentration-dependent with increased efficacy at 250 ppm nisin, and that (ii) 250 ppm nisin treatments led to a reduction in L. monocytogenes prevalence, independent of storage temperature and serotype; this effect of nisin could only be identified since low inoculation levels were used. While lower storage temperatures (i.e., 4°C) yielded lowered absolute L. monocytogenes counts on days 15 and 30 (as compared to 7°C), nisin efficacy did not differ between these two temperatures. Finally, the serotype 1/2b strain was found to be more susceptible to nisin compared with serotype 1/2a and 4b strains on samples incubated at 7°C or treated with 25 ppm nisin. This variation of nisin susceptibility across serotypes, which is affected by both the storage temperature and nisin concentration, needs to be considered while evaluating the efficacy of nisin.

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Section: Introductionmentioning

confidence: 77%

The efficacy of nisin against Listeria monocytogenes on cold-smoked salmon at natural contamination levels is concentration-dependent and varies by serotype

2022

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“…parahaemolyticus, and S. putrefaciens; − therefore, the inactivation potency of the PDI-mediated composite films against them on salmon was investigated.…”

Section: Resultsmentioning

confidence: 99%

Novel 2,3-Dialdehyde Cellulose-Based Films with Photodynamic Inactivation Potency by Incorporating the β-Cyclodextrin/Curcumin Inclusion Complex

et al. 2021

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Antibacterial packaging film mediated by photodynamic inactivation (PDI) is a new concept in food industry. The objective of this study was to fabricate a green 2,3-dialdehyde cellulose (DAC)-based antimicrobial film with PDI potency by incorporating the β-cyclodextrin/curcumin (β-CD/Cur) complex as a photosensitizer. The PDI-mediated films were characterized by evaluating the surface morphology, chemical structure, light transmittance, mechanical properties, photochemical and thermal stability, and water solubility. The results showed that the DAC-CD/Cur films were soluble in water and mechanically strong with a tensile strength of 63.87 MPa and an elongation break of 1.32%, which was attributed to the formation of hydrogen bonds between DAC and β-CD/Cur molecules. Meanwhile, the composite films possessed a good light transmittance but impeded the penetration of ultraviolet light and efficiently delayed the degradation of curcumin. More importantly, the PDI-mediated films exhibited a broad-spectrum ability to kill Listeria monocytogenes, Vibrio parahaemolyticus, and Shewanella putrefaciens in pure culture. Notably, they also potently inactivated these harmful bacteria on ready-to-eat salmon with a maximum of ∼4 Log CFU/g (99.99%) reduction after 60 min irradiation (13.68 J/cm2). Therefore, the PDI-mediated DAC-CD/Cur films are novel and promising antimicrobial food packaging films in food industry.

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“…S3). The two clusters discussed above exemplify situations in which isolates associated with the same source (i.e., smoked fish) but distinct geographical locations may be found to be closely related by WGS, using the threshold criteria previously proposed by authors from the FDA (6). We hypothesize that the most likely cause for such scenarios is the introduction of the same strain into multiple processing facilities through (i) shared raw material, (ii) acquisition of contaminated equipment by one operation from another operation, and less likely, (iii) exchange of products or employees (which could act as fomites, e.g., by carrying L. monocytogenes on their shoes).…”

Section: Resultsmentioning

confidence: 99%

Identification of Closely Related Listeria monocytogenes Isolates with No Apparent Evidence for a Common Source or Location: A Retrospective Whole Genome Sequencing Analysis

Orsi

Jagadeesan

Baert

et al. 2021

Journal of Food Protection

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Public health and regulatory agencies worldwide sequence all Listeria monocytogenes (Lm) isolates obtained as part of routine surveillance and outbreak investigations. Many of these entities submit the sequences to the NCBI Pathogen Detection (NCBI PD) database, which groups the Lm isolates into SNP clusters based on a pairwise SNP difference threshold of 50 SNPs. Our goal was to assess if isolates with metadata suggesting different sources or locations could show evidence for close genetic relatedness indicating a recent common ancestor and a possible unknown common source. We compared the WGS data of 249 Lm isolates sequenced here, which have detailed metadata, to WGS data of non-clinical isolates on NCBI PD. The 249 Lm isolates originated from natural environments (n = 91) as well as smoked fish (n = 62), dairy (n = 56), and deli-meat (n = 40) operations in the US. Using a combination of subtyping by cgMLST and hqSNP, we observed 5 SNP clusters where study isolates and SNP cluster isolates seemed to be closely related and either (i) share the same geolocation, but show different source types (1 SNP cluster); (ii) share the same source type, but show different geolocations (2 SNP clusters); or (iii) shared neither source type nor geolocation (2 SNP clusters). For one of the two clusters under (iii), there however was no strong bootstrap support for a common ancestor shared between the study isolates and SNP cluster isolates, indicating the value of in-depth evolutionary analyses when WGS data are used for traceback and epidemiological investigations. Overall, our results demonstrate that some Lm subtypes may be associated with specific locations or commodities; these associations can help in investigations involving multi-ingredient foods such as sandwiches. However, at least some Lm subtypes can be widespread geographically and be associated with different sources, which may present a challenge to traceback investigations involving these subtypes.

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Pre-growth conditions and strain diversity affect nisin treatment efficacy against Listeria monocytogenes on cold-smoked salmon

Cited by 15 publications

References 64 publications

The efficacy of nisin against Listeria monocytogenes on cold-smoked salmon at natural contamination levels is concentration-dependent and varies by serotype

The efficacy of nisin against Listeria monocytogenes on cold-smoked salmon at natural contamination levels is concentration-dependent and varies by serotype

Novel 2,3-Dialdehyde Cellulose-Based Films with Photodynamic Inactivation Potency by Incorporating the β-Cyclodextrin/Curcumin Inclusion Complex

Identification of Closely Related Listeria monocytogenes Isolates with No Apparent Evidence for a Common Source or Location: A Retrospective Whole Genome Sequencing Analysis

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