Antibacterial potential of essential oils against planktonic and sessile cells of Escherichia coli isolated from diarrhea cases in swine

Escherichia coli is a pathogen associated with infections in piglets in the post-weaning phase, its pathogenicity is related to the animal's susceptibility to bacterial enterotoxins. The objective of the present study was to determine the EOs activity against E. coli strain, in the form planktonic and sessile. Although the Disc-Diffusion tests to determine the Minimum Inhibitory Concentration, do not fully corroborate with the other analyzes of this study, it was noticed bacteria inhibition. The EOs were prepared at 0.4%, 0.8% and 1.0% for tests. The tested EOs were effective against E. coli planktonic cells (p<0.05). As for the sessile cells, the most significant result was inhibition and 100% sessile cells at the concentration of 1.0% of Cymbopogon citratus EO. Although there was resistance in some treatments, the tested EOs demonstrated inhibition capacity, constituting promising alternatives for the control of E. coli, especially of planktonic cells.

Cymbopogon citratus Essential Oil: Its Application as an Antimicrobial Agent in Food Preservation

Antimicrobial in vitro and in situ efficacies of Cymbopogon citratus essential oil (lemongrass, LGEO) against 17 spoilage microorganisms (bacteria, yeasts and fungi) were evaluated. Additionally, its chemical composition, and antioxidant and antibiofilm activities were investigated. The LGEO exhibited a strong antioxidant activity (84.0 ± 0.1%), and its main constituents were citral (61.5%), geraniol (6.6%) and 1,8-cineole (6.4%). An in vitro antimicrobial evaluation revealed the lowest inhibition zone (1.00 ± 0.00 mm) in Pseudomonas fluorescens, and the highest inhibition zone (18.00 ± 2.46 mm) in Candida krusei. The values for the minimal inhibitory concentration were determined to be the lowest for Salmonella enteritidis and the highest for C. albicans. Furthermore, the concentration of ≥250 µL/L of LGEO suppressed the growth of Penicillium aurantiogriseum, Penicillium expansum, Penicillium chrysogenum and Penicillium italicum. The changes in the molecular structure of the biofilms produced by Pseudomonas fluorescens and Salmonella enteritidis, after their treatment with LGEO, confirmed its action on both biofilm-forming bacteria. Moreover, an in situ antimicrobial activity evaluation displayed the most effective inhibitory effectiveness of LGEO against Micrococcus luteus, Serratia marcescens (250 µL/L) and Penicillium expansum (125, 250 and 500 µL/L) growing on a carrot. Our results suggest that LGEO, as a promising natural antimicrobial agent, can be applied in the innovative packaging of bakery products and different types of vegetables, which combines commonly used packing materials with the addition of LGEO.

Chemical Composition and Antibacterial Activity of Extracts of Cymbopogon Citratus (Lemon Grass) and Phyllantus Amarus (Stone Breaker) Leaves

This study described the chemical composition, antioxidant and antibacterial activities of the ethanol and aqueous extracts of fresh and dried leaves of Phyllantus amarus (PA) (Stone breaker), Cymbopogon citratus (CC) (Lemon grass) and combination of stone breaker and lemon grass (PA/CC and DL/DP) using standard methods. The proximate and mineral results showed that both fresh and dried samples of Phyllantus amarus and Cymbopogon citratus were rich in crude fibre (18.53%, 14.65%), ash (16.27%, 2.29%), potassium (95.56 mg/100g, 54.04 mg/100g), calcium (58.57 mg/100g, 7.05 mg/100g), and sodium (15.23 mg/100g, 9.84 mg/100g) respectively. The ability of the extracts to scavenge 2, 2 diphenyl -2- picryl-hydrazyl (DPPH) radical showed that the fresh PA had the highest scavenging activity of 91.12 mg/g, followed (PA/CC) 90.93 mg/g and dried PA (85.61mg/g). The phytochemical composition of the extracts also revealed that they contain high content of cardiac glycoside (11.62 mg/g - 64.81 mg/g), terpenoid (14.56 mg/g - 69.66 mg/g), phenol (14.73 mg/g - 53.93 mg/g), saponin (22.61 mg/g - 30.47mg/g). Dried lemon and dried Phyllantus amarus (DL/DP) was found to be rich in Vitamin A (22.22 mg/g), while the lowest value of Vitamin E (0.36 mg/g) was obtained from fresh lemon grass (0.36mg/g). Antibacterial assay carried out on the two leaves extracts showed that they produced mild antibacterial activity against some foodborne pathogen (Bacillus cereus, Shigella dysenteriae, Escherichia coli, Salmonella spp, Staphylococcus aureus, Pseudomonas spp). with zones of inhibition of 4.3 mm -9.1mm. Further studies should be carried out to investigate the employment of the leaves in production of functional food

Comparative antimicrobial activity of Cymbopogon citratus essential oil and thiosemicarbazones derived from this oil

Introduction: The presence of microbes in our environment is always a permanent public health problem. In this context, research on natural treatment, less expensive and accessible to fight these microbial germs would be beneficial. Methods: During this work, molecules of thiosemicarbazones due to their numerous biological activities were hemi-synthesized in situ in the essential oil of Cymbopogon citratus in order to evaluate their antimicrobial activities. Results: Analysis of the essential oil extracted by hydrodistillation revealed the presence of 72.91% of citral. Citralthiosemicarbazone (CThio) and citral 4-phenyl-3-thiosemicarbazone (CPthio) were hemi-synthesized in this oil with interesting yields of 83% and 91%, respectively. After purification and confirmation of the structures of these molecules, the three substances were tested on eleven strains of microbes. Determination of the inhibition diameters showed that the activity of the essential oil is best in over 80% of strains. However, the largest diameter of inhibition (26 mm) was noted with CPthio against Salmonella typhi R 30951401. The determination of the minimum inhibitory concentrations showed that the oil remains more active with the smallest value of 0.3125 mg / ml against Micrococcus luteus. The lower value of minimum bactericidal concentrations was also obtained with the essential oil against Enterococcus foecalis ATCC 29212. Conclusion: The essential oil of C. citratus remains more active in the majority cases. It could be a great alternative in the fight against bacteria, and the advantage is that it remains a natural substance.

Ovicidal and Repellent Activities of Several Plant Essential Oils Against Periplaneta americana L. and Enhanced Activities from their Combined Formulation

Natural ovicidal and repellent agents against Periplaneta americana are in urgent need, and plant essential oils (EOs) can assume this role quite readily. In this study, ovicidal and repellent activities against Periplaneta americana of EOs from Cymbopogon citratus, Cinnamomum verum, Eucalyptus globulus, Illicium verum, and Zanthoxylum limonella in soybean oil and in ethyl alcohol were determined by topical and dual-choice assays, as well as 10% cypermethrin and a combined formulation of 5% C. verum EO + 5% I. verum EO. Cypermethrin at 10% provided the highest toxicity (100% inhibition rate) against the eggs, but only slightly higher than that (99.3%) provided by the combined EO formulation, while the highest repellent activity against the adults was provided by the combined formulation (89.5% repelled cockroaches at 48 h after treatment). In addition, all EO formulations in soybean oil provided higher ovicidal and repellent activities than in ethyl alcohol. To conclude, the combined EO formulation in soybean oil can replace cypermethrin because their efficacy was nearly equivalent, but the combination should be much safer to use.