Insights into macrolide resistance in Arcobacter butzleri: potential resistance mechanisms and impact on bacterial fitness and virulence.

BACKGROUND: Macrolides are recommended for treating the emerging enteropathogen Arcobacter butzleri; nonetheless, this bacterium often exhibits highly variable resistance rates, and the mechanisms behind this resistance phenotype remain largely unexplored. OBJECTIVES: To understand the phenotypic and genotypic consequences associated with the acquisition of erythromycin resistance in A. butzleri, as well as the effects on the fitness of this species. METHODS: Resistant strains resulting from spontaneous mutations and adaptive laboratory evolution under increasing erythromycin concentrations were examined regarding their cross-resistance and collateral susceptibility profiles. Genetic causes of phenotypic antibiotic resistance were analysed by sequencing and bioinformatics, with functional correlation through ethidium bromide accumulation assays. Growth profiles in the presence and absence of erythromycin, motility and biofilm formation abilities were assessed to detect potential changes in fitness and virulence. RESULTS: Clones from spontaneous mutation rate evolution demonstrated decreased susceptibility to erythromycin and other classes of antibiotics, associated with mutations in the transcriptional repressor areR, causing overexpression of the AreABC efflux pump. In turn, WGS analysis of the evolved strain showed additional mutations in the ribosomal proteins L4 and L22 and in the areR gene. Furthermore, the acquisition of macrolide resistance altered A. butzleri virulence and entailed a high biological cost. CONCLUSIONS: The findings of this study have proved that efflux activity contributes synergistically with mutations in the ribosomal proteins L4 and L22 to A. butzleri's high-level macrolide resistance. The results further suggest an impact on the bacterial physiology and virulence, with the increased fitness cost justifying the low worldwide prevalence of high-level resistant circulating strains.

Therapeutic Potential of Resveratrol for Glioma: A Systematic Review and Meta-Analysis of Animal Model Studies.

Gliomas are aggressive malignant brain tumors, with poor prognosis despite available therapies, raising the necessity for finding new compounds with therapeutic action. Numerous preclinical investigations evaluating resveratrol's anti-tumor impact in animal models of glioma have been reported; however, the variety of experimental circumstances and results have prevented conclusive findings about resveratrol's effectiveness. Several databases were searched during May 2023, ten publications were identified, satisfying the inclusion criteria, that assess the effects of resveratrol in murine glioma-bearing xenografts. To determine the efficacy of resveratrol, tumor volume and animal counts were retrieved, and the data were then subjected to a random effects meta-analysis. The influence of different experimental conditions and publication bias on resveratrol efficacy were evaluated. Comparing treated to untreated groups, resveratrol administration decreased the tumor volume. Overall, the effect's weighted standardized difference in means was -2.046 (95%CI: -3.156 to -0.936; p-value < 0.001). The efficacy of the treatment was observed for animals inoculated with both human glioblastoma or rat glioma cells and for different modes of resveratrol administration. The combined administration of resveratrol and temozolomide was more effective than temozolomide alone. Reducing publication bias did not change the effectiveness of resveratrol treatment. The findings suggest that resveratrol slows the development of tumors in animal glioma models.

Development of Phenothiazine Hybrids with Potential Medicinal Interest: A Review.

The molecular hybridization approach has been used to develop compounds with improved efficacy by combining two or more pharmacophores of bioactive scaffolds. In this context, hybridization of various relevant pharmacophores with phenothiazine derivatives has resulted in pertinent compounds with diverse biological activities, interacting with specific or multiple targets. In fact, the development of new drugs or drug candidates based on phenothiazine system has been a promising approach due to the diverse activities associated with this tricyclic system, traditionally present in compounds with antipsychotic, antihistaminic and antimuscarinic effects. Actually, the pharmacological actions of phenothiazine hybrids include promising antibacterial, antifungal, anticancer, anti-inflammatory, antimalarial, analgesic and multi-drug resistance reversal properties. The present review summarizes the progress in the development of phenothiazine hybrids and their biological activity.

Characterization of AreABC, an RND-Type Efflux System Involved in Antimicrobial Resistance of Aliarcobacter butzleri.

Aliarcobacter butzleri is an emergent enteropathogen for which resistance to several classes of antimicrobial agents has been described, although the underlying mechanisms have been poorly addressed. We aimed to evaluate the contribution of the resistance-nodulation-division-type (RND) efflux system, AreABC, to drug resistance in A. butzleri. A. butzleri strains were first tested against several antimicrobials with and without an efflux pump inhibitor. Then, erythromycin-resistant strains were screened for the presence of a premature stop codon in a putative transcriptional regulator of the AreABC system, areR. Lastly, antimicrobial susceptibility and ethidium bromide (EtBr) accumulation were evaluated using an areB knockout strain and a strain overexpressing the AreABC system through areR truncation. The presence of the efflux pump inhibitor resulted in increased susceptibility to most of the antimicrobials tested. A correlation between erythromycin resistance and the presence of premature stop codons in areR was observed. The truncation of areR resulted in increased expression of the AreABC system and decreased susceptibility to various antimicrobials. In contrast, areB inactivation resulted in increased susceptibility and a higher intracellular accumulation of EtBr. In conclusion, the AreABC efflux pump plays a role in the resistance of A. butzleri to multiple drugs and is regulated by a putative transcriptional repressor, areR. Our results support the importance of efflux pumps in this bacterium's resistance to major classes of antibiotics and other antimicrobials.

Trends in microbial control techniques for poultry products.

Fresh poultry meat and poultry products are highly perishable foods and high potential sources of human infection due to the presence of several foodborne pathogens. Focusing on the microbial control of poultry products, the food industry generally implements numerous preventive measures based on the Hazard Analysis and Critical Control Points (HACCP) food safety management system certification together with technological steps, such as refrigeration coupled to modified atmosphere packaging that are able to control identified potential microbial hazards during food processing. However, in recent years, to meet the demand of consumers for minimally processed, high-quality, and additive-free foods, technologies are emerging associated with nonthermal microbial inactivation, such as high hydrostatic pressure, irradiation, and natural alternatives, such as biopreservation or the incorporation of natural preservatives in packaging materials. These technologies are discussed throughout this article, emphasizing their pros and cons regarding the control of poultry microbiota and their effects on poultry sensory properties. The discussion for each of the preservation techniques mentioned will be provided with as much detail as the data and studies provided in the literature for poultry meat and products allow. These new approaches, on their own, have proved to be effective against a wide range of microorganisms in poultry meat. However, since some of these emergent technologies still do not have full consumer's acceptability and, taking into consideration the hurdle technology concept for poultry processing, it is suggested that they will be used as combined treatments or, more frequently, in combination with modified atmosphere packaging.

Can Cranberries Contribute to Reduce the Incidence of Urinary Tract Infections? A Systematic Review with Meta-Analysis and Trial Sequential Analysis of Clinical Trials.

PURPOSE: We sought to clarify the association between cranberry intake and the prevention of urinary tract infections. MATERIALS AND METHODS: This systematic review, which complies with the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) statement, was done as a meta-analysis and trial sequential analysis of clinical trials. RESULTS: The findings clearly showed the potential use of cranberries for the clinical condition of urinary tract infection. Cranberry products significantly reduced the incidence of urinary tract infections as indicated by the weighted risk ratio (0.6750, 95% CI 0.5516-0.7965, p <0.0001). The results of subgroup analysis demonstrated that patients at some risk for urinary tract infections were more susceptible to the effects of cranberry ingestion. CONCLUSIONS: The results of the current study could be used by physicians to recommend cranberry ingestion to decrease the incidence of urinary tract infections, particularly in individuals with recurrent urinary tract infections. This would also reduce the administration of antibiotics, which could be beneficial since antibiotics can lead to the worldwide emergence of antibiotic resistant microorganisms.

Antimicrobial activity of coriander oil and its effectiveness as food preservative.

ABTRACT Foodborne illness represents a major economic burden worldwide and a serious public health threat, with around 48 million people affected and 3,000 death each year only in the USA. One of the possible strategies to reduce foodborne infections is the development of effective preservation strategies capable of eradicating microbial contamination of foods. Over the last years, new challenges for the food industry have arisen such as the increase of antimicrobial resistance of foodborne pathogens to common preservatives and consumers demand for naturally based products. In order to overcome this, new approaches using natural or bio-based products as food preservatives need to be investigated. Coriander (Coriandrum sativum L.) is a well-known herb widely used as spice, or in folk medicine, and in the pharmacy and food industries. Coriander seed oil is the world's second most relevant essential oil, exhibiting antimicrobial activity against Gram-positive and Gram-negative bacteria, some yeasts, dermatophytes and filamentous fungi. This review highlights coriander oil antimicrobial activity and possible mechanisms of action in microbial cells and discusses the ability of coriander oil usage as a food preservative, pointing out possible paths for the successful evolution for these strategies towards a successful development of a food preservation strategy using coriander oil.

Development of carboxymethyl xylan films with functional properties.

The aim of this work was focused on the development of carboxymethyl xylan (CMX) formulations with functional properties to produce edible films. Beechwood Xylan was firstly derivatized into carboxymethyl xylan and thereafter was blended with Agar (Ag), Ammonium zirconium carbonate (AZC) and linoleic acid (La) to produce CMX:Ag, CMX:AZC, CMX:Ag:La films. Mechanical, barrier, optical and thermal properties of the produced films and their antimicrobial activity against food pathogenic bacteria were evaluated. The obtained films were transparent and yellowish. Agar and AZC improved the tensile strength at break of the control CMX film from 4.79 to 27.67 and 20.95 MPa respectively, and the CMX:AZC film exhibited the greatest elastic modulus. Barrier properties of the films decreased when any of the components was incorporated into the CMX and all blended films were thermally more stable than control. The CMX:Ag:La film revealed a good antimicrobial activity against B. cereus and S. aureus.

Insights in the pathogenesis and resistance of Arcobacter: A review.

Arcobacter genus currently comprises 18 recognized species, among which Arcobacter butzleri, Arcobacter cryaerophilus and Arcobacter skirrowii have been associated with human and animal disease. Although these organisms, with special emphasis A. butzleri, are emerging as clinical pathogens, several aspects of their epidemiology and virulence are only starting to be clarified. In vitro human and animal cell culture assays have been used to show that several Arcobacter species can adhere to and invade eukaryotic cells, induce an immune response and produce toxins that damage host cells. In addition, data from genome sequencing highlighted several potential markers that may be helpful candidates for the study and understanding of these mechanisms; however, more work is necessary to clarify the molecular mechanisms involved in Arcobacter virulence. Arcobacter can be considered a relatively robust organism showing to be able to survive in adverse conditions, as the ones imposed by food processing and storage. Moreover, these bacteria have shown increased antibiotic resistance, along with high multidrug resistance. In this review, we seek to update the state-of-the-art concerning Arcobacter distribution, its interaction with the host, the trends of antibiotic resistance, its ability to survive, and finally the use of natural antimicrobials for control of Arcobacter.

Study of the major essential oil compounds of Coriandrum sativum against Acinetobacter baumannii and the effect of linalool on adhesion, biofilms and quorum sensing.

Acinetobacter baumannii is a pathogen that has the ability to adhere to surfaces in the hospital environment and to form biofilms which are increasingly resistant to antimicrobial agents. The aim of this work was to study the antimicrobial activity of the major oil compounds of Coriandrum sativum against A. baumannii. The effect of linalool on planktonic cells and biofilms of A. baumannii on different surfaces, as well as its effect on adhesion and quorum sensing was evaluated. From all the compounds evaluated, linalool was the compound with the best antibacterial activity, with minimum inhibitory concentration values between 2 and 8 µl ml(-1). Linalool also inhibited biofilm formation and dispersed established biofilms of A. baumannii, changed the adhesion of A. baumannii to surfaces and interfered with the quorum- sensing system. Thus, linalool could be a promising antimicrobial agent for controlling planktonic cells and biofilms of A. baumannii.

The antimicrobial action of resveratrol against Listeria monocytogenes in food-based models and its antibiofilm properties.

BACKGROUND: Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a natural phytoalexin synthesized by plants in response to stress. This compound has several beneficial documented properties, namely anti-inflammatory, antioxidant, neuroprotective and antimicrobial activities. In this study the antimicrobial activity of resveratrol against Listeria monocytogenes and Listeria innocua was investigated. RESULTS: Resveratrol had a minimum inhibitory concentration of 200 µg mL(-1) for the tested strains, with time-kill curves demonstrating bacteriostatic activity. Inhibition of biofilm formation was also assessed, with resveratrol strongly inhibiting biofilm formation by both species even at subinhibitory concentrations. Overall, resveratrol showed antimicrobial properties on planktonic cells and on biofilm formation ability. Considering the potential use of resveratrol as a food preservative, the antimicrobial efficacy of resveratrol in food was studied in milk, lettuce leaf model and chicken juice. Resveratrol retained greater efficacy in both lettuce leaf model and chicken juice, but milk had a negative impact on its antilisterial activity, indicating a possible reduction of resveratrol availability in milk. CONCLUSION: This study reinforces resveratrol as an antimicrobial agent, pointing out its antibiofilm activity and its potential use as preservative in some food matrices. © 2016 Society of Chemical Industry.

Genotypic and phenotypic features of Arcobacter butzleri pathogenicity.

Even though Arcobacter butzleri has been implicated in some human disease as diarrhoea and bacteraemia, much of its pathogenesis and virulence factors remain unclear. In this work we have compared pathogenic and genotypic properties of six A. butzleri isolates from human and non-human sources. The tested isolates showed to be susceptible to tetracyclines and aminoglycosides, however non-human isolates were all resistant to quinolones. The ability to form biofilms was variable among the tested strains, and all of them showed a weak haemolytic activity. The presence of nine putative virulence genes was determined, with cadF, ciaB, cj1349, mviN, pldA, tlyA being detected in all strains, while irgA (3/6), hecA (5/6), hecB (4/6) were detected only in some strains. High levels of adhesion were observed for A. butzleri on Caco-2 cells, with pre-existing inflammation showing no significant effect on the adherence ability; yet variable levels of invasion were observed. A. butzleri isolates were able to survive intracellularly in Caco-2 cells and to induce a significant up-regulation of interleukin-8 secretion and structural cell rearrangements. These data brings new insights on A. butzleri virulence and highlights its pathogenic potential.

Evaluation of the prebiotic potential of arabinoxylans from brewer's spent grain.

Arabinoxylans (AX) consumption has been related to the treatment and prevention of cardiovascular diseases, type II diabetes, colorectal cancer and obesity. The beneficial health effects are conferred through gut microbiota modulation, and therefore, they have been proposed as potential slowly fermentable prebiotic candidates. As the mechanisms are not yet well understood, the prebiotic potential of AX from brewer's spent grain (BSG) has been investigated. Two types of AX from BSG (AX1 and AX2) of different length and branching averages were fermented with human faecal inocula and compared to fermented cultures containing a commercial prebiotic (fructooligosaccharide (FOS)) and cultures with no added carbohydrate (control). Results demonstrated that the AX were extensively metabolised after 48 h of fermentation. The pH decreased along fermentation and the lowest value was achieved in AX1 cultures. The production of short chain fatty acids (SCFA) was higher in AX cultures than in cultures containing FOS and controls, with AX1 presenting the highest concentrations. The stimulatory effect of beneficial bacteria was higher in AX cultures, and AX2 presented the highest positive effect. Prebiotic potential of AX from BSG was confirmed by the production of SCFA and the modulation of gut microbiota, especially by the high increase in bifidobacteria populations.

Antistaphylococcal and biofilm inhibitory activities of gallic, caffeic, and chlorogenic acids.

Staphylococcus aureus is a Gram-positive pathogen which is able to form biofilms, exhibiting a more pronounced resistance to antibiotics and disinfectants. The hurdles posed in eradicating biofilms have driven the search for new compounds able to fight these structures. Phenolic compounds constitute one of the most numerous and ubiquitous group of plant secondary metabolites with many biological activities. The aim of the present work was to study the potential antimicrobial and antibiofilm properties of gallic, caffeic, and chlorogenic acids against S. aureus as well to elucidate its mechanism of action. It was concluded that the phenolic acids studied in this work have antistaphylococcal properties. For instance, gallic acid is able to influence the adhesion properties of S. aureus. The phenolic acids tested were also able to inhibit the production of α-hemolysin by this microorganism, with the exception of chlorogenic acid. Regarding its mechanism of action, caffeic acid interferes with the stability of the cell membrane and with the metabolic activity of the cells of S. aureus.

Stumps of Eucalyptus globulus as a source of antioxidant and antimicrobial polyphenols.

These past years have seen an enormous development of the area of natural antioxidants and antimicrobials. Eucalyptus globulus is widely cultivated in subtropical and Mediterranean regions in intensive short rotation coppice plantations. In the Portuguese context, E. globulus is the third species in terms of forest area. The stump is the basal part of the tree, including the near-the-ground stem portion and the woody roots that remain after stem felling. The purpose of this work was to study the phytochemical profile and to evaluate the antioxidant and antimicrobial properties of several crude stump wood and stump bark extracts of E. globulus, comparing it with similar extracts of E. globulus wood (industrial chips). The results showed the presence of high concentrations of total phenolic compounds (>200 mg GAE/g extract) and flavonoids (>10 mg QE/g extract) in E. globulus stump extracts. Generally the stump wood extracts stands out from the other ones, presenting the highest percentages of inhibition of linoleic acid oxidation. It was also possible to conclude that the extracts were more active against Gram-positive bacteria, presenting low MIC values. This study thus provides information supporting the economic valorization of E. globulus stump wood.

Linalool Reduces Virulence and Tolerance to Adverse Conditions of Listeria monocytogenes.

Listeria monocytogenes, a foodborne pathogen causing listeriosis, poses substantial societal, economic, and public health challenges due to its resistance, persistence, and biofilm formation in the food industry. Exploring subinhibitory concentrations of compounds to target virulence inhibition and increase susceptibility to adverse conditions presents a promising strategy to mitigate its impact of L. monocytogenes and unveils new potential applications. Thus, this study aims to explore the effect of linalool on virulence factors of L. monocytogenes and potential use in the reduction in its tolerance to stressful conditions. This action was analysed considering the use of two sub-inhibitory concentrations of linalool, 0.312 and 0.625 mg/mL. We found that even with the lowest tested concentrations, a 65% inhibition of violacein production by Chromobacterium violaceum, 55% inhibition in biofilm formation by L. monocytogenes and 62% reduction on haemolysis caused by this bacterium were observed. In addition to its impact on virulence factors, linalool diminished the tolerance to osmotic stress (up to 4.3 log reduction after 24 h with 12% NaCl), as well as to high (up to 3.8 log reduction after 15 min at 55 °C) and low temperatures (up to 4.6 log reduction after 84 days with 12% NaCl at 4 °C). Thus, this study paves the way to further investigation into the potential utilization of linalool to mitigate the threat posed by L. monocytogenes in the field of food safety and public health.

Action of Curcumin on Glioblastoma Growth: A Systematic Review with Meta-Analysis of Animal Model Studies.

Gliomas are aggressive brain tumors with poor prognosis even after surgical removal and radio-chemotherapy, stressing the urgency to find alternative therapies. Several preclinical studies evaluating the anticancer effect of curcumin in animal models of glioma are reported, but a systematic review with meta-analysis of these studies, considering the different experimental conditions used, has not been made up to this date. A search in different databases (Pubmed, Web of Science, Scopus, and SciELO) following the PRISMA statement was conducted during November 2023 to systematically identify articles assessing the effect of curcumin in murine xenograft models of glioma and identified 15 articles, which were subdivided into 24 studies. Tumor volume before and after treatment with curcumin or vehicle was extracted and the efficacy of curcumin was evaluated by performing a random effects meta-analysis of the data. Publication bias and the impact of different experimental conditions on curcumin efficacy were assessed. Treatment with curcumin decreased tumor volume. Comparing curcumin with control groups, the overall weighted standardized difference in means was -2.079 (95% CI: -2.816 to -1.341; p-value < 0.001). The curcumin effect was observed for different animal models, types of glioma cells, administration routes, and curcumin formulations. Publication bias was identified but does not invalidate curcumin's effectiveness. The findings suggest the potential therapeutic efficacy of curcumin against glioma.

Putative Role of an ABC Efflux System in Aliarcobacter butzleri Resistance and Virulence.

Aliarcobacter butzleri is considered a ubiquitous microorganism and emergent pathogen, for which increasing rates of multidrug resistance have been described. In line with this, the present work aimed to evaluate for the first time the contribution of an ABC efflux system, the YbhFSR, in the resistance and virulence of this bacterium. Following the in silico characterization of the YbhFSR transporter, a mutant strain was constructed by inactivating the gene responsible for ATP-binding. After ensuring that the mutation did not have an impact on bacterial growth, the resistance profile of parental and mutant strains to different antimicrobial agents was evaluated. The results suggest that the efflux pump may influence the resistance to benzalkonium chloride, ethidium bromide, and cadmium, and several other compounds were identified as potential substrates. Regarding the evaluation of the accumulation of ethidium bromide, a slight increase was observed for the mutant strain, demonstrating a potential role of the YbhFSR efflux pump in the extrusion of toxic compounds from A. butzleri. Subsequently, the role of this efflux pump on the A. butzleri known virulence properties was evaluated, but no difference was seen among mutant and parental strains for the motility, biofilm formation ability, susceptibility to oxidative stress, or the ability to adhere and invade Caco-2 cells. However, in contrast to the parental strain, the mutant strain showed a resistance to human serum. Overall, the results support the role of efflux pumps in A. butzleri resistance to antimicrobials, highlighting the particular role of the YbhFSR system.

Optimization of Whey Protein-Based Films Incorporating Foeniculum vulgare Mill. Essential Oil.

Petroleum-based plastics used in food packaging are not biodegradable. They accumulate in the environment in large amounts, causing a decrease in soil fertility, jeopardizing marine habitats, and causing serious problems to human health. Whey protein has been studied for applications in food packaging, either because of its abundant availability or because it confers transparency, flexibility, and good barrier properties to packaging materials. Taking advantage of whey protein to produce new food packaging materials is a clear example of the so-called circular economy. The present work focuses on optimizing the formulation of whey protein concentrate-based films to enhance their general mechanical properties applying the Box-Behnken experimental design. Foeniculum vulgare Mill. (fennel) essential oil (EO) was incorporated into the optimized films, which were then further characterized. The incorporation of fennel EO in the films leads to a significant increase (p < 0.05) in peak elongation (from 14.03 to 31.61%) and tensile index (from 0.40 to 0.50 N.m/g). The optimized whey protein films were yellowish and very transparent (>90%). The results of the bioactive activities of the optimized films showed their ability to be applied as active materials for food packaging to improve the shelf-life of food products and also to prevent foodborne diseases associated with the growth of pathogenic microorganisms.

Evaluation of Bile Salts on the Survival and Modulation of Virulence of Aliarcobacter butzleri.

Aliarcobacter butzleri is a Gram-negative bacterium associated with infections of the gastrointestinal tract and widely distributed in various environments. For successful infection, A. butzleri should be able to tolerate various stresses during gastrointestinal passage, such as bile. Bile represents an antimicrobial host barrier that acts against external noxious agents and consists of a variety of bile salts. The intestinal bile salts act as detergents involved in the antimicrobial host defense; although, on the bacterial side, they could also serve as a signal to activate virulence mechanisms. The aim of this work was to understand the effects of bile salts on the survival and virulence of A. butzleri. In our study, A. butzleri was able to survive in the presence of human physiological concentrations of bile salts. Regarding the virulence features, an increase in cellular hydrophobicity, a decrease in motility and expression of flaA gene, as well as an increase in biofilm formation with a concomitant change in the type of biofilm structure were observed in the presence of sub-inhibitory concentration of bile salts. Concerning adhesion and invasion ability, no significant difference was observed. Overall, the results demonstrated that A. butzleri is able to survive in physiological concentrations of bile salts and that exposure to bile salts could change its virulence mechanisms.