Cinnamaldehyde: a compound with antimicrobial and synergistic activity against ESBL-producing quinolone-resistant pathogenic Enterobacteriaceae

Citral and triclosan synergistically silence quorum sensing and potentiate antivirulence response in Pseudomonas aeruginosa

Among the ESKAPE pathogens, Pseudomonas aeruginosa is an extensively notorious superbug that causes difficult-to-treat infections. Since quorum sensing (QS) directly promotes pseudomonal virulence, targeting QS circuits is a promising approach for disarming phenotypic virulence. Hence, this study scrutinizes the anti-QS, antivirulence, and anti-biofilm potential of citral (CiT; phytochemical) and triclosan (TcN; disinfectant), alone and in combination, against P. aeruginosa PAO1/PA14. The findings confirmed synergism between CiT and TcN and revealed their quorum quenching (QQ) potential. At sub-inhibitory levels, CiT-TcN combination significantly impeded pyocyanin, total bacterial protease, hemolysin, and pyochelin production alongside inhibiting biofilm formation in P. aeruginosa. Moreover, the QQ and antivirulence potential of CiT and TcN was positively correlated by molecular docking studies that predicted strong associations of the drugs with QS receptors of P. aeruginosa. Collectively, the study identifies CiT-TcN as an effective drug combination that harbors QQ, antivirulence, and anti-biofilm prospects against P. aeruginosa.

Antibacterial effectiveness of trans-cinnamaldehyde against foodborne Enterobacteriaceae and its adjuvant effect with gentamicin

The Enterobacteriaceae family is recognized as a primary group of Gram-negative pathogens responsible for foodborne illnesses and is frequently associated with antibiotic resistance. The present study explores the natural-based compound trans-cinnamaldehyde (TC) against drug-resistant Enterobacteriaceae and its synergism with gentamicin (GEN) to address this issue. The research employs three strains of Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae, previously isolated from shrimp. The antibacterial activity was evaluated by the disk diffusion method, microdilution test, kinetics of growth, and time-kill curve. In addition, the synergistic effect between TC/GEN was investigated by checkerboard assay. All strains showed sensitivity to TC with an inhibition zone diameter > 35 mm. The TC showed inhibitory and bactericidal action in the most tested bacteria around 625 μg/mL. Sub-inhibitory amounts (1/2 and 1/4 MIC) of TC interfered with the growth kinetics by lag phase extension and decreased the log phase. Time-kill curves show a reduction of viable cells after the first hour of TC treatment at bactericidal concentrations. The synergistic effect between TC/GEN was observed for E. coli and E. cloacae strains with FICi ranging from 0.15 to 0.50. These findings, therefore, suggest TC as a promising alternative in the fight against drug-resistant Enterobacteriaceae that can cause foodborne illnesses.

In vitro effects of phytogenic feed additive on Piscirickettsia salmonis growth and biofilm formation

Piscirickettsiosis is the main cause of mortality in salmonids of commercial importance in Chile, which is caused by Piscirickettsia salmonis, a Gram-negative, γ-proteobacteria that can produce biofilm as one of its virulence factors. The Chilean salmon industry uses large amounts of antibiotics to control piscirickettsiosis outbreaks, which has raised concern about its environmental impact and the potential to induce antibiotic resistance. Thus, the use of phytogenic feed additives (PFA) with antibacterial activity emerges as an interesting alternative to antimicrobials. Our study describes the antimicrobial action of an Andrographis paniculate-extracted PFA on P. salmonis planktonic growth and biofilm formation. We observed complete inhibition of planktonic and biofilm growth with 500 and 400 μg/mL of PFA for P. salmonis LF-89 and EM-90-like strains, respectively. Furthermore, 500 μg/mL of PFA was bactericidal for both evaluated bacterial strains. Sub-inhibitory doses of PFA increase the transcript levels of stress (groEL), biofilm (pslD), and efflux pump (acrB) genes for both P. salmonis strains in planktonic and sessile conditions. In conclusion, our results demonstrate the antibacterial effect of PFA against P. salmonis in vitro, highlighting the potential of PFA as an alternative to control Piscirickettsiosis.

Formulation of novel bioactive gelatin inspired by cinnamaldehyde for combating multi-drug resistant bacteria: Characterization, molecular docking, pharmacokinetic analyses, and in vitro assessments

This study set out to formulate antibacterial and antioxidant gelatin boosted by cinnamaldehyde for combating multi-drug resistant bacteria previously obtained from chronic wounds. Towards this end, gelatin amine groups were conjugated with carbonyl groups of cinnamaldehyde, producing cinnamyl-gelatin Schiff bases. The physicochemical attributes of cinnamyl-gelatin Schiff bases were probed concerning alterations in chemical structures and microstructures compared to native gelatin. Besides, cinnamyl-gelatin Schiff bases exhibited higher thermal stability than gelatin, with a diminishing in solubility due to increases in hydrophobicity features. Interestingly, cinnamyl-gelatin derivatives exerted antibacterial activities versus multi-drug resistant Gram-negative and Gram-positive bacteria, showing maximum growth inhibition at the highest concentration of cinnamaldehyde incorporated into gelatin. The scavenging activities of gelatin against DPPH and ABTS•+ were promoted in cinnamyl-gelatin derivatives from 11.93 ± 0.6 % to 49.9 ± 2.5 % and 12.54 ± 0.63 % to 49.9 ± 3.12 %, respectively. Remarkably, cinnamyl-gelatin derivatives induced the proliferation of fibroblast cells, implying their prospective applications in tissue engineering. Molecular docking and pharmacokinetic investigations disclosed the potential antibacterial mechanisms of cinnamyl-gelatin derivatives alongside their biopharmaceutical applications. Altogether, these findings suggest that cinnamyl-gelatin derivatives could be utilized to tailor antibacterial-free antibiotics and antioxidant wound dressings against virulent bacteria to promote chronic wound recovery.

Bioactive Compounds from Plant Origin as Natural Antimicrobial Agents for the Treatment of Wound Infections

The rising prevalence of drug-resistant bacteria underscores the need to search for innovative and nature-based solutions. One of the approaches may be the use of plants that constitute a rich source of miscellaneous compounds with a wide range of biological properties. This review explores the antimicrobial activity of seven bioactives and their possible molecular mechanisms of action. Special attention was focused on the antibacterial properties of berberine, catechin, chelerythrine, cinnamaldehyde, ellagic acid, proanthocyanidin, and sanguinarine against Staphylococcus aureus, Enterococcus spp., Klebsiella pneumoniae, Acinetobacter baumannii, Escherichia coli, Serratia marcescens and Pseudomonas aeruginosa. The growing interest in novel therapeutic strategies based on new plant-derived formulations was confirmed by the growing number of articles. Natural products are one of the most promising and intensively examined agents to combat the consequences of the overuse and misuse of classical antibiotics.

Comparative reassessment of AcrB efflux inhibitors reveals differential impact of specific pump mutations on the activity of potent compounds

Multidrug resistance poses global challenges, particularly with regard to Gram-negative bacterial infections. In view of the lack of new antibiotics, drug enhancers, such as efflux pump inhibitors (EPIs), have increasingly come into focus. A number of chemically diverse agents have been reported to inhibit AcrB, the main multidrug transporter in Escherichia coli, and homologs in other Gram-negative bacteria. However, due to the often varying methodologies used for their characterization, results remain difficult to compare. In this study, using a defined selection of antibiotics known to be efflux substrates, we reevaluated 38 published compounds for their in vitro EPI activity. When examined in an E. coli strain with stable wild-type AcrB overexpression, we found 17 compounds showing at least fourfold enhancing potency with more than 2 out of 10 test drugs (belonging to eight antibiotic classes). Pyranopyridines (MBX series) were confirmed as the most potent inhibitors among agents reported so far. A new and surprising finding was that their activity, unlike that of the pyridylpiperazine EPI BDM88855, was highly susceptible to the AcrB double-mutation G141D_N282Y, which had previously been shown to diminish drug enhancing of 1-(1-naphthylmethyl)piperazine in a predominantly substrate-specific manner. Conversely, transmembrane region mutation V411A, while eliminating the drug potentiating of the BDM compound, did not decrease the activity of the MBX EPIs. Besides comparative reassessment of the potency of reported EPIs, the study demonstrated the usefulness of mutagenesis approaches providing tools for an initial discrimination of EPIs regarding their mode of function.IMPORTANCEInfections with difficult-to-treat multidrug-resistant bacteria pose an urgent global threat in view of the stagnating development of new antimicrobial substances. Efflux pumps in Gram-negative pathogens are known to substantially contribute to multidrug resistance making them promising targets for chemotherapeutic interventions to restore the efficacy of conventional antibiotics. In the present study, the in vitro activity of previously reported efflux pump inhibitors was reassessed using standardized conditions. Relevant drug sensitizing activity could be proven for almost half of the tested compounds. Further characterization of potent inhibitors was achieved by investigating the impact of specific efflux pump mutations. A double-mutation previously known to decrease the activity of the arylpiperazine 1-(1-naphthylmethyl)piperazine also impaired that of the highly efficient pyranopyridine efflux pump inhibitors. Our findings provide direct comparability of reported efflux pump inhibitors and contribute to the elucidation of their mode of action.

Antibacterial and Anti-Biofilm Activities of Cinnamon Oil against Multidrug-Resistant Klebsiella pneumoniae Isolated from Pneumonic Sheep and Goats

The primary objectives were to isolate and identify Klebsiella pneumoniae (K. pneumoniae), and determine the antimicrobial resistance patterns and biofilm formation abilities of the isolates. Additionally, the study aimed to investigate the antimicrobial and anti-biofilm effects of cinnamon oil against K. pneumoniae isolates. A cross-sectional study was conducted from March 2022 to April 2023 to collect 200 samples (including 156 nasal swabs and 44 lung specimens) from pneumonic sheep and goats admitted to the Veterinary Teaching Hospital of Zagazig University, Egypt. K. pneumoniae was isolated from a total of 72 (36%) samples, with 53 (73.6%) isolates recovered from nasal swabs and 19 (26.4%) from lung samples. Among the samples, 52 (36.9%) were from sheep and 20 (33.9%) were from goats. Antimicrobial susceptibility testing of the 72 K. pneumoniae isolates to 18 antimicrobials revealed that all isolates were resistant to ampicillin, amoxicillin/clavulanic acid, cefotaxime, ceftriaxone, tetracycline, colistin, fosfomycin, and trimethoprim/sulphamethoxazole. None of the isolates were resistant to amikacin, imipenem, and norfloxacin. Multidrug resistance (MDR) was observed in all K. pneumoniae isolates recovered from sheep and goats. The average MAR index was 0.71, ranging from 0.50 to 0.83. Regarding biofilm formation, among the K. pneumoniae isolates with a high MAR index (n = 30), 10% exhibited strong formation, 40% showed moderate formation, 43.3% displayed weak formation, and 6.7% did not form biofilms. Additionally, the biofilm-forming genes treC and fimA were present in all 28 biofilm-forming K. pneumoniae isolates, while the mrkA gene was detected in 15 (53.6%) of the 28 isolates. MDR K. pneumoniae isolates with strong biofilm formation abilities were treated with cinnamon oil at varying concentrations (100%, 75%, 50%, and 25%). This treatment resulted in inhibition zone diameters ranging from 35 to 45 mm. Cinnamon oil exhibited lower minimum inhibitory concentration and minimum bactericidal concentration values compared to norfloxacin for all isolates. Additionally, cinnamon oil significantly reduced the expression of biofilm-associated genes (treC, fimA, and mrkA) when compared to isolates treated with norfloxacin or untreated. In conclusion, this study identified a high level of MDR K. pneumoniae with strong and moderate biofilm formation abilities in pneumonic sheep and goats in Sharika Governorate, Egypt. Although cinnamon oil demonstrated potential antibacterial and anti-biofilm properties against K. pneumoniae, further research is required to investigate its effectiveness in treating K. pneumoniae infections in pneumonic sheep and goats.

Biological activity of cinnamaldehyde, citronellal, geraniol and anacardic acid on Haemonchus contortus isolates susceptible and resistant to synthetic anthelmintics

Parasitism by gastrointestinal nematodes is a challenge for small ruminant farming worldwide. It causes productive and economic losses, especially due to parasite resistance to conventional anthelmintics. Natural compounds with antiparasitic activity are a potential alternative for controlling these parasites especially when considering the widespread occurrence of anthelmintic resistance. Our objective was to evaluate the activity of anacardic acid, geraniol, cinnamaldehyde and citronellal on Haemonchus contortus isolates with different levels of anthelmintic resistance profiles. These compounds were tested using egg hatch assays (EHAs), larval development tests (LDTs) as well as LDTs on mini-fecal cultures, on the Haemonchus contortus isolates Kokstad (KOK-resistant to all anthelmintics), Inbred-Strain-Edinburgh (ISE-susceptible to all anthelmintics) and Echevarria (ECH-susceptible to all anthelmintics). Effective concentrations to inhibit 50% (EC50) and 95% (EC95) of egg hatching and larval development were calculated. Results for EHA and LDT for all tested compounds, considering EC50 and EC95 values, showed low variation among the studied isolates with most RF values below 2x. All studied compounds showed efficacy against egg hatching and larval development of H. contortus isolates regardless of anthelmintic resistance profiles. The compounds with the smallest EC50 and EC95 values were cinnamaldehyde and anacardic acid making them promising candidates for future in vivo studies.

Cinnamaldehyde Restores Ceftriaxone Susceptibility against Multidrug-Resistant Salmonella

In recent years, infections caused by multidrug-resistant (MDR) bacteria have greatly threatened human health and imposed a burden on global public health. To overcome this crisis, there is an urgent need to seek effective alternatives to single antibiotic therapy to circumvent drug resistance and prevent MDR bacteria. According to previous reports, cinnamaldehyde exerts antibacterial activity against drug-resistant Salmonella spp. This study was conducted to investigate whether cinnamaldehyde has a synergistic effect on antibiotics when used in combination, we found that cinnamaldehyde enhanced the antibacterial activity of ceftriaxone sodium against MDR Salmonella in vitro by significantly reduced the expression of extended-spectrum beta-lactamase, inhibiting the development of drug resistance under ceftriaxone selective pressure in vitro, damaging the cell membrane, and affecting its basic metabolism. In addition, it restored the activity of ceftriaxone sodium against MDR Salmonella in vivo and inhibited peritonitis caused by ceftriaxone resistant strain of Salmonella in mice. Collectively, these results revealed that cinnamaldehyde can be used as a novel ceftriaxone adjuvant to prevent and treat infections caused by MDR Salmonella, mitigating the possibility of producing further mutant strains.

Inhibition of AcrAB-TolC enhances antimicrobial activity of phytochemicals in Pectobacterium brasiliense

Introduction

The eons-long co-evolvement of plants and bacteria led to a plethora of interactions between the two kingdoms, in which bacterial pathogenicity is counteracted by plant-derived antimicrobial defense molecules. In return, efflux pumps (EP) form part of the resistance mechanism employed by bacteria to permit their survival in this hostile chemical environment. In this work we study the effect of combinations of efflux pump inhibitors (EPIs) and plant-derived phytochemicals on bacterial activity using Pectobacteriun brasiliense 1692 (Pb1692) as a model system.

Methods

We measured the minimal inhibitory concentration (MIC) of two phytochemicals, phloretin (Pht) and naringenin (Nar), and of one common antibiotic ciprofloxacin (Cip), either alone or in combinations with two known inhibitors of the AcrB EP of Escherichia coli, a close homolog of the AcrAB-TolC EP of Pb1692. In addition, we also measured the expression of genes encoding for the EP, under similar conditions.

Results

Using the FICI equation, we observed synergism between the EPIs and the phytochemicals, but not between the EPIs and the antibiotic, suggesting that EP inhibition potentiated the antimicrobial activity of the plant derived compounds, but not of Cip. Docking simulations were successfully used to rationalize these experimental results.

Discussion

Our findings suggest that AcrAB-TolC plays an important role in survival and fitness of Pb1692 in the plant environment and that its inhibition is a viable strategy for controlling bacterial pathogenicity.

Herbal Products and Their Active Constituents Used Alone and in Combination with Antibiotics against Multidrug-Resistant Bacteria

The purpose of this review is to summarize the current knowledge acquired on herbal products and their active constituents with antimicrobial activity used alone and in combination with antibiotics against multidrug-resistant bacteria. The most promising herbal products and active constituents used alone against multidrug-resistant bacteria are Piper betle (methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, extended-spectrum beta-lactamase, Acinetobacter baumannii, Pseudomonas aeruginosa), Glycyrrhiza glabra (methicillin-resistant S. aureus, vancomycin-resistant Enterococcus, P. aeruginosa), and berberine (methicillin-resistant S. aureus, A. baumannii, P. aeruginosa), respectively. The synergistic effect of the combination of herbal products and their active constituents with antibiotics against multidrug-resistant bacteria are also described. These natural antibacterial agents can be promising sources of inhibitors, which can modulate antibiotic activity against multidrug-resistant bacteria, especially as efflux pump inhibitors. Other possible mechanisms of action of herbal therapy against multidrug-resistant bacteria including modification of the bacterial cell wall and/or membrane, inhibition of the cell division protein filamenting temperature sensitive Z-ring, and inhibition of protein synthesis and gene expression, all of which will also be discussed. Our review suggests that combination herbal therapy and antibiotics can be effectively used to expand the spectrum of their antimicrobial action. Therefore, combination therapy against multidrug-resistant bacteria may enable new choices for the treatment of infectious diseases and represents a potential area for future research.

trans-Cinnamaldehyde as a Novel Candidate to Overcome Bacterial Resistance: An Overview of In Vitro Studies

The increasing of drug-resistant bacteria and the scanty availability of novel effective antibacterial agents represent alarming problems of the modern society, which stimulated researchers to investigate novel strategies to replace or assist synthetic antibiotics. A great deal of attention has been devoted over the years to essential oils that contain mixtures of volatile compounds and have been traditionally exploited as antimicrobial remedies. Among the essential oil phytochemicals, remarkable antimicrobial and antibiotic-potentiating activities have been highlighted for cinnamaldehyde, an α,β-unsaturated aldehyde, particularly abundant in the essential oils of Cinnamomum spp., and widely used as a food additive in industrial products. In line with this evidence, in the present study, an overview of the available literature has been carried out in order to define the bacterial sensitizing profile of cinnamaldehyde. In vitro studies displayed the ability of the substance to resensitize microbial strains to drugs and increase the efficacy of different antibiotics, especially cefotaxime, ciprofloxacin, and gentamicin; however, in vivo, and clinical trials are lacking. Based on the collected findings, cinnamaldehyde appears to be of interest as an adjuvant agent to overcome superbug infections and antibiotic resistance; however, future more in-dept studies and clinical investigations should be encouraged to clarify its efficacy and the mechanisms involved.

Design, synthesis and anticancer activity studies of 3-(coumarin-3-yl)-acrolein derivatives: Evidenced by integrating network pharmacology and vitro assay

Coumarin derivatives have diverse structures and show various significant biological activities. Aiming to develop more potent coumarin derivatives for cancer treatment, a series of coumarin acrolein hybrids were designed and synthesized by using molecular hybridization approach, and investigated for their antiproliferative activity against A549, KB, Hela and MCF-7 cancer cells as well as HUVEC and LO2 human normal cells. The results indicated that most of the synthesized compounds displayed remarkable inhibitory activity towards cancer cells but low cytotoxicity on normal cells. Among all the compounds, 5d and 6e were the most promising compounds against different cancer cell lines, especially for A549 and KB cells. The preliminary action mechanism studies suggested that compound 6e, the representative compound, was capable of dose-dependently suppressing migration, invasion and inducing significant apoptosis. Furthermore, the combined results of network pharmacology and validation experiments revealed that compound 6e induced mitochondria dependent apoptosis via the PI3K/AKT-mediated Bcl-2 signaling pathway. In summary, our study indicated compound 6e could inhibit cell proliferation, migration, invasion and promote cell apoptosis through inhibition of PI3K/AKT signaling pathway in human oral epidermoid carcinoma cells. These findings demonstrated the potential of 3-(coumarin-3-yl)-acrolein derivatives as novel anticancer chemotherapeutic candidates, providing ideas for further development of drugs for clinical use.

Current State of Knowledge Regarding WHO Critical Priority Pathogens: Mechanisms of Resistance and Proposed Solutions through Candidates Such as Essential Oils

The rise of multidrug-resistant (MDR) pathogens has become a global health threat and an economic burden in providing adequate and effective treatment for many infections. This large-scale concern has emerged mainly due to mishandling of antibiotics (ABs) and has resulted in the rapid expansion of antimicrobial resistance (AMR). Nowadays, there is an urgent need for more potent, non-toxic and effective antimicrobial agents against MDR strains. In this regard, clinicians, pharmacists, microbiologists and the entire scientific community are encouraged to find alternative solutions in treating infectious diseases cause by these strains. In its "10 global issues to track in 2021", the World Health Organization (WHO) has made fighting drug resistance a priority. It has also issued a list of bacteria that are in urgent need for new ABs. Despite all available resources, researchers are unable to keep the pace of finding novel ABs in the face of emerging MDR strains. Traditional methods are increasingly becoming ineffective, so new approaches need to be considered. In this regard, the general tendency of turning towards natural alternatives has reinforced the interest in essential oils (EOs) as potent antimicrobial agents. Our present article aims to first review the main pathogens classified by WHO as critical in terms of current AMR. The next objective is to summarize the most important and up-to-date aspects of resistance mechanisms to classical antibiotic therapy and to compare them with the latest findings regarding the efficacy of alternative essential oil therapy.

New tools to mitigate drug resistance in Enterobacteriaceae - Escherichia coli and Klebsiella pneumoniae

Treatment to common bacterial infections are becoming ineffective of late, owing to the emergence and dissemination of antibiotic resistance globally. Escherichia coli and Klebsiella pneumoniae are the most notorious microorganisms and are among the critical priority pathogens listed by WHO in 2017. These pathogens are the predominant cause of sepsis, urinary tract infections (UTIs), pneumonia, meningitis and pyogenic liver abscess. Concern arises due to the resistance of bacteria to most of the beta lactam antibiotics like penicillin, cephalosporin, monobactams and carbapenems, even to the last resort antibiotics like colistin. Preventing influx by modulation of porins, extruding the antibiotics by overexpression of efflux pumps, mutations of drug targets/receptors, biofilm formation, altering the drug molecules and rendering them ineffective are few resistance mechanisms that are adapted by Enterobacteriaeceae upon exposure to antibiotics. The situation is exacerbated due to the process of horizontal gene transfer (HGT), wherein the genes encoding resistance mechanisms are transferred to the neighbouring bacteria through plasmids/phages/uptake of free DNA. Carbapenemases, other beta lactamases and mcr genes coding for colistin resistance are widely disseminated leading to limited/no therapeutic options against those infections. Development of new antibiotics can be viewed as a possible solution but it involves major investment, time and labour despite which, the bacteria can easily adapt to the new antibiotic and evolve resistance in a relatively short time. Targeting the resistance mechanisms can be one feasible alternative to tackle these multidrug resistant (MDR) pathogens. Removal of plasmid (plasmid curing) causing resistance, use of bacteriophages and bacteriotherapy can be other potential approaches to combat infections caused by MDR E. coli and K. pneumoniae. The present review discusses the efficacies of these therapies in mitigating these infections, which can be potentially used as an adjuvant therapy along with existing antibiotics.

Cinnamaldehyde as antimicrobial in cellulose-based dental appliances

AIMS

In the context of minor orthodontic intervention using clear aligner technologies, we determined antimicrobial properties of a cellulose-based material loaded with essential oils such as cinnamaldehyde.

METHODS AND RESULTS

Isothermal microcalorimetry was used to assess the growth of bacterial biofilms at the interface between the tested material and the solid growth medium. The calorimetric data were analyzed using conventional growth models (Gompertz and Richards), and inhibition at 12 and 24 h was calculated.

CONCLUSIONS

The tested material showed antimicrobial properties against Staphylococcus epidermidis as well as Streptococcus mutans and Streptococcus mitis clinical isolates. The inhibition was more pronounced against S. epidermidis, for which growth rate was reduced by 70% and lag phase was extended by 12 h. For S. mutans and S. mitis, the decrease in growth rate was 20% and 10%, and the lag phase increased by 2 and 6 h, respectively.

SIGNIFICANCE AND IMPACT

Clear aligners for minor teeth alignment are becoming very popular. As they must be worn for at least 22 h per day for up to 40 weeks, it is important that they remain clean and do not promote caries formation or other oral infections. Therefore, introducing material with antimicrobial properties is expected to maintain oral hygiene during the aligner therapy. Here, we demonstrate the use of cinnamaldehyde for reducing microbial growth and biofilm formation on cellulose-based dental clear aligners.

In vitro activity of carvacrol in combination with meropenem against carbapenem-resistant Klebsiella pneumoniae

Carbapenem resistance observed in Klebsiella pneumoniae strains limits treatment options. Therefore, use of antibiotics combined with bioactive compounds may be an important strategy to control K. pneumoniae. The purpose of this study was to evaluate the activity of combination of carvacrol and meropenem on carbapenem-resistant K. pneumoniae (CRKP) strains. The presence of bla_OXA-48 carbapenemase in all 25 CRKP strains was identified using the PCR technique. The combination of carvacrol and meropenem was tested for antimicrobial activity on CRKP strains. The minimum inhibitory concentrations of carvacrol and meropenem were detected within a range of 32-128 µg/mL using the broth microdilution method. Synergy between carvacrol and meropenem was observed on 8 of the 25 CRKP strains by checkerboard assay (FICI = 0.5) and confirmed by time-kill assay. According to the live-dead test results, the viability percentage of the cells exposed to synergistic combination was 35.47% at the end of 24 h. The membrane damage caused by the synergistic combination was spectrophotometrically measured (A = 0.21) and further confirmed by SEM analysis. According to the MTT assay, both carvacrol and meropenem did not show any statistically significant cytotoxic effect on Vero cells (p > 0.05). In conclusion, the results suggest that carvacrol and meropenem can act synergistically to inhibit the growth of CRKP.

Chestnut Shell Tannins: Effects on Intestinal Inflammation and Dysbiosis in Zebrafish

Simple Summary

With the increase in global population the production of animal proteins becomes increasingly crucial. Aquaculture is the first animal protein supply industry for human consumption. Intensive farming techniques are employed to increase productivity, but these may cause stressful conditions for fish, resulting in impaired growth and poor health conditions. Intestinal inflammation is one of the most common diseases of fish in intensive farming. Intestinal inflammation is usually accompanied by an alteration of the microbiota or dysbiosis. Inflammation and dysbiosis are so tightly intertwined that inflammation may contribute to or result from dysregulation of gut microbiota. Natural substances of plant origin rich in bioactive molecules or more simply phytochemicals, have been proved to be able to reduce inflammation and improve the general health status in various commercially relevant species. In this study, we evaluated the effect of tannins, a class of polyphenols, the most abundant phytochemicals, on intestinal inflammation and microbiota in zebrafish (Danio rerio), a small freshwater fish become an attractive biomedicine and aquaculture animal model during the last decades. The zebrafish has been employed in a vast array of studies aiming at investigating the essential processes underlying intestinal inflammation and injury due to its conservative gut morphology and functions. In this study, we administered a diet enriched with chestnut shell extract rich in tannins to a zebrafish model of intestinal inflammation. The treatment ameliorated the damaged intestinal morphophysiology and the microbiota asset. Our results sustain that products of natural origin with low environmental impact and low cost, such as tannins, may help to ease some of the critical issues affecting the aquaculture sector.

Abstract

The aim of the present study was to test the possible ameliorative efficacy of phytochemicals such as tannins on intestinal inflammation and dysbiosis. The effect of a chestnut shell (Castanea sativa) extract (CSE) rich in polyphenols, mainly represented by tannins, on k-carrageenan-induced intestinal inflammation in adult zebrafish (Danio rerio) was tested in a feeding trial. Intestinal inflammation was induced by 0.1% k-carrageenan added to the diet for 10 days. CSE was administered for 10 days after k-carrageenan induced inflammation. The intestinal morphology and histopathology, cytokine expression, and microbiota were analyzed. The k-carrageenan treatment led to gut lumen expansion, reduction of intestinal folds, and increase of the goblet cells number, accompanied by the upregulation of pro-inflammatory factors (TNFα, COX2) and alteration in the number and ratio of taxonomic groups of bacteria. CSE counteracted the inflammatory status enhancing the growth of health helpful bacteria (Enterobacteriaceae and Pseudomonas), decreasing the pro-inflammatory factors, and activating the anti-inflammatory cytokine IL-10. In conclusion, CSE acted as a prebiotic on zebrafish gut microbiota, sustaining the use of tannins as food additives to ameliorate the intestinal inflammation. Our results may be relevant for both aquaculture and medical clinic fields.

Synergistic interactions of plant essential oils with antimicrobial agents: a new antimicrobial therapy

The problem of drug resistance of food borne pathogens is becoming more and more serious. Although traditional antimicrobial agents have good therapeutic effects on a variety of food borne pathogens, more effective antimicrobial agents are still needed to combat the development of drug-resistant food borne pathogens. Plant-based natural essential oils (EOs) are widely used because of their remarkable antimicrobial activity. A potential strategy to address food borne pathogens drug resistance is to use a combination of EOs and antimicrobial agents. Because EOs have multi-target inhibitory effects on microorganisms, combining them with drugs can enhance the activity of the drugs and avoid the emergence of food borne pathogens drug resistance. This paper introduces the main factors affecting the antibacterial activity of EOs and describes methods for evaluating their synergistic antibacterial effects. The possible mechanisms of action of EOs and the synergistic inhibitory effects on pathogens of EOs in combination with antimicrobial agents is described. In summary, the combined use of EOs and existing antimicrobial agents is a promising potential new antibacterial therapy.

Acaricidal activity of (E)-cinnamaldehyde and α-bisabolol on populations of Rhipicephalus microplus (Acari: Ixodidae) with different resistance profiles

This study aimed to investigate the acaricidal activity of (E)-cinnamaldehyde and α-bisabolol on populations of Rhipicephalus microplus with different resistance profiles. The adult immersion test (AIT) was used to characterize the susceptibility of tick populations (50 field populations) to synthetic acaricides: deltamethrin, amitraz, and chlorfenvinphos. The larval packet test (LPT) was used to determine the LC₅₀ values for (E)-cinnamaldehyde (populations 1-25) and α-bisabolol (populations 26-50) at the concentrations of 0.31, 0.62, 1.25, 2.0, 2.5, 5.0 and 10.0 mg/mL. The susceptible strain Porto Alegre (POA) was used as a reference for calculating the resistance ratio (RR). In the AIT, deltamethrin did not show efficacy >95 % for any of the populations, whereas amitraz and chlorfenvinphos have presented efficacy >95 % for three (6 %) and 15 (30 %) populations, respectively. In the LPT, the LC₅₀ values of (E)-cinnamaldehyde and α-bisabolol varied from 0.23 to 2.36 mg/mL and 1.57-3.01 mg/mL, respectively. The RR₅₀ for (E)-cinnamaldehyde showed 20 (80 %) populations with values <1.0 and no population with values>1.5. As for α-bisabolol, only two (8%) populations have presented RR₅₀ <1.0, whereas three (12 %) populations showed incipient resistance to this sesquiterpene (RR₅₀ between 1.5 and 2.0). The results indicate that all studied tick populations showed low susceptibility to at least one of the commercial acaricides tested. In addition, comparison between the LC₅₀ values of (E)-cinnamaldehyde and α-bisabolol for the field populations and the susceptible strain POA suggests that there is no cross-resistance of (E)-cinnamaldehyde and α-bisabolol for the tick populations evaluated, and that the differences in the LC₅₀ values are due to population variations.

The use of eugenol in combination with cefotaxime and ciprofloxacin to combat ESBL-producing quinolone-resistant pathogenic Enterobacteriaceae

AIM

Emergence of extended-spectrum beta-lactamase (ESBL) producing with quinolone-resistant (QR) pathogenic Enterobacteriaceae augmented the need to establish therapeutic options against them. Present study aimed towards determination of synergistic combination of eugenol (EG) with cefotaxime (CTX) and ciprofloxacin (CIP) to combat against this resistance and potentiation of antibacterial drugs by EG against these bacteria.

METHODS AND RESULTS

Synergistic interaction between EG and CTX/CIP (FICI: 0·08-0·5) were observed among ESBL-QR bacteria using checkerboard assay. Approximately, 2- to 1024-fold minimum inhibitory concentration value reduction and 17- to 165 030-fold dose reduction index strongly suggested synergistic interaction between EG and antibiotics. Cell viability assay showed reduction in log₁₀ CFU per ml from 16·6 to 3·1 at synergistic concentration. Scanning electron microscopy further proved disruptive effect of EG on cell architecture. Eugenol and/or its combination also altered genes' expressions that imparted antibiotic resistance by ~1·6 to ~1226 folds.

CONCLUSIONS

Reduced doses of antibiotics, bacterial morphological alterations, efflux pump down regulation, porin over expression and beta-lactamase gene inhibition of ESBL-QR bacteria by EG alone or in combination with CTX/CIP might have reversed antibiotic resistance profile of ESBL-QR bacteria.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provided a molecular insight into action of EG and/with CTX and CIP, which might have potentiated antibiotic's activity against ESBL-QR bacteria.

Sub-acute toxicological and behavioural effects of two candidate therapeutics, cinnamaldehyde and eugenol, for treatment of ESBL producing-quinolone resistant pathogenic Enterobacteriaceae

Present study deals with evaluation of antibacterial activity of cinnamaldehyde and eugenol against both extended-spectrum-β-lactamase (ESBL)-producing and quinolone resistant (QR) (ESBL-QR) pathogenic Enterobactericeae along with determination of its in vivo toxicity level in a murine model to investigate their pharmacological potential. Broth microdilution assay was used to determine minimum inhibitory concentrations (MICs) of cinnamaldehyde (CIN), eugenol (EG) and traditional antibiotics against ESBL-QR Enterobactericeae. Sub-acute oral toxicity study (14 days) was carried out in Swiss albino mice to evaluate any toxicological and behavioural effect viz novelty suppressed feeding (NSF), novel object recognition (NOR), tail suspension test (TST) and social interaction test of cinnamaldehyde and eugenol. Cinnamaldehyde and eugenol demonstrated mode-MIC of 7.28 and 7.34 μg/mL among maximum numbers of Escherichia coli (32.1%) and 0.91 and 3.67 μg/mL among maximum numbers of Klebsiella  pneumoniae (24.2%) isolates, respectively. For haematological and toxicological analyses, after 14 days of oral administration of cinnamaldehyde (0.91-10 mg/kg) and eugenol (7.34-70 mg/kg), blood was collected from the murine model, while histological examinations were performed on liver and kidney. There was no alteration in food and water intake among treated animals. Toxicological and behavioural studies displayed good safety profiles of cinnamaldehyde and eugenol. The results indicated potential antibacterial efficacy of cinnamaldehyde and eugenol against pathogenic ESBL-QR Enterobacteriaceae, without any significant toxicological and behavioural effects.