Issue cover
Research Article | 10 Jun 2026

Comparative in vitro antibacterial efficacy of Melaleuca alternifolia and Copaifera officinalis essential oils against multidrug-resistant bovine mastitis pathogens

Marcela Calciolari Branquinho1 ORCID , Margarete Kimie Falbo1,2 ORCID , Itacir Eloi Sandini1 ORCID , Marina Szychta1 ORCID , and Kate Aparecida Buzi2 ORCID Show more
VETERINARY WORLD | Article No. 8 | pg no. 2371-2378 | Vol. 19, Issue 6 | DOI: 10.14202/vetworld.2026.2371-2378
Citations: —
View PDF

Cite this Article

  • APA
  • MLA
  • Chicago
  • Vancouver
  • Harvard

                            
                        


                    


                


            


            


            
        

              


                  

                      
ABSTRACT

                      
Background and Aim: Bovine mastitis remains a major constraint in dairy production, leading to substantial economic losses, compromised animal welfare, and increased antimicrobial use. The emergence of multidrug-resistant (MDR) pathogens has reduced therapeutic efficacy and intensified the search for alternative antimicrobial strategies. Essential oils (EOs) have gained attention due to their bioactive properties and potential role as adjunct or alternative therapeutics. This study aimed to evaluate the in vitro antibacterial activity of Melaleuca alternifolia and Copaifera officinalis EOs against reference strains and clinically characterized mastitis-associated bacteria. 
Materials and Methods: Reference strains Escherichia coli American Type Culture Collection (ATCC) 25922, Klebsiella pneumoniae ATCC 13883, Staphylococcus aureus ATCC 25923, and methicillin-resistant S. aureus ATCC 43300, along with clinical isolates of Streptococcus agalactiae and Streptococcus uberis, were used. Antimicrobial susceptibility was assessed using the Kirby–Bauer disk diffusion method following Clinical and Laboratory Standards Institute guidelines. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by broth microdilution. EOs were tested over a concentration range of 0.49–250 mg/mL, and bactericidal activity was defined as an MBC/MIC ratio ≤ 4. 
Results: The antimicrobial susceptibility profiles confirmed MDR phenotypes in methicillin-resistant S. aureus ATCC 43300 and the clinical isolate of S. agalactiae. M. alternifolia EO exhibited broader antibacterial activity, inhibiting E. coli ATCC 25922 (MIC = 10 mg/mL; MBC/MIC = 1) and showing inhibitory effects against S. uberis (MIC = 15 mg/mL) and S. agalactiae (MIC = 31 mg/mL). However, bactericidal activity against streptococcal isolates was not observed (MBC/MIC > 4). C. officinalis EO demonstrated limited antibacterial activity, with growth inhibition detected only against S. uberis (MIC = 10 mg/mL) and S. agalactiae (MIC = 7.5 mg/mL), without bactericidal effects. No activity was observed against K. pneumoniae or methicillin-resistant S. aureus within the tested range. 
Conclusion: M. alternifolia EO exhibited broader antibacterial activity than C. officinalis, particularly against streptococcal mastitis pathogens. Although bactericidal effects were limited, the observed inhibitory activity highlights the potential of EOs as adjunct antimicrobial agents. Further in vivo studies, formulation optimization, and investigation of synergistic interactions with conventional antimicrobials are warranted to support their application in bovine mastitis management. 
                      
Keywords: antimicrobial resistance, bovine mastitis, Copaifera officinalis, essential oils, Melaleuca alternifolia, minimum bactericidal concentration, minimum inhibitory concentration, Streptococcus uberis.