Screening of medicinal plants for antibacterial activities on Staphylococcus aureus strains isolated from bovine mastitis

Liposomal nanoformulations with trans-caryophyllene and caryophyllene oxide: do they have an inhibitory action on the efflux pumps NorA, Tet(K), MsrA, and MepA?

This study aimed to evaluate the antibacterial and inhibitory action of NorA, Tet(K), MsrA and MepA efflux pumps in S. aureus strains using the sesquiterpenes named trans-caryophyllene and caryophyllene oxide, both isolated and encapsulated in liposomes. The antibacterial and inhibitory action of these efflux pumps was evaluated through the serial microdilution test in 96-well microplates. Each sesquiterpene and liposome/sesquiterpene was combined with antibiotics and ethidium bromide (EtBr). The antibiotics named norfloxacin, tetracycline and erythromycin were used. The 1199 B, IS-58, RN4220 and K2068 S. aureus strains carrying NorA, Tet(K), MsrA and MepA, respectively, were tested. In the fluorescence measurement test, K2068 S. aureus was incubated with the sesquiterpenes and EtBr, and the fluorescence emission by EtBr was measured. The tested substances did not show direct antibacterial activity, with MIC >1024 μg/mL. Nonetheless, the isolated trans-caryophyllene and caryophyllene oxide reduced the MIC of antibiotics and EtBr, indicating inhibition of NorA, Tet(K) and MsrA. In the fluorescence test, these same sesquiterpenes increased fluorescence emission, indicating inhibition of MepA. Therefore, the sesquiterpenes named trans-caryophyllene and caryophyllene oxide did not show direct antibacterial action; however, in their isolated form, they showed possible inhibitory action on NorA, Tet(K), MsrA and MepA efflux pumps. They may also act in antibiotic potentiation. Further studies are needed to identify the mechanisms involved in antibiotic potentiation and efflux pump inhibitory action.

Antibacterial activity of medicinal plants on the management of mastitis in dairy cows: A systematic review

BACKGROUND

Mastitis is a disease of economic importance in dairy production systems. The common management regime for mastitis is the use of synthetic antibiotics, giving a new problem of antibiotic resistance. There is, therefore, a need to prospect for alternatives to conventional antibiotics from herbal plants.

OBJECTIVES

This systematic review evaluates the use of plants as alternatives for the control of mastitis in dairy cattle, focussing on the effectiveness of studied plants and plant-based products and possible implications on the use of these products in livestock health.

METHODOLOGY

The PRISMA model was implemented with searches done in five electronic databases: Scopus, ScienceDirect, PubMed, Ovid and Research4Life. Data were extracted from 45 studies with 112 plant species from plant species belonging to 42 different families. The specific keywords were 'mastitis', 'dairy cows' and 'medicinal plants'.

RESULTS

The most cited plant species included Allium sativum L., Azadirachta indica and Eucalyptus globulus Labill with the latter further exploring its components. Microbial species causing mastitis mainly were Staphylococcus aureus and Escherichia coli. The extraction methods used included maceration approach using ethanol, methanol and water as solvents for phytochemicals and chromatographic techniques for essential oils. A few studies explored the mode of action, and toxicities of the herbal extracts as well as evaluating their efficacy in clinical trials using animal models.

CONCLUSION

Plants with defined levels of phytochemicals were essential sources of antibacterials. Standardisation of analytical methods is required.

Bovine Mastitis: Causes and Phytoremedies

Mastitis is a highly frequent chronic ailment with inflammation in the udder of the milking cows. The causative agents are mostly microbes. It is economically prominent contamination of lactating cows resulting in reduced milk production. The disease is diagnosed by chemical, physical and nutritional changes in the milk and pathological changes in the milk glands. Prevention measures for the disease can be taken by proper and timely sanitation of the cowshed through and time again disinfection of the teat, mechanized milking process, etc. The application of bactericidal drugs generates resistant varieties of microbes that cross the allopathic boundary. In this regard, an attempt is taken to focus the plant-based pharmacopoeia. Medicinal plants are traditionally used to cure various diseases as they are comparatively accessible to administer orally in different forms and can be along with fodder. Keeping the above facts in view, the present review deals with different types of mastitis, causative pathogens, detection and diagnosis, and effective plant-based treatment process available to date.

Formulation and evaluation of anti-MRSA nanoemulsion loaded with Achyrocline satureioides: a new sustainable strategy for the bovine mastitis

Methicillin-resistant Staphylococcus aureus (MRSA) causes mastitis in dairy cattle with serious economic and public health significance. This study developed nanoemulsions of Linum usitatissimun oil loaded with Achyrocline satureioides (macela) extract and investigated their in vitro antimicrobial activity against MRSA. Macela-nanoemulsions (NE-ML) were prepared using high-pressure homogenization (HPH) with different proportions of flaxseed oil, Tween 80 and crude extract. Four majoritarian flavonoids were identified in the macela extract: 3-O methylquercetin, achyrobichalcone, quercetin and luteolin (187.3 ± 0.1, 155.4 ± 11.6, 76.3 ± 0.1 and 30.4 ± 0.0 μg ml−1, respectively). NE-ML nanoemulsions were successfully obtained by the HPH method and showed a milky aspect with yellowish color. The mean particle size was around 200 nm with monodisperse distribution (PdI < 0.2), remaining stable for 160 days at room temperature. When analyzed on a LUMiSizer high-end dispersion analyzer, low values were found (≤0.5), indicating high stability index, mainly for NE-ML1:5 (0.2). The encapsulation efficiency of macela-nanoemulsions was greater than 94%, considering the four chemical compounds from extract. Minimum inhibitory concentration (MIC) against planktonic bacteria, inhibition of biofilm formation (MBIC), and eradication of MRSA biofilms (MBEC) were determined through in vitro tests on microplates. The MIC of NE-ML against planktonic MRSA showed values ranging from 1.2 to 10% (v/v), while blank-nanoemulsions (NE-B, without macela extract) showed values ranging from 6 to 50% (v/v). MBIC and MBEC of NE-ML were 25 and 80% (v/v), respectively. MBIC showed a mass reduction greater than 64%, and MBEC showed a mass reduction greater than 73%. Macela-nanoemulsions (NE-ML), mainly NE-ML1:5, showed high antimicrobial activity and appeared to represent a new alternative of sustainable antimicrobial product for the control of MRSA. Since this innovative nanoemulsion can impact animal health, future research should include in vitro and in vivo studies to evaluate intramammary therapy and control of MRSA infections in organic and agroecological milk production systems.

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.

Use of plant extracts and essential oils in the control of bovine mastitis

Bovine mastitis is the most important disease affecting dairy herds worldwide, causing direct impacts on farms' profitability and food safety issues. The prevention and treatment of this pathology is especially done through antimicrobials, but the increasing antimicrobial resistance of pathogens to this disease may affect the efficiency of conventional drugs. Besides, antimicrobials residues in milk and the environment are a potential threat to human health. Thereby, the use of plant extracts and essential oils may become promising alternatives for the control of bovine mastitis. Antimicrobial properties present in several plants are well described and plant extracts and essential oils are often considered safe to animals, humans and environment. This review summarizes the current problems encountered in the conventional treatment of mastitis, the possibilities of the use of plant extracts and essential oils as alternative agents for the control of these pathogens and the limitations found in the use of these plant derivatives. Finally, the perspectives to the use of plant extracts and essential oils for the treatment of bovine mastitis are presented.

Plant Extracts Display Synergism with Different Classes of Antibiotics

One manner in which plant-derived compounds exert their antibiotic potential is the synergism, a positive interaction between two compounds. Studies indicate that the use of plant extracts combined with antimicrobials may promote a significant reduction of the minimum inhibitory concentrations of antibiotics for bacterial strains. This study aimed to evaluate the activity of plant extracts and antibiotics as well as their combination on Staphylococcus aureus. The activity of 15 plant extracts was evaluated using diffusion assay. The minimum inhibitory concentrations (MICs) and the interactions between the extracts and antibiotics as well as compound emodin were evaluated with the checkerboard method. The active extracts were a hexane extract of the leaves of Baccharis dracunculifolia and the ethanol extracts of the leaves of Plectranthus ornatus, Inga edulis, Salvia officinalis and Senna macranthera. The Plectranthus ornatus extract displayed synergism with ampicillin (a β-lactam), kanamycin and gentamicin (aminoglycosides), with 8-fold reductions in the MIC. The same reduction was observed for the extracts of Salvia officinalis and Senna macranthera, which displayed the lowest MIC. Using these combinations resulted in a reduction in the minimum dose required for effective antimicrobial effects, which is interesting because it may decrease both the risk of side effects and the costs of treatment.

Anti-biofilm activity of hydromethanolic plant extracts against Staphylococcus aureus isolates from bovine mastitis

Bovine mastitis (BM) presents a high incidence, being Staphylococcus aureus one of the major causative agents. Antibiotics comprise the most common therapeutic approach, but due to their indiscriminate use, high rates of increasingly resistant bacterial species have been markedly pointed out. Particularly, S. aureus possesses a pronounced ability to form biofilms, and therefore, are of pivotal interest due to its alarming pathogenicity. The present study investigates the antibacterial properties of Eucalyptus globulus methanol: water extracts, alone and in combination with Juglans regia, against S. aureus isolates from BM. All isolates and reference strain proved to be good biofilm producers after 24 h of bacterial growth. Individually, the studied plant extracts (PE) lead to a considerable biofilm cells reduction, but their combination revealed to be the most effective strategy. When tested in combination, both extracts led to a 3 and 5 log reduction for S. aureus ATCC 25923 and S. aureus 1, respectively. Based on these findings, both PE seem to be promissory antimicrobial agents for upcoming use on dairy industry contaminations, BM and even S. aureus-triggered food poisoning. Further studies are needed to understand which of the compounds present in the extracts are responsible for the observed effects, including their corresponding modes of action.

Antibiotic activity of Plectranthus ornatus Codd., a Traditional Medicinal Plant

The dichloromethane extract of Plectranthus ornatus Codd., a tradicional medicinal plant, showed antibiotic activity with minimum inhibitory concentration (MIC) values of 0.4 mg.mL-1 and 100 percent of biofilm inhibition against Staphylococcus aureus strains isolated from animals with mastitis infections. Based on these antibacterial activities, in addition to ethnopharmacological reports from healing men and farmers in Brazil, an herbal soap was produced from this active extract and was tested both in vitro and in vivo. In vivo assays conducted on these herbal soaps led to results similar to those previously conducted with the active extract. These results indicated the great potential of this plant for use as an excipient by preparing herbal antibacterial soaps as an alternative veterinary medicine aimed at controlling bovine mastitis infections on small Brazilian farms.

Medicinal Plants Based Products Tested on Pathogens Isolated from Mastitis Milk

Bovine mastitis a major disease that is commonly associated with bacterial infection. The common treatment is with antibiotics administered intramammary into infected quarters of the udder. The excessive use of antibiotics leads to multidrug resistance and associated risks for human health. In this context, the search for alternative drugs based on plants has become a priority in livestock medicine. These products have a low manufacturing cost and no reports of antimicrobial resistance to these have been documented. In this context, the main objective of this study was to determine the antimicrobial effect of extracts and products of several indigenous, or acclimatized plants on pathogens isolated from bovine mastitis. A total of eleven plant alcoholic extracts and eight plant-derived products were tested against 32 microorganisms isolated from milk. The obtained results have shown an inhibition of bacterial growth for all tested plants, with better results for Evernia prunastri, Artemisia absinthium, and Lavandula angustifolia. Moreover, E. prunastri, Populus nigra, and L. angustifolia presented small averages of minimum inhibitory and bactericidal concentrations. Among the plant-derived products, three out of eight have shown a strong anti-microbial effect comparable with the effect of florfenicol and enrofloxacin, and better than individual plant extracts possibly due to synergism. These results suggest an important anti-microbial effect of these products on pathogens isolated from bovine mastitis with a possible applicability in this disease.

USE OF HYDROALCOHOLIC EXTRACT OF Schinus terebinthifolius Raddi IN PRE- AND POST-MILKING ANTISEPSIS OF THE TEAT IN DAIRY COWS

Abstract Medicinal plants have been used for centuries as an alternative treatment for health problems. Schinus terebinthifolius Raddi is a median tree that belongs to the Anacardiaceae family. The antibacterial effect of leaves extract of this plant has already been demonstrated. The objective of this study was to test a substance derived from this plant to be used in pre- and post-milking teat antisepsis. The hydroalcoholic extract of Brazilian pepper tree was used in opposite quarters for twelve consecutive weeks, and commercial iodine was used as control. None of the indices analyzed - black background mug, CMT, intramammary infections, skin health, and teat health - showed a statistical difference between the treatments, suggesting that the plant extract can be used in pre- and post-milking teat antisepsis, as a substitute for conventional products for herds in an agroecological production system.

Chemical Constituents and an Alternative Medicinal Veterinary Herbal Soap Made from Senna macranthera

Upon undergoing biomonitoring, the most active dichloromethane extract retrieved from Senna macranthera roots led to the isolation of three main compounds: emodine, physione, and chrysophanol. In this sequence, these compounds revealed a potential antibacterial activity against Staphylococcus aureus strains isolated from animals with mastitis infections with minimum inhibitory concentration (MIC) values of 20, 90, and 90 μg mL⁻¹, respectively. Therefore, an herbal soap was also produced from this same active extract. This soap was tested in vitro using gloves contaminated by animals with bovine mastitis that had been discarded after use by milkers and showed similar results to previously tested compounds. These results indicate the potential of this plant as an alternative veterinary medicine for the production of antibacterial soaps that aimed at controlling bovine mastitis infections in small Brazilian farms.