Lactococcus lactis subsp. lactis as a natural anti-listerial agent in the mushroom industry

peer-reviewedMushroom growth substrates from different commercial producers of mushrooms (Agaricus bisporus) were screened for the presence of bacteria with potential for use as biocontrol agents for controlling Listeria monocytogenes in the mushroom production environment. Eight anti-listerial strains were isolated from different sources and all were identified using 16s rRNA gene sequencing as Lactococcus lactis subsp. lactis. Whole-genome sequencing of the Lc. lactis isolates indicated that strains from different sites and substrate types were highly similar. Colony MALDI-TOF mass spectrometry found that these strains were Nisin Z producers but inhibitory activity was highly influenced by the incubation conditions and was strain dependant. The biofilm forming ability of these strains was tested using a crystal violet assay and all were found to be strong biofilm formers. Growth of Lc. lactis subsp. lactis using mixed-biofilm conditions with L. monocytogenes on stainless steel resulted in a 4-log reduction of L. monocytogenes cell numbers. Additional sampling of mushroom producers showed that these anti-listerial Lc. lactis strains are commonly present in the mushroom production environment. Lc. lactis has a generally regarded as safe (GRAS) status and therefore has potential for use as an environmentally benign solution to control L. monocytogenes in order to prevent product contamination and to enhance consumer confidence in the mushroom industry

Examining the efficacy of mushroom industry biocides on Listeria monocytogenes biofilm

Aims: The aim of this study was to test the efficacy of new and currently used biocides in the mushroom industry for inactivating L. monocytogenes biofilm. Methods and results: A lab‐scale study was initially carried out to test the efficacy of eleven biocidal products against a cocktail of five L. monocytogenes strains that were grown to three‐day biofilms on stainless steel coupons. Biocidal efficacy was then tested under clean and dirty conditions based on the EN 13697:2015 method. The results for the biocides tested ranged between 1.7‐log to 6‐log reduction of biofilm, with only the efficacy of the sodium hypochlorite‐based biocide being significantly reduced in dirty conditions. A pilot‐scale trial was then carried out on a subset of biocides against L. monocytogenes on concrete floors in a mushroom growing room and it was found that biocide efficacy in lab‐scale did not translate well in pilot‐scale. Conclusions: Biocides that are used in the mushroom industry and potential alternative biocides were determined to be effective against L. monocytogenes biofilm in both lab‐scale and pilot‐scale experiments. Significance and impact of the study: This study has direct impact for the industry as it provides information on the efficacy of currently used biocides and other biocidal products against L. monocytogenes, an added benefit to their primary use

Effectiveness of current hygiene practices on minimization of Listeria monocytogenes in different mushroom production‐related environments

peer-reviewedBackground: The commercial production of Agaricus bisporus is a three stage process: 1) production of compost, also called “substrate”; 2) production of casing soil; and 3) production of the mushrooms. Hygiene practices are undertaken at each stage: pasteurization of the substrate, hygiene practices applied during the production of casing soil, postharvest steam cookout, and disinfection at the mushroom production facilities. However, despite these measures, foodborne pathogens, including Listeria monocytogenes, are reported in the mushroom production environment. In this work, the presence of L. monocytogenes was evaluated before and after the application of hygiene practices at each stage of mushroom production with swabs, samples of substrate, casing, and spent mushroom growing substrates. Results: L. monocytogenes was not detected in any casing or substrate sample by enumeration according to BS EN ISO 11290-2:1998. Analysis of the substrate showed that L. monocytogenes was absent in 10 Phase II samples following pasteurization, but was then present in 40% of 10 Phase III samples. At the casing production facility, 31% of 59 samples were positive. Hygiene improvements were applied, and after four sampling occasions, 22% of 37 samples were positive, but no statistically significant difference was observed (p > .05). At mushroom production facilities, the steam cookout process inactivated L. monocytogenes in the spent growth substrate, but 13% of 15 floor swabs at Company 1 and 19% of 16 floor swabs at Company 2, taken after disinfection, were positive. Conclusion: These results showed the possibility of L. monocytogenes recontamination of Phase III substrate, cross-contamination at the casing production stage and possible survival after postharvest hygiene practices at the mushroom growing facilities. This information will support the development of targeted measures to minimize L. monocytogenes in the mushroom industry.Food Institutional Research Measur

Coral benchmarks in the center of biodiversity

There is an urgent need to quantify coral reef benchmarks that assess changes and recovery rates through time and serve as goals for management. Yet, few studies have identified benchmarks for hard coral cover and diversity in the center of marine diversity. In this study, we estimated coral cover and generic diversity benchmarks on the Tubbataha reefs, the largest and best-enforced no-take marine protected area in the Philippines. The shallow (2–6 m) reef slopes of Tubbataha were monitored annually, from 2012 to 2015, using hierarchical sampling. Mean coral cover was 34% (σ ± 1.7) and generic diversity was 18 (σ ± 0.9) per 75 m by 25 m station. The southeastern leeward slopes supported on average 56% coral cover, whereas the northeastern windward slopes supported 30%, and the western slopes supported 18% coral cover. Generic diversity was more spatially homogeneous than coral cover. © 2016 Elsevier Lt

Lactococcus lactis subsp. lactis as a natural anti-listerial agent in the mushroom industry

Mushroom growth substrates from different commercial producers of mushrooms (Agaricus bisporus) were screened for the presence of bacteria with potential for use as biocontrol agents for controlling Listeria monocytogenes in the mushroom production environment. Eight anti-listerial strains were isolated from different sources and all were identified using 16s rRNA gene sequencing as Lactococcus lactis subsp. lactis. Whole-genome sequencing of the Lc. lactis isolates indicated that strains from different sites and substrate types were highly similar. Colony MALDI-TOF mass spectrometry found that these strains were Nisin Z producers but inhibitory activity was highly influenced by the incubation conditions and was strain dependant. The biofilm forming ability of these strains was tested using a crystal violet assay and all were found to be strong biofilm formers. Growth of Lc. lactis subsp. lactis using mixed-biofilm conditions with L. monocytogenes on stainless steel resulted in a 4-log reduction of L. monocytogenes cell numbers. Additional sampling of mushroom producers showed that these anti-listerial Lc. lactis strains are commonly present in the mushroom production environment. Lc. lactis has a generally regarded as safe (GRAS) status and therefore has potential for use as an environmentally benign solution to control L. monocytogenes in order to prevent product contamination and to enhance consumer confidence in the mushroom industry

Antibacterial activity of camellia sinensis (green tea) leaf extract on the growth rate of staphylococcus aureus, escherichia coli, and salmonella typhi

The antibacterial activity of green tea (camellia sinensis) leaf extract was determined against the growth rate of staphylococcus aureus, escherichia coli, and salmonella typhi. Two methods were done for bacterial susceptibility namely agar gal diffusion and paper disc diffusion. Different concentrations of GT were used such as 625ug, 1250ug, and 2500ug, and these were tested with the controls such as penicillin, ampicillin, and NSS. The green tea extract produced inhibition zone ranging from 0.2-13.4 mm against staphylococcus aureus only. Escherichia coli and Salmonella typhi were not found to be susceptible to the antibacterial activity of green tea. With the susceptibility of staphylococcus aureus to green tea, its effects were compared with the control, and were found to be statistically significant. Moreover, with increasing dose/concentration of the green tea, the zone of inhibition of green tea also increased or became wider. With the two methods used for the antibacterial activity of green tea, it was also found that agar gel diffusion yielded better results than paper disc diffusion method. As per the effects of green tea on the growth rate of the bacteria, no changes were found hours after incubation (zone of inhibition did not changed)