Antibacterial Activity of Essential Oil of Cinnamon and Trans-cinnamaldehyde against Staphylococcus spp. Isolated from Clinical Mastitis of Cattle and Goats

Background: Milk production plays a role as a source of protein and constitutes an important socioeconomic factor for small farms. The lack of planning of the creators, together with the lack of specialized technical assistance, and the precarious hygienic and sanitary management, are barriers that hinder the development of the activity. Bovine and caprine mastitis is an inflammation process of the mammary gland caused by microorganisms. Staphylococcus spp. is the main causative agent of mastitis, with higher prevalence in cases of clinical and subclinical manifestations. The most common treatment is based on intramammary infusion of antibacterial agents. However, cure rates obtained with such drugs are not always effectives, because it may determine the emergence of resistant bacteria as well increase amounts of antibiotic residues in milk. Nevertheless, the treatment of bovine subclinical mastitis caused by Staphylococcus spp. in the lactation can be economically unviable. Alternative treatments of bovine mastitis with plant derived compounds have been described. The investigation of its antimicrobial activity against bacterial agents of mastitis is justifiable. Materials, Methods & Results: This study evaluated the antimicrobial activity of essential oil (EO) of Cinnainomum zeylanicum (cinnamon) and the fraction trans-cinnamaldehyde (TC) against 65 isolates of Staphylococcus spp. from mastitis of cows (n = 32) and goats (n = 33). The cinnamon EO was extracted from the leaves and was composed majority by isoeugenol (96%), while the TC was acquired commercially. The antimicrobial susceptibility tests were performed according to CLSI M31-A3 agar diffusion method. Based on these tests, the isolates were divided into subgroups according to the resistance profiles. Subsequently, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by broth microdilution technique CLSI M31-A3. The MICs (geometric mean, GM) for cinnamon EO were 2032 mg/L and 2102 mg/L, respectively, for cattle and goats, while the majority fraction TC. was most active with MICs (GM) of 598 mg/L and 875 mg/L, respectively, for cattle and goats. Discussion: Some differences between these results and those reported by other authors can be attributed to the composition of OEs or techniques employed. In this study, we used the broth microdilution technique based on the document M31-A3, from CLSI, for the determination of MICs and MBCs. The lack of an internationally standardized technique for evaluating OEs and plant extracts that allow different protocols undermines the comparisons of results. The results of this study confirmed the antimicrobial activity of cinnamon EO and TC against clinical Staphylococcus spp. independent of the antibacterial susceptibility profile. The best antimicrobial activity was observed with TC than in the cinnamon EO, which deserves further research investigating the use of these compound in the treatment of mastitis. The TC can be found in high concentration in cinnamon bark. However, the essential oil used in this work was extracted from the leaves, and the major component was isoeugenol. The cinnamon EO composition can be varied depending on the part of the plant where it is extracted.