Susceptibility of Clostridium perfringens to antimicrobials produced by lactic acid bacteria: Reuterin and nisin

Cell-Free Culture Supernatant of Lactobacillus acidophilus AG01 and Bifidobacterium animalis subsp. lactis AG02 Reduces the Pathogenicity of NetB-Positive Clostridium perfringens in a Chicken Intestinal Epithelial Cell Line

The worldwide reduction in the use of antibiotics in animal feed is fueling the need for alternatives for the prevention and control of poultry intestinal diseases such as necrotic enteritis (NE), which is caused by Clostridium perfringens. This is the first report on the use of an intestinal epithelial chicken cell line (CHIC-8E11) to study the pathogenic traits of C. perfringens and to investigate the mode of action of cell-free supernatants (CFS) from probiotic Lactobacillus acidophilus AG01 and Bifidobacterium animalis subsp. lactis AG02 in reducing the pathogenicity of C. perfringens. The cell adhesion, permeability and cytotoxicity were assessed under challenge with four C. perfringens strains isolated from broiler NE episodes of differing geographical origin (CP1-UK; CP10-Sweden; 25037-CP01 and CP22-USA). All the C. perfringens strains could adhere to the CHIC-8E11 cells, with varying affinity (0.05-0.48% adhesion across the strains). The CFS from one out of two strains (CP22) increased the cell permeability (+4.5-fold vs. the control, p < 0.01), as measured by the fluorescein isothiocyanate-dextran (FD4) content, with NetB toxin implicated in this effect. The CFS from all the strains was cytotoxic against the CHIC-8E11 cells in a dose- and strain-dependent manner (cytotoxicity 23-62% across the strains when dosed at 50 µL/mL, as assessed by the MTT cell viability assay). Pre-treatment of the cells with CFS from B. animalis subsp. lactis AG02 but not L. acidophilus AG01 reduced the cell adhesion of three out of four C. perfringens strains (by 77-85% vs. the control, p < 0.001) and reduced the negative effect of two NetB-positive strains on the cell permeability. The CFS of both probiotics alleviated the cytotoxicity of all the C. perfringens strains, which was dependent on the dose. The results confirm the suitability of the CHIC-8E11 cell line for the study of host-pathogen cell interactions in the context of NE caused by C. perfringens and reveal a beneficial mode of action of B. animalis subsp. lactis AG02 in reducing C. perfringens cell adhesion and, together with L. acidophilus AG01, in reducing C. perfringens cytotoxicity.

Effects of exogenous lactic acid bacteria and maize meal on fermentation quality and microbial community of Orychophragmus violaceus silage

Orychophragmus violaceus is a local Brassicaceae in China, while most of it is directly mowed and discarded after the ornamental period. In order to develop forage resources, this study firstly evaluated the potential preservation of O. violaceus silage. O. violaceus was harvested at full-bloom stage, and ensiled without (CK) or with maize meal (Y5), lactic acid bacteria inoculant (Z) and compound additive (Y5Z) for 60 d. Results of chemical and microbiological analysis showed that a large amount of lactic acid was produced and the final pH value was below 4.1 in silages regardless of additive application. CK silage was well preserved as indicated by the low levels of dry matter loss and butyric acid content, and the predominant genus were identified as Enterococcus and Pediococcus. Y5 silage had potential health risks for humans and animals as seen by frequent occurrence of pathogenic bacteria Clostridium and Achromobacter. Z and Y5Z silages were poorly preserved, resulting in great dry matter loss and butyric acid content. Considering the abundant acetic acid production, the dominant Lactobacillus might possess a heterofermentative pathway in Z and Y5Z silages. In conclusion, O. violaceus has the potential to be long stored as silage because of its sufficient water-soluble carbohydrates, while exogenous lactic acid bacteria and maize meal generally provided little positive effect. In future research, efficient homofermentative Lactobacillus strains were suggested to be screened to further enhance the ensiling process of O. violaceus silage.

Microbiota Transplantation in Day-Old Broiler Chickens Ameliorates Necrotic Enteritis via Modulation of the Intestinal Microbiota and Host Immune Responses

A microbiota transplant (MT) originating from mature adult chicken ceca and propagated in bioreactors was administered to day-old broiler chicks to ascertain the degree to which, and how, the MT affects Clostridium perfringens (Cp)-incited necrotic enteritis (NE). Using a stress predisposition model of NE, birds administered the MT and challenged with Cp showed fewer necrotic lesions, and exhibited a substantially higher α- and β-diversity of bacteria in their jejunum and ceca. Birds challenged with Cp and not administered the MT showed decreased Lactobacillus and increased Clostridium sensu strico 1 in the jejunum. In ceca, Megamonas, a genus containing butyrate-producing bacteria, was only present in birds administered the MT, and densities of this genus were increased in birds challenged with Cp. Metabolite profiles in cecal digesta were altered in birds administered the MT and challenged with the pathogen; 59 metabolites were differentially abundant following MT treatment, and the relative levels of short chain fatty acids, butyrate, valerate, and propionate, were decreased in birds with NE. Birds administered the MT and challenged with Cp showed evidence of enhanced restoration of intestinal barrier functions, including elevated mRNA of MUC2B, MUC13, and TJP1. Likewise, birds administered the MT exhibited higher mRNA of IL2, IL17A, and IL22 at 2-days post-inoculation with Cp, indicating that these birds were better immunologically equipped to respond to pathogen challenge. Collectively, study findings demonstrated that administering a MT containing a diverse mixture of microorganisms to day-old birds ameliorated NE in broilers by increasing bacterial diversity and promoting positive immune responses.

Antimicrobial Impacts of Microbial Metabolites on the Preservation of Fish and Fishery Products: A Review with Current Knowledge

Microbial metabolites have proven effects to inhibit food spoilage microbiota, without any development of antimicrobial resistance. This review provides a recent literature update on the preservative action of metabolites derived from microorganisms on seafood. Fish and fishery products are regarded as a myriad of nutrition, while being highly prone to spoilage. Several proven controversies (antimicrobial resistance and health issues) related to the use of synthetic preservatives have caused an imminent problem. The demand for minimally processed and naturally preserved clean-label fish and fishery products is on rise. Metabolites derived from microorganisms have exhibited diverse preservation capacities on fish and fishery products' spoilage. Inclusions with other preservation techniques, such as hurdle technology, for the shelf-life extension of fish and fishery products are also summarized.

Phytic Acid against Clostridium perfringens Type A: A Food Matrix Study

This study evaluated the inhibitory effect of phytic acid (PA) on the spore germination and vegetative cells growth of Clostridium perfringens type A, as well as its effect in combination with maltodextrin (MD) in cooked sausages. The addition of 1% PA showed a satisfactory inhibition of spores’ germination and vegetative cells growth of C. perfringens in BHI media. The inhibitory effect of 1% PA on vegetative cells was similar to the additive sodium sorbate (SS) at 10%. Subsequently, a mixture of PA-MD (1:1; w/w) was evaluated for the inhibition of C. perfringens spores in cooked sausages. The PA-MD 1.5% and 2.5% had a similar performance to SS 10% and a similar or higher performance than 0.015% NO₂ (p < 0.05). In an unprecedented way, the present study demonstrated that PA inhibited spore germination and vegetative cells growth of C. perfringens, highlighting its potential use as an alternative and natural preservative for the meat industry.

Virulent phage vB_CpeP_HN02 inhibits Clostridium perfringens on the surface of the chicken meat

Clostridium perfringens is a well-known pathogen that causes foodborne disease. With a high prevalence of contamination in food, an efficient strategy is needed to decontaminate those contaminated foods and control the emergence of foodborne disease. In this study, the C. perfringens-specific lytic phage vB_CpeP_HN02 (designated as phage HN02) was isolated from chicken feces. Electron microscopy and phylogenetic analysis suggested that phage vB_CpeP_HN02 is a novel phage of the family Podoviridae. Phage HN02 had good pH (5-11) and temperature tolerance (< 70 °C). Phage HN02 exhibited a broad host range of C. perfringens isolates (42.86%). The complete genome of the phage HN02 was sequenced and revealed a linear double-stranded DNA genome. The 17,754-bp genome (GenBank MW815121) with average GC content of 28.2% includes 22 predicted open reading frames, of which only 10 were annotated with known functions. Phylogenetic analysis of the available C. perfringens phage major capsid protein demonstrated that phage HN02 is closely related to virulent C. perfringens phage phi24R and CPD2. When phage HN02 was applied to chicken meat samples stored at 4 °C for 72 h with 1 × 10⁶ to 1 × 10⁹ PFU/g, 95% to 99% of C. perfringens were inactivated on chicken meat surfaces after storage at 4 °C for 72 h, respectively. It should be noted that C. perfringens could be completely lysed by a high dose of phage HN02 (1 × 10¹⁰ PFU/g) after 48 h treatment in chicken samples. Through the lytic activity testing, phage HN02 showed good antimicrobial effects, and can be used as an antibacterial agent for biocontrol of C. perfringens in meat products.

Microbial biopreservatives for controlling the spoilage of beef and lamb meat: their application and effects on meat quality

Biopreservation is a recognized natural method for controlling the growth of undesirable bacteria on fresh meat. It offers the potential to inhibit spoilage bacteria and extend meat shelf-life, but this aspect has been much less studied compared to using the approach to target pathogenic bacteria. This review provides comprehensive information on the application of biopreservatives of microbial origin, mainly bacteriocins and protective cultures, in relation to bacterial spoilage of beef and lamb meat. The sensory effect of these biopreservatives, an aspect that often receives less attention in microbiological studies, is also reviewed. Microbial biopreservatives were found to be able to retard the growth of the major meat spoilage bacteria, Brochothrix thermosphacta, Pseudomonas spp., and Enterobacteriaceae. Their addition did not have any discernible negative impact on the sensory properties of meat, whether assessed by human sensory panels or instrumental and chemical analyses. Although results are promising, the concept of biopreservation for controlling spoilage bacteria on fresh meat is still in its infancy. Studies in this area are still lacking, especially for lamb. Biopreservatives need more testing under conditions representative of commercial meat production, along with studies of any possible sensory effects, in order to validate their potential for large-scale industrial applications.

Antagonistic effects of Lactobacillus reuteri against Escherichia coli O157:H7 in white-brined cheese under different storage conditions

This study aimed to investigate the survival of the foodborne pathogen Escherichia coli O157:H7 in white-brined cheeses as influenced by the presence of Lactobacillus reuteri. The white cheeses were made from pasteurized bovine milk inoculated with E. coli O157:H7 (cocktail of 3 strains) to achieve ∼5 log₁₀ cfu/g with absence or presence of Lb. reuteri (∼6 log₁₀ cfu/g). Cheese samples were brined in 10% or 15% NaCl solution and stored at 10°C and 25°C for 28 d. The white-brined cheeses were assessed for salt content, pH, water activity (A_w), and numbers of E. coli O157:H7, Lb. reuteri, nonstarter lactic acid bacteria (NSLAB), yeasts, and molds. Results showed that E. coli O157:H7 survived in cheese stored in both brine solutions at 10°C and 25°C regardless of the presence of Lb. reuteri. A substantial reduction was observed in cheese stored in 10% NaCl brine at 25°C, followed by cheese stored in 15% NaCl brine at 10°C by 2.64 and 2.16 log₁₀ cfu/g, respectively, in the presence of Lb. reuteri and by 1.02 and 1.87 log₁₀ cfu/g, respectively, in the absence of Lb. reuteri under the same conditions. The pathogen in brine solutions survived but at a lower rate. Furthermore, the growth of Lb. reuteri and NSLAB were enhanced or slightly decreased in cheese and brine by 28 d, respectively. The salt concentrations of cheese ranged from 4 to 6% and 5 to 7% (wt/wt), during 28-d ripening in 10 and 15% brine, respectively. Values of pH and A_w slightly increased at d 1 after exposure to brine and reached 4.69 to 6.08 and 0.91 to 0.95, respectively, in all treatments. Therefore, the addition of Lb. reuteri can be used as a biopreservation method to inhibit the survival of E. coli O157:H7 in white-brined cheese when combined with the appropriate temperature, NaCl level, and storage time.

Review on Natural Preservatives for Extending Fish Shelf Life

Fish is extremely perishable as a result of rapid microbial growth naturally present in fish or from contamination. Synthetic preservatives are widely used in fish storage to extend shelf life and maintain quality and safety. However, consumer preferences for natural preservatives and concerns about the safety of synthetic preservatives have prompted the food industry to search natural preservatives. Natural preservatives from microorganisms, plants, and animals have been shown potential in replacing the chemical antimicrobials. Bacteriocins and organic acids from bacteria showed good antimicrobial activities against spoilage bacteria. Plant-derived antimicrobials could prolong fish shelf life and decrease lipid oxidation. Animal-derived antimicrobials also have good antimicrobial activities; however, their allergen risk should be paid attention. Moreover, some algae and mushroom species can also provide a potential source of new natural preservatives. Obviously, the natural preservatives could perform better in fish storage by combining with other hurdles such as non-thermal sterilization processing, modified atmosphere packaging, edible films and coatings.

Use of fluorescent CTP1L endolysin cell wall-binding domain to study the evolution of Clostridium tyrobutyricum during cheese ripening

Clostridium tyrobutyricum is a bacteria of concern in the cheese industry, capable of surviving the manufacturing process and causing butyric acid fermentation and late blowing defect of cheese. In this work, we implement a method based on the cell wall-binding domain (CBD) of endolysin CTP1L, which detects C. tyrobutyricum, to monitor its evolution in cheeses challenged with clostridial spores and in the presence or absence of reuterin, an anti-clostridial agent. For this purpose, total bacteria were extracted from cheese samples and C. tyrobutyricum cells were specifically labelled with the CBD of CTP1L attached to green fluorescent protein (GFP), and detected by fluorescence microscopy. By using this GFP-CBD, germinated spores were visualized on day 1 in all cheeses inoculated with clostridial spores. Vegetative cells of C. tyrobutyricum, responsible for butyric acid fermentation, were detected in cheeses without reuterin from 30 d onwards, when LBD symptoms also became evident. The number of fluorescent Clostridium cells increased during ripening in the blowing cheeses. However, vegetative cells of C. tyrobutyricum were not detected in cheese containing the antimicrobial reuterin, which also did not show LBD throughout ripening. This simple and fast method provides a helpful tool to study the evolution of C. tyrobutyricum during cheese ripening.

Plant-expressed bacteriophage lysins control pathogenic strains of Clostridium perfringens

The anaerobic spore-forming bacterium Clostridium perfringens is a source of one of the most common food-borne illnesses in the United States and Europe. The costs associated with disease management are high and interventions are limited; therefore, effective and safe antimicrobials are needed to control food contamination by C. perfringens. A viable solution to this problem could be bacteriophage lysins used as food additives or food processing aids. Such antimicrobials could be produced cost-effectively and in ample supply in green plants. By using edible plant species as production hosts the need for expensive product purification can be reduced or obviated. We describe the first successful expression in plants of C. perfringens-specific bacteriophage lysins. We demonstrate that six lysins belonging to two different families (N-acetylmuramoyl-L-alanine amidase and glycosyl hydrolase 25) are active against a panel of enteropathogenic C. perfringens strains under salinity and acidity conditions relevant to food preparation environments. We also demonstrate that plant-expressed lysins prevent multiplication of C. perfringens on cooked meat matrices far better than nisin, the only currently approved bacteriocin food preservative to control this pathogen.

The effects of probiotic Bacillus subtilis on the cytotoxicity of Clostridium perfringens type a in Caco-2 cell culture

Background

Some Bacillus strains have recently been identified for potential use as probiotics and food additives. The present study evaluated the antimicrobial effects of Bacillus subtilis ATCC 6633 and its metabolite on the enterotoxin and vegetative cells, spore and germinated spore of Clostridium perfringens type A in Caco-2 cells.

Results

We used flow cytometry and MTT assays to evaluate the cytotoxicity effect of treatments. According to the results, the most cell survival was found in the 4% crude antimicrobial substance (CAS) with the vegetative form of C. perfringens among co-cultured groups. Furthermore, the apoptosis and necrosis in co-cultured groups were significantly decreased (P < 0.05).

Conclusion

The present results suggested the crucial role of the current probiotic in the control of various forms of C. perfringens type A which was investigated for the first time. Also, the majority of treatments showed higher cell viability in flow cytometry compared to the MTT assay.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-017-1051-1) contains supplementary material, which is available to authorized users.

Inhibitory activity of Lactobacillus plantarum TF711 against Clostridium sporogenes when used as adjunct culture in cheese manufacture

Bacteriocins produced by lactic acid bacteria are of great interest to the food-processing industry as natural preservatives. This work aimed to investigate the efficacy of bacteriocin-producing Lactobacillus plantarum TF711, isolated from artisanal Tenerife cheese, in controlling Clostridium sporogenes during cheese ripening. Cheeses were made from pasteurised milk artificially contaminated with 10(4) spores m/l C. sporogenes. Experimental cheeses were manufactured with Lb. plantarum TF711 added at 1% as adjunct to commercial starter culture. Cheeses made under the same conditions but without Lb. plantarum TF711 served as controls. Evolution of microbiological parameters, pH and NaCl content, as well as bacteriocin production was studied throughout 45 d of ripening. Addition of Lb. plantarum TF711 did not bring about any significant change in starter culture counts, NaCl content and pH, compared with control cheese. In contrast, clostridial spore count in experimental cheeses were significantly lower than in control cheeses from 7 d onwards, reaching a maximum reduction of 2·2 log units on day 21. Inhibition of clostridia found in experimental cheeses was mainly attributed to plantaricin activity, which in fact was recovered from these cheeses.