Antibacterial activity of positively charged carbon quantum dots without detectable resistance for wound healing with mixed bacteria infection. - Related Documents




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909301.0000Antibacterial activity of positively charged carbon quantum dots without detectable resistance for wound healing with mixed bacteria infection. Widespread bacterial infection and the spread of antibiotic resistance exhibit increasing threat to the public and thus require new antibacterial strategies. Carbon quantum dots (CQDs) have been extensively investigated to play fluorescent, catalytic roles and even potential biomedical functions containing sterilization. However, synthetic understanding of the interaction of CQDs and bacteria, the exhibition of antibacterial ability, and the risk of resistance evolution remain lacking. Herein, a simple one-pot method was fabricated to prepare positively charged CQDs (PC-CQDs) as a broad-spectrum antibacterial agent. PC-CQDs possessed effective antibacterial activity against all tested Gram-positive, Gram-negative, and drug-resistant bacteria. Investigation of the antibacterial mechanism of PC-CQDs indicated that small-sized PC-CQDs functionalized with -NH(2) and -NH induced strong adherence behavior on the bacterial cell membrane. Moreover, the entry of PC-CQDs caused conformational changes in the genes and generation of reactive oxygen species in the bacteria. Safety evaluation illustrated that PC-CQDs did not trigger detectable drug resistance or hemolysis. Furthermore, PC-CQDs effectively promoted the antibacterial treatment of mixed Staphylococcus aureus and Escherichia coli infected wound in rats with low in vivo toxicity. These results suggested that PC-CQDs are a potential antibacterial candidate for real wound healing applications in complex bacterial infections and even resistant bacteria-caused infections.202133812599
897610.9992Biosynthesis of H(2)S and Siderophores Targeting Gram-Negative Bacterial Resistance to Reactive Oxygen Species. Reactive oxygen species (ROS) are a promising alternative bactericide. However, it is questioned that bacteria can potentially develop resistance to ROS, similar to their resistance against antibiotics and silver. Herein, it is reported that Gram-negative bacteria, including Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae, develop resistance to ROS after six repeated exposures. Notably, ROS minimum inhibitory concentration of Pseudomonas aeruginosa significantly increases to 256-fold after ten passages. The resistance mechanism predominantly originates from the intensified biosynthesis of the highly reductive hydrogen sulfide (H(2)S) and pyoverdine (PVD) siderophores, effectively neutralizing ROS. Simultaneously, PVD transports Fe(3+) from the extracellular space into the bacteria, releasing H(2)S bound to Fe(3+) and enhancing ROS scavenging. Additionally, the enhanced outer membrane (OM) biogenesis establishes a robust OM barrier, impeding ROS penetration. The acquired resistance to ROS can be significantly reduced by incorporating additional Fe(3+) into the culture medium or disrupting the H(2)S biosynthetic gene. These observations suggest that careful consideration is required when utilizing ROS against Gram-negative bacteria. It is anticipated that understanding this resistance mechanism can inform the development of future antimicrobial agents, particularly for Gram-negative bacteria.202540948366
895120.9991Response mechanisms of resistance in L-form bacteria to different target antibiotics: Implications from oxidative stress to metabolism. Due to the specific action on bacterial cell wall, β-lactam antibiotics have gained widespread usage as they exhibit a high degree of specificity in targeting bacteria, but causing minimal toxicity to host cells. Under antibiotic pressure, bacteria may opt to shed their cell walls and transform into L-form state as a means to evade the antibiotic effects. In this study, we explored and identified diverse optimal conditions for both Gram-negative bacteria (E. coli DH5α (CTX)) and Gram-positive bacteria (B. subtilis ATCC6633), which were induced to L-form bacteria using lysozyme (0.5 ppm) and meropenem (64 ppm). Notably, when bacteria transformed into L-form state, both bacterial strains showed varying degrees of increased resistance to antibiotics polymyxin E, meropenem, rifampicin, and tetracycline. E. coli DH5α (CTX) exhibited the most significant enhancement in resistance to tetracycline, with a 128-fold increase, while B. subtilis ATCC6633 showed a 32-fold increase in resistance to tetracycline and polymyxin E. Furthermore, L-form bacteria maintained their normal metabolic activity, combined with enhanced oxidative stress, served as an adaptive strategy promoting the sustained survival of L-form bacteria. This study provided a theoretical basis for comprehending antibiotic resistance mechanisms, developing innovative treatment strategies, and confronting global antibiotic resistance challenges.202438735077
885130.9991Sequence-Specific Targeting of Bacterial Resistance Genes Increases Antibiotic Efficacy. The lack of effective and well-tolerated therapies against antibiotic-resistant bacteria is a global public health problem leading to prolonged treatment and increased mortality. To improve the efficacy of existing antibiotic compounds, we introduce a new method for strategically inducing antibiotic hypersensitivity in pathogenic bacteria. Following the systematic verification that the AcrAB-TolC efflux system is one of the major determinants of the intrinsic antibiotic resistance levels in Escherichia coli, we have developed a short antisense oligomer designed to inhibit the expression of acrA and increase antibiotic susceptibility in E. coli. By employing this strategy, we can inhibit E. coli growth using 2- to 40-fold lower antibiotic doses, depending on the antibiotic compound utilized. The sensitizing effect of the antisense oligomer is highly specific to the targeted gene's sequence, which is conserved in several bacterial genera, and the oligomer does not have any detectable toxicity against human cells. Finally, we demonstrate that antisense oligomers improve the efficacy of antibiotic combinations, allowing the combined use of even antagonistic antibiotic pairs that are typically not favored due to their reduced activities.201627631336
910340.9991Development of cannabidiol derivatives as potent broad-spectrum antibacterial agents with membrane-disruptive mechanism. The emergence of antibiotic resistance has brought a significant burden to public health. Here, we designed and synthesized a series of cannabidiol derivatives by biomimicking the structure and function of cationic antibacterial peptides. This is the first report on the design of cannabidiol derivatives as broad-spectrum antibacterial agents. Through the structure-activity relationship (SAR) study, we found a lead compound 23 that killed both Gram-negative and Gram-positive bacteria via a membrane-targeting mechanism of action with low resistance frequencies. Compound 23 also exhibited very weak hemolytic activity, low toxicity toward mammalian cells, and rapid bactericidal properties. To further validate the membrane action mechanism of compound 23, we performed transcriptomic analysis using RNA-seq, which revealed that treatment with compound 23 altered many cell wall/membrane/envelope biogenesis-related genes in Gram-positive and Gram-negative bacteria. More importantly, compound 23 showed potent in vivo antibacterial efficacy in murine corneal infection models caused by Staphylococcus aureus or Pseudomonas aeruginosa. These findings would provide a new design idea for the discovery of novel broad-spectrum antibacterial agents to overcome the antibiotic resistance crisis.202438266554
974950.9991Nanotransformation of Vancomycin Overcomes the Intrinsic Resistance of Gram-Negative Bacteria. The increased emergence of antibiotic-resistant bacteria is a growing public health concern, and although new drugs are constantly being sought, the pace of development is slow compared with the evolution and spread of multidrug-resistant species. In this study, we developed a novel broad-spectrum antimicrobial agent by simply transforming vancomycin into nanoform using sonochemistry. Vancomycin is a glycopeptide antibiotic largely used for the treatment of infections caused by Gram-positive bacteria but inefficient against Gram-negative species. The nanospherization extended its effect toward Gram-negative Escherichia coli and Pseudomonas aeruginosa, making these bacteria up to 10 and 100 times more sensitive to the antibiotic, respectively. The spheres were able to disrupt the outer membranes of these bacteria, overcoming their intrinsic resistance toward glycopeptides. The penetration of nanospheres into a Langmuir monolayer of bacterial membrane phospholipids confirmed the interaction of the nanoantibiotic with the membrane of E. coli cells, affecting their physical integrity, as further visualized by scanning electron microscopy. Such mechanism of antibacterial action is unlikely to induce mutations in the evolutionary conserved bacterial membrane, therefore reducing the possibility of acquiring resistance. Our results indicated that the nanotransformation of vancomycin could overcome the inherent resistance of Gram-negative bacteria toward this antibiotic and disrupt mature biofilms at antibacterial-effective concentrations.201728393523
909460.9991Pathogen-Specific Polymeric Antimicrobials with Significant Membrane Disruption and Enhanced Photodynamic Damage To Inhibit Highly Opportunistic Bacteria. Highly pathogenic Gram-negative bacteria and their drug resistance are a severe public health threat with high mortality. Gram-negative bacteria are hard to kill due to the complex cell envelopes with low permeability and extra defense mechanisms. It is challenging to treat them with current strategies, mainly including antibiotics, peptides, polymers, and some hybrid materials, which still face the issue of drug resistance, limited antibacterial selectivity, and severe side effects. Together with precise bacteria targeting, synergistic therapeutic modalities, including physical membrane damage and photodynamic eradication, are promising to combat Gram-negative bacteria. Herein, pathogen-specific polymeric antimicrobials were formulated from amphiphilic block copolymers, poly(butyl methacrylate)- b-poly(2-(dimethylamino) ethyl methacrylate- co-eosin)- b-ubiquicidin, PBMA- b-P(DMAEMA- co-EoS)-UBI, in which pathogen-targeting peptide ubiquicidin (UBI) was tethered in the hydrophilic chain terminal, and Eosin-Y was copolymerized in the hydrophilic block. The micelles could selectively adhere to bacteria instead of mammalian cells, inserting into the bacteria membrane to induce physical membrane damage and out-diffusion of intracellular milieu. Furthermore, significant in situ generation of reactive oxygen species was observed upon light irradiation, achieving further photodynamic eradication. Broad-spectrum bacterial inhibition was demonstrated for the polymeric antimicrobials, especially highly opportunistic Gram-negative bacteria, such as Pseudomona aeruginosa ( P. aeruginosa) based on the synergy of physical destruction and photodynamic therapy, without detectable resistance. In vivo P. aeruginosa-infected knife injury model and burn model both proved good potency of bacteria eradication and promoted wound healing, which was comparable with commercial antibiotics, yet no risk of drug resistance. It is promising to hurdle the infection and resistance suffered from highly opportunistic bacteria.201930632740
910670.9991tRNA methylation: An unexpected link to bacterial resistance and persistence to antibiotics and beyond. A major threat to public health is the resistance and persistence of Gram-negative bacteria to multiple drugs during antibiotic treatment. The resistance is due to the ability of these bacteria to block antibiotics from permeating into and accumulating inside the cell, while the persistence is due to the ability of these bacteria to enter into a nonreplicating state that shuts down major metabolic pathways but remains active in drug efflux. Resistance and persistence are permitted by the unique cell envelope structure of Gram-negative bacteria, which consists of both an outer and an inner membrane (OM and IM, respectively) that lay above and below the cell wall. Unexpectedly, recent work reveals that m(1) G37 methylation of tRNA, at the N(1) of guanosine at position 37 on the 3'-side of the tRNA anticodon, controls biosynthesis of both membranes and determines the integrity of cell envelope structure, thus providing a novel link to the development of bacterial resistance and persistence to antibiotics. The impact of m(1) G37-tRNA methylation on Gram-negative bacteria can reach further, by determining the ability of these bacteria to exit from the persistence state when the antibiotic treatment is removed. These conceptual advances raise the possibility that successful targeting of m(1) G37-tRNA methylation can provide new approaches for treating acute and chronic infections caused by Gram-negative bacteria. This article is categorized under: Translation > Translation Regulation RNA Processing > RNA Editing and Modification RNA Structure and Dynamics > Influence of RNA Structure in Biological Systems.202032533808
897480.9991Escherichia coli Bacteria Develop Adaptive Resistance to Antibacterial ZnO Nanoparticles. Antibacterial agents based on nanoparticles (NPs) have many important applications, e.g., for the textile industry, surface disinfection, wound dressing, water treatment, and food preservation. Because of their prevalent use it is important to understand whether bacteria could develop resistance to such antibacterial NPs similarly to the resistance that bacteria are known to develop to antibiotics. Here, it is reported that Escherichia coli (E. coli) develops adaptive resistance to antibacterial ZnO NPs after several days' exposure to the NPs. But, in contrast to antibiotics-resistance, the observed resistance to ZnO NPs is not stable-after several days without exposure to the NPs, the bacteria regain their sensitivity to the NPs' antibacterial properties. Based on the analyses it is suggested that the observed resistance is caused by changes in the shape of the bacteria and the expressions of membrane proteins. The findings provide insights into the response of bacteria to antibacterial NPs, which is important to elucidate for designing and evaluating the risk of applications based on antibacterial NPs.201833103858
910290.9991An Organogold Compound as Potential Antimicrobial Agent against Drug-Resistant Bacteria: Initial Mechanistic Insights. The rise of antimicrobial resistance has necessitated novel strategies to efficiently combat pathogenic bacteria. Metal-based compounds have been proven as a possible alternative to classical organic drugs. Here, we have assessed the antibacterial activity of seven gold complexes of different families. One compound, a cyclometalated Au(III) C^N complex, showed activity against Gram-positive bacteria, including multi-drug resistant clinical strains. The mechanism of action of this compound was studied in Bacillus subtilis. Overall, the studies point towards a complex mode of antibacterial action, which does not include induction of oxidative stress or cell membrane damage. A number of genes related to metal transport and homeostasis were upregulated upon short treatment of the cells with gold compound. Toxicity tests conducted on precision-cut mouse tissue slices ex vivo revealed that the organogold compound is poorly toxic to mouse liver and kidney tissues, and may thus, be treated as an antibacterial drug candidate.202134181818
8969100.9990Breaching the Barrier: Genome-Wide Investigation into the Role of a Primary Amine in Promoting E. coli Outer-Membrane Passage and Growth Inhibition by Ampicillin. Gram-negative bacteria are problematic for antibiotic development due to the low permeability of their cell envelopes. To rationally design new antibiotics capable of breaching this barrier, more information is required about the specific components of the cell envelope that prevent the passage of compounds with different physiochemical properties. Ampicillin and benzylpenicillin are β-lactam antibiotics with identical chemical structures except for a clever synthetic addition of a primary amine group in ampicillin, which promotes its accumulation in Gram-negatives. Previous work showed that ampicillin is better able to pass through the outer membrane porin OmpF in Escherichia coli compared to benzylpenicillin. It is not known, however, how the primary amine may affect interaction with other cell envelope components. This study applied TraDIS to identify genes that affect E. coli fitness in the presence of equivalent subinhibitory concentrations of ampicillin and benzylpenicillin, with a focus on the cell envelope. Insertions that compromised the outer membrane, particularly the lipopolysaccharide layer, were found to decrease fitness under benzylpenicillin exposure, but had less effect on fitness under ampicillin treatment. These results align with expectations if benzylpenicillin is poorly able to pass through porins. Disruption of genes encoding the AcrAB-TolC efflux system were detrimental to survival under both antibiotics, but particularly ampicillin. Indeed, insertions in these genes and regulators of acrAB-tolC expression were differentially selected under ampicillin treatment to a greater extent than insertions in ompF. These results suggest that maintaining ampicillin efflux may be more significant to E. coli survival than full inhibition of OmpF-mediated uptake. IMPORTANCE Due to the growing antibiotic resistance crisis, there is a critical need to develop new antibiotics, particularly compounds capable of targeting high-priority antibiotic-resistant Gram-negative pathogens. In order to develop new compounds capable of overcoming resistance a greater understanding of how Gram-negative bacteria are able to prevent the uptake and accumulation of many antibiotics is required. This study used a novel genome wide approach to investigate the significance of a primary amine group as a chemical feature that promotes the uptake and accumulation of compounds in the Gram-negative model organism Escherichia coli. The results support previous biochemical observations that the primary amine promotes passage through the outer membrane porin OmpF, but also highlight active efflux as a major resistance factor.202236409154
8981110.9990Response mechanisms of different antibiotic-resistant bacteria with different resistance action targets to the stress from photocatalytic oxidation. The stress response of antibiotic-resistant bacteria (ARB) and the spread of antibiotic resistance genes (ARGs) pose a serious threat to the aquatic environment and human beings. This study mainly explored the effect of the heterogeneous photocatalytic oxidation (UVA-TiO(2) system) on the stress response mechanism of ARB with different antibiotic resistance action targets, including the cell wall, proteins, DNA, RNA, folate and the cell membrane. Results indicate that the stress response mechanism of tetracycline- and sulfamethoxazole-resistant E. coli DH5α, which targets the synthesis of protein and folate, could rapidly induce global regulators by the overexpression of relative antibiotic resistance action target genes. Different stress response systems were mediated via cross-protection mechanism, causing stronger tolerance to an adverse environment than other ARB. Moreover, the photocatalytic inactivation mechanism of bacterial cells and a graded response of cellular stress mechanism caused differences in the intensity of the stress mechanism of antibiotic resistance action targets. E. coli DH5α resistant to cefotaxime and polymyxin, targeting synthesis of the cell wall and cell membrane, respectively, could confer greater advantages to bacterial survival and higher conjugative transfer frequency than E. coli DH5α resistant to nalidixic acid and rifampicin, which target the synthesis of DNA and RNA, respectively. This new perspective provides detailed information on the practical application of photocatalytic oxidation for inactivating ARB and hampering the spreading of ARGs in the aquatic environment.202235453030
8978120.9990Revealing the antibacterial power of hydrogen-releasing PdH nanohydride against drug resistant Staphylococcus aureus: an in-depth mechanism study. Currently, multidrug resistant (MDR) bacterial infections are a great threat to public health, and the development of novel strategies for high efficiency combatting of MDR bacteria is in urgent demand. Hydrogen (H(2)) is a small gas with a high reducing ability, and plenty of recent studies have demonstrated its therapeutic effect on many diseases. However, the antibacterial effectiveness and mechanism of H(2) against MDR bacteria are still unknown. In the present work, using PdH nanohydride with a temperature responsive H(2)-releasing property as the H(2) source, we demonstrated that H(2) was not only able to inhibit the growth of normal Staphylococcus aureus (S. aureus), but could also effectively eliminate single drug resistant S. aureus (CRSA) and multidrug resistant S. aureus (MRSA), as well as the biofilms formed by those bacteria. Moreover, an in-depth mechanism regarding the anti-antibiotic-resistance activity of H(2) was elucidated by us, in which H(2) exerted its antibacterial effect by firstly causing severe membrane damage, followed by boosting generation of intracellular ROS, which subsequently triggered DNA damage and finally led to bacterial death. The proposed mechanism was further verified by genomic analysis, where a cluster of genes related to bacterial membrane integrity, biofilm formation, metabolism and DNA functions was significantly perturbed by the released H(2). In particular, H(2) boosted intracellular ROS generation by destroying the redox homeostasis of bacterial metabolism. More importantly, we revealed that H(2) was able to alleviate the antibiotic resistance of CRSA and MRSA by significantly down-regulating the expression of many drug-resistant genes, e.g. the norG gene of CRSA, and fmtA, gpsB, sarA and marR genes of MRSA, as well as reducing the minimal inhibitory concentration (MIC) of ciprofloxacin/ampicillin against CRSA/MRSA. The findings in our work suggested that H(2) therapy is a promising tool for combating antibiotic-resistant bacteria.202336655922
8223130.9990Biogenic ammonia modifies antibiotic resistance at a distance in physically separated bacteria. Bacteria release low-molecular-weight by-products called secondary metabolites, which contribute to bacterial ecology and biology. Whereas volatile compounds constitute a large class of potential infochemicals, their role in bacteria-bacteria interactions remains vastly unexplored. Here we report that exposure to gaseous ammonia released from stationary-phase bacterial cultures modifies the antibiotic resistance spectrum of all tested Gram-negative and Gram-positive bacteria. Using Escherichia coli K12 as a model organism, and increased resistance to tetracycline as the phenotypic read-out, we demonstrate that exposure to ammonia generated by the catabolism of l-aspartate increases the level of intracellular polyamines, in turn leading to modifications in membrane permeability to different antibiotics as well as increased resistance to oxidative stress. We show that the inability to import ammonia via the Amt gas channel or to synthesize polyamines prevent modification in the resistance profile of aerially exposed bacteria. We therefore provide here the first detailed molecular characterization of widespread, long-range chemical interference between physically separated bacteria.201121651627
9015140.9990A D-enantiomer of the antimicrobial peptide GL13K evades antimicrobial resistance in the Gram positive bacteria Enterococcus faecalis and Streptococcus gordonii. Antimicrobial peptides represent an alternative to traditional antibiotics that may be less susceptible to bacterial resistance mechanisms by directly attacking the bacterial cell membrane. However, bacteria have a variety of defense mechanisms that can prevent cationic antimicrobial peptides from reaching the cell membrane. The L- and D-enantiomers of the antimicrobial peptide GL13K were tested against the Gram-positive bacteria Enterococcus faecalis and Streptococcus gordonii to understand the role of bacterial proteases and cell wall modifications in bacterial resistance. GL13K was derived from the human salivary protein BPIFA2. Minimal inhibitory concentrations were determined by broth dilution and a serial assay used to determine bacterial resistance. Peptide degradation was determined in a bioassay utilizing a luminescent strain of Pseudomonas aeruginosa to detect peptide activity. Autolysis and D-alanylation-deficient strains of E. faecalis and S. gordonii were tested in autolysis assays and peptide activity assays. E. faecalis protease inactivated L-GL13K but not D-GL13K, whereas autolysis did not affect peptide activity. Indeed, the D-enantiomer appeared to kill the bacteria prior to initiation of autolysis. D-alanylation mutants were killed by L-GL13K whereas this modification did not affect killing by D-GL13K. The mutants regained resistance to L-GL13K whereas bacteria did not gain resistance to D-GL13K after repeated treatment with the peptides. D-alanylation affected the hydrophobicity of bacterial cells but hydrophobicity alone did not affect GL13K activity. D-GL13K evades two resistance mechanisms in Gram-positive bacteria without giving rise to substantial new resistance. D-GL13K exhibits attractive properties for further antibiotic development.201829566082
9101150.9990A Novel Bactericidal Drug Effective Against Gram-Positive and Gram-Negative Pathogenic Bacteria: Easy as AB569. Global antibiotic resistance, driven by intensive antibiotic exposure/abuse, constitutes a serious challenge to all health care, particularly in an era when new antimicrobial development has slowed to a trickle. Recently, we published work demonstrating the discovery and partial mechanism of action of a novel bactericidal agent that is effective against both gram-positive and gram-negative multidrug-resistant bacteria. This drug, called AB569, consists of acidified nitrite (A-NO(2)(-)) and EDTA, of which there is no mechanism of resistance. Using both chemistry-, genetic-, and bioinformatics-based techniques, we first discovered that AB569 was able to generate bactericidal levels of nitric oxide (NO), while the EDTA component stabilized S-nitrosyl thiols, thereby furthering NO and downstream reactive nitrogen species production. This elegant chemistry triggered a paralytic downregulation of vital genes using RNA-seq involved in the synthesis of DNA, RNA, ATP, and protein in the representative ESKAPE pathogen, Pseudomonas aeruginosa.202032721230
8848160.9990Harnessing the effect of iron deprivation to attenuate the growth of opportunistic pathogen Acinetobacter baumannii. Acinetobacter baumannii is an opportunistic pathogen having high infectivity among immunocompromised patients. The bacteria are resistant to major first-line antibiotics and have become a serious concern in the aspect of nosocomial and community-acquired infections. To overcome this dire situation, the necessity of introducing new approaches is undeniable, which can bypass the need for conventional antibiotic therapy. In this article, we have pinpointed the importance of iron in A. baumannii. Iron is an essential micronutrient in all bacteria. Loss of iron acquisition leads to membrane destabilization, and change in the expression of iron-transporting or -metabolizing genes causes death of the bacteria. Iron scavenging was primarily mediated by different chelators, and β-thujaplicin showed the best antibacterial efficacy with respect to time killing assay and CFU analysis. When iron (Fe(2+)) was supplemented after initial deficiency, the growth of the bacteria was seen to be restored. Iron deprivation also disintegrates the biofilm matrix, a major cause of bacterial resistance against different types of antibiotics. Moreover, iron scavenging promotes inhibition of biofilm sessile persister cells, the root cause of recalcitrant and chronic infection. As a part of antimicrobial therapy, β-thujaplicin was treated alongside colistin and chloramphenicol at an amount significantly lower than its MIC value. Our results indicated that β-thujaplicin nicely complemented those antibiotics to potentiate their antimicrobial action. In a nutshell, iron chelating agents are potential alternative therapeutics that can be used alongside different antibiotics to circumvent the resistance of different nosocomial pathogens.202540202344
8962170.9990A Dietary Source of High Level of Fluoroquinolone Tolerance in mcr-Carrying Gram-Negative Bacteria. The emergence of antibiotic tolerance, characterized by the prolonged survival of bacteria following antibiotic exposure, in natural bacterial populations, especially in pathogens carrying antibiotic resistance genes, has been an increasing threat to public health. However, the major causes contributing to the formation of antibiotic tolerance and underlying molecular mechanisms are yet poorly understood. Herein, we show that potassium sorbate (PS), a widely used food additive, triggers a high level of fluoroquinolone tolerance in bacteria carrying mobile colistin resistance gene mcr. Mechanistic studies demonstrate that PS treatment results in the accumulation of intracellular fumarate, which activates bacterial two-component system and decreases the expression level of outer membrane protein OmpF, thereby reducing the uptake of ciprofloxacin. In addition, the supplementation of PS inhibits aerobic respiration, reduces reactive oxygen species production and alleviates DNA damage caused by bactericidal antibiotics. Furthermore, we demonstrate that succinate, an intermediate product of the tricarboxylic acid cycle, overcomes PS-mediated ciprofloxacin tolerance. In multiple animal models, ciprofloxacin treatment displays failure outcomes in PS preadministrated animals, including comparable survival and bacterial loads with the vehicle group. Taken together, our works offer novel mechanistic insights into the development of antibiotic tolerance and uncover potential risks associated with PS use.202337808177
8847180.9990Phage-delivered sensitisation with subsequent antibiotic treatment reveals sustained effect against antimicrobial resistant bacteria. Temperate phages integrated with clustered regularly interspaced short palindromic repeat (CRISPR)/Cas systems have been gaining attention as potential strategies for combating bacteria resistant to antimicrobials. To further advance this technology, phage recombination procedure should be improved, and the bactericidal effect should be examined in detail and compared with conventional lytic phage strategy. The possibility of the emergence of mutational resistance, a phenomenon commonly observed with lytic phage therapy, should be illustrated. Methods: Here, we developed a novel one-step cloning method to fulfil the recombination of CRISPR/Cas9 system within the genome of a new isolated lysogenic Escherichia coli phage. Then, we proposed and developed a phage-delivered resistance eradication with subsequent antibiotic treatment (PRESA) strategy. The removal efficiency and antimicrobial effect of the plasmids were analysed. Long-term antimicrobial effect was evaluated by continued OD(600) monitoring for 240 hours to illustrate the potential mutational resistance, compared with the lytic phage strategy. The treatment effect of PRESA was evaluated in vivo by determining bacterial loads in the skin and intestine of infected mice, in contrast with lytic phage therapy. Genome sequencing was performed to identify mutations in bacterial cells treated with phage strategies. Results: Phage-delivered CRISPR targeting efficiently eradicated and blocked the transfer of the antibiotic resistance plasmid. PRESA decreased the bacterial load by over 6- and 5-logs in vitro and in vivo, respectively. Importantly, while lytic phages induced mutational phage resistance at 24 h in vitro and 48 hours in vivo, PRESA demonstrated a constant effect and revealed no resistant mutants. Genes involved in DNA mismatch repair were upregulated in cells undergoing Cas9-based plasmid cleavage, which may reduce the development of mutations. Conclusion: The PRESA strategy for eradicating resistant bacteria showed high bactericidal efficacy and a sustained inhibition effect against resistant bacteria. By restoring the efficacy of low-cost antibiotics, PRESA could be developed as an efficient and economical therapy for infections of antibiotic resistant bacteria.202032483454
8908190.9990Characterization and Transcriptome Analysis of Acinetobacter baumannii Persister Cells. Acinetobacter baumannii is a nonfermenting Gram-negative bacillus. A. baumannii resistance is a significant obstacle to clinical infection treatment. The existence of persister cells (persisters) might represent the reason for therapy failure and relapse, and such cells may be the driving force behind rising resistance rates. In this study, A. baumannii ATCC 19606 was used as a target to explore the essential features of A. baumannii persisters. Antibiotic treatment of A. baumannii cultures at 50-fold the minimum inhibitory concentration resulted in a distinct plateau of surviving drug-tolerant persisters. The sensitive bacteria were lysed with ceftazidime, and the nonreplicating bacteria were isolated for transcriptome analysis using RNA sequencing. We analyzed the transcriptome of A. baumannii persisters and identified significantly differentially expressed genes, as well as their enriched pathways. The results showed that both the GP49 (HigB)/Cro (HigA) and DUF1044/RelB toxin/antitoxin systems were significantly increased during the persister incubation period. In addition, the activities of certain metabolic pathways (such as electron transport, adenosine triphosphate [ATP], and the citrate cycle) decreased sharply after antibiotic treatment and remained low during the persister period, while aromatic compound degradation genes were only upregulated in persisters. These results suggest the involvement of aromatic compound degradation genes in persister formation and maintenance. They further provide the first insight into the mechanism of persister formation in A. baumannii.201829902105