Antibacterial effect of plant-derived antimicrobials on major bacterial mastitis pathogens in vitro

Effects of essential oils on economically important characteristics of ruminant species: A comprehensive review

Essential oils derived from plants can provide biological impacts to livestock species. Scientific studies researching essential oils in livestock have investigated various essential oils for prevention and treatment of microbial infection and parasites as well as to enhance milk production, animal performance and rumen function. Despite the availability of several commercial products containing essential oils to promote animal health and production, the vast amount of essential oils, modes of application, and effective concentrations of the essential oils suggest there are more opportunities for essential oils to be utilized in commercial livestock production and veterinary medicine. The objective of this review is to contribute to the understanding of the value that essential oils can provide to the ruminant diet and to examine the biological impact of various essential oils on economically important production traits of ruminant species.

UPLC-Q-TOF-MS profiling of Viola stocksii Boiss. and evaluation of aphrodisiac potential and risk factors associated with erectile dysfunction

ETHNOPHARMACOLOGICAL RELEVANCE

Viola stocksii Boiss. locally known as makhni or makhanr booti, is an important medicinal food plant with multiple therapeutic applications, including erectile dysfunction (ED). It is mixed with butter and used for boosting energy and sexual health in the subcontinent.

AIMS OF THE STUDY

This study was designed to evaluate the chemical composition, aphrodisiac potential and effect of V. stocksii on the risk factors associated with ED.

METHODOLOGY

The hydroethanolic extract of V. stocksii (HEEVS) was prepared through the microwave-assisted extraction (MAE) technique. The chemical composition was evaluated using preliminary phytochemical screening and UPLC-Q-TOF-MS analysis. Metals and minerals analysis was performed by an atomic absorption spectrophotometer. The aphrodisiac activity of HEEVS was evaluated using an in vivo aphrodisiac model established in male albino rats and the effect on various sexual parameters such as mount, intromission, ejaculation frequencies and mount, intromission, ejaculation latencies, postejaculatory interval, penile reflexes and serum hormone concentration were analyzed. The effect of HEEVS on various risk factors associated with ED, including prostate cancer (PC), bacterial infections, diabetes and obesity, was evaluated using various in vitro assays. Moreover, four compounds were selected from the UPLC-Q-TOF-MS profile and evaluated for in silico computational analysis against phosphodiesterase-5 (PDE-5) for possible interaction.

FINDINGS

The phytochemical screening revealed the presence of various secondary metabolites in HEEVS, while 58 compounds were tentatively identified in the UPLC-Q-TOF-MS analysis. Various important minerals and metals such as zinc, calcium, cadmium and magnesium were detected in the atomic absorption spectrometry analysis. The in vivo aphrodisiac evaluation showed a significant (p < 0.05) increase in the mount, intromission and ejaculation frequencies and a decrease in the mount, intromission latencies and post-ejaculatory intervals at a dose of 300 mg/kg. A marked (p < 0.05) increase was observed in the concentration of serum testosterone and luteinizing hormones in HEEVS treated animals with a significant increase in total penile reflexes. The extract displayed significant anti-prostate cancer activity and a potential antibacterial spectrum against E. coli and S. aureus, with MIC50 values of 215.72 μg/mL and 139.05 μg/mL, respectively. Similarly, HEEVS was found active towards pancreatic lipase (67.34 ± 1.03%), α-glucosidase (3.87 ± 0.54 mmol ACAE/g d.w.) and α-amylase (6.98 ± 1.63 mmol ACAE/g d.w.). The in silico docking study presented a potential interaction between the selected compounds and residues of the active site of PDE-5.

CONCLUSION

This report highlights the aphrodisiac potential of V. stocksii and provides experimental support for its traditional use in ED with an attenuative effect on the risk factors associated with ED. Moreover, the chemical composition displayed the presence of functional phytoconstituents and minerals in HEEVS and paves the way for the isolation of compounds with potent aphrodisiac activity.

Enhancing Commercial Antibiotics with Trans-Cinnamaldehyde in Gram-Positive and Gram-Negative Bacteria: An In Vitro Approach

One strategy to mitigate the emergence of bacterial resistance involves reducing antibiotic doses by combining them with natural products, such as trans-cinnamaldehyde (CIN). The objective of this research was to identify in vitro combinations (CIN + commercial antibiotic (ABX)) that decrease the minimum inhibitory concentration (MIC) of seven antibiotics against 14 different Gram-positive and Gram-negative pathogenic bacteria, most of them classified as ESKAPE. MIC values were measured for all compounds using the broth microdilution method. The effect of the combinations on these microorganisms was analyzed through the checkboard assay to determine the type of activity (synergy, antagonism, or addition). This analysis was complemented with a kinetic study of the synergistic combinations. Fifteen synergistic combinations were characterized for nine of the tested bacteria. CIN demonstrated effectiveness in reducing the MIC of chloramphenicol, streptomycin, amoxicillin, and erythromycin (94-98%) when tested on Serratia marcescens, Staphylococcus aureus, Pasteurella aerogenes, and Salmonella enterica, respectively. The kinetic study revealed that when the substances were tested alone at the MIC concentration observed in the synergistic combination, bacterial growth was not inhibited. However, when CIN and the ABX, for which synergy was observed, were tested simultaneously in combination at these same concentrations, the bacterial growth inhibition was complete. This demonstrates the highly potent in vitro synergistic activity of CIN when combined with commercial ABXs. This finding could be particularly beneficial in livestock farming, as this sector witnesses the highest quantities of antimicrobial usage, contributing significantly to antimicrobial resistance issues. Further research focused on this natural compound is thus warranted for this reason.

Future scope of plant-derived bioactive compounds in the management of methicillin-resistant Staphylococcus aureus: In vitro antimicrobial and antivirulence prospects to combat MRSA

Methicillin-resistant Staphylococcus aureus (MRSA) is a foremost human and animal pathogen with public health and veterinary significance causing hospital and community infections and contagious bovine mastitis. Due to its ability to develop multidrug resistance (MDR) and its pathogenicity, MRSA infection control is becoming a global concern. Natural antibacterial options are needed to combat MDR development and infectious dissemination. This study investigated the antimicrobial resistance and virulence genes profiling of MRSA isolates and explored the antivirulence efficacy of trans-cinnamaldehyde, thymol, and carvacrol essential oils (EOs) against multivirulent and MDR-MRSA isolates. Thirty six S. aureus isolates (25%) were retrieved, of which 34 (94.4%) were MRSA. A high prevalence of MDR (66.7%) was monitored and all 53 molecularly verified isolates possessed icaA and cna virulence genes. Moreover, 94.1% of these isolates were multivirulent with 23.5% of them carrying icaA, cna, eta, tst, and sea virulence genes. Our data proved superior in vitro antimicrobial and antivirulence activities of trans-cinnamaldehyde, thymol, and carvacrol. They inhibited the growth of multi-virulent and MDR-MRSA isolates and downregulated the transcription of examined virulence genes. Our study suggests using EOs as prospective antimicrobials with excellent antivirulence activities against MRSA isolates. We provided data regarding the eventual role of phytogenics in prevention and control of MRSA infection.

Novel Study Antimicrobial and Biocompatibility Effect of Magnesium Silver Alloys 1% on Bovine Bacterial Species

MgAg 1% alloys inhibit bacterial growth during the dry-off period. MgAg1% silver and magnesium amount was determined and the supernatant was used for the detection of antibacterial tests against S. aureus and E. coli and Geobacillus stearothermophilus var. calidolacits. The antibacterial effect of AgNO3 solution and degradation medium of MgAg1% sticks were evaluated. The bouillon dilution test showed a 5-fold reduction in bacterial colonies. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) calculations were used to test the antibacterial activity. The Brilliant Black Reduction Test (BRT-MRL screening test) showed inhibition of Geobacillus stearothermophilus bacteria at AgNO3 concentrations 0.01 mmol/l and 3 ml of degradation medium. Results were satisfying, concerning biocompatibility, degradation, and antibacterial effects.

Intramammary Ethno-Veterinary Formulation in Bovine Mastitis Treatment for Optimization of Antibiotic Use

Increasing pressure on animal and human health as well as food security, due to antimicrobial resistance, is leading to increased demand for natural-product-derived antibiotics worldwide. Considering the importance of bovine mastitis as well as the huge challenge posed by mastitis therapy in cattle production, the main goal of this research was to evaluate the effectiveness of the essential oil-based pharmaceutical (Phyto-Bomat), as an alternative to the existing treatment with antibiotics. The therapeutic response of the cows was monitored using clinical and bacteriological cure of the proposed formulation. Among 550 dairy cows, 75 were diagnosed with a clinical or subclinical form of mastitis and divided into three experimental groups: treated with antibiotic; Phyto-Bomat; antibiotic and Phyto-Bomat. Indicators of bacteriological cure were somatic cell count (SCC), total bacterial count, and causative agent isolation, while the clinical cure was accessed by observing physical udder conditions. All mentioned indicators were assessed before and after the treatment (1st and 7th day post-treatment), with all of the three therapeutic protocols. After Phyto-Bomat treatment, no visible signs of irritation were noticed, while no significant effect in reducing SCC and total bacterial count was observed. Phyto-Bomat has shown promising results in the treatment of mastitis, without the risk of udder irritation, alone or in combination with antibiotics as part of a mastitis control program during lactation.

Chemical Composition, Antimicrobial Activity, and Withdrawal Period of Essential Oil-Based Pharmaceutical Formulation in Bovine Mastitis Treatment

Due to the emergence of antibiotic-resistant bacteria, the risk it represents to public health, and the possible consequences for animal health and welfare, there is an increasing focus on reducing antimicrobial usage (AMU) in animal husbandry. Therefore, a great interest in developing alternatives to AMU in livestock production is present worldwide. Recently, essential oils (EOs) have gained great attention as promising possibilities for the replacement of antibiotics. The current study aimed to test the potential of using a novel EO-based pharmaceutical formulation (Phyto-Bomat) in bovine mastitis treatment. The antibacterial activity was performed using the microdilution technique. Lactating dairy cows were treated with 15 mL of Phyto-Bomat in the inflamed quarter for 5 consecutive days in order to analyze blood and milk samples for thymol and carvacrol residues using gas chromatography and mass spectrometry (GC-MS). Antimicrobial activity expressed as the minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) indicates that this formulation has the highest activity against Gram-positive strains. The dominant compounds in Phyto-Bomat were thymol and carvacrol, at 12.58 ± 1.23 mg/mL and 23.11 ± 2.31 mg/mL, respectively. The quantification of these two compounds in evaluated biological samples showed that 24 h after administration the concentration of thymol and carvacrol in milk samples was at the same level as before application. On the other hand, thymol and carvacrol were detectable in plasma samples even after 24 h post-treatment, with values ranging from 0.15-0.38 and 0.21-0.66 µg/mL, respectively. The tested formulation showed encouraging results of antibacterial activity against bovine mastitis pathogens, as well as the withdrawal period of dominant compounds, which implies that further testing regarding the bacteriological and clinical cure rates in clinical settings is needed.

Streptococcosis a Re-Emerging Disease in Aquaculture: Significance and Phytotherapy

Simple Summary

Streptococcosis is an economical important bacterial disease that can seriously cause huge losses in the global aquaculture sector. In recent years studies have focused on to use extracts or essences of medicinal herbs and plants to control or treat the disease outbreaks and, in most cases the results were promising. The essential oils of the herbs or plants are more effective than the extracts and, the extracts examined have moderate efficacy in term of increasing fish survival against fish streptococcosis that could be due to the enhancement of fish immunity by the herb bio-compounds. The lack of dosage optimization, toxicity and bioavailability assays of a specific herb/plant or its bioactive compound in fish organs make it difficult to judge the validation of clinical efficacy of a particular herb/plant against fish streptococcosis, and thus, required further investigations.

Abstract

Streptococcosis, particularly that caused by S. iniae and S. agalactiae, is a major re-emerging bacterial disease seriously affecting the global sustainability of aquaculture development. Despite a wide spread of the disease in aquaculture, few studies have been directed at assessing the in vitro antagonistic activity and in vivo efficacy of medicinal herbs and other plants against streptococcal agents. Most in vitro studies of plant extractives against S. iniae and S. agalactiae have found antibacterial activity, but essential oils, especially those containing eugenol, carvacrol or thymol, are more effective. Although essential oils have shown better anti-streptococcal activity in in vitro assays, in vivo bioassays require more attention. The extracts examined under in vivo conditions show moderate efficacy, increasing the survival rate of infected fish, probably through the enhancement of immunity before challenge bioassays. The available data, however, lack dosage optimization, toxicity and bioavailability assays of a specific plant or its bioactive compound in fish organs; hence, it is difficult to judge the validation of clinical efficacy for the prevention or treatment of fish streptococcosis. Despite the known bioactive compounds of many tested plants, few data are available on their mode of action towards streptococcal agents. This review addresses the efficacy of medicinal plants to fish streptococcosis and discusses the current gaps.

Antibacterial activity and mechanism of essential oils in combination with medium-chain fatty acids against predominant bovine mastitis pathogens

Bovine mastitis has become a significant economic importance for dairy industry. Concerns regarding poor milk quality, and emergence of bacterial resistance has necessitated to develop alternative therapeutic approach to antibiotics for treatment of mastitis. Saturated medium-chain fatty acids (MCFAs) and essential oils (EOs) are known natural antimicrobials, but their combined effect has not been investigated extensively. The objective of the present investigation was to examine the bactericidal effect of various combined treatments of eight EOs and three saturated MCFAs to inactivate predominant mastitis pathogens, including Staphylococcus aureus ATCC 29213; Escherichia coli ATCC 25922; Klebsiella pneumoniae ATCC 27736; and Streptococcus agalactiae ATCC 27956. The minimum inhibition concentration (MIC) values confirmed that all the tested pathogens were variably susceptible to both EOs and saturated MCFAs. Among essential oils, carvacrol (CAR), trans-cinnamaldehyde (TC), and thymol (TM) showed highest inhibitory activity at concentration 0.38-1.32 mg/mL. Carvacrol exhibited effective additive antibacterial activity in combined treatment with octanoic acid (OA) in terms of its fractional inhibitory index (0.63-0.88) and time-kill effect in reducing about 6 log CFU/mL bacterial cells in less than 5 min. Effort was also made to elucidate mechanism of antibacterial action of CAR and OA against selected mastitis pathogens by observing changes in cell microstructure, permeability and integrity of cell membrane and their membrane potential. After adding CAR and OA at MIC level, there were obvious changes in cell morphology, leakage of small electrolytes, and macromolecules at the initial few hours of treatment i.e. within 1-2 h were observed. Our results indicated that CAR and OA could be evaluated as alternatives or adjuncts to antibiotics as intramammary infusion or topical application to treat bovine mastitis, significantly improving the microbiological safety of milk.

Review of trends in essential oils as alternatives to antibiotics in bovine mastitis treatment

Bovine mastitis is an important disease in the dairy industry responsi?ble for the welfare and significant economic losses in dairy cows. The treatment of choice for mastitis is the administration of antibiotics. However, this therapeutic choice has some disadvantages including presence of antibiotics residues in the milk, low cure rate as well as rapid increase in antibiotic-resistant pathogens. Therefore, new alternative approaches to antibiotics were investigated by different groups of researchers in order to find an effective approach for bovine mastitis therapy. This review was conducted in order to analyze different publications on usage of essential oils in relation to bovine mastitis. There are many in vitro studies for evaluating the antimicrobial efficacy of essential oils against many mastitis associated pathogens. In addition, numerous of tested essential oils have shown good efficacy with a wide range of minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs). On the other hand, only several in vivo studies have focused on therapeutic effects of essential oils. Moreover, recent studies indicate the possibility of using essential oils in the fight against biofilm which could be promising fight against bovine mastitis since unsuccessful antibiotic treatment can be associated with the presence of biofilms.

An overview on mastitis-associated Escherichia coli: Pathogenicity, host immunity and the use of alternative therapies

Escherichia coli is one of the leading causes of bovine mastitis; it can cause sub-clinical, and clinical mastitis characterized by systemic changes, abnormal appearance of milk, and udder inflammation. E. coli pathogenicity in the bovine udder is due to the interaction between its virulence factors and the host factors; it was also linked to the presence of a new pathotype termed mammary pathogenic E. coli (MPEC). However, the presence of this pathotype is commonly debated. Its main virulence factor is the lipopolysaccharide (LPS) that is responsible for causing an endotoxic shock, and inducing a strong immune response by binding to the toll-like receptor 4 (TLR4), and stimulating the expression of chemokines (such as IL-8, and RANTES) and pro-inflammatory cytokines (such as IL-6, and IL-1β). This strong immune response could be used to develop alternative and safe approaches to control E. coli causing bovine mastitis by targeting pro-inflammatory cytokines that can damage the host tissue. The need for alternative treatments against E. coli is due to its ability to resist many conventional antibiotics, which is a huge challenge for curing ill animals. Therefore, the aim of this review was to highlight the pathogenicity of E. coli in the mammary gland, discuss the presence of the new putative pathotype, the mammary pathogenic E. coli (MPEC) pathotype, study the host's immune response, and the alternative treatments that are used against mastitis-associated E. coli.

New Perspective of Origanum vulgare L. and Satureja montana L. Essential Oils as Bovine Mastitis Treatment Alternatives

Mastitis represents a heavy burden for the dairy sector worldwide with high economic and animal welfare impact. Antibiotic treatment is an important component of mastitis control programs. However, emergence and transfer of antimicrobial-resistant (AMR) bacteria is becoming a growing concern. Therefore, the development of novel agents is required for prevention and treatment of mastitis. Hence, our aim was to assess the antibacterial properties of two essential oils (EOs) obtained from oregano (Origanum vulgare L., Lamiaceae) and mountain savory (Satureja montana L., Lamiaceae) against mastitis-associated bacteria in Serbia. The chemical composition and antioxidant potential of these EOs were also evaluated. The present study was conducted on strains derived from aseptic milk samples collected from Holstein-Friesian cows with clinical or subclinical mastitis, during the morning milking. Clinical mastitis was assessed by clinical examination, while subclinical mastitis was confirmed using somatic cell count in the milk samples. The microdilution method was used to determine the antibacterial activity, while antioxidant potential of the EOs was evaluated in several in vitro assays. The values of minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) were used to quantitatively measure the antibacterial activity of each EO. MIC/MBC ranged from 0.78/6.25 and 0.39/0.78 mg/mL for oregano and mountain savory, respectively. A total of 25 compounds were identified in the oregano EO, while 47 were identified in winter savory EO, among which aromatic oxygenated monoterpenes were the most abundant compounds. The tested EOs have shown promising antimicrobial activity and could be considered as one of the treatment approaches in mastitis-affected cows.

The Role of Streptococcus spp. in Bovine Mastitis

The Streptococcus genus belongs to one of the major pathogen groups inducing bovine mastitis. In the dairy industry, mastitis is the most common and costly disease. It not only negatively impacts economic profit due to milk losses and therapy costs, but it is an important animal health and welfare issue as well. This review describes a classification, reservoirs, and frequencies of the most relevant Streptococcus species inducing bovine mastitis (S. agalactiae, S. dysgalactiae and S. uberis). Host and environmental factors influencing mastitis susceptibility and infection rates will be discussed, because it has been indicated that Streptococcus herd prevalence is much higher than mastitis rates. After infection, we report the sequence of cow immune reactions and differences in virulence factors of the main Streptococcus species. Different mastitis detection techniques together with possible conventional and alternative therapies are described. The standard approach treating streptococcal mastitis is the application of ß-lactam antibiotics. In streptococci, increased antimicrobial resistance rates were identified against enrofloxacin, tetracycline, and erythromycin. At the end, control and prevention measures will be considered, including vaccination, hygiene plan, and further interventions. It is the aim of this review to estimate the contribution and to provide detailed knowledge about the role of the Streptococcus genus in bovine mastitis.

Evaluation of the in vitro antibacterial activity of some essential oils and their blends against Staphylococcus spp. isolated from episodes of sheep mastitis

Staphylococcus aureus and coagulase-negative staphylococci are among the major causes of mastitis in sheep. The main goal of this research was to determine the in vitro antibacterial activity of several essential oils (EOs, n 30), then five of them were chosen and tested alone and in blends against staphylococci isolates. Five bacteria were isolated from episodes of ovine mastitis (two S. aureus and three S. xylosus). Biochemical and molecular methods were employed to identify the isolates and disk diffusion method was performed to determine their antimicrobial-resistance profile. The relative percentage of the main constituents in the tested essential oils and their blends was detected by GC-EIMS analysis. Antibacterial and bactericidal effectiveness of essential oils and blends were evaluated through minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). All of them showed sensitivity to the used antimicrobials. The EOs with the highest antibacterial activity were those belonging to the Lamiaceae family characterized by high concentrations of thymol, carvacrol and its precursor p-cymene, together with cinnamon EO, rich in cinnamaldehyde. In terms of both MIC and MBC values, the blend composed by Thymus capitatus EO 40%, Cinnamomum zeylanicum EO 20%, Thymus serpyllum EO 20% and Satureja montana EO 20% was found to be the most effective against all the isolates. Some essential oils appear to represent, at least in vitro, a valid tool against ovine mastitis pathogens. Some blends showed a remarkable effectiveness than the single oils, highlighting a synergistic effect in relation to the phytocomplex.

Biotechnological Potential of Eugenol and Thymol Derivatives Against Staphylococcus aureus from Bovine Mastitis

Bovine mastitis is an infectious disease that affects the mammary gland of dairy cattle with considerable economic losses. Staphylococcus aureus is the main microorganism involved in this highly contagious process, and the treatment is only using antibiotics. Currently, the search for new treatment and/or compounds is still in need due to microbial resistance. In this work, we evaluated the potential of eugenol and thymol derivatives against S. aureus strains from bovine mastitis. On that purpose, nine derivatives were synthesized from eugenol and thymol (1-9), and tested against 15 strains of S. aureus from subclinical bovine mastitis. Initially, the strains were evaluated for the biofilm production profile, and those with strong adherence were selected to the antimicrobial sensitivity determination in the Minimum Inhibitory Concentration (MIC) assays. Herein the compounds toxicity was also evaluated by in silico analysis using Osiris DataWarrior® software. The results showed that 60% of the strains were considered strongly adherent and three strains (S. aureus 4271, 4745 and 4746) were selected for the MIC tests. Among the nine eugenol and thymol derivatives tested, four were active against the evaluated strains (MIC = 32 µg mL^-1) within CLSI standard values. In silico analysis showed that all derivatives had cLopP < 5, cLogS > - 4 and TPSA < 140 Å2, and similar theoretical toxicity parameters to some antibiotics currently on the market. These molecules also showed negative drug-likeness values, pointing to the originality of these structures and theoretical feasibility on escaping of resistance mechanism and act against resistant strains. Thus, these eugenol derivatives may be considered as promising for the development of new treatments against bovine mastitis and future exploring on this purpose.

Antimicrobial and antibiofilm potentials of cinnamon oil and silver nanoparticles against Streptococcus agalactiae isolated from bovine mastitis: new avenues for countering resistance

BACKGROUND

Streptococcus agalactiae (S. agalactiae) is a contagious pathogen of bovine mastitis. It has financial implications for the dairy cattle industry in certain areas of the world. Since antimicrobial resistance increases in dairy farms, natural antimicrobials from herbal origins and nanoparticles have been given more attention as an alternative therapy. Hence, this study reported the antimicrobial and antibiofilm potentials of cinnamon oil, silver nanoparticles (AgNPs), and their combination against multidrug-resistant (MDR) S. agalactiae recovered from clinical bovine mastitis in Egypt.

RESULTS

Our findings revealed that 73% (146/200) of the examined milk samples collected from dairy cows with clinical mastitis were infected with Streptococci species. Of these, 9.59% (14/146) were identified as S. agalactiae and categorized as MDR. S. agalactiae isolates expressed four virulence genes (Hyl, cylE, scpB, and lmb) and demonstrated an ability to produce biofilms. Cinnamon oil showed high antimicrobial (MICs ≤0.063 μg /mL) and antibiofilm (MBIC50 = 4 μg/mL) potentials against planktonic and biofilms of S. agalactiae isolates, respectively. However, AgNPs showed reasonable antimicrobial (MICs ≤16 μg/mL) and relatively low antibiofilm (MBIC50 = 64 μg/mL) activities against screened isolates. Synergistic antimicrobial or additive antibiofilm interactions of cinnamon oil combined with AgNPs were reported for the first time. Scanning electron microscope (SEM) analysis revealed that biofilms of S. agalactiae isolates treated with cinnamon oil were more seriously damaged than observed in AgNPs cinnamon oil combination. Moreover, reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) showed that cinnamon oil exerted a remarkable down-regulation of pili biosynthesis genes (pilA and pilB) and their regulator (rogB) against S. agalactiae biofilms, meanwhile the AgNPs cinnamon oil combination demonstrated a lower efficacy.

CONCLUSIONS

This is an in vitro preliminary approach that documented the antibiofilm potential of cinnamon oil and the inhibitory activity of cinnamon oil and its combination with AgNPs against MDR S. agalactiae recovered from clinical mastitis. Further in vivo studies should be carried out in animal models to provide evidence of concept for implementing these alternative candidates in the treatment of dairy farms infected by streptococcal mastitis in the future.

Natural Agents against Bovine Mastitis Pathogens

Bovine mastitis is the most widespread and economically important disease worldwide. The present study aimed to determine bioactive compounds in two essential oils (EOs) from wild (Thymus serpyllum) and common thyme (Thymus vulgaris) and to assess the antioxidant potential as well as antibacterial efficacy of the EOs against mastitis-associated bacteria. The study also included antibiotic susceptibility tests. The strains were previously isolated from lactating animals with clinical and subclinical mastitis. The antioxidant potential of the commercial EOs of wild and common thyme was evaluated by five in vitro assays. The antibacterial activity was performed using the microdilution technique, while antibiotic susceptibility testing was performed by the Kirby-Bauer disc diffusion method. The dominant compound in wild thyme was thymol (45.22%), followed by p-cymene (23.83%) and γ-terpinene (3.12%), while in common thyme, it was thymol (54.17%), followed by γ-terpinene (22.18%) and p-cymene (16.66%). Among the fourteen mastitis-associated bacteria, strain IX Streptococcus spp. (β-hemolytic) was the most sensitive to the tested EOs (minimum inhibitory concentration (MIC)/minimal bactericidal concentration (MBC) were 0.78/1.56 and 0.39/0.78 mg/mL for T. serpyllum (TS) and T. vulgaris (TV), respectively). Regarding Streptococcus spp. β heamoliticus, MICs for TS ranged from 0.78 to 1.56 mg/mL, while for the same oil, MBCs ranged from 1.56 to 12.5 mg/mL. In the case of T. vulgaris, MICs ranged from 0.39 to 3.125 mg/ mL, while MBCs ranged from 3.125 to 6.25 mg/mL. TV is more active against E. coli, E. sakazakii, and Streptococcus spp., while it is less effective against Staphylococcus spp. than TS. The study revealed that the tested EOs possess remarkable antioxidative and antibacterial activities and could be used in the development of pharmaceutical formulation as an alternative to conventional mastitis therapy.

Overall assessment of antibiotic substitutes for pigs: a set of meta-analyses

Background

Antibiotic growth promoters are widely used to improve weight gain. However, the abuse of antibiotics can have many negative effects on people. Developing alternatives to antibiotics is an urgent need in livestock production. We aimed to perform a meta-analysis and network meta-analysis (NMA) to investigate the effects of feed additives as potential antibiotic substitutes (ASs) on bacteriostasis, growth performance, intestinal morphology and immunity. Furthermore, the primary, secondary, and tertiary ASs were defined by comparing their results with the results of antibiotics.

Results

Among 16,309 identified studies, 37 were summarized to study the bacteriostasis effects of feed additives, and 89 were included in the meta-analysis and NMA (10,228 pigs). We summarized 268 associations of 57 interventions with 32 bacteria. The order of bacteriostasis effects was as follows: antimicrobial peptides (AMPs) ≈ antibiotics>organic acids>plant extracts>oligosaccharides. We detected associations of 11 feed additives and 11 outcomes. Compared with a basal diet, plant extract, AMPs, probiotics, microelements, organic acids, bacteriophages, lysozyme, zymin, and oligosaccharides significantly improved growth performance (P < 0.05); organic acids, probiotics, microelements, lysozyme, and AMPs remarkably increased the villus height:crypt depth ratio (V/C) (P < 0.05); and plant extracts, zymin, microelements, probiotics, and organic acids notably improved immunity (P < 0.05). The optimal AMP, bacteriophage, lysozyme, microelements, oligosaccharides, organic acids, plants, plant extracts, probiotics, and zymin doses were 0.100%, 0.150%, 0.012%, 0.010%, 0.050%, 0.750%, 0.20%, 0.040%, 0.180%, and 0.100%, respectively. Compared with antibiotics, all investigated feed additives exhibited no significant difference in effects on growth performance, IgG, and diarrhoea index/rate (P > 0.05); AMPs and microelements significantly increased V/C (P < 0.05); and zymin significantly improved lymphocyte levels (P < 0.05). Furthermore, linear weighting sum models were used to comprehensively estimate the overall impact of each feed additive on pig growth and health.

Conclusions

Our findings suggest that AMPs and plant extracts can be used as primary ASs for weaned piglets and growing pigs, respectively. Bacteriophages, zymin, plants, probiotics, oligosaccharides, lysozyme, and microelements can be regarded as secondary ASs. Nucleotides and organic acids can be considered as tertiary ASs. Future studies should further assess the alternative effects of combinational feed additives.

Staphylococcus aureus persistence properties associated with bovine mastitis and alternative therapeutic modalities

Staphylococcus aureus is an important agent of contagious bovine intramammary infections in dairy cattle. Its ability to persist inside the udder is based on the presence of important mechanisms such as its ability to form biofilms, polysaccharide capsules small colony variants, and their ability to invade professional and nonprofessional cells, which will protect S. aureus from the innate and adaptive immune response of the cow, and from antibiotics that are no longer considered to be sufficient against S. aureus bovine mastitis. In this review, we present the recent research outlining S. aureus persistence properties inside the mammary gland, including its regulation mechanisms, and we highlight alternative therapeutic strategies that were tested against S. aureus isolated from bovine mastitis such as the use of probiotic bacteria, bacteriocins and bacteriophages. Overall, the persistence of S. aureus inside the mammary gland remains a pressing veterinary problem. A thorough understanding of staphylococcal persistence mechanisms will elucidate novel ways that can help in the identification of novel treatments.

Bactericidal Effect of Clove Oil against Multidrug-Resistant Streptococcus suis Isolated from Human Patients and Slaughtered Pigs

Streptococcus suis is a zoonotic pathogen that is currently considered an emerging multidrug-resistant (MDR). Increasing antibiotic resistance can lead to the unsuccessful treatment of S. suis infection. Recently, many investigations of medicinal plants were conducted for the treatment of infection as a result of the increase of antibiotic-resistant bacteria. The aims of this study were to determine the chemical composition of essential oil from Syzygium aromaticum (L.) Merr. & L.M. Perry and the antibacterial activities of clove oil on MDR S. suis. Using gas chromatography coupled to a mass spectrometer, eugenol (97.76%) was found to be the major active ingredient of clove oil. In vitro antibacterial activities of clove oil against MDR S. suis were evaluated. Using the agar disc diffusion test, the clove oil showed a maximum zone of inhibition at 15% (v/v) oil concentration. In a broth microdilution method, the minimum bactericidal concentration of clove oil against all MDR S. suis isolates was 0.1% (v/v). A time-kill analysis was performed, and the killing kinetics of clove oil showed that MDR S. suis was completely reduced after 15 min of exposure to clove oil. In addition, clove oil exhibited a strong antibacterial activity at all pH values applied following incubation of MDR S. suis in pH-adjusted media with clove oil. Moreover, scanning electron microscopy revealed the nonviable S. suis isolates clearly showed atypical form and cell membrane lysis after incubation with clove oil. This study confirms the efficacy of clove oil as a natural antimicrobial against MDR S. suis and suggests the possibility of employing it as a promising alternative product for control of infectious diseases caused by S. suis in animal and human patients.

Prevalence of antibiotic resistant mastitis pathogens in dairy cows in Egypt and potential biological control agents produced from plant endophytic actinobacteria

Dairy production is threatened by antibiotic resistant pathogens worldwide, and alternative solutions to treat mastitis are not available. The prevalence of antibiotic resistant strains is not well known in less developed countries. The prevalence of pathogenic bacteria and their resistance to 21 commercial antibiotics were studied in milk samples taken from 122 dairy cows suffering from the symptoms of mastitis in Egypt. The bacterial species were identified with molecular methods, and antibiotic resistance was studied with disc diffusion method. The prevalence of Streptococcus aureus, Escherichia coli and Pseudomonas aeruginosa were 30%, 17% and 3.5%, respectively. Most (90%) of the S. aureus strains showed resistance to penicillin whereas only 10% of the strains were resistant to oxacillin. Nearly half (40%) of E. coli strains showed resistance to streptomycin. Six P. aeruginosa strains showed resistance to several antibiotics, including ceftriaxone, enrofloxacin and levofloxacin. This points out that despite P. aeruginosa was not common, it should be followed up carefully. Potential biocontrol agents against antibiotic resistant mastitis bacteria were searched among 30 endophytic actinobacterial strains derived from wild medicinal plants. Three plants, namely Mentha longifolia, Malva parviflora and Pulicaria undulata were chosen for a more detailed study; their endophytic actinobacteria were used to prepare metabolic extracts. The crude metabolites of the actinobacteria were extracted with ethyl acetate. All metabolic extracts inhibited the growth of S. aureus, methicillin-resistant Staphylococcus aureus (MRSA), E. coli and P. aeruginosa in vitro. The 16S rRNA sequence analysis revealed that the most efficient actinobacterial strains were two Micromonospora sp. and one Actinobacteria bacterium. We conclude that the combination of the metabolites of several endophytic actinobacteria derived from several medicinal plants would be the most efficient against pathogens. Different metabolite cocktails should be studied further in order to develop novel biocontrol agents to treat antibiotic resistant mastitis bacteria in dairy cows.

Role of Natural Product in Modulation of Drug Transporters and New Delhi Metallo-β Lactamases

A rapid growth in drug resistance has brought options for treating antimicrobial resistance to a halt. Bacteria have evolved to accumulate a multitude of genes that encode resistance for a single drug within a single cell. Alternations of drug transporters are one of the causes for the development of resistance in drug interactions. Conversely, the production of enzymes also inactivates most antibiotics. The discovery of newer classes of antibiotics and drugs from natural products is urgently needed. Alternative medicines play an integral role in countries across the globe but many require validation for treatment strategies. It is essential to explore this chemical diversity in order to find novel drugs with specific activities which can be used as alternative drug targets. This review describes the interaction of drugs with resistant pathogens with a special focus on natural product-derived efflux pump and carbapenemase inhibitors.

Effect of cinnamaldehyde on feed intake, rumen fermentation, and nutrient digestibility, in lactating dairy cows1

The objective of this study was to evaluate the effect of cinnamaldehyde, on feed intake, rumen fermentation, nutrient digestibility, milk yield, and components in lactating dairy cows. Six lactating Holstein dairy cows (3 ruminally cannulated and 3 noncannulated) averaging 263 ± 41 d in milk (DIM) and 754 ± 45 kg of BW at the beginning of the study were used. Cows were randomly assigned to 1 of 3 treatments in a replicated 3 × 3 Latin square design with 19 d periods (14 d for diet adaptation and 5 d for sample collection). Treatments were 0, 2, or 4 mg/kg of BW of cinnamaldehyde. Cinnamaldehyde was mixed with 40 g of corn meal and top-dressed onto the total mixed ration (TMR). Diet was fed as a TMR and contained 37% corn silage, 18.5% mixed-mostly grass silage, 24.5% energy supplement, 16.5% protein supplement, and 3.5% vitamin and mineral mix on a DM basis. The dietary nutrient composition averaged 15.1% CP, 37.8% NDF, and 24.7% ADF. Cows were fed and milked twice daily. No differences were observed for DMI (mean = 24.6 kg/d), milk yield (mean = 28.4 kg/d), 3.5% fat-corrected milk (FCM; mean = 30.6 kg/d), and 3.5% energy-corrected milk (ECM; mean = 30.7 kg/d). The dose of cinnamaldehyde did not have any effect on milk components, rumen fermentation, or pH. There were no differences in nutrient digestibility, but there was a trend for a quadratic effect for DM digestibility (P = 0.09): 74.4%, 76.3%, and 73.7% for treatments 0, 2, and 4 mg/kg of BW of cinnamaldehyde, respectively. A linear effect (P = 0.02) and a quadratic effect (P < 0.02) observed for urinary urea N and a quadratic effect (P = 0.03) for allantoin and total purine derivatives with the 2 mg/kg treatment being the lesser value. These data suggest that cinnamaldehyde at these dosages may have an antimicrobial effect in the rumen as suggested by a lesser concentration of urinary total purine derivatives. Overall, supplementing lactating dairy cows with cinnamaldehyde had no effect on feed intake, milk yield, or milk components. However, it appears that cinnamaldehyde has a negative effect on rumen microbial protein synthesis as suggested by the reduced concentration of urinary purine derivatives.

Antimicrobial potential of myristic acid against Listeria monocytogenes in milk

Listeria monocytogenes (L. monocytogenes), an important food-borne pathogenic microorganism, has resistance immune function to many commonly used drugs. Myristic acid is a traditional Chinese herbal medicine, but it has been rarely used as a food additive, limiting the development of natural food preservatives. In this study, the antibacterial activity and mechanism of myristic acid against L. monocytogenes were studied. The minimum inhibitory concentration (MIC) of myristic acid against 13 L. monocytogenes strains ranged from 64 to 256 μg ml^-1. The time-kill assay demonstrated that when myristic acid was added to dairy products, flow cytometry confirmed that myristic acid influenced cell death and inhibited the growth of L. monocytogenes. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and NPN uptake studies illustrated that myristic acid changed the bacterial morphology and membrane structure of L. monocytogenes, which led to rapid cell death. Myristic acid could bind to DNA and lead to changes in DNA conformation and structure, as identified by fluorescence spectroscopy. Our studies provide additional evidence to support myristic acid being used as a natural antibacterial agent and also further fundamental understanding of the modes of antibacterial action.

Ultrasound combined with manganese-oxide nanoparticles loaded on activated carbon for extraction and pre-concentration of thymol and carvacrol in methanolic extracts of Thymus daenensis, Salvia officinalis, Stachys pilifera, Satureja khuzistanica, and mentha, and water samples

A dispersive micro solid-phase extraction (DMSPE) technique was developed using manganese-oxide nanoparticles loaded on activated carbon (Mn₃O₄-NPs-AC) as an effective sorbent combined with ultrasound for the extraction and determination of a trace amount of thymol and carvacrol in methanolic extracts of Thymus daenensis, Salvia officinalis, Stachys pilifera, Satureja khuzistanica and mentha, and water samples.

Chromobacterium violaceum and Pseudomonas aeruginosa PAO1: Models for Evaluating Anti-Quorum Sensing Activity of Melaleuca alternifolia Essential Oil and Its Main Component Terpinen-4-ol

The problem of antibiotic resistance among pathogens encourages searching for novel active molecules. The aim of the research was to assay the anti-quorum sensing (anti-QS) and antibiofilm potential of Melaleuca alternifolia essential oil and its main constituent, terpinen-4-ol, to prevent the infections due to methicillin-resistant Staphylococcus aureus strains as an alternate to antibiotics. The tea tree oil (TTO) was evaluated for its potential in inhibiting QS-dependent phenomena such as violacein production in Chromobacterium violaceum, swarming motility of Pseudomonas aeruginosa PAO1, and biofilm formation in MRSA strains on glass. The results showed that terpinen-4-ol was able to inhibit MRSA strain biofilm formation on the glass strips by 73.70%. TTO inhibited the violacein production at a mean inhibitory concentration (MIC) value of 0.048 mg/mL by 69.3%. At 100 µg/mL TTO and terpinen-4-ol exhibited inhibition in swarming motility of PAO1 by 33.33% and 25%, respectively. TTO revealed anti-QS and anti-biofilm activities at very low concentrations, but it could be further investigated for new molecules useful for the treatment of MRSA infections.

Short communication: Effect of 3 phytoceutical products on elimination of bacteria in experimentally induced Streptococcus uberis clinical mastitis

Our objective was to assess the ability of 3 herbal products to eliminate experimentally induced Streptococcus uberis mastitis. These herbal products, also known as phytoceuticals, are used in organically managed dairy cattle to maintain or promote udder health. The products tested were an intramammary product, a topical product, and a product applied to the vulvar area. These products are not approved by the US Food and Drug Administration for treatment of mastitis but they are sold to enhance milk quality or for maintenance or improvement of udder health. Each of the products contains at least one component shown to have antibacterial activity. In this study, we successfully challenge-inoculated 25 lactating dairy cows maintained under organic conditions with an isolate of S. uberis. All challenged cows were positive for S. uberis by milk culture after challenge. When cows met predefined criteria indicating the presence of clinical mastitis, treatment with 1 of the 3 products was initiated based upon a predetermined random allocation. Culture of aseptically collected quarter milk samples was performed before, during, and following challenge with S. uberis. Eight, 8, and 9 cows received the intravulvar, intramammary, and topical treatments, respectively. Milk from all cows that were treated with phytoceuticals were culture-positive for S. uberis at every time point following treatment through 168 h following the last phytoceutical treatment. Based upon the presence of clinical signs and for humane reasons, 2 intravulvar-treated cows, 1 topical-treated, and 4 intramammary-treated cows received intramammary antibiotic therapy. We concluded that the phytoceuticals tested, as dosed and used in this trial, did not produce bacterial cures in S. uberis-induced mastitis.

Antibacterial activity and mode of action of totarol against Staphylococcus aureus in carrot juice

Food contaminated with pathogenic bacteria such as Staphylococcus aureus (S. aureus), represents a serious health risk to human beings. Totarol is an antibacterial novel phenolic diterpenes. In present study, the antibacterial activity of totarol against S. aureus was investigated in a food system. The antibacterial activity of totarol was determined by measuring the zones of inhibition and minimum inhibitory concentrations (MICs). The MICs for S. aureus strains were in the range of 2-4 μg/ml. The probable antibacterial mechanism of totarol was the alteration in cell membranes integrity and permeability, which leading to the leakage of cellular materials. The electric conductivity showed a time- and dose-dependent increasing manner, and we utilized totarol to induce the production of cytoplasmic β-galactosidase in S. aureus. Scanning electron microscopy and transmission electron microscopy analysis further confirmed that S. aureus cell membranes were damaged by totarol. The time-kill assay and detection of the kinetics of S. aureus deactivation in situ indicated that totarol has good preservative activities in a food model. Totarol successfully inhibited S. aureus development in carrot juice, at room temperature (25 °C) and in refrigerator (4 °C) respectively. Our works provided not only additional evidences in support of totarol being regarded as a natural antibacterial food preservative but also fundamental understanding on the mode of antibacterial action. It is necessary to consider that totarol will become a promising antibacterial additive for food preservative.

Bovine mastitis: An appraisal of its alternative herbal cure

Bovine mastitis is globally recognized as the most common and costly disease affecting dairy herds. The disease causes huge financial losses to dairy industries by reduced yield and milk quality, deaths and culling of affected cows and also by associated treatment costs. The disease occurs due to invasion of the mammary glands by pathogenic bacteria followed by their multiplication in the milk producing tissues. The most common treatment method available against bovine mastitis is the intra-mammary infusion of antibiotics. However, their use is associated with the problem of antimicrobial resistance. This scenario has made search for alternative treatment approaches necessary. Medicinal plants with their well-established history are an excellent natural product resource used as an alternative therapy. Antibacterial agents from plants can act as important sources of novel antibiotics, efflux pump inhibitors, compounds that target bacterial virulence or can be used in combination with existing drugs. The plants form an essential component of ethno-veterinary medicine used in the treatment of different diseases like bovine mastitis. This review article attempts to provide an overview of the different medicinal plants used in the treatment of bovine mastitis. Antimicrobial studies of these plant species and some of their isolated constituents have been reviewed in detail. It highlights the logic and precedence behind mining this important natural product resource. Our own research findings in this direction and future scope of research are also discussed briefly.

Potential of phytoceuticals to affect antibiotic residue detection tests in cow milk in a randomised trial

Mastitis is a costly disease for dairy farmers. Some dairy farmers use herbal products, or phytoceuticals, to treat mastitis. Phytoceuticals have not been approved for this use by the United States Food and Drug Administration, and have not been tested to determine how they impact antibiotic residue detection testing. The current study tested the potential for phytoceuticals to cause positive results on two milk antibiotic residue screening tests, the Delvotest P and Charm SL Beta-lactam test, or to interfere with the detection of antibiotics by these tests.

The three phytoceuticals tested were labelled for intramammary, topical or intravulvar administration. Testing was performed in vitro using the products diluted in milk obtained from healthy organic dairy cows. Phytoceuticals were tested at concentrations ranging from 1.5 per cent to 100 per cent. Concentration levels were replicated at least twice on each milk antibiotic residue screening test. The Delvotest P is based on detection of bacterial inhibitors and no positive results were obtained for any product at concentrations less than 50 per cent. The Charm SL Beta-lactam test uses a receptor for the detection of beta-lactam antibiotics and no concentration of phytoceuticals caused an interference with these tests.

Based on dilution of the products in bovine milk at physiologically achievable levels, phytoceutical products tested at levels expected after treatment do not cause positive test results for the Delvotest P nor do they interfere with the Charm SL Beta-lactam test in detection of various antibiotics.

Effects of intramammary infusion of sage (Salvia officinalis) essential oil on milk somatic cell count, milk composition parameters and selected hematology and serum biochemical parameters in Awassi sheep with subclinical mastitis

Aim:

The aims of this study were to evaluate the effects of intramammary infusion of sage (Salvia officinalis) essential oil (EO) on milk somatic cell count (SCC), milk composition parameters and selected hematology and serum biochemical parameters in 20 Awassi ewes affected with subclinical mastitis.

Materials and Methods:

The dried leaves of sage were used to extract the EO by hydrodistillation. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of sage EO against Staphylococcus aureus were determined by the broth dilution method. Ewes were divided randomly into three main groups and received one of the following treatments; Group 1 (n=5): Dimethyl sulfoxide (DMSO) alone (5 ml; 0.2 ml of DMSO in 4.8 ml of saline), Group 2 (n=5): Amoxicillin alone (3 ml), and Group 3 (n=10): Sage EO (5 ml of sage EO solution [0.2 ml DMSO+1 ml EO+3.8 ml sterile saline]). All treatments were administered by intramammary infusion into each teat twice per day for 3 consecutive days. Milk samples for SCC and milk components determination and whole blood samples for hematology and serum biochemical analyses were collected before treatment (T0) and at 24 (T24) and 48 (T48) h after the last treatment.

Results:

The MIC and MBC of sage EO against S. aureus were 12.5% and 6.1%, respectively. SCC was decreased significantly (p<0.05) at T24 and T48 h in sage EO and amoxicillin treated groups. Milk fat and lactose were increased significantly (p<0.05) in sage EO and amoxicillin treated ewes while no significant changes were observed in the percentages of solids-not-fat, protein and total solids. No significant effects of sage EO treatment on any of the hematology or serum biochemical parameters were observed. There were no local or systemic side effects observed in any of the treated ewes. However, further clinical trials are warranted to determine safety and possible withdrawal times in milk before its recommendation for use in organic operations.

Conclusion:

In this study, the intramammary infusion of sage EO to ewes affected with subclinical mastitis resulted in a significant decrease in SCC 24 h and 48 h posttreatment. In addition, milk fat and lactose were increased in animals that received the EO as well as in those treated with the antibiotic.

In vitro synergistic activities of cefazolin and nisin A against mastitis pathogens

First-generation cephalosporins such as cefazolin (CEZ) have been widely used for mastitis treatment in dairy cattle. However, the use of antibiotics results in the presence of antibiotic residues in milk, which is used for human consumption. Nisin A, a bacteriocin produced by Lactococcus lactis, has been used as a broad-spectrum food preservative for over 50 years. Therefore, a combination of CEZ and nisin A might provide an extended activity spectrum against mastitis pathogens and reduce the antibiotic dose for mastitis treatment. This study aimed to evaluate the combined effect of CEZ and nisin A against mastitis pathogens using the checkerboard and time-kill assays. In the checkerboard assay, the CEZ-nisin A combination exhibited a synergistic effect against Staphylococcus aureus (n=20/20) and Enterococcus faecalis (n=13/18), and meanwhile exhibited a mostly additive effect against Staphylococcus intermedius (n=12/20), Streptococcus agalactiae (n=10/10), Streptococcus dysgalactiae (n=18/18), and Escherichia coli (n=14/18). There were no indifferent or antagonistic effects between CEZ and nisin A. In the time-kill assay, the CEZ-nisin A combination at 0.5 × or 1 × minimum inhibitory concentration exhibited synergistic reduction of bacterial growth by over 3 log₁₀ colony forming units per ml relative to that observed with either antimicrobial substance alone. These results suggest that the CEZ-nisin A combination can be used for developing an intramammary infusion for mastitis treatment, with lower antibiotic concentrations than normal.

Antibiotic resistance in bacteria Staphylococcus spp. isolated from samples of raw sheep's milk

From samples of raw sheep's milk were determined results of bacteriological examination from two herds in region of Eastern Slovakia in three years lasting study. The occurrence of Staphylococcus spp. 41.6% (124) was determined from 298 samples. The seven species of staphylococci were on a regular basis isolated: S. epidermidis (34), S. chromogenes (26), S. aureus (16). Alternately have been recorded S. warneri (16), S. schleiferi (15), S. haemolyticus (9) and S. xylosus (8). All isolated pathogens were tested by in vitro test on Mueller-Hinton agar by disc methods on resistance to 10 types of antibiotics.  Highest value of resistance was determined to Penicilin 21.0%, Neomycin 10.5% and Novobiocin 9.7%. Lower resistance was in to Oxacilin 7.2% and Amoxicilin 6.5%. Minimal resistance was founded to Cefoxitin 0.8%, Linkomycin 2.4%, Erytromycin, and Streptomycin 3.2%. Was founded total resistance (21.0%) to all antibiotics in S. epidermidis (34) during the three years, S. chromogenes (26) showed resistance to 8 types of antibiotics (12.9%), S. aureus (16) to 6 antibiotics (10.5%) and S. warneri (16) to 4 antibiotics (5.6%). It was confirmed that sheep's milk remains a major source of staphylococci. Bacteria in comparison with isolates from cows' raw milk, showed lower values of resistance, but were resistant to more than two antibiotics. Recorded occurrence of resistance in staphylococci may be connected with a minimum use of antibiotics in the treatment of mastitis and other diseases in sheep herds. Reported resistance to the tested antibiotics became the basis for the recommendation to use preparations to treat mastitis in sheep principally by the detection of resistance to antibiotics contained.

Development of a HS-SPME-GC-MS/MS Method for the Quantitation of Thymol and Carvacrol in Bovine Matrices and To Determine Residue Depletion in Milk and Tissues

Thymol and carvacrol may be present in several phytoceutical products but there are no well-defined methods to measure these compounds in meat and milk from treated animals. U.S. regulatory authorities deem their presence as an adulteration of food. A rapid and sensitive HS-SPME-GC-MS/MS method was developed for the detection of thymol and carvacrol in bovine milk, plasma, liver, kidney, and fat. Inter- and intraday precision values were all less than 15.7 and 20.2% for thymol and carvacrol, respectively. The accuracy was in ranges of 69.9-111.8% for thymol and 74.0-119.2% for carvacrol. With the exception of fat tissue, stability studies showed that both compounds are stable over a 2 month period. A pilot pharmacokinetic study was conducted to evaluate the developed analytical method and to provide initial estimates of thymol and carvacrol depletion in plasma, milk, and several tissues. Treatment of lactating dairy cattle with phytoceutical products containing these substances resulted in low but measurable residue levels at 96 h for liver and 36 h for milk with very short apparent plasma and milk half-lives (<3.0 h).

Medicinal attributes of major phenylpropanoids present in cinnamon

Background

Excessive production of free radicals has been implicated in many diseases including cancer. They are highly reactive and bring about oxidation of biomolecules i.e., proteins, lipids and nucleic acids which are associated with many degenerative diseases. Natural products acting as antioxidants have ability to neutralize free radicals and their actions and hence they mitigate their harmful effects. The present study was designed to investigate pharmacological properties viz., antioxidant, antibacterial and antiproliferative activities of cinnamaldehyde and eugenol, the two naturally occurring phenylpropanoids present in Cinnamomum spp. and other plants.

Methods

The antioxidant potential of test compounds was evaluated by measuring DPPH free radical scavenging, reducing power and metal ion chelating activities. Protection against membrane damage was assayed by inhibition of lipid peroxidation in rat liver homogenate. Antibacterial activity was measured by Kirby-Bauer disc diffusion method while antiproliferative activity of test compounds was measured by sulforhodamine-B (SRB) assay.

Results

Eugenol exhibited noticeable antioxidant potential in DPPH radical scavenging (81 %) and reducing power (1.12) assays at 1.0 μM/ml and 0.1 μM/ml concentrations, respectively. IC₅₀ value of eugenol for radical scavenging activity was found to be 0.495 μM/ml. Cinnamaldehyde demonstrated considerable metal ion chelating ability (75 %) at 50 μM/ml and moderate lipo-protective activity in lipid peroxidation assay at 3 μM/ml. In addition cinnamaldehyde also showed appreciable antibacterial activity (zone of inhibition 32–42 mm) against Bacillus cereus (MTCC 6840), Streptococcus mutans (MTCC 497), Proteus vulgaris (MTCC 7299), Salmonella typhi (MTCC 3917) and Bordetella bronchiseptica (MTCC 6838) while eugenol produced moderate activity at 80 μM/disc. Cinnamaldehyde exhibited comparatively better antiproliferative potential against breast (T47D) and lung (NCI-H322) cancer cell lines than eugenol in SRB assay at 50 μM concentration.

Conclusion

Cinnamaldehyde possessed metal ion chelating, lipo-protective, antibacterial and antiproliferative activities while eugenol showed potent H-atom donating potential indicating radical quenching and reducing power abilities. Medicinal attributes shown by both the compounds indicated their usefulness in food and pharmaceutical sector.

Control of Bovine Mastitis: Old and Recent Therapeutic Approaches

Mastitis is defined as the inflammatory response resulting of the infection of the udder tissue and it is reported in numerous species, namely in domestic dairy animals. This pathology is the most frequent disease of dairy cattle and can be potentially fatal. Mastitis is an economically important pathology associated with reduced milk production, changes in milk composition and quality, being considered one of the most costly to dairy industry. Therefore, the majority of research in the field has focused on control of bovine mastitis and many efforts are being made for the development of new and effective anti-mastitis drugs. Antibiotic treatment is an established component of mastitis control programs; however, the continuous search for new therapeutic alternatives, effective in the control and treatment of bovine mastitis, is urgent. This review will provide an overview of some conventional and emerging approaches in the management of bovine mastitis' infections.

Prevalence of bovine subclinical mastitis, its etiology and diagnosis of antibiotic resistance of dairy farms in four municipalities of a tropical region of Mexico

A region-wide survey was conducted in the tropical area of Tierra Caliente, State of Guerrero, Mexico to estimate the prevalence of subclinical bovine mastitis (SCM), distribution of mastitis pathogens, and in vitro antimicrobial susceptibility of different mastitis pathogens in dairy farms. In total, 1036 quarter milk samples were obtained from 259 cows at 87 different dairy farms. Collected quarter milk samples were submitted for California Mastitis Test (CMT), bacteriological examination, and testing for antimicrobial susceptibility. Overall prevalence of SCM in the studied area was 20.5 %. Prevalence in the different regions was as follows: 28 % in Arcelia municipality, 21 % in Tlalchapa municipality, 19.4 % in Pungarabato municipality, and 14.3 % in Finch Cutzamala municipality. Of all positive isolates, 97.5 % were Gram-negative bacteria. Moreover, of all positive isolates, 37.5 % were Proteus vulgaris, 25 % Salmonella spp., 12.5 % Enterobacter aerogenes, and 10 % Escherichia coli. Klebsiella pneumonia and E. coli were sensitive for netilmicin antimicrobial. However, E. coli was sensitive for pefloxacin and gentamicin with a sensitivity for pefloxacin for E. aerogenes, while Staphylococci were sensitive for gentamicin and dicloxacillin. It could be concluded that practices such as the implementation of mastitis control programs, improved milking hygiene together with an intramammary treatment with netilmicin, pefloxacin, and gentamicin antimicrobials should be considered for mastitis prevention in the study area of Tierra Caliente, in the tropical area of Guerrero, Mexico.

Effect of Eugenol against Streptococcus agalactiae and Synergistic Interaction with Biologically Produced Silver Nanoparticles

Streptococcus agalactiae (group B streptococci (GBS)) is an important infections agent in newborns associated with maternal vaginal colonization. Intrapartum antibiotic prophylaxis in GBS-colonized pregnant women has led to a significant reduction in the incidence of early neonatal infection in various geographic regions. However, this strategy may lead to resistance selecting among GBS, indicating the need for new alternatives to prevent bacterial transmission and even to treat GBS infections. This study reported for the first time the effect of eugenol on GBS isolated from colonized women, alone and in combination with silver nanoparticles produced by Fusarium oxysporum (AgNPbio). Eugenol showed a bactericidal effect against planktonic cells of all GBS strains, and this effect appeared to be time-dependent as judged by the time-kill curves and viability analysis. Combination of eugenol with AgNPbio resulted in a strong synergistic activity, significantly reducing the minimum inhibitory concentration values of both compounds. Scanning and transmission electron microscopy revealed fragmented cells and changes in bacterial morphology after incubation with eugenol. In addition, eugenol inhibited the viability of sessile cells during biofilm formation and in mature biofilms. These results indicate the potential of eugenol as an alternative for controlling GBS infections.