Synergistic Interaction Between Paired Combinations of Natural Antimicrobials Against Poultry-Borne Pathogens

Exploring the Therapeutical Potential of Asparagopsis armata Biomass: A Novel Approach for Acne Vulgaris Treatment

Acne vulgaris, a high-prevalence skin condition afflicting people, persists as a significant challenge in the absence of effective treatments and emerging antibiotic resistance. To address this pressing concern, exploration of innovative approaches is of the utmost importance. Asparagopsis armata, an invasive red seaweed renowned for its diverse array of bioactive compounds, emerges as a promising candidate. This study seeks to elucidate the potential utility of A. armata biomass in the treatment of acne vulgaris. Crude extracts were obtained through solid-liquid extraction, and fractions were obtained using liquid-liquid extraction. The analyzed bioactivities included antioxidant, antimicrobial, and anti-inflammatory. Also, chemical characterization was performed to identify free fatty acids and compounds through LC-MS and elements. The present findings unveil compelling attributes, including anti-Cutibacterium acnes activity, cytotoxic and non-cytotoxic effects, antioxidant properties, and its ability to reduce nitric oxide production with consequent anti-inflammatory potential. Additionally, chemical characterization provides insights into its mineral elements, free fatty acids, and diverse compounds. The observed antimicrobial efficacy may be linked to halogenated compounds and fatty acids. Cytoprotection appears to be associated with the presence of glycerolipids and glycosylated metabolites. Furthermore, its antioxidant activity, coupled with anti-inflammatory properties, can be attributed to phenolic compounds, such as flavonoids. This study underscores the potential of A. armata as a natural ingredient in skincare formulations, offering an important contribution to the ongoing battle against acne vulgaris.

Thymol and carvacrol against Klebsiella: anti-bacterial, anti-biofilm, and synergistic activities-a systematic review

Introduction

Klebsiella poses a significant global threat due to its high antibiotic resistance rate. In recent years, researchers have been seeking alternative antimicrobial agents, leading to the introduction of natural compounds such as monoterpenes, specifically thymol and carvacrol. This review aims to illustrate the potential antimicrobial, anti-biofilm, and synergistic traits of thymol and carvacrol in combat against Klebsiella.

Methods

Searching PubMed, Scopus, and Web of Science, we reviewed available evidence on the antibacterial effects of thymol, carvacrol, or combined with other compounds against Klebsiella until May 2024. Reference checking was performed after the inclusion of studies. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), fractional inhibitory concentration (FIC), and anti-biofilm activity were gathered, and the MBC/MIC ratio was calculated to assess the bactericidal efficacy.

Results

We retrieved 38 articles out of 2,652 studies screened. The gathered data assessed the anti-microbial activity of thymol, carvacrol, and both compounds in 17, 10, and 11 studies, respectively. The mean (± standard deviation) non-weighted MIC was 475.46 μg/mL (±509.95) out of 60 MIC for thymol and 279.26 μg/mL (±434.38) out of 68 MIC for carvacrol. Thymol and carvacrol showed anti-biofilm activities in the forms of disruption, inhibition, and mass reduction of biofilms. The MBC/MIC ratio was lower than 4 in 45 out of 47 cases, showing high bactericidal efficacy. FIC values were gathered for 68 combinations of thymol and carvacrol with other compounds, and they were mostly synergistic or additive.

Conclusion

Thymol and carvacrol alone or in combination with other compounds, specifically known antibiotics, show great antimicrobial activity.

Enhancing Commercial Antibiotics with Trans-Cinnamaldehyde in Gram-Positive and Gram-Negative Bacteria: An In Vitro Approach

One strategy to mitigate the emergence of bacterial resistance involves reducing antibiotic doses by combining them with natural products, such as trans-cinnamaldehyde (CIN). The objective of this research was to identify in vitro combinations (CIN + commercial antibiotic (ABX)) that decrease the minimum inhibitory concentration (MIC) of seven antibiotics against 14 different Gram-positive and Gram-negative pathogenic bacteria, most of them classified as ESKAPE. MIC values were measured for all compounds using the broth microdilution method. The effect of the combinations on these microorganisms was analyzed through the checkboard assay to determine the type of activity (synergy, antagonism, or addition). This analysis was complemented with a kinetic study of the synergistic combinations. Fifteen synergistic combinations were characterized for nine of the tested bacteria. CIN demonstrated effectiveness in reducing the MIC of chloramphenicol, streptomycin, amoxicillin, and erythromycin (94-98%) when tested on Serratia marcescens, Staphylococcus aureus, Pasteurella aerogenes, and Salmonella enterica, respectively. The kinetic study revealed that when the substances were tested alone at the MIC concentration observed in the synergistic combination, bacterial growth was not inhibited. However, when CIN and the ABX, for which synergy was observed, were tested simultaneously in combination at these same concentrations, the bacterial growth inhibition was complete. This demonstrates the highly potent in vitro synergistic activity of CIN when combined with commercial ABXs. This finding could be particularly beneficial in livestock farming, as this sector witnesses the highest quantities of antimicrobial usage, contributing significantly to antimicrobial resistance issues. Further research focused on this natural compound is thus warranted for this reason.

Inhibition of Salmonella Enteritidis by Essential Oil Components and the Effect of Storage on the Quality of Chicken

This research investigates the antibacterial potential of plant essential oil components including thymol, carvacrol, citral, cinnamaldehyde, limonene, and β-pinene against Salmonella Enteritidis (S. Enteritidis). Through the determination of minimum inhibitory concentration, three kinds of natural antibacterial agents with the best inhibitory effect on S. Enteritidis were determined, namely thymol (128 μg/mL), carvacrol (256 μg/mL), and cinnamaldehyde (128 μg/mL). Physical, chemical, microbial, and sensory characteristics were regularly monitored on days 0, 2, 4, and 6. The findings of this study reveal that both thymol at MIC of 128 μg/mL and carvacrol at MIC of 256 μg/mL not only maintained the sensory quality of chicken, but also decreased the pH, moisture content, and TVB-N value. Additionally, thymol, carvacrol and cinnamaldehyde successfully inhibited the formation of S. Enteritidis biofilm, thereby minimizing the number of S. Enteritidis and the total aerobic plate count in chicken. Hence, thymol, carvacrol, and cinnamaldehyde have more effective inhibitory activities against S. Enteritidis, which can effectively prevent the spoilage of chicken and reduce the loss of its functional components.

A Systematic Quantitative Determination of the Antimicrobial Efficacy of Grape Seed Extract against Foodborne Bacterial Pathogens

Concerns regarding the role of antimicrobial resistance (AMR) in disease outbreaks are growing due to the excessive use of antibiotics. Moreover, consumers are demanding food products that are minimally processed and produced in a sustainable way, without the use of chemical preservatives or antibiotics. Grape seed extract (GSE) is isolated from wine industry waste and is an interesting source of natural antimicrobials, especially when aiming to increase sustainable processing. The aim of this study was to obtain a systematic understanding of the microbial inactivation efficacy/potential of GSE against Listeria monocytogenes (Gram-positive), Escherichia coli and Salmonella Typhimurium (Gram-negative) in an in vitro model system. More specifically, for L. monocytogenes, the effects of the initial inoculum concentration, bacterial growth phase and absence of the environmental stress response regulon (SigB) on the GSE microbial inactivation potential were investigated. In general, GSE was found to be highly effective at inactivating L. monocytogenes, with higher inactivation achieved for higher GSE concentrations and lower initial inoculum levels. Generally, stationary phase cells were more resistant/tolerant to GSE as compared to exponential phase cells (for the same inoculum level). Additionally, SigB appears to play an important role in the resistance of L. monocytogenes to GSE. The Gram-negative bacteria under study (E. coli and S. Typhimurium) were less susceptible to GSE as compared to L. monocytogenes. Our findings provide a quantitative and mechanistic understanding of the impact of GSE on the microbial dynamics of foodborne pathogens, assisting in the more systematic design of natural antimicrobial-based strategies for sustainable food safety.