Huge demand of safe and natural preservatives has opened new area for intensive research on bacteriocins to unravel the novel range of antimicrobial compounds that could efficiently fight off the ...food-borne pathogens. Since food safety has become an increasingly important international concern, the application of bacteriocins from lactic acid bacteria that target food spoilage/pathogenic bacteria without major adverse effects has received great attention. Different modes of actions of these bacteriocins have been suggested and identified, like pore-forming, inhibition of cell-wall/nucleic acid/protein synthesis. However, development of resistance in the food spoilage and pathogenic bacteria against these bacteriocins is a rising concern. Emergence and spread of mutant strains resistant to bacteriocins is hampering food safety. It has spurred an interest to understand the bacteriocin resistance phenomenon displayed by the food pathogens, which will be helpful in mitigating the resistance problem. Therefore, present review is focused on the different resistance mechanisms adopted by food pathogens to overcome bacteriocin.
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•Bacteriocins are ribosomally-synthesized bacterial antimicrobial peptides (AMPs).•It kills food spoilage/pathogenic bacteria from both Gram-positive and Gram-negative group.•It forms pores in bacterial cell-membrane, resulting in dissipation of proton-motive force leading to cell death.•Changes in bacterial cell-surface charge and membrane fluidity render the bacteriocins ineffective.•Pairing of bacteriocins with other AMPs and their bioengineering can tackle bacteriocins resistance.
One of the most striking features of
is its outstanding capacity for developing antimicrobial resistance to nearly all available antipseudomonal agents through the selection of chromosomal mutations, ...leading to the failure of the treatment of severe hospital-acquired or chronic infections. Recent whole-genome sequencing (WGS) data obtained from
assays on the evolution of antibiotic resistance,
monitoring of antimicrobial resistance development, analysis of sequential cystic fibrosis isolates, and characterization of widespread epidemic high-risk clones have provided new insights into the evolutionary dynamics and mechanisms of
antibiotic resistance, thus motivating this review. Indeed, the analysis of the WGS mutational resistome has proven to be useful for understanding the evolutionary dynamics of classical resistance pathways and to describe new mechanisms for the majority of antipseudomonal classes, including β-lactams, aminoglycosides, fluoroquinolones, or polymixins. Beyond addressing a relevant scientific question, the analysis of the
mutational resistome is expected to be useful, together with the analysis of the horizontally-acquired resistance determinants, for establishing the antibiotic resistance genotype, which should correlate with the antibiotic resistance phenotype and as such, it should be useful for the design of therapeutic strategies and for monitoring the efficacy of administered antibiotic treatments. However, further experimental research and new bioinformatics tools are still needed to overcome the interpretation limitations imposed by the complex interactions (including those leading to collateral resistance or susceptibility) between the 100s of genes involved in the mutational resistome, as well as the frequent difficulties for differentiating relevant mutations from simple natural polymorphisms.
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•Direct/Cross-resistances were induced in Salmonella treated by essential oil (EO).•161–324 differentially expressed genes were screened by a transcriptomics analysis.•Metabolomics ...analysis revealed changes of 47 significant metabolites and pathways.•Thyme oil induced a more conservative strategy compared with cinnamon oil.
Essential oils (EOs), such as thyme (Thy) and cinnamon (Cin) oils, present promising antibacterial properties against foodborne pathogens (e.g., Salmonella enterica serovar Typhimurium). However, the food matrix might result in sublethal EO stress, and little information about direct and/or cross-resistance development after sublethal EO exposure is available. This study revealed that S. Typhimurium under sublethal Thy and Cin (50% minimum inhibitory concentration, MIC50) treatments exhibited a lower growth rate and an extended lag phase. EO adapted cells showed direct-resistance to subsequent lethal EO treatment, and cross-resistance to thermal (58 °C) and oxidative (hydrogen peroxide, 50 mmol/L) stresses. Metabolomics analysis revealed changes of 47 significant metabolites (variable importance in projection > 1, false discovery rate (FDR) < 0.05), including lipids, oligopeptides, amino acids, nucleotide related compounds, and organic acids. Metabolic pathways, such as aminoacyl-tRNA biosynthesis, were shown to be involved in EO adaptation. Furthermore, a transcriptomics study identified 161 differentially expressed genes (DEGs, fold change > 2, FDR < 0.05) in MIC50 Thy treated cells, while more DEGs (324) were screened from the MIC50 Cin group. The integrated omics analysis allowed us to speculate on the molecular mechanisms. Under harsher Thy stress, S. Typhimurium cells adopted a conservative strategy to survive. By contrast, more radical responses were observed during Cin adaptation. In conclusion, the food industry should be more cautious in the use of EOs because sublethal EO stress might result in the development of resistance.
Since the initial use of Bordeaux mixture in 1885 for plant disease control, a large number of copper-based antimicrobial compounds (CBACs) have been developed and applied for crop protection. While ...these compounds have revolutionized crop protection in the twentieth century, their continuous and frequent use has also raised concerns about the long-term sustainability of copper (Cu)-based crop protection system. Here, we review CBACs used in crop protection and highlight their benefits and risks, and potential for their improvement and opportunities for further research to develop alternatives to CBACs. The major findings are (i) the relatively high toxicity to plant pathogens, low cost, low mammalian toxicity of the fixed Cu compounds, and their chemical stability and prolonged residual effects are major benefits of these compounds; (ii) phytotoxicity, development of copper-resistant strains, soil accumulation, and negative effects on soil biota as well as on food quality parameters are key disadvantages of CBACs; (iii) regulatory pressure in agriculture worldwide to limit the use of CBACs has led to several restrictions, including that imposed by the regulation 473/2002 in the European Union; and (iv) mitigation strategies to limit the negative effects of CBACs include their optimized use, soil remediation, and development and application of alternatives to CBACs for a sustainable crop protection. We conclude that recent research and policy efforts have led to the development of a number of alternatives to CBACs, which should be further intensified to ensure that growers have sufficient tools for the implementation of sustainable crop protection strategies.
Antibiotic use in the healthcare and agriculture sectors has resulted in levels being found in environmental compartments including surface waters. This can create a selective pressure toward ...antibiotic resistance development, representing a potential risk to human health. Examining the Irish scenario, this screening paper develops a novel risk ranking model to comparatively assess, on a national scale, the predicted amount of antibiotics entering water bodies as a result of their use in healthcare and agricultural sectors, and the subsequent risk of antibiotic resistance development. Probabilistic modelling approaches, based on data sourced from published literature on antibiotics, are used to account for inherent uncertainty and variability in the input factors; usage, metabolism, degradation and wastewater removal rates, estimating the mass of six antibiotic classes released daily from both sectors. These mass estimates are used to generate predicted concentrations and risk quotient values for each drug class, utilising estimated minimum inhibitory concentration values sourced from the literature. Modelled results predict higher risk quotient (RQ) values in the healthcare compared to agriculture sector, with macrolides and penicillins ranking highest in terms of RQ value. A lower RQ is also predicted from human-use tetracyclines, trimethoprim, and quinolones. Avenues for runoff reduction for each antibiotic class, in particular the higher-risk classes, in both usage sectors are discussed. For validation, predicted levels are compared to observed levels of antibiotic residues in Ireland. Key knowledge gaps to assist prediction and modelling of antibiotic pollution in future studies are also discussed. This research paper establishes a protocol and model structure, applicable to other regions, to compare the contributions of healthcare and agriculture to antibiotic pollution, and identifies highest-ranked antibiotic classes in terms of potential resistance development for prioritisation in the Irish situation.
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•Model directly comparing antibiotic pollution arising from healthcare and agriculture•Release amount and resistance development risk for six antibiotic classes•Suggestions for reducing release of key antibiotic groups•Key risk groups for resistance development identified for Irish context
Vaborbactam (formerly RPX7009) is a new β-lactamase inhibitor based on a cyclic boronic acid pharmacophore with potent inhibitory activity against
arbapenemases (KPC). It has been developed in ...combination with meropenem. The objective of these studies was to identify the concentrations of both agents associated with the selection or prevention of single-step mutations leading to reduced sensitivity to the combination and to characterize the selected mutations. Eighteen strains of KPC-producing
with various degrees of sensitivity to meropenem (MICs, 8 to 512 μg/ml) and meropenem-vaborbactam (MICs, ≤0.06 to 32 μg/ml) and preexisting resistance mechanisms were selected from a worldwide collection of isolates recovered from surveillance studies, emphasizing strains for which MICs were in the upper range of the meropenem-vaborbactam MIC distribution. Meropenem and vaborbactam at 8 μg/ml each suppressed the drug resistance mutation frequency to <1 × 10
in 77.8% (14/18) of strains, and all strains were inhibited when the meropenem concentration was increased to 16 μg/ml. Mutants selected at lower drug concentrations showed phenotypes associated with previously described carbapenem resistance mechanisms, including
inactivation in mutants selected from OmpK36-proficient strains and an increased
gene copy number in strains with partially functional
No mutations in the coding region of
were identified. These data indicate that the selection of mutants with reduced sensitivity to meropenem-vaborbactam from KPC-producing
strains is associated with previously described mechanisms involving porin mutations and the increase in the
gene copy number and not changes in the KPC enzyme and can be prevented by the drug concentrations achieved with optimal dosing of the combination.
Rifampicin (RIF) resistance imposes a challenge on the antimicrobial treatment of pathogen infections. Figuring out the development mechanism of RIF resistance is critical to improving antimicrobial ...therapy strategy in clinics and biological treatment strategy of RIF polluted sewage in environmental engineering. The RIF resistance development of Staphylococcus aureus (S. aureus) with exposure to RIF at sub-inhibitory concentrations was comprehensively investigated via genomic and transcriptomic approaches in this study. RIF minimal inhibitory concentration (MIC) for S. aureus rapidly increased from 0.032 to 256 mg/L. Membrane permeability decrease, biofilm formation enhancement, and ROS production increase associated with RIF resistance were observed in RIF-induced strains. Through comparative genomic analysis, mutations in rpoB and rpoC were considered to be associated with RIF resistance in S. aureus mutants. Pan-genome-wide single-nucleotide variant analysis indicated that mutations at rpoB-1412, rpoB-1451, and rpoB-1457 were prevalent in 13849 public genomes of S. aureus, while mutations at rpoB-2256, and rpoC-3092 were first discovered in this study. The panorama of adaptative alteration of cellular physiological processes was observed via transcriptomic analysis. The oxidation pressure responses, metabolism, transporters, virulence factors, and multiple steps of DNA and RNA machinery were found to be perturbed by RIF in S. aureus.
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•RIF at sub-inhibitory concentration rapidly induced RIF resistance for S. aureus.•Adaptive alterations in phenotypes were discovered in RIF resistant strains.•Mutations in rpoB and rpoC were considered to be associated with RIF resistance.•Mutations at rpoB-2256 and rpoC-3092 were first discovered in S. aureus.•A transcriptional panorama of cellular physiological processes was revealed.
Wastewater treatment plants (WWTPs) have been reported as major anthropogenic reservoirs for the spread of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) into the ...environment, worldwide. While most studies mainly focus on the intracellular DNA (iDNA), extracellular DNA (exDNA) accounting for a significant proportion of the total DNA in wastewater, was usually neglected. Following the One Health approach, this study focuses on wastewaters of municipal, clinical, and livestock origins (n = 45) that undergo different treatment processes (i.e., conventional activated sludge, ultrafiltration, and ozonation). Water samples were analysed for 12 ARGs as indicators of the different compartments associated with iDNA and exDNA by quantitative real-time PCR (qPCR). Taxonomic profiling of exDNA-fractions, obtained using nucleic acid adsorption particles, was conducted by sequencing the V3–V4 hypervariable regions of the 16S rRNA gene. Notified exDNA concentrations varied between on-site WWTPs and treatment stages, and ranged from 314.0 ± 70.2 ng/mL in untreated livestock wastewater down to 0.7 ± 0.1 ng/mL in effluents after ultrafiltration. In general, influents exhibited higher concentrations compared to effluents, while wastewater treated by advanced treatment processes (i.e., ultrafiltration and ozonation) showed the lowest exDNA concentrations. Despite the lower concentrations, free-floating exDNA accounted for up to 80.0 ± 5.8% of the total DNA in effluents. Target ARGs were more common in the iDNA (100%, n = 45/45), compared to the exDNA-fractions (51.1%, n = 23/45), whereas exDNA-ARGs were mostly detected in clinical and slaughterhouse wastewaters as well as in the municipal influents. Compared to the iDNA-ARGs, the concentrations of exDNA-ARGs were in general lower. Nevertheless, significant higher concentrations for exDNA-associated genes were measured in clinical wastewaters for blaNDM (4.07 ± 0.15 log gene copies (GC)/L) and blaVIM-2 (6.0 ± 0.2 log GC/L). Overall, our results suggest that depending on the origin of wastewater and its treatment methods, exDNA represents an important reservoir for ARGs, particularly in clinical wastewater.
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•Free-floating exDNA makes up a significant part of the total DNA in wastewater.•ExDNA-fraction increases after wastewater treatment.•ExDNA-ARGs were mostly detected in untreated wastewaters.•Clinical wastewater is a reservoir for exDNA-associated carbapenem resistance genes.
Introduction Antibiotic resistance represents one of the most significant threats to public health in the 21st century. Polyphenols, natural molecules with antibacterial activity produced by plants, ...are being considered as alternative antimicrobial strategies to manage infections caused by drug-resistant bacteria. In this study, we investigated the antibacterial activity of a polyphenol mixture extracted from citrus fruits, against both antibiotic-susceptible and resistant strains of Staphylococcus aureus and Staphylococcus epidermidis . Methods Broth microdilution and time-kill curve experiments were used to test the extract anti-staphylococcal activity. Cytotoxicity was assessed by the hemolysis assay. The interaction between the mixture and antibiotics was investigated by the checkerboard assay. The effect of B alone and in combination with oxacillin on the membrane potential was investigated by the 3,3′-dipropylthiadicarbocyanine iodide assay. The ability of the extract to induce the development of resistance was verified by propagating S. aureus for 10 transfers in the presence of sub-inhibitory concentrations. Results The citrus extract was found to be active against all Staphylococcus strains at remarkably low concentrations (0.0031 and 0.0063%), displaying rapid bactericidal effects without being toxic on erythrocytes. In particular, B was found to rapidly cause membrane depolarization. When combined with methicillin, meropenem, and oxacillin, the mixture displayed synergistic activity exclusively against methicillin-resistant strains. We additionally show that the sequential exposure of S. aureus to sub-inhibitory concentrations did not induce the development of resistance against the extract. Discussion Overall, these findings support the potential use of the citrus extract as promising option to manage staphylococcal infections and suggest that it may counteract the mechanism behind methicillin-resistance.
•We established a novel methodology for risk assessment of resistance development.•Risk assessment employed selection effect, resistance prevalence and stability.•Effect of antibiotic load on ...resistance risk was seasonal- and category-dependent.•Source tracking by fate and transport modeling revealed antibiotic load hotspots.•We proposed resistance-risk-targeted load reduction strategy in lake-river complex.
Antibiotic stewardship is hindered by a lack of consideration for complicated environmental fate of antibiotics and their role in resistance development, while the current methodology of eco-toxicological risk assessment has not been fully protective against their potential to select for antibiotic resistance. To address this problem, we established a novel methodologic framework to perform comprehensive environmental risk assessment of antibiotics in terms of resistance development, which was based on selection effect, phenotype resistance level, heteroresistance frequency, as well as prevalence and stability of antibiotic resistance genes. We tracked the contribution of antibiotic load reduction to the mitigation of environmental risk of resistance development by fate and transport modeling. The method was instantiated in a lake-river network-basin complex system, taking the Taihu Basin as a case study. Overall, antibiotic load posed no eco-toxicological risk but an average medium-level environmental risk for resistance development in Taihu Lake. The effect of antibiotic load on resistance risk was both seasonal-dependent and category-dependent, while quinolones posed the greatest environmental risk for resistance development. Mass-flow analysis indicated that temporal-spatial variation in hydrological regime and antibiotic fate together exerted a significant effect on antibiotic load in the system. By apportioning antibiotic load to riverine influx, we identified the hotspots for load reduction and predicted the beneficial response of resistance risk under load-reduction scenarios. Our study proposed a risk-oriented strategy of basin-scaled antibiotic load reduction for environmental risk control of resistance development.
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