Antibacterial efficacy and mechanisms of action of medicinal plants against multidrug-resistant bacteria: A review with relevance to veterinary practice

Introduction

Bacterial disease remains a leading cause of production loss and mortality in livestock and poultry and antibacterial drugs are central to its control. The same drug classes are used in human and veterinary medicine and resistance selected in one sector can move to the other through the food chain, the farm environment and direct contact. Antimicrobial resistance is therefore a shared problem, and projections suggest that it could account for as many as ten million deaths each year by 2050 if current trends continue (Kong et al., 2026) [1] . Resistant phenotypes are now routinely recovered from food animals, including methicillin-resistant Staphylococcus aureus from bovine mastitis, extended-spectrum beta-lactamase-producing Escherichia coli from poultry and calves, and multidrug-resistant Salmonella, Pseudomonas aeruginosa and Klebsiella pneumoniae from clinical and environmental samples (Jubair et al., 2021) [2] . Restrictions on the use of antibiotic growth promoters, the withdrawal of several critically important antimicrobials from food-animal use and the shortage of new antibacterial classes have all increased interest in plant-derived alternatives. Plants produce a large range of secondary metabolites, including alkaloids, quinones, tannins, terpenoids and polyphenols, that function as constitutive or induced chemical defences against microbial attack (Kong et al., 2026; Pérez-Flores et al., 2025) [1,3] . A substantial share of newly approved drugs remains derived from, or inspired by, natural products (Newman et al., 2016) [4] . Because most phytochemicals act on several bacterial targets at once rather than on a single enzyme, single-step mutational resistance is less readily selected than it is with conventional antibiotics (Pérez-Flores et al., 2025; Wylie et al., 2022) [3,5] . Azadirachta indica A. Juss. (neem) is used here as the principal model species because its antibacterial, antibiofilm and synergistic properties are unusually well documented (Wylie et al., 2022; Sarkar et al., 2021) [5, 6] , and because it is already widely used in Indian ethnoveterinary practice. The objectives of this review are to summarise the antibacterial efficacy of medicinal plants for which well-characterised evidence exists, to describe the molecular mechanisms underlying that activity, to identify the factors that determine reproducibility, and to assess what would be required before such preparations could be used responsibly in veterinary practice.

Materials and Methods

This is a narrative review. Literature was retrieved from PubMed, Scopus, Web of Science and Google Scholar using combinations of the terms "medicinal plant", "plant extract", "essential oil", "antibacterial", "antimicrobial resistance", "multidrug resistant", "MRSA", "biofilm", "efflux pump" and "mechanism of action", together with the names of individual plant species. Records published between 1984 and 2026 were screened. Studies were included when they reported an experimentally determined endpoint (zone of inhibition, minimum inhibitory concentration, minimum bactericidal concentration, fractional inhibitory concentration index, time-kill data or a defined mechanistic assay) for a named plant species or an isolated constituent against a named bacterial species. Reports in which the plant material was not identified to species, in which no quantitative endpoint was given, or for which full bibliographic details could not be verified were excluded. Chemical and microbiological data are reported as they appear in the source publications; units were not converted, and values from different studies have not been pooled.

Results and Discussion

Plants with documented antibacterial activity

Eighteen species for which complete primary evidence could be verified are summarised in Table 1. They span 15 plant families and include leaf, bark, root, rhizome, seed, flower-bud and essential-oil preparations. Azadirachta indica is a tropical evergreen of the family Meliaceae, native to the Indian subcontinent and naturalised throughout the tropics and subtropics; its leaves, bark, seeds, roots, flowers and gum are all used medicinally (Wylie et al., 2022; Sarkar et al., 2021) [5,6] . Most of the remaining species are similarly multipurpose plants already present in traditional livestock husbandry. Activity in every case is attributable to secondary metabolites, conventionally grouped by biosynthetic origin into terpenoids, polyketides, phenylpropanoids and alkaloids (Kong et al., 2026) [1] . Azadirachta indica alone contains more than 300 characterised compounds, of which the limonoids are the most studied (Wylie et al., 2022; Sarkar et al., 2021) [5,6] ; gas chromatography-mass spectrometry of a methanolic leaf extract identified 30 major constituents, including n-hexadecanoic acid, coumarins and the monoterpene glycoside beta-D-mannofuranoside, O-geranyl (Altayb et al., 2022) [7] .

Antibacterial efficacy

Activity against Gram-positive bacteria

Gram-positive organisms, and staphylococci in particular, are the most susceptible group. In a screen of 60 folk medicinal plants, methanolic extracts of C. sinensis and A. citrodora were the most active against methicillin-resistant and methicillin-sensitive S. aureus, with minimum inhibitory concentrations of 0.5-1.5 mg/mL and inhibition zones of approximately 19-20 mm; H. sabdariffa, T. vulgaris and G. glabra followed (Bataineh et al., 2021) [8] . Thymoquinone from N. sativa inhibited 99 methicillin-resistant S. aureus strains at 8-16 µg/mL with an MIC 90 of 16 µg/mL, produced a greater than threelog reduction in viability and a post-antibiotic effect of 3.2 ± 0.2 h, and yielded no detectable resistant mutants under the exposure conditions used (Hariharan et al., 2016) [9] . Plumbagin from P. zeylanica inhibited 100 methicillin-resistant S. aureus isolates over a narrow range of 4-8 µg/mL and killed approximately 99% of a reference strain within 8 h (Periasamy et al., 2019) [10] .

Activity against Gram-negative bacteria

The Gram-negative outer membrane restricts the penetration of hydrophobic phytochemicals, and activity is correspondingly lower and less consistent. Important exceptions exist. Benzyl isothiocyanate and the root volatiles of S. persica were markedly more active against Gram-negative than Gram-positive bacteria, causing rapid membrane protrusion and loss of envelope integrity (Sofrata et al., 2011) [11] .

Methanolic miswak extract was likewise more active against Gramnegative than Gram-positive organisms in a panel of ten multidrug-resistant clinical isolates (Al-Ayed et al., 2016) [12] . Oregano oil rich in carvacrol inhibited all ten multidrug-resistant Acinetobacter baumannii isolates tested, at 1.75-3.50 mg/mL (Amaral et al., 2020) [13] , and tea tree oil was bactericidal against carbapenem-resistant K. pneumoniae, A. baumannii and P. aeruginosa (Oliva et al., 2018) [14] . In the neem-leaf study, the lowest methanolic-extract concentration showing bactericidal activity against P. aeruginosa was 3.125% (v/v) (Altayb et al., 2022) [7] . In contrast, P. aeruginosa was the most refractory organism in the 60-plant screen and was inhibited by only one of the ten active extracts (Bataineh et al., 2021) [8] , which illustrates how strongly outcomes depend on the isolate and the preparation.

Activity against multidrug-resistant bacteria

Several preparations retain activity against isolates that are resistant to multiple antibiotic classes. Neem extract inhibited extended-spectrum beta-lactamase-and carbapenemase-producing uropathogenic E. coli, with a mean inhibition zone of 20.18 mm (Khairnar et al., 2025) [15] . Clove extract inhibited all groups within a panel of 221 Gram-negative uropathogens screened for extended-spectrum beta-lactamase, metallo-beta-lactamase and AmpC production; activity was highest against Proteus spp., for which the inhibition zone was 19 mm (Faujdar et al., 2020) [16] . Fresh garlic extract was active against methicillin-resistant S. aureus, vancomycin-resistant Enterococcus faecalis, metallo-beta-lactamase-producing E. coli and extended-spectrum beta-lactamase-producing K. pneumoniae (Magryś et al., 2021) [17] . Extracts of T. chebula and T. bellirica inhibited S. aureus and methicillin-resistant S. aureus at 94-392 µg/mL and extended-spectrum beta-lactamase-producing E. coli and K. pneumoniae at 755 µg/mL (Tiwana et al., 2024) [18] .

Biofilm inhibition

Biofilms are central to chronic veterinary infections such as bovine mastitis, otitis, endometritis and catheter-and implant-associated disease, and they confer tolerance to antibiotics by restricting diffusion and promoting metabolic dormancy (Kong et al., 2026) [1] . Nimbolide from neem substantially disrupted and reduced methicillin-resistant S. aureus biofilm and was also active intracellularly (Sarkar et al., 2016) [19] . Thymoquinone inhibited biofilm formation and reduced the metabolic activity of established biofilms (Chaieb et al., 2011) [20] , and clove essential oils markedly reduced biofilm formation while increasing cell permeability and causing leakage of intracellular protein (Al-Mijalli et al., 2023) [21] . Asarone-containing fractions of A. calamus reduced biofilm formation alongside their membrane effects (Kongkham et al., 2024) [22] .

Comparison with conventional antibiotics

On a weight-for-weight basis, crude extracts are far less potent than purified antibiotics: inhibitory concentrations are typically expressed in milligrams per millilitre for extracts and in micrograms per millilitre for antibiotics. Isolated constituents narrow this gap considerably. Compounds 4 and 9 from M. micrantha inhibited methicillin-resistant S. aureus at 6.25 µg/mL against 3.125 µg/mL for vancomycin in the same assay system (Dong et al., 2023) [23] , and plumbagin and thymoquinone are active in the same low microgram range (Hariharan et al., 2016; Periasamy et al., 2019) [9,10] . Direct comparison of inhibition-zone diameters between an undiluted crude extract and a standard antibiotic disc, as is often reported, is not a valid measure of relative potency because the two are applied at very different molar concentrations; such comparisons should be interpreted with caution.

Mechanisms of antibacterial action

Phytochemicals generally act on several targets simultaneously, which both broadens their spectrum and reduces the likelihood of single-step resistance (Kong et al., 2026; Pérez-Flores et al., 2025) [1,3] . The principal mechanisms are summarised in Table 2.

Damage to the cell wall and cytoplasmic membrane

Envelope damage is the best-supported mechanism across the literature. Tea tree oil acts predominantly at the cytoplasmic membrane, increasing permeability, causing potassium leakage and inhibiting respiration (Cox et al., 2000) [24] . Asarone-rich fractions of A. calamus increase membrane permeability, cause leakage of nucleic acid and protein, and alter membrane fatty-acid composition (Kongkham et al., 2024; Al-Mijalli et al., 2025) [22,25] . Benzyl isothiocyanate produces rapid membrane protrusion and loss of integrity (Sofrata et al., 2011) [11] , and carvacrol-rich oregano oil destabilises and ruptures the mem-brane, as shown by flow cytometry (Amaral et al., 2020) [13] . Cinnamaldehyde acts more specifically: transcriptomic and proteomic analysis showed altered glycerophospholipid biosynthesis with changed production of phosphatidylethanolamine and phosphatidylglycerol, indicating that disturbance of membrane lipid homeostasis rather than simple partitioning underlies its activity (Pang et al., 2021) [26] . Molecular docking indicates that beta-D-mannofuranoside from neem binds S. aureus penicillin-binding protein 4 with an affinity of -9.7 kcal/mol 7 ; this is supportive in silico evidence and does not by itself establish inhibition of peptidoglycan cross-linking.

Interference with macromolecular synthesis

Evidence for direct inhibition of bacterial protein synthesis by the plant preparations reviewed here is limited, and claims of ribosomal targeting are generally not supported by binding or in vitro translation data; this mechanism should therefore be described as plausible but unproven for these species (Jubair et al., 2021) [2] . Evidence for interference with cell division is stronger for isolated compounds: plumbagin binds purified B. subtilis FtsZ and inhibits both its assembly and its GTPase activity, thereby disturbing Z-ring formation (Bhattacharya et al., 2013) [27] . This finding was obtained in B. subtilis and should not be presented as an established mechanism in S. aureus. Inhibition of bacterial DNA gyrase has been reported for chebulinic acid from T. chebula (Jubair et al., 2021) [2] .

Oxidative and thiol stress

Allicin inhibits bacterial growth by depleting glutathione and by S-allylmercapto modification of protein cysteine residues, which lowers cellular thiol concentrations, inactivates metabolic enzymes, causes protein aggregation and triggers oxidative and heat-stress responses (Müller et al., 2016) [28] . This is a genuinely multitarget mechanism and is the best-characterised explanation for the activity of garlic. It should be noted that endoplasmic reticulum stress and autophagy, which are sometimes cited in this context, are eukaryotic processes and cannot occur in bacteria; these effects have been described in host cells, not in the target organism.

Antibiofilm, quorum-sensing and anti-virulence effects

Several constituents interfere with adhesion, matrix production and cell-to-cell signalling rather than killing the organism outright. Because they impose weaker selection than bactericidal agents, such anti-virulence strategies are attractive where prolonged exposure is likely, as in mastitis control or in-feed use. Nimbolide, thymoquinone, eugenol-rich clove oils and asarone-containing fractions all reduce biofilm formation (Sarkar et [19,21,20,22] , and catechins alter the expression of genes associated with toxin production and stress response in S. aureus (Kitichalermkiat et al., 2020) [29] .

Synergy with antibiotics and efflux pump inhibition

The most clinically relevant property of these compounds may be their ability to restore the activity of failing antibiotics. Gallated catechins reverse beta-lactam resistance in methicillin-resistant S. aureus, substantially lowering the oxacillin minimum inhibitory concentration (Stapleton et al., 2004) [30] , and epicatechin gallate and epigallocatechin gallate inhibit efflux and potentiate norfloxacin against a NorAoverexpressing strain (Gibbons et al., 2004) [31] . Carvacrol-rich oregano oil is synergistic with polymyxin B against multidrug-resistant A. baumannii, with fractional inhibitory concentration indices of 0.18-0.37 and up to a 16-fold reduction in the polymyxin B minimum inhibitory concentration (Amaral et al., 2020) [13] . Tea tree oil is synergistic with oxacillin against methicillin-resistant S. aureus (Oliva et al., 2018) [14] , plumbagin with ciprofloxacin and piperacillin (Periasamy et al., 2019) [10] , and an A. calamus fraction with ampicillin, with fractional inhibitory concentration indices of 0.245-0.456 (Kongkham et al., 2024) [22] . Synergy is not universal: strong antagonism was recorded when Terminalia extracts were combined with polymyxin B (Tiwana et al., 2024) [18] , which is a reminder that combinations must be tested empirically rather than assumed.

Table 2. Principal mechanisms of antibacterial action of plant-derived compounds

Mechanism

Compound or extract Organism studied Experimental evidence Ref.

Cytoplasmic membrane disruption

Factors affecting antibacterial activity

Reported activity varies widely between studies of the same species, and the variation is largely methodological rather than biological (Pérez-Flores et al., 2025) [3] . Four factors are dominant. First, the plant part: in A. indica, seed material is richest in azadirachtin whereas leaves yield a different profile of flavonoids and fatty acids (Wylie et al., 2022; Sarkar et al., 2021) [5,6] . Second, the extraction solvent: methanol recovers a broader polarity range of antibacterial constituents than water, and aqueous and methanolic extracts of the same material can differ severalfold in activity (Al-Ayed et al., 2016; Tiwana et al., 2024) [12,18] . Third, chemotype and composition: the oregano oil examined in one study was dominated by terpinen-4-ol at 38.35% with an MIC of 1.18 mg/mL against S. aureus (Fikry et al., 2019) [32] , whereas the oil in a second study was dominated by carvacrol at 71.0% (Amaral et al., 2020) [13] . These are chemically different oils, and their data must not be pooled. Fourth, provenance and season: soil, climate and harvest stage determine secondary metabolite biosynthesis, which makes batch-to-batch consistency the single largest obstacle to standardisation.

Toxicity and safety

Cytotoxicity data for the more active extracts are reassuring but limited. Methanolic extracts of C. sinensis, A. citrodora and H. sabdariffa showed low cytotoxicity against Vero cells and fibroblasts and did not lyse human erythrocytes; in a murine model of systemic infection produced by intraperitoneal inoculation of methicillin-resistant S. aureus, mice given 300 mg/kg body weight of extract daily for seven days remained in good general health, with C. sinensis the most effective preparation (Bataineh et al., 2021) [8] . Computational absorption, distribution, metabolism, excretion and toxicity predictions for beta-D-mannofuranoside satisfied the standard drug-likeness rules and indicated a negative Ames result and negative rat carcinogenicity (Altayb et al., 2022) [7] ; these are in silico predictions and are not a substitute for toxicological testing. Against this, high doses of crude extracts can be non-specifically cytotoxic or allergenic (Kong et al., 2026) [1] , and essential oils containing carvacrol, thymol, eugenol or cinnamaldehyde are mucosal irritants at the concentrations used in vitro. For food-producing animals, no withdrawal periods, maximum residue limits or tissue-residue data exist for any of these preparations, and β-asarone in A. calamus is a recognised genotoxic carcinogen in rodents, which argues against its oral use in food animals.

Relevance to veterinary practice and animal husbandry

Three applications are realistic in the near term. The first is topical and intramammary use, where high local concentrations can be achieved without systemic exposure; the activity of tea tree oil, clove oil and neem preparations against methicillin-resistant S. aureus and against biofilm is directly relevant to mastitis, wound management, footrot and otitis (Sarkar et al., 2016; Al-Mijalli et al., 2023; Oliva et al., 2018) [19,21,14] . The second is as antibiotic adjuvants: catechins, carvacrol-rich oregano oil and plumbagin restore or potentiate the activity of oxacillin, polymyxin B, norfloxacin and ciprofloxacin (Stapleton et al., 2004; Gibbons et al., 2004; Amaral et al., 2020; Periasamy et al., 2019) [30,31,13,10] , which could allow dose reduction or re-use of older agents. The third is the use of standardised phytogenic feed additives to reduce enteric pathogen load and lower prophylactic antibiotic demand in poultry and pigs, although efficacy data from controlled production trials remain scarce. Integrating locally available ethnoveterinary plants into herd health planning also reduces reliance on veterinary antibiotics and, with it, the environmental dissemination of resistance genes, which aligns directly with One Health objectives.

Current challenges and research gaps

The evidence base has four structural weaknesses. Chemical complexity makes it difficult to attribute activity to defined constituents and complicates regulatory approval; many phytochemicals have poor oral bioavailability and are rapidly metabolised (Kong et al., 2026) [1] ; in vivo veterinary efficacy data are almost entirely absent; and crude preparations are difficult to patent, which limits commercial investment in the trials that would be required. Specific gaps and the work needed to close them are listed in Table 3. Green synthesis of silver nanoparticles using plant extracts as reducing and capping agents, and other encapsulation approaches, offer a route to improved stability, targeted delivery and sustained release with lower host cytotoxicity (Wylie et al., 2022) [5] , but these formulations themselves require residue and safety evaluation before use in food animals.

Conclusion

Medicinal plants offer a chemically diverse and biologically plausible source of antibacterial agents at a time when resistance is limiting the usefulness of conventional drugs in both human and veterinary medicine. The strongest and most reproducible evidence concerns damage to the bacterial envelope, disturbance of membrane lipid homeostasis, thiol and oxidative stress, suppression of biofilm formation and inhibition of efflux, with several constituents restoring the activity of beta-lactam and fluoroquinolone antibiotics against resistant staphylococci. These properties are most immediately applicable in veterinary practice as topical and intramammary preparations and as adjuvants to existing antibiotics rather than as replacements for them. Progress now depends less on further in vitro screening than on chemically standardised preparations, properly controlled trials in target species and the pharmacokinetic and residue data without which no product can be used responsibly in food-producing animals.

Acknowledgement

AcknowledgementThe authors sincerely acknowledge and thank all researchers whose valuable research articles and scientific contributions provided the foundation and supporting evidence for this review.

References

1. Kong SS, Park CH. Plant extracts: a potential approach to combating multidrug-resistant bacteria. EXCLI Journal. 2026;25:372374.
2. Jubair N, Rajagopal M, Chinnappan S, Abdullah NB, Fatima A. Review on the antibacterial mechanism of plant-derived compounds against multidrug-resistant bacteria (MDR). EvidenceBased Complementary and Alternative Medicine. 2021;2021:3663315.
3. Pérez-Flores JG, García-Curiel L, Pérez-Escalante E, ContrerasLópez E, Ocampo-Salinas IO, Guerrero-Solano JA, et al. Plant antimicrobial compounds and their mechanisms of action on spoilage and pathogenic bacteria: A bibliometric study and literature review. Applied Sciences. 2025;15:3516.
4. Newman DJ, Cragg GM. Natural products as sources of new drugs from 1981 to 2014. Journal of Natural Products. 2016;79(3):629-661.
5. Wylie MR, Merrell DS. The antimicrobial potential of the neem tree Azadirachta indica. Frontiers in Pharmacology. 2022;13:891535.
6. Sarkar S, Singh RP, Bhattacharya G. Exploring the role of Azadirachta indica (neem) and its active compounds in the regulation of biological pathways: an update on molecular approach. 3 Biotech. 2021;11(4):178.
7. Altayb HN, Yassin NF, Hosawi S, Kazmi I. In-vitro and in-silico antibacterial activity of Azadirachta indica (neem), methanolic extract, and identification of beta-D-mannofuranoside as a promising antibacterial agent. BMC Plant Biology. 2022;22:262.
8. Bataineh SMB, Tarazi YH, Ahmad WA. Antibacterial efficacy of some medicinal plants on multidrug resistance bacteria and their toxicity on eukaryotic cells. Applied Sciences. 2021;11(18):8479.
9. Hariharan P, Paul-Satyaseela M, Gnanamani A. In vitro profiling of antimethicillin-resistant Staphylococcus aureus activity of thymoquinone against selected type and clinical strains. Letters in Applied Microbiology. 2016;62(3):283-289.
10. Periasamy H, Iswarya S, Pavithra N, Senthilnathan S, Gnanamani A. In vitro antibacterial activity of plumbagin isolated from Plumbago zeylanica L. against methicillin-resistant Staphylococcus aureus. Letters in Applied Microbiology. 2019;69(1):41-49.
11. Sofrata A, Santangelo EM, Azeem M, Borg-Karlson AK, Gustafsson A, Pütsep K. Benzyl isothiocyanate, a major component from the roots of Salvadora persica is highly active against Gram-negative bacteria. PLoS ONE. 2011;6(8):e23045.
12. Al-Ayed MSZ, Asaad AM, Qureshi MA, Attia HG, AlMarrani AH. Antibacterial activity of Salvadora persica L. (miswak) extracts against multidrug resistant bacterial clinical isolates. Evidence-Based Complementary and Alternative Medicine. 2016;2016:7083964.
13. Amaral SC, Pruski BB, de Freitas SB, Allend SO, Ferreira MRA, Moreira C Jr et al. Origanum vulgare essential oil: antibacterial activities and synergistic effect with polymyxin B against multidrug-resistant Acinetobacter baumannii. Molecular Biology Reports. 2020;47(12):9615-9625.
14. Oliva A, Costantini S, De Angelis M, Garzoli S, Božović M, Mascellino MT et al. High potency of Melaleuca alternifolia essential oil against multi-drug resistant Gram-negative bacteria and methicillin-resistant Staphylococcus aureus. Molecules. 2018;23(10):2584.
15. Khairnar NP, Dawande P, Bankar NJ, Ghangale SS, Musale PS, Handore AV. Antibacterial potential of Azadirachta indica against ESBL-and carbapenemase-producing multidrug-resistant UPEC. Journal of Natural Remedies. 2025;25(6):1431-1437.
16. Faujdar SS, Bisht D, Sharma A. Antibacterial activity of Syzygium aromaticum (clove) against uropathogens producing ESBL, MBL, and AmpC beta-lactamase: are we close to getting a new antibacterial agent? Journal of Family Medicine and Primary Care. 2020;9(1):180-186.
17. Magryś A, Olender A, Tchórzewska D. Antibacterial properties of Allium sativum L. against the most emerging multidrug-resistant bacteria and its synergy with antibiotics. Archives of Microbiology. 2021;203(5):2257-2268.
18. Tiwana G, Cock IE, Cheesman MJ. Combinations of Terminalia bellirica (Gaertn.) Roxb. and Terminalia chebula Retz. extracts with selected antibiotics against antibiotic-resistant bacteria: bioactivity and phytochemistry. Antibiotics. 2024;13(10):994.
19. Sarkar P, Acharyya S, Banerjee A, Patra A, Thankamani K, Koley H, et al. Intracellular, biofilm-inhibitory and membrane-damaging activities of nimbolide isolated from Azadirachta indica A. Juss (Meliaceae) against meticillin-resistant Staphylococcus aureus. Journal of Medical Microbiology. 2016;65(10):1205-1214.
20. Chaieb K, Kouidhi B, Jrah H, Mahdouani K, Bakhrouf A. Antibacterial activity of thymoquinone, an active principle of Nigella sativa, and its potency to prevent bacterial biofilm formation. BMC Complementary and Alternative Medicine. 2011;11:29.
21. Al-Mijalli SH, El Hachlafi N, Abdallah EM, Jeddi M, Assaggaf H, Qasem A et al. Exploring the antibacterial mechanisms of chemically characterized essential oils from leaves and buds of Syzygium aromaticum (L.) Merr. et Perry against Staphylococcus aureus and Pseudomonas aeruginosa. Industrial Crops and Products. 2023;205:117561.
22. Kongkham B, Duraivadivel P, Hariprasad P. Acorus calamus L. rhizome extract and its bioactive fraction exhibits antibacterial effect by modulating membrane permeability and fatty acid composition. Journal of Ethnopharmacology. 2024;331:118323.
23. Dong LM, Xu QL, Liu SB, Zhang SX, Liu MF, Duan JL et al. Germacrane sesquiterpene dilactones from Mikania micrantha and their antibacterial and cytotoxic activity. Molecules. 2023;28(5):2119.
24. Cox SD, Mann CM, Markham JL, Bell HC, Gustafson JE, Warmington JR et al. The mode of antimicrobial action of the essential oil of Melaleuca alternifolia (tea tree oil). Journal of Applied Microbiology. 2000;88(1):170-175.
25. Al-Mijalli SH, Mrabti HN, Abdallah EM, Assaggaf H, Qasem A, Alenazy R et al. Acorus calamus as a promising source of new antibacterial agent against Pseudomonas aeruginosa and Staphylococcus aureus: deciphering volatile compounds and mode of action. Microbial Pathogenesis. 2025;200:107357.
26. Pang D, Huang Z, Li Q, Wang E, Liao S, Li E et al. Antibacterial mechanism of cinnamaldehyde: modulation of biosynthesis of phosphatidylethanolamine and phosphatidylglycerol in Staphylococcus aureus and Escherichia coli. Journal of Agricultural and Food Chemistry. 2021;69(45):13628-13636.
27. Bhattacharya A, Jindal B, Singh P, Datta A, Panda D. Plumbagin inhibits cytokinesis in Bacillus subtilis by inhibiting FtsZ assembly: a mechanistic study of its antibacterial activity. The FEBS Journal. 2013;280(18):4585-4599.
28. Müller A, Eller J, Albrecht F, Prochnow P, Kuhlmann K, Bandow JE et al. Allicin induces thiol stress in bacteria through S-allylmercapto modification of protein cysteines. Journal of Biological Chemistry. 2016;291(22):11477-11490.
29. Kitichalermkiat A, Katsuki M, Sato J, Sonoda T, Masuda Y, Honjoh KI, et al. Effect of epigallocatechin gallate on gene expression of Staphylococcus aureus. Journal of Global Antimicrobial Resistance. 2020;22:854-859.
30. Stapleton PD, Shah S, Anderson JC, Hara Y, Hamilton-Miller JMT, Taylor PW. Modulation of beta-lactam resistance in Staphylococcus aureus by catechins and gallates. International Journal of Antimicrobial Agents. 2004;23(5):462-467.
31. Gibbons S, Moser E, Kaatz GW. Catechin gallates inhibit multidrug resistance in Staphylococcus aureus. Planta Medica. 2004;70(12):1240-1242.
32. Fikry S, Khalil N, Salama O. Chemical profiling, biostatic and biocidal dynamics of Origanum vulgare L. essential oil. AMB Express. 2019;9:41.
33. Radji M, Agustama RA, Elya B, Tjampakasari CR. Antimicrobial activity of green tea extract against isolates of methicillin-resistant Staphylococcus aureus and multi-drug resistant Pseudomonas aeruginosa. Asian Pacific Journal of Tropical Biomedicine. 2013;3(8):663-667.
34. Alizadeh Behbahani B, Falah F, Lavi Arab F, Vasiee M, Tabatabaee Yazdi F. Chemical composition and antioxidant, antimicrobial, and antiproliferative activities of Cinnamomum zeylanicum bark essential oil. BioMed Research International. 2020;2020:5190603.
35. Tiwana G, Cock IE, Cheesman MJ. Phytochemical analysis and antimicrobial activity of Terminalia bellirica (Gaertn.) Roxb. and Terminalia chebula Retz. fruit extracts against gastrointestinal pathogens: enhancing antibiotic efficacy. Microorganisms. 2024;12(12):2664.
36. Wang LY, Huang SL, Zhang YW, Huang X, Sun F, Fu YW et al. Antibacterial effects of chebulagic acid and chebulinic acid isolated from Terminalia chebula against Vibrio parahaemolyticus. Aquaculture Reports. 2025;45:103085.
37. Chanda S, Rakholiya K. Combination therapy: synergism between natural plant extracts and antibiotics against infectious diseases. In: Méndez-Vilas A (ed). Science Against Microbial Pathogens: Communicating Current Research and Technological Advances. Formatex Research Center, Badajoz, Spain; 2011:520529. How to cite this article: Warhade GM, Warhade RM, Hangarkar MD, Vaghela SS, Jadhav MM, Sabale SC, et al. Antibacterial efficacy and mechanisms of action of medicinal plants against multidrug-resistant bacteria: A review with relevance to veterinary practice. International Journal of Veterinary Sciences and Animal Husbandry. 2026;11(9S):162-168. doi: https://www.doi.o rg/10.22271/veterinary.2026.v11.i9Sc.3790