NEW NATURAL ANTIMICROBIAL AGENTS FROM OLEA EUROPAEA L. IN DAIRY INDUSTRY PATHOGENS CONTROL

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

Publication . Gomes, Fernanda; Martins, Natália; Ferreira, Isabel C.F.R.; Henriques, Mariana

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.

2019Journal article

Open access

Plant phenolic extracts as an effective strategy to control Staphylococcus aureus, the dairy industry pathogen

Publication . Gomes, Fernanda; Martins, Natália; Barros, Lillian; Rodrigues, Maria Elisa; Oliveira, Beatriz; Henriques, Mariana; Ferreira, Isabel C.F.R.

Staphylococcus aureus is one of the most common contagious mastitis pathogens. Bovine mastitis is considered an important reservoir for dairy industry contamination, and therefore to ensure S. aureus control has gained a pivotal importance. Natural matrices present multiple biological effects, being its antimicrobial potential increasingly reported. Thus, the present study aims to assess the antibacterial activity of several methanol:water extracts, obtained from plants, against Staphylococcus aureus. Moreover, the most effective extract was characterized in terms of phenolic compounds, by using high performance liquid chromatography coupled to diode array and mass spectrometer detectors. Among the tested extracts, Eucalyptus globulus was the most effective against all tested S. aureus strains, followed by Juglans regia and Foeniculum vulgare. Inhibition halos of the plant extracts varied between 8.0–16.0 mm, excepting for F. vulgare in which two evident halos were observed: one with growth inhibition (5.0–7.0 mm) and a second one with visible cell density reduction (13.0–14.0 mm). Susceptibility assays evidenced that E. globulus extract exerted the highest antibacterial activity (MICs = 0.195–0.39 mg/mL), being effective against all the tested strains. Among the phenolic compounds identified in this extract, gallotannins, ellagic acid glycoside, and quercetin derivatives, were the most abundant; and therefore, may exert a positive and contributive effect to the observed antibacterial effect. Overall, the use of plant extracts to control bovine mastitis caused by S. aureus is a promising solution that could contribute to the reduction of the occurrence of dairy food industry contaminations, providing considerable benefits to agro-industries on the formulation of high-quality and safety dairy products.

2018Journal article

Open access

Phenolic plant extracts versus penicillin G: In vitro susceptibility of Staphylococcus aureus isolated from bovine mastitis

Publication . Gomes, Fernanda; Rodrigues, Maria Elisa; Martins, Natália; Ferreira, Isabel C.F.R.; Henriques, Mariana

Antibiotics are the elective drugs in bovine mastitis (BM) treatment, despite their low rates of e ciency and e ectiveness and increasing risk of pathogen resistance. In this sense, it is urgent to discover new and e ective antimicrobial agents to apply in BM control and even treatment. Plant extracts have been widely recognized as a rich source of phytochemicals with antimicrobial potential. Thus, the present work aims to compare the bioactivity of Eucalyptus globulus and Juglans regia extracts against Staphylococcus aureus bovine mastitis strains with penicillin G. At non-toxic concentrations, E. globulus exerted a bacteriostatic e ect in planktonic cells and J. regia had no antimicrobial activity. Penicillin G, at minimum inhibitory concentration (MIC), demonstrated bactericidal activity, but just for S. aureus 3, 5, 6 and ATCC 25923, while the other strains seem to have acquired resistance. On the other hand, E. globulus and penicillin G in combination demonstrated synergy, being the most e ective approach against S. aureus 1, 2 and 4. Thus, penicillin alone and in combination with E. globulus or J. regia seems to be promissory strategies to control bovine mastitis infections.

2019Journal article

Open access