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The aim of this review is to provide a review of the immune system in fish, including the ontogeny, mechanisms of unspecific and acquired immunity and the action of some immunomodulators. Fish rely on their innate immune system for an extended period of time, beginning at the early stages of embryogenesis. The components of the innate immune response are divided into physical, cellular and humoral factors and include humoral and cellular receptor molecules that are soluble in plasma and other body fluids. The lymphoid organs found in fish include the thymus, spleen and kidney. Immunoglobulins are the principal components of the immune response against pathogenic organisms. Immunomodulatory products, including nucleotides, glucans and probiotics, are increasingly used in aquaculture production. The use of these products reduces the need for therapeutic treatments, enhances the effects of vaccines and, in turn, improves the indicators of production.

Essential oils (EOs) are important aromatic components of herbs and spices and their biological activities have been known and utilised since ancient times in perfumery, food preservation, flavouring, and medicine. Some of their biological activities include antibacterial, antifungal, anti-oxidant and anti-inflammatory effects amongst others. EOs have received attention in recent years as potential 'natural' alternatives for replacing antibiotic growth promoters (AGPs) in animal diets due to their positive impact on growth performance, gut microbiota and welfare. The purpose of this paper is to provide an overview of our own published and unpublished data on the antibacterial, antifungal and insecticidal activity of thymol and cinnamaldehyde (TC blend), and to describe the effects of this specific EO blend on gut microbiota, growth performance and welfare, carcass characteristics and food safety. The possible modes of action of EOs are discussed and areas for future research are proposed.

The aim of this study was to prepare some phenolic acids alkyl esters (methyl, ethyl, propyl, butyl and hexyl) and to determine their antioxidant and antimicrobial activities. The antimicrobial activity against Escherichia coli DMF 7503, Bacillus cereus DMF 2001, Listeria monocytogenes DMF 5776, Fusarium culmorum DMF 0103, and Saccharomyces cerevisiae DMF 1017 was investigated and expressed by minimum inhibitory concentration (MIC) in the range of 1.2-20mM. The inhibitory activity of phenolic acids butyl esters was found to be higher than that of methyl esters (MIC below 1.25mM). The antioxidant activity of the selected phenolic acids alkyl esters was investigated by Rancimat method. The esters of 3,4-dihydroxyphenolic acids (protocatechuic and caffeic acids) exhibited higher antioxidant activities in comparison with the respective phenolic acids. The highest antioxidant activity was found in the case of caffeic alkyl esters.

We described the in vitro antioxidant and antimicrobial activities of ethanol, acetone, and water extracts of beet root pomace. Total contents of phenolics (316.30-564.50 mg GAE/g of dry extract), flavonoids (316.30-564.50 mg RE/g of dry extract), betacyanins (18.78-24.18 mg/g of dry extract), and betaxanthins (11.19-22.90 mg/g of dry extract) after solid-phase extraction were determined spectrophotometrically. The antioxidant activity was determined by measuring the reducing power and DPPH scavenging activity by spectrometric method, and hydroxyl and superoxide anion radical scavenging activity by ESR spectroscopy. In general, the reducing power of all the beet root pomace extracts increased with increasing concentrations. The DPPH-free radical scavenging activity of the extracts, expressed as EC50, ranged from 0.133 mg/mL to 0.275 mg/mL. Significant correlation was observed between all phytochemical components and scavenging activity. Ethanol extract (0.5 mg/mL) completely eliminated hydroxyl radical which had been generated in Fenton system, while the same concentration of this extract scavenged 75% of superoxide anion radicals. In antibacterial tests, Staphylococcus aureus and Bacillus cereus showed higher susceptibility than Escherichia coli and Pseudomonas aeruginosa.

Oleoresin of Capsicum sp. is considered a food additive due to its color and pungency, and its active compound, capsaicin, is characterized by antimicrobial and antioxidant properties. However, Chilean variety of Capsicum sp. has not been characterized yet. The purpose of this study was to characterize the oleoresin of Capsicum annuum var. Cacho de cabra (OCc). Solvent extraction of OCc was carried out with hexane and physical properties of the OCc obtained were determined. Antimicrobial and antioxidant properties of OCc were compared with its active compound, capsaicin. Results showed that OCc has good optical properties compared with other commercial oleoresins and better antimicrobial properties than pure capsaicin. Due to the good optical properties obtained for OCc, this oleoresin could have a higher commercial value to be used as a coloring and flavor of various products, giving an added value to this variety of pepper.

The antimicrobial activity of fatty acids (C8 to C14), monolaurin, citric, succinic, fumaric, malic and lactic acids was determined in cultures of 2 strains of Escherichia coli, 3 strains of Salmonella sp. and 2 strains of Clostridium perfringens. Caprylic acid was the only acid inhibiting glucose utilization in all cultures. Strains CCM 3954 and CCM 4225 of E. coli were inhibited also by capric acid at 5 mg/mL. Strains CCM 4435T and CNCTC 5459 of C. perfringens were inhibited by fatty acids, oleic acid and one strain also by linoleic acid. Growth of C. perfringens was inhibited also by monoglyceride of lauric acid and by citric acid. The separation of inner and outer cell membranes was apparent in C. perfringens CCM 4435T treated with lauric acid at 1 mg/mL, or with its monoglyceride at 5 mg/mL. Medium-chain fatty acids were more efficient antimicrobials than the other, more polar, organic acids tested.

Ag ions are known for their antibacterial effects. Ag containing silicate glasses have been extended to create bioactive glasses that exhibit inhibitory effects on bacterial growth using different techniques. In this work, calcium and calcium/silver silicophosphate glasses were synthesized from the sol-gel process and their physicochemical and in vitro biological properties were studied and compared. The effect of silver concentration on in vitro bioactivity and antibacterial properties of the glasses was investigated. Ag₂O was substituted for CaO in the glass formula up to 2 mol% and in vitro bioactivity of the samples was evaluated by soaking them in simulated body fluid followed by structural characterization using XRD, FTIR and SEM techniques. The results showed that both glasses favored precipitation of the calcium phosphate layer when they were soaked in simulated body fluid; however, the morphology of apatite crystals changed for the 2% mol silver containing sample. Substitution of 2% mol Ag₂O for CaO seemed to slightly stimulate the rate of precipitation. The in vitro biodegradation rate of the silver/calcium silicophosphate glasses was lower than that of the silver-free one (control). Also, the antibacterial properties of the samples indicated that these effects were improved by increasing silver concentration in bioactive glass composition.

The relationship between the structural degradation of veterinary antibiotics, their antimicrobial activity, and possible mutagenicity after heating have not been well investigated sequentially. This study aimed to evaluate the heat stability of 14 veterinary antibiotics under a short-term heating scenario by characterization of their structural degradation and their relationship to resultant changes in antimicrobial activity. Mutagenicity was also examined in four representative antibiotics after 15-min-heat treatments at two temperatures (100 deg C and 121 deg C). Differential heat stabilities of antibiotics between drug classes, between temperature levels, and among the same class of drugs were discovered. Heat treatment resulted in the reduction of the main peak and the production of new peaks in certain antibiotics, contributing to minimum inhibitory concentration increases of 2- to 1,024-fold. Ranking of heat stability by antibiotic classes at 121 deg C was highest for sulfonamides, followed by lincomycin, colistin, tetracyclines and beta-lactams while at 100 deg C sulfonamides equaled lincomycin, but variability was observed within different tetracyclines and beta-lactams. Correlation analysis suggested that except for doxycycline, structural degradation of the drugs was in good agreement with the reduction in antimicrobial activity. Mutagenicity (Ames) tests on heated chlortetracycline resulted in 2- to 6-fold revertant changes in Salmonella typhimurium TA98 and TA100. The combined results suggest that correlation analysis of structural degradation and antimicrobial activity offers dual evaluation of a drug's heat stability but gives little advantage over assessment of the resultant toxicity.