In vitro assessment of antimicrobial activity of carvacrol, thymol and cinnamaldehyde towards Salmonella serotype Typhimurium DT104: effects of pig diets and emulsification in hydrocolloids

Effects of dietary supplementation by modified palygorskite and essential oil/palygorskite complex on growth performance and intestinal flora composition of broilers with diarrhea

With the development trend of the industry, it can be seen that the substitution of antibiotics and reduction of zinc oxiden is still the hot spot of the industry. Diarrhea and inflammation occur frequently during livestock and poultry production, which is difficult to control. This experiment aimed to explore the effects and mechanisms of dietary supplementation of modified palygorskite (Mpal) and essential oil/ palygorskite composite (EO-PGS) on disease resistance and intestinal inflammatory damage in diarrhea broiler. In this experiment, there were a total of 420 broilers of 10-day-old selected and divided into 7 groups (n = 60), which were the nondiarrhea group fed with basal diet (normal control, NC), the diarrhea group fed with basal diet (diarrhea control, DC), and the rest were the diarrhea test group (diarrhea), supplemented with 1 kg/t, 2 kg/t and 4 kg/t of essential oils/ palygorskite complex (EO-PGS 1kg/T, EO-PGS 2kg/T, EO-PGS 4kg/T) in the basal diet, respectively, and 2 kg/t, 4 kg/t modified palygorskite group (Mpal 2kg/T, Mpal 4kg/T) in the basal diets, respectively. The experiment lasted for 8 d. The results showed that compared to normal broilers, the diarrhea index of diarrhea broilers remained around 2.0 with persistent mild diarrhea during the test period. The duodenal epithelial cells were damaged and shed, goblet cells increased, inflammatory cells infiltrated, diffuse congestion and hemorrhage in lamina propria, the serum lipopolysaccharides (LPS) content, and malondialdehyde (MDA) content increased significantly (P < 0.05). The serum superoxide dismutase (SOD) activity and immunoglobulin-M (IgM) levels significantly decreased, while serum immunoglobulin-G (IgG) and complement 3 (C3) levels significantly increased (P < 0.05). The expression of inflammatory cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and nuclear factor κB (NF-κB) in duodenal epithelial cells was significantly upregulated on d 5 (P < 0.05). The abundance of Bacteroides in the duodenum of diarrhea broilers was significantly decreased, while the abundance of Proteobacteria was significantly increased (P < 0.05). Feeding diets supplemented with EO-PSG and 4 kg/t Mpal increased the average weight of diarrhea broilers (P < 0.05), reduced diarrhea index, improved immunity by increasing serum IgG, IgM, C3 and complement 4 (C4) levels (P < 0.05), enhanced the activity of serum antioxidant enzyme glutathione peroxidase (GSH-PX) and SOD activity, reduced serum MDA content, serum LPS levels, and decreased the expression of proinflammatory factors in the duodenal epithelial cell on d 5 (P < 0.05), alleviated duodenal epithelial cell injury, hemorrhage, inflammation infiltration and intestinal injury of diarrhea broilers from d 5 to d 8. Meanwhile, supplemented with EO-PSG and Mpal in diets regulated the intestinal microbiota, significantly increased the abundance of Bacteroidetes and decreased the abundance of Proteobacteria at the phylum level (P < 0.05). Microbial richness and diversity of microbiota were significantly increased by feeding the diet supplemented with 2 kg/t EO-PGS. In the beta diversity of the intestinal flora of the diets supplemented with 4 kg/t Mpal and 2 kg/t EO-PGS, the microbial community composition could be relatively easily distinguished with NC and DC groups. As a result of LEfSe analysis, the diets supplemented with 2 kg/t EO-PGS f_Clostridiaceae and g_Coprococcus were enriched in the caecum of diarrhea broilers, and the diets supplemented with 4 kg/t Mpal o_Bacteroidales, f_Rikenllaceae and g_Peptococcus were enriched in caecum of diarrhea broilers, between normal and diarrhea broilers (P<0.05). In conclusion, dietary supplementation with EO-PGS and Mpal could improve disease resistance and alleviate intestinal inflammatory damage in diarrhea broilers, but the effect of 2 kg/t Mpal was not significant. It was recommended that 2 kg/t EO-PGS or 4 kg/t Mpal be added to the broilers' diet according to the degree of diarrhea, and continuous feeding for more than 5 d.

Validating the use of a newly developed cinnamaldehyde product in commercial broiler production

Essential oils (EOs) have been considered as an alternative to antibiotics for animal production. In the current study, 4 trials were conducted on a commercial broiler farm to investigate the effects of dietary supplementation of an encapsulated cinnamon EO product (NE-OFF) on the bird growth performance, gut health, and gene expression in the ileum, spleen, and liver relating to the host response to heat and other stresses, including potential NE challenge. In each trial, approximately 30,000 Cobb or Ross broilers were randomly allocated to 4 treatments: a raised without antibiotics (RWA) commercial diet as positive control, an adjusted RWA commercial diet as negative control, and the negative control diet supplemented with 2 different dosages of NE-OFF, which was added during feed pelleting. Although the final average body weight did not differ significantly among treatment groups, birds fed NE-OFF had an increased ratio of villus height and crypt depth in the jejunum, and reduced fecal oocyst counts. Trial 2 was conducted in the summer and had a necrotic enteritis (NE) outbreak. The supplementation of NE-OFF reduced the NE incidence and bird mortality. The samples from Trial 2 were hence selected for the analyses of Clostridium perfringens and NetB toxin gene abundance in the ileum, and host responses. The C. perfringens population appeared to be positively correlated with the NetB gene abundance. The gene expression analysis suggested that NE-OFF supplementation improved nutrient absorption and transportation as well as antioxidant activities to help the birds against stress. These on-farm trial results support the hypothesis that the use of NE-OFF as a feed additive can improve bird gut health and performance in commercial broiler production, especially for preventing NE outbreaks when birds are under stress.

An Encapsulated Organic Acid and Essential Oil Mixture Improves the Intestinal Health of Weaned Piglets by Altering Intestinal Inflammation and Antioxidative Capacity

This study investigates the effects of an encapsulated organic acid and essential oil mixture (OAEO) on the growth performance, immuno-antioxidant capacity and intestinal health of weaned piglets. In total, 120 weaned piglets (23 days of age; 6.96 ± 0.08 kg) were randomly allotted to four treatments (six replicates/group; five piglets/replicate): the control group (CON) was fed the basal diet (BD), the antibiotic growth promoters group (AGP) received the BD with 20 mg/kg colistin sulphate and 10 mg/kg bacitracin zinc, and OAEO1 and OAEO2 were fed the BD with 1000 mg/kg and 2000 mg/kg OAEO, respectively. The trial lasted 21 days and then one piglet per replicate was selected for sample collection. OAEO increased the average daily gain, spleen index, serum interleukin (IL)-10, immunoglobulin (Ig) G and IgA levels; serum superoxide dismutase and glutathione peroxidase (GPX) activities; and jejunal villus height (VH), VH/crypt depth, goblet cell number, and amylase and trypsin activities (p < 0.05) compared with CON but reduced the diarrhea rate, serum tumor necrosis factor (TNF)-α, malondialdehyde (MDA), and D-lactic acid contents and diamine oxidase (DAO) activity (p < 0.05). OAEO also increased the jejunal zonula occludens-1, occludin, claudin-1, mucin-2, nuclear factor erythroid 2-related factor 2 (Nrf2), GPX and IL-10 mRNA levels, GPX activity and IL-10 content (p < 0.05) compared with CON but reduced jejunal MDA, IL-1β and TNF-α contents and Toll-like receptor (TLR) 4, nuclear factor (NF)-κB and TNF-α mRNA levels (p < 0.05). In addition, AGP increased ADG, serum IgA level and GPX activity, jejunal trypsin activity and IL-10 content and mRNA level (p < 0.05) compared with CON but reduced the serum TNF-α content and DAO activity and jejunal NF-κB mRNA level (p < 0.05). Overall, OAEO as an alternative to AGP improved the growth performance, immuno-antioxidant status and gut health of weaned piglets partly via activating the Nrf2 signaling pathway and suppressing the TLR4/NF-κB signaling pathway.

Development of Geraniol-Loaded Liposomal Nanoformulations against Salmonella Colonization in the Pig Gut

Salmonella is a global health threat, with pig production being one of the main sources of human salmonellosis. The current study investigated the antivirulence properties of geraniol for inhibiting the in vitro colonization of Salmonella. The minimum inhibitory (MIC) and bactericidal concentrations (MBC) of geraniol against Salmonella typhimurium followed by the sub-MIC of geraniol were determined. Results provided clear evidence that geraniol at 1/8 MIC can be used as an effective, non-toxic antivirulence compound to inhibit virulence factors (motility, adhesion, and invasiveness) affecting the colonization of S. typhimurium on IPEC-J2 cells. Additionally, the findings signified that microfluidics is an emerging technology suitable for the preparation of stable liposomes with a small size (<200 nm) and high encapsulation efficiency (EE) of up to 92.53%, which can act as effective carriers of geraniol into the pig gastrointestinal tract (GIT), targeting Salmonella, preventing colonization, and thus increasing the safety of the food supply chain.

Synergistic Interaction Between Paired Combinations of Natural Antimicrobials Against Poultry-Borne Pathogens

Natural antimicrobials (NAM) are promising candidates for the successful control of poultry-borne bacteria, carrying potent antimicrobial activity (AMA) against a wide range of multidrug-resistant pathogens. Individual activities of carvacrol, eugenol, trans-cinnamaldehyde, oregano, and thymol, along with the combined activity of paired compounds, were examined using broth microdilution and checkerboard techniques. The characteristic interactions between the compounds were calculated using an improved method, based on combination index (CI) values. The bacteria examined herein were selected due to their known genetic resistance to at least one antibiotic. Our results indicated that thymol was most effective, exhibiting the lowest minimum inhibitory concentration (MIC) value against Salmonella pullorum, Escherichia coli, and Klebsiella pneumoniae, establishing the order of antimicrobial efficacy as: thymol > oregano > carvacrol > trans-cinnamaldehyde > eugenol. In the interaction study, the paired combination of carvacrol and thymol showed synergistic effects and was highly effective in reducing the antibiotic resistance of all the evaluated pathogens. Notably, all CI values were <1.0 in evaluations of S. pullorum, indicating the absence of antagonism between eugenol and thymol (or oregano). In K. pneumoniae, majority of CI values, which had a few concentration points, were smaller than 1.0, indicating a synergistic effect between eugenol and carvacrol (oregano or thymol), and trans-cinnamaldehyde and carvacrol. In E. coli, apart from some concentration points, some CI values were smaller than 1.0, demonstrating a synergistic effect between eugenol and carvacrol, and thymol and carvacrol (eugenol or oregano). It is therefore of great significance to investigate and illuminate the minimal effect concentration of these five components when they are used in combination as feed additives. Moreover, the improved evaluation method of this study provides a precise and extensive means to assess the synergistic effects of NAM.

In vitro stability and ex vivo absorption of thymol monoglucosides in the porcine gut

Thymol α-D-glucopyranoside (TαG) and thymol β-D-glucopyranoside (TβG) are believed to have different kinetic behaviours in the porcine gut than its parent aglycon thymol. However, recently, it was shown that concentrations of both glucosides decreased rapidly in the stomach and proximal small intestine following oral supplementation to piglets as did thymol. Yet, the stability of thymol glucosides in gut contents and their absorption route remains obscure. Therefore, a series of in vitro incubations were performed, simulating the impact of pH, digestive enzymes, bacterial activity and mucosal extracts on stability of these glucosides. Their absorption mechanisms were investigated using the Ussing chamber model in the presence or the absence of inhibitors of sodium-dependent glucose linked transporter 1 and lactase phlorizin hydrolase. Both glucosides remained intact at physiological pH levels in the presence of digestive enzymes. Recoveries from TαG and TβG were below 90% when incubated with small intestinal homogenates from the distal jejunum or from all sampled sites, respectively. However, no aglycon could be detected in these samples. Bacterial inoculum of the small intestine, on the other hand, hydrolysed TβG quickly with up to 44% of free aglycon appearing. TαG proved more resistant to porcine gastro-intestinal bacterial glucosidases with only trace amounts (<1%) of free thymol at the end of the incubations. Electrophysiological measurements in Ussing chambers did not suggest active transport of the glucosides. Mucosal TαG and TβG concentrations were unchanged between start and end of the absorption measurements. Additionally, no TαG and only a very limited amount of TβG were retrieved from the serosal side. Tissue associated concentrations, although marginal (<1% of luminal concentration), were mainly as intact glucoside or as aglycon for TαG and TβG, respectively. Addition of both inhibitors significantly increased the amount of intact glucosides retrieved from the mucosal tissues as compared to controls. In conclusion, bacterial hydrolysis was identified as the most important source of TβG loss, whereas TαG seemed less prone to degradation or absorption in these in vitro and ex vivo models.

Free and Microencapsulated Essential Oils Incubated In Vitro: Ruminal Stability and Fermentation Parameters

Essential oils (EOs) are generally considered as an alternative to antibiotics because of their antimicrobial properties. Despite their vast variety, their volatile nature poses hindrance on their use in animal feeds, which demands a high degree of stability. This study aimed at testing the susceptibility of three EOs (mixtures of EOs based on cinnamaldehyde, named Olistat-Cyn, Olistat-G, and Olistat-P) in two forms (free: fEOs; and microencapsulated: mEOs) to in vitro ruminal degradation using the Ankom DaisyII technique. The microencapsulation was made using a matrix based on vegetable hydrogenated fatty acids. Compared to the fEOs, which were completely degraded within 48 h of in vitro incubation, the mEOs showed a low ruminal disappearance. In comparison to the fermentation profile at 0 h, Olistat-G significantly decreased the pH and the total protozoa number after 48 h, while the total VFAs increased. However, the other EOs (Olistat-Cyn and Olistat-P) had no effect on the rumen fermentation parameters. In conclusion, the protection of EOs from ruminal degradation by microencapsulation was found to be very effective to ensure rumen by-pass. Among the EOs, Olistat-G was capable of changing rumen fermentation, potentially reducing methane emissions.

Effects of a microencapsulated formula of organic acids and essential oils on nutrient absorption, immunity, gut barrier function, and abundance of enterotoxigenic Escherichia coli F4 in weaned piglets challenged with E. coli F4

The objective was to study the effects of microencapsulated organic acids (OA) and essential oils (EO) on growth performance, immune system, gut barrier function, nutrient digestion and absorption, and abundance of enterotoxigenic Escherichia coli F4 (ETEC F4) in the weaned piglets challenged with ETEC F4. Twenty-four ETEC F4 susceptible weaned piglets were randomly distributed to 4 treatments including (1) sham-challenged control (SSC; piglets fed a control diet and challenged with phosphate-buffered saline (PBS)); (2) challenged control (CC; piglets fed a control diet and challenged with ETEC F4); (3) antibiotic growth promoters (AGP; CC + 55 mg·kg-1 of Aureomycin); and (4) microencapsulated OA and EO [P(OA+EO); (CC + 2 g·kg-1 of microencapsulated OA and EO]. The ETEC F4 infection significantly induced diarrhea at 8, 28, 34, and 40 hr postinoculation (hpi) (P < 0.05) in the CC piglets. At 28 d postinoculation (dpi), piglets fed P(OA+EO) had a lower (P < 0.05) diarrhea score compared with those fed CC, but the P(OA+EO) piglets had a lower (P < 0.05) diarrhea score compared with those fed the AGP diets at 40 dpi. The ETEC F4 infection tended to increase in vivo gut permeability measured by the oral gavaging fluorescein isothiocyanate-dextran 70 kDa (FITC-D70) assay in the CC piglets compared with the SCC piglets (P = 0.09). The AGP piglets had higher FITC-D70 flux than P(OA+EO) piglets (P < 0.05). The ETEC F4 infection decreased mid-jejunal VH in the CC piglets compared with the SCC piglets (P < 0.05). The P(OA+EO) piglets had higher (P < 0.05) VH in the mid-jejunum than the CC piglets. The relative mRNA abundance of Na+-glucose cotransporter and B0AT1 was reduced (P < 0.05) by ETEC F4 inoculation when compared with the SCC piglets. The AGP piglets had a greater relative mRNA abundance of B0AT1 than the CC piglets (P < 0.05). The ETEC F4 inoculation increased the protein abundance of OCLN (P < 0.05), and the AGP piglets had the lowest relative protein abundance of OCLN among the challenged groups (P < 0.05). The supplementation of microencapsulated OA and EO enhanced intestinal morphology and showed anti-diarrhea effects in weaned piglets challenged with ETEC F4. Even if more future studies can be required for further validation, this study brings evidence that microencapsulated OA and EO combination can be useful within the tools to be implemented in strategies for alternatives to antibiotics in swine production.

Fate of Thymol and Its Monoglucosides in the Gastrointestinal Tract of Piglets

The monoterpene thymol has been proposed as a valuable alternative to in-feed antibiotics in animal production. However, the effectiveness of the antimicrobial is comprised by its fast absorption in the upper gastrointestinal tract. In this work, two glucoconjugates, thymol α-d-glucopyranoside (TαG) and thymol β-d-glucopyranoside (TβG), were compared with free thymol for their potential to deliver higher concentrations of the active compound to the distal small intestine of supplemented piglets. Additionally, an analytical method was developed and validated for the simultaneous quantification of thymol and its glucoconjugates in different matrices. In stomach contents of pigs fed with 3333 μmol kg^-1 thymol, TαG, or TβG, total thymol concentrations amounted to 3048, 2357, and 1820 μmol kg^-1 dry matter, respectively. In glucoconjugate-fed pigs, over 30% of this concentration was present in the unconjugated form, suggesting partial hydrolysis in the stomach. No quantifiable levels of thymol or glucoconjugates were detected in the small intestine or cecum for any treatment, indicating that conjugation with one glucose unit did not sufficiently protect thymol from early absorption.

Effects of Thymol and Thymol α-D-Glucopyranoside on Intestinal Function and Microbiota of Weaned Pigs

The present study evaluated gluco-conjugation as a measure to delay thymol absorption and enhance its antimicrobial activity in the gut of weaned piglets. The three dietary treatments consisted of a basal diet without additives (TCON), supplemented with thymol at 3.7 mmol/kg dry matter (TTHY), or with an equimolar amount of thymol α-D-glucopyranoside (TTαG). Each dietary treatment was replicated in 6 pens with 2 piglets per pen (n = 12 for analytical parameters) and was supplemented for 14 days. The total (free plus gluco-conjugated) thymol concentrations in the stomach contents were 14% lower in TTαG as compared to TTHY piglets. Neither of the additives could be detected further down the gut. E.coli counts in the proximal small intestine were significantly lower in TTHY than in TTαG pigs (3.35 vs. 4.29 log10 CFU/g); however, other bacterial counts and their metabolites were unaffected by treatment. A metagenomic bacterial analysis revealed a great relative abundance of Lactobacillus spp. in the distal small intestine (range 88.4%-99.9%), irrespective of treatment. The intestinal barrier function was improved by TTHY, but not TTαG, compared to TCON. In conclusion, gluco-conjugation did not result in higher thymol concentrations in the gut, but conversely, it seemed to diminish the biological effects of thymol in vivo.

Evaluation of lipid matrix microencapsulation for intestinal delivery of thymol in weaned pigs

Essential oils (EO) are defined as plant-derived natural bioactive compounds, which can have positive effects on animal growth and health due to their antimicrobial and antioxidative properties. However, EO are volatile, can evaporate quickly, and be rapidly absorbed in the upper gastrointestinal tract. Also, due to their labile nature, the stability of EO during feed processing is often questionable, leading to variations in the final concentration in feed. Encapsulation has become one of the most popular methods of stabilizing EO during feed processing, storage, and delivery into the lower gut. The objectives of the present study were to 1) evaluate the stability of thymol microencapsulated in combination with organic acids in commercially available lipid matrix microparticles during the feed pelleting process and storage; 2) validate and demonstrate the slow release of thymol from the lipid matrix microparticles in a simulated pig gastric fluid (SGF) and a simulated pig intestinal fluid (SIF); and 3) evaluate in vivo release of thymol from the lipid matrix microparticles along the pig gut. The results showed that thymol concentration was not significantly different in the mash and pelleted feeds (P > 0.05). In the in vitro study, 26.04% thymol was released in SGF, and the rest of the thymol was progressively released in SIF until completion, which was achieved by 24 h. The in vivo study showed that 15.5% of thymol was released in the stomach, and 41.85% of thymol was delivered in the mid-jejunum section. Only 2.21% of thymol was recovered in feces. In conclusion, the lipid matrix microparticles were able to maintain the stability of thymol during a feed pelleting process and storage and allow a slow and progressive intestinal release of thymol in weaned pigs.

Phytochemical Profile and Antimicrobial Potential of Extracts Obtained from Thymus marschallianus Willd

Thymus marschallianus Willd. is a Lamiaceae species spread in a large variety of habitats worldwide. The aim of the present research was to analyse two different samples belonging to this species, one obtained from the spontaneous flora and one from culture. The total polyphenols, flavonoids, and phenolic acid contents were spectrophotometrically determined. Qualitative and quantitative analysis of polyphenols was performed by an HPLC-DAD-ESI (+)-MS method. For the antibacterial assay, the well-diffusion and the broth microdilution methods were used. Analysis of polyphenols revealed for both samples the presence of flavonoids like luteolin, quercetin, apigenin and their derivatives, but also of rosmarinic acid and methyl-rosmarinate. Differences regarding the amount of these compounds were emphasized. Significantly larger amounts of flavonoids were found for the sample harvested in the spontaneous flora, while for the rosmarinic acid, larger amounts were found for the cultured sample. Both samples displayed promising antibacterial activity, particularly towards Gram positive organisms. T. marschallianus represents, therefore, a rich source of polyphenolic compounds that prove its promising potential as a medicinal species.

Effects of different levels of dietary protein with or without plant extract YGF251 on growth performance, nutrient digestibility, blood profiles, fecal microbial shedding, and fecal gas emission in growing pigs

This experiment was conducted to evaluate the effects of plant extract YGF251 supplementation in different protein level diets on growth performance, nutrient digestibility, blood profiles, fecal microbial shedding, and fecal gas emission in growing pigs. A total of 144 pigs (24.72 ± 1.54 kg) were randomly assigned to the treatments in a 2 × 3 factorial arrangement of dietary protein levels (15.50%, 14.00% or 12.50%) and plant extract YGF251 levels (0 or 0.05%) with 6 replications per treatment and 4 pigs per pen. Pigs fed low protein diets had reduced average daily gain (p < 0.05) and increased feed conversion ratio (p < 0.01) compared with pigs fed high protein diets. The apparent total tract digestibility of nitrogen was decreased (p < 0.05) when reducing dietary protein level. Fecal ammonia and hydrogen sulfide emissions were reduced (p < 0.05) when reducing dietary protein level. In conclusion, the results of the current study indicated that reducing dietary protein level impaired growth performance and nitrogen digestibility but reduced ammonia and hydrogen sulfide emissions in growing pigs. Dietary supplementation with 0.05% herbal extract YGF251 was not effective in improving growth performance, nutrient digestibility, or in decreasing gas emission in different protein diets.

Development of Novel Microparticles for Effective Delivery of Thymol and Lauric Acid to Pig Intestinal Tract

Antibiotics have been widely supplemented in feeds at subtherapeutic concentrations to prevent postweaning diarrhea and increase the overall productivity of pigs. However, the emergence of antimicrobial-resistant bacteria worldwide has made it urgent to minimize the use of in-feed antibiotics. The development of promising alternatives to in-feed antibiotics is crucial for maintaining the sustainability of swine production. Both medium-chain fatty acids (MCFA) and essential oils exhibit great potential to postweaning diarrhea; however, their direct inclusion has compromised efficacy because of several factors including low stability, poor palatability, and low availability in the lower gut. Therefore, the objective of this study was to develop a formulation of microparticles to deliver a model of essential oil (thymol) and MCFA (lauric acid). The composite microparticles were produced by the incorporation of starch and alginate through a melt-granulation process. The release of thymol and lauric acid from the microparticles was in vitro determined using simulated salivary fluid (SSF), simulated gastric fluid (SGF), and simulated intestinal fluid (SIF), consecutively. The microparticles prepared with 2% alginate solution displayed a slow release of thymol and lauric acid in the SSF (21.2 ± 2.3%; 36 ± 1.1%), SGF (73.7 ± 6.9%; 54.8 ± 1.7%), and SIF (99.1 ± 1.2%; 99.1 ± 0.6%), respectively, whereas, the microparticles without alginate showed a rapid release of thymol and lauric acid from the SSF (79.9 ± 11.8%; 84.9 ± 9.4%), SGF (92.5 ± 3.5%; 75.8 ± 5.9%), and SIF (93.3 ± 9.4%; 93.3 ± 4.6%), respectively. The thymol and lauric acid in the developed microparticles with or without alginate both exhibited excellent stabilities (>90%) during being stored at 4 °C for 12 weeks and after being stored at room temperature for 2 weeks. These results evidenced that the approach developed in the present study could be potentially employed to deliver thymol and lauric acid to the lower gut of pigs, although further in vivo investigations are necessary to validate the efficacy of the microparticles.

Essential oils as alternatives to antibiotics in swine production

This review article summarizes the efficacy, feasibility and potential mechanisms of the application of essential oils as antibiotic alternatives in swine production. Although there are numerous studies demonstrating that essential oils have several properties, such as antimicrobial, antioxidative and anti-inflammatory effects, feed palatability enhancement and improvement in gut growth and health, there is still a need of further investigations to elucidate the mechanisms underlying their functions. In the past, the results has been inconsistent in both laboratory and field studies because of the varied product compositions, dosages, purities and growing stages and conditions of animals. The minimal inhibitory concentration (MIC) of essential oils needed for killing enteric pathogens may not ensure the optimal feed intake and the essential oils inclusion cost may be too high in swine production. With the lipophilic and volatile nature of essential oils, there is a challenge in effective delivery of essential oils within pig gut and this challenge can partially be resolved by microencapsulation and nanotechnology. The effects of essential oils on inflammation, oxidative stress, microbiome, gut chemosensing and bacterial quorum sensing (QS) have led to better production performance of animals fed essential oils in a number of studies. It has been demonstrated that essential oils have good potential as antibiotic alternatives in feeds for swine production. The combination of different essential oils and other compounds (synergistic effect) such as organic acids seems to be a promising approach to improve the efficacy and safety of essential oils in applications. High-throughput systems technologies have been developed recently, which will allow us to dissect the mechanisms underlying the functions of essential oils and facilitate the use of essential oils in swine production.

Effects of complex probiotic supplementation in growing pig diets with and without palm kernel expellers on growth performance, nutrient digestibility, blood parameters, fecal microbial shedding and noxious gas emission

In Experiment 1, a total of 100 growing pigs (Duroc × [Landrace × Yorkshire]) with an average initial body weight (BW) of 24.88 ± 1.57 kg were randomly allotted to 2 × 2 factorial arrangement with two concentrations of palm kernel expellers (PKE) in diets at 0% or 10%, and two concentrations of supplemental probiotics at 0 or 6.0 × 10⁷  colony-forming units/kg. There were five replicate pens per treatment with five pigs per pen. In Experiment 2, eight barrows with average initial BW of 25.78 ± 0.19 kg were allotted to a replicated 4 × 4 Latin square design with four diets and four periods per square. Four experimental diets were the same as Experiment 1. In Experiment 1, dietary probiotic supplementation improved (P < 0.05) the average daily gain (ADG), nutrient digestibility and the fecal Lactobacillus counts. Furthermore, interactive effects (P < 0.05) between PKE and probiotics were observed on ADG and growth-to-feed ratio. In Experiment 2, an interactive effect (P < 0.05) of PKE and probiotics was observed in apparent ileal digestibility of nitrogen and some amino acids. In conclusion, dietary probiotics did not improve PKE utilization and the use of probiotics in non-PKE-containing diet was more favorable than in PKE-containing diet.

Chemistry, Antimicrobial Mechanisms, and Antibiotic Activities of Cinnamaldehyde against Pathogenic Bacteria in Animal Feeds and Human Foods

Cinnamaldehyde is a major constituent of cinnamon essential oils produced by aromatic cinnamon plants. This compound has been reported to exhibit antimicrobial properties in vitro in laboratory media and in animal feeds and human foods contaminated with disease-causing bacteria including Bacillus cereus, Campylobacter jejuni, Clostridium perfringens, Escherichia coli, Listeria monocytogenes, and Salmonella enterica. This integrated review surveys and interprets our current knowledge of the chemistry, analysis, safety, mechanism of action, and antibiotic activities of cinnamaldehyde in food animal (cattle, lambs, calves, pigs, poultry) diets and in widely consumed liquid (apple, carrot, tomato, and watermelon juices, milk) and solid foods. Solid foods include various fruits (bayberries, blueberries, raspberries, and strawberries), vegetables (carrots, celery, lettuce, spinach, cucumbers, and tomatoes), meats (beef, ham, pork, and frankfurters), poultry (chickens and turkeys), seafood (oysters and shrimp), bread, cheese, eggs, infant formula, and peanut paste. The described findings are not only of fundamental interest but also have practical implications for food safety, nutrition, and animal and human health. The collated information and suggested research needs will hopefully facilitate and guide further studies needed to optimize the use of cinnamaldehyde alone and in combination with other natural antimicrobials and medicinal antibiotics to help prevent and treat food animal and human diseases.

A review on influencing factors on the minimum inhibitory concentration of essential oils

With growing interest in essential oils as natural preservatives in the food industry, the literature is expanding enormously. To understand the antimicrobial activity of essential oils, the antimicrobial mechanism of individual essential oil (EO) compounds, and their minimum inhibitory concentrations (MICs), are interesting starting points for research. Therefore, and to get insight into the factors influencing their antimicrobial activities, the Web of Science was searched for MICs of EO compounds (1995-2016). Many MICs for individual EO compounds have already been reported in the literature, but there is large variability in these data, even for the MIC of the same compound against the same species. No correlation was found between the tested structural parameters of EO compounds (polarity, water solubility, dissociation constant, molecular weight and molecular complexity) and their MICs against all microorganisms, Gram-negative bacteria, Gram-positive bacteria and fungi. Few clear differences in sensitivity between microorganisms could be found. Based on this review it is clear that different incubation conditions, culture media and the use of emulsifiers/solvents have an influence on the MIC, causing big variance. This review points out the need for a good international standard method to assess the antimicrobial activity of EO compounds for better comparability between studies.

Trans-Cinnamaldehyde, Carvacrol, and Eugenol Reduce Campylobacter jejuni Colonization Factors and Expression of Virulence Genes in Vitro

Campylobacter jejuni is a major foodborne pathogen that causes severe gastroenteritis in humans characterized by fever, diarrhea, and abdominal cramps. In the human gut, Campylobacter adheres and invades the intestinal epithelium followed by cytolethal distending toxin mediated cell death, and enteritis. Reducing the attachment and invasion of Campylobacter to intestinal epithelium and expression of its virulence factors such as motility and cytolethal distending toxin (CDT) production could potentially reduce infection in humans. This study investigated the efficacy of sub-inhibitory concentrations (SICs, concentration not inhibiting bacterial growth) of three GRAS (generally recognized as safe) status phytochemicals namely trans-cinnamaldehyde (TC; 0.005, 0.01%), carvacrol (CR; 0.001, 0.002%), and eugenol (EG; 0.005, 0.01%) in reducing the attachment, invasion, and translocation of C. jejuni on human intestinal epithelial cells (Caco-2). Additionally, the effect of these phytochemicals on Campylobacter motility and CDT production was studied using standard bioassays and gene expression analysis. All experiments had duplicate samples and were replicated three times on three strains (wild type S-8, NCTC 11168, 81-176) of C. jejuni. Data were analyzed using ANOVA with GraphPad ver. 6. Differences between the means were considered significantly different at P < 0.05. The majority of phytochemical treatments reduced C. jejuni adhesion, invasion, and translocation of Caco-2 cells (P < 0.05). In addition, the phytochemicals reduced pathogen motility and production of CDT in S-8 and NCTC 11168 (P < 0.05). Real-time quantitative PCR revealed that phytochemicals reduced the transcription of select C. jejuni genes critical for infection in humans (P < 0.05). Results suggest that TC, CR, and EG could potentially be used to control C. jejuni infection in humans.

Protective Effect of Carvacrol against Gut Dysbiosis and Clostridium difficile Associated Disease in a Mouse Model

This study investigated the effect of carvacrol (CR), a phytophenolic compound on antibiotic-associated gut dysbiosis and C. difficile infection in a mouse model. Five to six-week-old C57BL/6 mice were randomly divided into seven treatment groups (challenge and control) of eight mice each. Mice were fed with irradiated feed supplemented with CR (0, 0.05, and 0.1%); the challenge groups were made susceptible to C. difficile by orally administering an antibiotic cocktail in water and an intra-peritoneal injection of clindamycin. Both challenge and control groups were infected with 10⁵CFU/ml of hypervirulent C. difficile (ATCC 1870) spores or PBS, and observed for clinical signs for 10 days. Respective control groups for CR, antibiotics, and their combination were included for investigating their effect on mouse enteric microflora. Mouse body weight and clinical and diarrhea scores were recorded daily post infection. Fecal samples were collected for microbiome analysis using rRNA sequencing in MiSeq platform. Carvacrol supplementation significantly reduced the incidence of diarrhea and improved the clinical and diarrhea scores in mice (p < 0.05). Microbiome analysis revealed a significant increase in Proteobacteria and reduction in the abundance of protective bacterial flora in antibiotic-treated and C. difficile-infected mice compared to controls (p < 0.05). However, CR supplementation positively altered the microbiome composition, as revealed by an increased abundance of beneficial bacteria, including Firmicutes, and significantly reduced the proportion of detrimental flora such as Proteobacteria, without significantly affecting the gut microbiome diversity compared to control. Results suggest that CR could potentially be used to control gut dysbiosis and reduce C. difficile infection.

Development of gold nanoparticles coated with silica containing the antibiofilm drug cinnamaldehyde and their effects on pathogenic bacteria

Emerging resistance to antibiotics is a mounting worldwide health concern and increases the need for nonantibiotic strategies to combat infectious diseases caused by bacterial pathogens. In this study, the authors used the antibiofilm activity of the naturally occurring antimicrobial cinnamaldehyde (CNMA) conjugated to the surface of gold nanoparticles (GNPs) to deliver CNMA efficiently and eradicate biofilms of Gram-negative organisms (enterohemorrhagic Escherichia coli O157:H7, and Pseudomonas aeruginosa), Gram positive (methicillin-sensitive Staphylococcus aureus organisms, and methicillin-resistant Staphylococcus aureus) bacteria. CNMA-GNPs containing 0.005% (v/v) of CNMA were found to inhibit biofilm formation efficiently. The distributions of nanoparticles in biofilm cells and their biofilm disruption activities, including distorted cell morphology, were determined by transmission electron microscopy. In addition to their antibiofilm activities, CNMA-GNPs attenuated S. aureus virulence and protected Caenorhabditis elegans (C. elegans) worms. Here, the authors report the antibiofilm effects of CNMA-GNPs and suggest that they could be used to treat pathogenic bacterial infections in vivo.

Effects of essential oil (blended and single essential oils) on anti-biofilm formation of Salmonella and Escherichia coli

Background

Biofilms were the third-dimensional structure in the solid surface of bacteria. Bacterial biofilms were difficult to control by host defenses and antibiotic therapies. Escherichia coli (E. coli) and Salmonella were popular pathogenic bacteria that live in human and animal intestines. Essential oils are aromatic oily liquids from plant materials and well known for their antibacterial activities.

Method

This study was conducted to determine effect of essential oil on anti-biological biofilm formation of E. coli and Salmonella strains in in vitro experiment. Two kinds of bacterial strains were separated from 0.2 g pig feces. Bacterial strains were distributed in 24 plates per treatment and each plates as a replication. The sample was coated with a Bacterial biofilm formation was.

Result

Photographic result, Escherichia coli (E. coli) and Salmonella bacteria colony surface were thick smooth surface in control. However, colony surface in blended and single essential oil treatment has shown crack surface layer compared with colony surfaces in control.

Conclusion

In conclusion, this study could confirm that essential oils have some interesting effect on anti-biofilm formation of E. coli and Salmonella strains from pig feces.

Subinhibitory concentrations of phloretin repress the virulence of Salmonella typhimurium and protect against Salmonella typhimurium infection

Phloretin, a natural component of many fruits, exhibits anti-virulence effects and provides a new alternative to counter bacterial infection. The aim of this study was to determine the effect of subinhibitory concentrations of phloretin on the virulence of Salmonella typhimurium. At concentrations where growth of Salmonella was not inhibited, phloretin significantly inhibited bacteria biofilm formation and motility. Subinhibitory concentrations of phloretin repressed eight genes involved in the Salmonella pathogenicity island 1 and 3 genes involved in flagella production. Furthermore, subinhibitory concentrations of phloretin inhibited the adhesion and invasion of Salmonella in IEC-6 cells and reduced the LDH levels of S. typhimurium-infected IEC-6 cells. Additionally, phloretin significantly decreased the cecum bacterial loads of the mice infected with live S. typhimurium containing subinhibitory concentrations of phloretin by gavage. These results suggested that subinhibitory concentrations of phloretin attenuate the virulence of S. typhimurium and protect against S. typhimurium infection.

Functional assessment of encapsulated citral for controlling necrotic enteritis in broiler chickens

Development of viable alternatives to antibiotics to control necrotic enteritis (NE) caused by Clostridium perfringensis becoming urgent for chicken production due to pessures on poultry producers to limit or stop the use of antibiotics in feed. We have previously identified citral as a potential alternative to antibiotics. Citral has strong antimicrobial activity and can be encasupsulated in a powder form for protection from loss during feed processing, storage, and intestinal delivery. In the present study, encapsulated citral was evaluated both in vitro and in vivo for its antimicrobial activity against C. perfringens Encapsulation did not adversely affect the antimicrobial activity of citral. In addition, encapsulated citral was superior to the unencapsulated form in retaining its antimicrobial activity after treatment with simulated gastrointestinal fluids and in the presence of chicken intestinal digesta. In addition, the higher antimicrobial activity of encapsulated citral was confirmed in digesta samples from broilers that had been gavaged with encapsulated or unencapsulated citral. In broilers infected with C. perfringens, the diets supplemented with encapsualted citral at both 250 and 650 μg/g significantly reduced intestinal NE lesions, which was comparable to the effect of bacitracin- and salinomycin-containing diets. However, supplementation with the encapsulated citral appeared to have no significant impact on the intestinal burden of Lactobacillus These data indicate that citral can be used to control NE in chickens after proper protection by encapsulation.

Anthelmintic activity of trans-cinnamaldehyde and A- and B-type proanthocyanidins derived from cinnamon (Cinnamomum verum)

Cinnamon (Cinnamomum verum) has been shown to have anti-inflammatory and antimicrobial properties, but effects on parasitic worms of the intestine have not been investigated. Here, extracts of cinnamon bark were shown to have potent in vitro anthelmintic properties against the swine nematode Ascaris suum. Analysis of the extract revealed high concentrations of proanthocyanidins (PAC) and trans-cinnamaldehyde (CA). The PAC were subjected to thiolysis and HPLC-MS analysis which demonstrated that they were exclusively procyanidins, had a mean degree of polymerization of 5.2 and 21% of their inter-flavan-3-ol links were A-type linkages. Purification of the PAC revealed that whilst they had activity against A. suum, most of the potency of the extract derived from CA. Trichuris suis and Oesophagostomum dentatum larvae were similarly susceptible to CA. To test whether CA could reduce A. suum infection in pigs in vivo, CA was administered daily in the diet or as a targeted, encapsulated dose. However, infection was not significantly reduced. It is proposed that the rapid absorption or metabolism of CA in vivo may prevent it from being present in sufficient concentrations in situ to exert efficacy. Therefore, further work should focus on whether formulation of CA can enhance its activity against internal parasites.

Phytogenic compounds as alternatives to in-feed antibiotics: potentials and challenges in application

This article summarizes current experimental knowledge on the efficacy, possible mechanisms and feasibility in the application of phytogenic products as feed additives for food-producing animals. Phytogenic compounds comprise a wide range of plant-derived natural bioactive compounds and essential oils are a major group. Numerous studies have demonstrated that phytogenic compounds have a variety of functions, including antimicrobial/antiviral, antioxidative and anti-inflammation effects and improvement in the palatability of feed and gut development/health. However, the mechanisms underlying their functions are still largely unclear. In the past, there has been a lack of consistency in the results from both laboratory and field studies, largely due to the varied composition of products, dosages, purities and growing conditions of animals used. The minimal inhibitory concentration (MIC) of phytogenic compounds required for controlling enteric pathogens may not guarantee the best feed intake, balanced immunity of animals and cost-effectiveness in animal production. The lipophilic nature of photogenic compounds also presents a challenge in effective delivery to the animal gut and this can partially be resolved by microencapsulation and combination with other compounds (synergistic effect). Interestingly, the effects of photogenic compounds on anti-inflammation, gut chemosensing and possible disruption of bacterial quorum sensing could explain a certain number of studies with different animal species for the better production performance of animals that have received phytogenic feed additives. It is obvious that phytogenic compounds have good potential as an alternative to antibiotics in feed for food animal production and the combination of different phytogenic compounds appears to be an approach to improve the efficacy and safety of phytogenic compounds in the application. It is our expectation that the recent development of high-throughput and "omics" technologies can significantly advance the studies on the mechanisms underlying phytogenic compounds' functions and, therefore, guide the effective use of the compounds.

Comparative effect of thymol or its glucose conjugate, thymol-β-D-glucopyranoside, on Campylobacter in avian gut contents

Campylobacter jejuni is an important human food-borne pathogen that can contaminate meat and poultry during processing. Consequently, strategies are sought to reduce the carriage of C. jejuni in food animals before they arrive at the abattoir. Thymol is a natural product that reduces survivability of Campylobacter in vitro, but its rapid absorption from the proximal alimentary tract limits its bactericidal efficacy in vivo. Thymol-β-D-glucopyranoside is more resistant to absorption than free thymol, but its administration to chickens has not been reported. In the present studies, 1 mM thymol-β-D-glucopyranoside was shown to exhibit near equal anti-Campylobacter activity as 1 mM thymol when incubated anaerobically in avian crop or cecal contents in vitro, resulting in reductions of 1.10-2.32 log10 colony forming units mL(-1) in C. jejuni concentrations after 24 h incubation. In a follow-up live animal study, oral administration of thymol-β-D-glucopyranoside, but not free thymol, significantly lowered (>10-fold) recovery of Campylobacter from the crop of market-aged broilers when compared to placebo-treated controls (n = 6 broilers/treatment). Neither thymol-β-D-glucopyranoside nor thymol affected recovery of Campylobacter from cecal contents of the treated broilers. These results indicate that rapid absorption or passage of free thymol from the crop precluded its anti-Campylobacter activity at this site and throughout the entire gastrointestinal tract. Conversely, lower recovery of Campylobacter from the crop of birds treated with thymol-β-D-glucopyranoside indicates this conjugate was retained and able to be hydrolyzed to biologically active free thymol at this site as intended, yet was not sufficiently protected to allow passage of efficacious amounts of the intact glycoside to the lower gut. Nevertheless, these results warrant further research to see if higher doses or encapsulation of thymol-β-D-glucopyranoside or similar glycosides may yield an efficacious additive to reduce carriage of Campylobacter as well as other pathogens throughout the avian gut.

Holy basil (Ocimum sanctum Linn.) essential oil delivery to swine gastrointestinal tract using gelatin microcapsules coated with aluminum carboxymethyl cellulose and beeswax

Holy basil essential oil (HBEO) can be applied as a feed additive; however, its benefits depend on the available amount in the gastrointestinal tract. In this study, the physicochemical properties, including the release properties of three different microcapsules, HBEO-loaded gelatin microcapsules (UC), UC coated with aluminum carboxymethyl cellulose (CC), and UC coated with aluminum carboxymethyl cellulose-beeswax composite (CB), were compared. The encapsulation efficiency, HBEO content, and 2,2-diphenyl-2-picrylhydrazyl radical scavenging activity for the microcapsules were 95.4 ± 0.17%, 66.7-67.7%, and 94.3-96.5%, respectively. Scanning electron microscopy and confocal laser scanning microscopy (CLSM) revealed nonuniform HBEO distributions in honeycomb-like networks in the microcapsules. An X-ray diffraction analysis determined that UC and CC microcapsules were amorphous, but CB microcapsules were semicrystalline. UV-vis spectrophotometer and CLSM analyses results determined that HBEO was released from CC and CB microcapsules in greater amounts than from UC microcapsules in simulated intestinal fluid. Therefore, the HBEO amount reaching the intestine can be controlled using the optimal encapsulation system.

Effects of essential oil supplementation of a low-energy diet on performance, intestinal morphology and microflora, immune properties and antioxidant activities in weaned pigs

A total of 144 weaned piglets were used to evaluate the effects of essential oil (EO) supplementation of a low-energy diet on performance, apparent nutrient digestibility, small intestinal morphology, intestinal microflora, immune properties and antioxidant activities in weaned pigs. Pigs received a low-energy diet (negative control, NC, digestible energy = 3250 kcal/kg), NC plus 0.025% EO or a positive control diet (PC, digestible energy = 3400 kcal/kg) for 28 days. Growth performance was similar between the EO group and PC group. However, EO supplementation increased (P < 0.05) average daily gain and the apparent digestibility of dry matter, crude protein and energy compared with pigs fed the NC diet. Greater (P < 0.05) villus height and lower (P < 0.05) counts of Escherichia coli and total anaerobes in the rectum in the EO group were observed compared with NC or PC groups. Pigs fed EO diet had higher (P < 0.05) concentrations of albumin, immunoglobulin A (IgA), IgG and total antioxidant capacity and lower fecal score than pigs fed the PC and NC diets. Above all, this study indicates that supplementation of EO to a low-energy pig diet has beneficial results and obtains similar performance compared with normal energy (PC) diet.

Review: Chinese herbs as alternatives to antibiotics in feed for swine and poultry production: Potential and challenges in application

Gong, J., Yin, F., Hou, Y. and Yin, Y. 2014. Chinese herbs as alternatives to antibiotics in feed for swine and poultry production: Potential and challenges in application. Can. J. Anim. Sci. 94: 223–241. Traditional Chinese medicine (TCM) has a long history of clinical practice, and its own theoretical framework focused on functions at the whole-body level. However, due to cultural differences, TCM has not been fully recognized in Western countries. With the recent development of the theory of whole-body systems biology and “-omics”, there is a new opportunity to study TCM and to close the gap between TCM and Western medicine, because of the similarity in the theoretical foundations between TCM and whole-body systems biology. The uniqueness of TCM theory and practice is the approach to maintain and restore the body balance as a whole with no or little unfavourable side effects. Recent studies have also shown that Chinese herbs used as feed additives can modulate nutritional metabolism, immune responses, and intestinal health of food-producing animals, demonstrating good potential as substitutes for dietary antibiotics. Nonetheless, some issues need to be addressed before Chinese herbs can reach their full application. This article has critically reviewed recent progresses in scientific research of Chinese herbs as feed additives and their potential to replace dietary antibiotics. Possible challenges in future application for swine and poultry production are also discussed.

Carvacrol and trans-cinnamaldehyde reduce Clostridium difficile toxin production and cytotoxicity in vitro

Clostridium difficile is a nosocomial pathogen that causes a serious toxin-mediated enteric disease in humans. Reducing C. difficile toxin production could significantly minimize its pathogenicity and improve disease outcomes in humans. This study investigated the efficacy of two, food-grade, plant-derived compounds, namely trans-cinnamaldehyde (TC) and carvacrol (CR) in reducing C. difficile toxin production and cytotoxicity in vitro. Three hypervirulent C. difficile isolates were grown with or without the sub-inhibitory concentrations of TC or CR, and the culture supernatant and the bacterial pellet were collected for total toxin quantitation, Vero cell cytotoxicity assay and RT-qPCR analysis of toxin-encoding genes. The effect of CR and TC on a codY mutant and wild type C. difficile was also investigated. Carvacrol and TC substantially reduced C. difficile toxin production and cytotoxicity on Vero cells. The plant compounds also significantly down-regulated toxin production genes. Carvacrol and TC did not inhibit toxin production in the codY mutant of C. difficile, suggesting a potential codY-mediated anti-toxigenic mechanism of the plant compounds. The antitoxigenic concentrations of CR and TC did not inhibit the growth of beneficial gut bacteria. Our results suggest that CR and TC could potentially be used to control C. difficile, and warrant future studies in vivo.

Impacts of sample preparation methods on solubility and antilisterial characteristics of essential oil components in milk

Essential oil components (EOCs) have limited water solubility and are used at much higher concentrations in complex food matrices than in growth media to inhibit pathogens. However, the correlation between solubility and activity has not been studied. The objective of this work was to characterize the solubility of EOCs in solvents and milk and correlate solubility with antilisterial activity. The solubilities of four EOCs, thymol, carvacrol, eugenol, and trans-cinnamaldehyde, in water was significantly increased in the presence of 5% (vol/vol) ethanol. In milk, the solubility of EOCs was lower than in water, with lower solubility in higher-fat milk. EOCs applied to milk as stock solutions (in 95% aqueous ethanol) enabled quicker dissolution and higher solubility in milk serum than other methods of mixing, such as end to end, and greater reductions of Listeria monocytogenes Scott A after 0 and 24 h. When the EOC concentration detected in milk serum was above the minimum bactericidal concentration, complete inhibition of L. monocytogenes in tryptic soy broth resulted. Therefore, the antilisterial properties in milk could be correlated with the solubility by comparison to the minimum inhibitory or bactericidal concentrations of EOCs. While the EOCs applied using ethanol generally had solubility and activity characteristics superior to those of other mixing methods, ethanol is not used to a great extent in nonfermented foods. Therefore, mixing methods without an organic solvent may be more readily adaptable to enhancing the distribution of EOCs in complex food systems.

Improvement of thymol properties by complexation with cyclodextrins: in vitro and in vivo studies

Thymol, an effective agent for microbial diseases, has a low aqueous solubility and a strong bitter/irritating taste. These physicochemical characteristics need to be improved to develop pharmaceutical preparations. This study evaluates whether β-cyclodextrin and a copolymer based on dimethylaminoethyl methacrylate (DMAEMA) interact with thymol in order to control powderization, solubilization, and taste-masking properties. The thymol-β-cyclodextrin complex was prepared by co-precipitation and sealed-heating methods. The DMAEMA copolymer was mixed with the complex using a new approach, instead of spray coating, to decrease thymol volatility. In vivo studies were performed. Sealed-heating is a suitable method for including thymol in β-cyclodextrin with a good loading efficiency; thymol volatility control is achieved by mixing the complex with the DMAEMA copolymer. β-Cyclodextrin accelerates the in vivo thymol absorption rate compared with the free drug; the thymol half-life is still long. Therefore, a low number of administrations per day are required. Although bioavailability is unchanged with respect to free thymol, high doses could be administered of a selected formulation without compromising the compliance. Furthermore, thymol that is not absorbed is held along the intestine, where it can useful in the treatment and/or prevention of intestinal bacterial diseases.

Impact of bioactive substances on the gastrointestinal tract and performance of weaned piglets: a review

The EU ban on in-feed antibiotics has stimulated research on weaning diets as a way of reducing post-weaning gut disorders and growth check in pigs. Many bioactive components have been investigated but only few have shown to be effective. Amongst these, organic acids (OA) have been shown to exert a bactericidal action mediated by non-dissociated OA, by lowering gastric pH, increasing gut and pancreas enzyme secretion and improving gut wall morphology. It has been postulated that they may also enhance non-specific immune responses and improve disease resistance. In contrast, relatively little attention has been paid to the impact of OA on the stomach but recent data show they can differently affect gastric histology, acid secretion and gastric emptying. Butyrate and precursors of butyric acid have received special attention and although promising results have been obtained, their effects are dependent upon the dose, treatment duration, initial age of piglets, gastrointestinal site and other factors. The amino acids (AA) like glutamine, tryptophan and arginine are supportive in improving digestion, absorption and retention of nutrients by affecting tissue anabolism, stress and (or) immunity. Glutamine, cysteine and threonine are important for maintaining mucin and permeability of intestinal barrier function. Spray-dried plasma (SDP) positively affects gut morphology, inflammation and reduces acquired specific immune responses via specific and a-specific influences of immunoglobulins and other bioactive components. Effects are more pronounced in early-weaned piglets and under poorer health conditions. Little interaction between plasma protein and antibiotics has been found, suggesting distinct modes of action and additive effects. Bovine colostrum may act more or less similarly to SDP. The composition of essential oils is highly variable, depending on environmental and climatic conditions and distillation methods. These oils differ widely in their antimicrobial activity in vitro and some components of weaning diets may decrease their activity. Results in young pigs are highly variable depending upon the product and doses used. These studies suggest that relatively high concentrations of essential oils are needed for beneficial effects to be observed and it has been assumed that these plant extracts mimic most of the effects of antibiotics active on gut physiology, microbiology and immunology. Often, bioactive substances protective to the gut also stimulate feed intake and growth performance. New insights on the effects of selected OA and AA, protein sources (especially SDP, bovine colostrum) and plant extracts with anti-bacterial activities on the gut are reported in this review.

Biodegradable polymer (PLGA) coatings featuring cinnamaldehyde and carvacrol mitigate biofilm formation

Biofilm-associated infections are one of the leading causes of death in the United States. Although infections may be treated with antibiotics, the overuse of antibiotics has led to the spread of antibiotic resistance. Many natural antimicrobial compounds derived from edible plants are safe for human use and target bacteria nonspecifically. Therefore, they may impair biofilm formation with less evolutionary pressure on pathogens. Here, we explore the use of two natural antimicrobial compounds, cinnamaldehyde (CA, from cinnamon) and carvacrol (CARV, from oregano), for biofilm prevention. We have fabricated and characterized films that incorporate CA and CARV into the biodegradable, FDA-approved polymer poly(lactic-co-glycolic acid), PLGA. The addition of CA and CARV to PLGA films not only adds antimicrobial activity but also changes the surface properties of the films, making them more hydrophilic and therefore more resistant to bacterial attachment. An addition of 0.1% CA to a PLGA film significantly impairs biofilm development by Staphylococcus aureus, and 0.1% CARV in PLGA significantly decreases biofilm formation by both Escherichia coli and S. aureus. Pseudomonas aeruginosa, which is less susceptible to CA and CARV, was not affected by the addition of 0.1% CA or CARV to the PLGA coatings; however, P. aeruginosa biofilm was significantly reduced by 1.0% CA. These results indicate that both CA and CARV could potentially be used in low concentrations as natural additives in polymer coatings for indwelling devices to delay colonization by bacteria.