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

Abstract

Natural antimicrobials (NAM) are promising candidates for the successful control of poultry-borne bacteria, carrying potent antimicrobial activity (AMA) against a wide range of multidrug-resistant pathogens. Individual activities of carvacrol, eugenol, trans-cinnamaldehyde, oregano, and thymol, along with the combined activity of paired compounds, were examined using broth microdilution and checkerboard techniques. The characteristic interactions between the compounds were calculated using an improved method, based on combination index (CI) values. The bacteria examined herein were selected due to their known genetic resistance to at least one antibiotic. Our results indicated that thymol was most effective, exhibiting the lowest minimum inhibitory concentration (MIC) value against Salmonella pullorum, Escherichia coli, and Klebsiella pneumoniae, establishing the order of antimicrobial efficacy as: thymol > oregano > carvacrol > trans-cinnamaldehyde > eugenol. In the interaction study, the paired combination of carvacrol and thymol showed synergistic effects and was highly effective in reducing the antibiotic resistance of all the evaluated pathogens. Notably, all CI values were <1.0 in evaluations of S. pullorum, indicating the absence of antagonism between eugenol and thymol (or oregano). In K. pneumoniae, majority of CI values, which had a few concentration points, were smaller than 1.0, indicating a synergistic effect between eugenol and carvacrol (oregano or thymol), and trans-cinnamaldehyde and carvacrol. In E. coli, apart from some concentration points, some CI values were smaller than 1.0, demonstrating a synergistic effect between eugenol and carvacrol, and thymol and carvacrol (eugenol or oregano). It is therefore of great significance to investigate and illuminate the minimal effect concentration of these five components when they are used in combination as feed additives. Moreover, the improved evaluation method of this study provides a precise and extensive means to assess the synergistic effects of NAM.

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

“…For K. pneumoniae, our results (500 µg/mL, Table 1) agree with those found in the literature, ranging from 281 [65] to 519 µg/mL [63], although the strains are different.…”

“…For Gram-negative bacteria, on the contrary, it was possible to find MICs referenced in the literature for the same strains of E. coli and P. aeruginosa used in our study ( Table 1 ). Other authors proposed MIC values for CIN ranging from 400 [ 61 ] to 519 µg/mL on different strains of the two cited bacteria [ 63 ]. The E. coli outer membrane has proven to be completely lysed by CIN [ 51 ].…”

“…Both authors give results higher than those found in our study (500 µg/mL) ( Table 1 ). Structural changes were also observed in S. enterica [ 25 ] and K. pneumoniae [ 63 ] when treated with CIN, while some other researchers hypothesized that the CIN carbonyl group might bind to proteins, provoking the inhibition of amino acid decarboxylase [ 67 ], modifying the production of bacteria metabolites.…”

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

“…Therefore, cinnamaldehyde's ability to inhibit itidis in chicken was weaker than thymol and carvacrol, which was confirmed search of Hoffman et al [42] Furthermore, there are researchers who have pro order of antibacterial effectiveness of EOs as follows: thymol > oregano > carvacro cinnamaldehyde > eugenol. Among these, thymol has demonstrated the stron bacterial effect against Salmonella, Escherichia coli, and Klebsiella pneumoniae [43]. extension of storage time, the number of Salmonella in each group increased rap one hand, due to the volatilization of thymol and carvacrol over time, the ant effects of thymol and carvacrol are weakened.…”

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

“…The possibility of using natural antimicrobials to replace chemical preservatives and the extensive use of antibiotics has been one of the major goals of the food industry [12]. By using natural antimicrobial components, health risks associated with chemical additives and AMR could be reduced [13][14][15].…”