Effect of the essential oil of Minthostachys verticillata (Griseb.) Epling and limonene on biofilm production in bovine mastitis pathogens

CERIOLI F; MONTIRONI I; MOLIVA M; CAMPRA NA; CARIDDI LN; REINOSO E

Congreso; Asociación Argentina de Microbiología General XII Congreso de Microbiología General; 2017

Bovine mastitis is a disease that causes large annual economic losses. Different microorganisms are associated with the disease, as well as their ability to form biofilm. The development and establishment of the biofilm depend on the ability of the pathogen to adhere to bovine mammary epithelial cells and leads to antibiotic resistance. The intensive administration of antibiotics for prevention or treatment, leads to the emergence of resistant strains. Research is now leading to the search for alternative control methods, and medicinal plants can be a natural, safe, effective and inexpensive option for the treatment of this disease. Minthostachys verticillata is an autochthonous medicinal plant with multiple ethnobotanical properties. In a previous study, we demonstrated that the essential oil (EO) of this species and limonene, one of its compounds, inhibited the growth of pathogens causing bovine mastitis. The objective of the present work was to determine the inhibitoryeffect of the essential oil of M. verticillata and limonene, before and after biofilm formation produced by pathogens isolated from bovine mastitis. Time kill assay and bacterial lysis were also determined. Six samples were used in the present study. The bacterial isolates were identified by conventional bacteriological methods and later confirmed by molecular methods. Strains were identified as Escherichia coli, Bacillus pumilus and Enterococcus faecium. It was observed that MIC values for EO were 3.6 mg/ml for Enterococcus faecium; 3.6 to 14.5 mg/ml for Escherichia coli strains; 3.6 to 29.03 for Bacillus pumilus strains. Whereas, MIC values for limonene were 52.5 mg/ml for E. faecium; 105 to210 mg/ml for E. coli strains; 52.5 to 210 mg/ml for Bacillus pumilus strains. These results demonstrated that the EO was more effective than limonene against the isolated strains, since it requires lower concentrations exert an inhibitory effect. However, EO demonstrated bactericidal action against E. faecium and MBC was 29.03 mg/ml. This result was corroborated by time of death assays in which was observed a significant decreased of cells since 6 h and then by bacterial lysis assay. Both EO and limonene were able to inhibit biofilm after formation in E. faecium (p