Antibiotic Activity Research Articles

Copper(II) aromatic heterocyclic complexes of Gatifloxacin with multi-targeting capabilities for antibacterial therapy and combating antibiotic resistance

In recent years, the pace of novel antibiotic development has been relatively slow, intensifying the urgency of the antibiotic resistance issue. Consequently, scientists have turned their attention to enhancing antibiotic activity by coordinating antibiotics with metal elements. This study designs and synthesizes three novel antibacterial copper complexes based on Gatifloxacin. These complexes exhibit potent antibacterial activity, notably Cu-1, with a minimum inhibitory concentration (MIC) of only 0.063 μg/mL against Staphylococcus aureus (S.aureus), demonstrating potent bacteriostatic capabilities. Further investigations unveil the antibacterial mechanisms of complex Cu-1, revealing its ability not only to suppress the activities of DNA gyrase and topoisomerases IV, but also to effectively inhibit biofilm formation and disrupt the integrity of cell membrane. This multi-targeting action contributes to mitigating the risk of bacterial resistance emergence. Additionally, synergy between Cu-1 and conventional antibiotics is confirmed through checkerboard assays, offering novel strategies for antibacterial therapy. In vivo experiments using a murine model of S.aureus infection demonstrate the significant antibacterial efficacy of Cu-1, providing robust support for its potential in treating S.aureus infections. This study demonstrates that the coordination complexes formed by copper, Gatifloxacin and suitable aromatic heterocyclic ligands exhibit multi-targeting characteristics against bacteria, offering a new direction for combating antibiotic resistance in antibacterial therapy.

Cpx-signalling in Yersinia pseudotuberculosis modulates Lipid-A remodelling and resistance to last-resort antimicrobials

AbstractAntibiotic resistance is a global healthcare crisis. Bacteria are highly adaptable and can rapidly acquire mechanisms of resistance towards conventional antibiotics. The permeability barrier conferred by the Gram-negative bacteria cell envelope constitutes a first line of defence against the action of antibiotics. Exposure to extracytoplasmic stresses can negatively affect cell envelope homoeostasis and this causes localised protein misfolding, compromised envelope integrity and impairs barrier function. The CpxA-CpxR two-component regulatory system has evolved to sense extracytoplasmic stresses and to regulate processes that restore homoeostasis of the cell envelope. Hence, controlled Cpx-signalling assists bacteria in adapting, surviving and proliferating in harsh environments, including exposure to antibiotics. Herein, we determined that an intact Cpx-signalling is key to maintaining the Yersinia pseudotuberculosis resistance to colistin and polymyxin B. The susceptibility displayed by Cpx-signalling defective mutants, correlated with cell-envelope deformity and specific modifications of Lipid-A. In vivo transcriptional analysis and in vitro protein-DNA binding studies demonstrated that these modifications were dependent on the direct regulation of Lipid-A biogenesis and modifications of operons by the active phosphorylated CpxR~P isoform. Altogether, our work defines the regulatory mechanism that enables Cpx-signalling to actively control cell envelope remodelling and the permeability of antibiotics in the clinically relevant enteropathogen Y. pseudotuberculosis.

Monte Carlo simulation for dosage optimization of the best available therapy for bloodstream infections secondary to carbapenemase-producing Klebsiella pneumoniae in critically ill patients.

We aimed to use Monte Carlo simulation, based on pharmacokinetic/ pharmacodynamic (PK/PD) targets, to investigate and determine the optimal dosage of the available combination therapies for carbapenem-resistant Klebsiella pneumoniae (CRKP) in critically ill patients. We collected CRKP clinical isolates from Phramongkutklao Hospital between October 2020 and June 2022. A molecular study of resistant genes was performed using polymerase chain reaction (PCR). Broth microdilution checkerboards were used to evaluate the mono- and synergistic antibiotic activities. Monte Carlo simulation was used to determine the optimal antibiotic regimens, based on the probability of target achievement (PTA) and cumulative fraction of response (CFR). The 54 CRKP isolates were resistant to tigecycline (100%), colistin (75.9%), amikacin (70.4%), and gentamicin (63.0%). The most common carbapenemase genotype was blaoxacillinases (OXA)-48-like (42.6%), followed by blaNew Delhi metallo beta lactamase (NDM) (29.6%) and coexistence of blaOXA-48-like and blaNDM (22.2%). Based on the PTA, synergistic and additive activities against CRKP isolates were observed with appropriate dosages of tigecycline-colistin (67.9%), tigecycline-gentamicin (62.2%), and tigecycline-amikacin (51.4%). Tigecycline-colistin was the best available combination therapy for critically ill patients with CRKP, especially NDM. When used in combination with tigecycline, a colistin creatinine clearance (CrCl) of <90 mL/min can raise the CFR target and less nephrotoxicity.

Diversity pattern and antibiotic activity of microbial communities inhabiting a karst cave from Costa Rica.

The studies of cave bacterial communities worldwide have revealed their potential to produce antibiotic molecules. In Costa Rica, ~400 caves have been identified; however, their microbial diversity and biotechnological potential remain unexplored. In this work, we studied the chemical composition and microbial diversity of a Costa Rican cave (known as the Amblipigida cave) located in Puntarenas, Costa Rica. Additionally, through culture-dependent methods, we evaluated the potential of its microbiota to produce antibiotic molecules. Mineralogical and elemental analyses revealed that the Amblipigida cave is primarily composed of calcite. However, small variations in chemical composition were observed as a result of specific conditions, such as light flashes or the input of organic matter. The 16S rRNA gene metabarcoding revealed an extraordinarily high microbial diversity (with an average Shannon index of ~6.5), primarily comprising bacteria from the phyla Pseudomonadota, Actinomycetota, Firmicutes and Acidobacteriota, with the family Pseudomonadaceae being the most abundant. A total of 93 bacteria were isolated, of which 15% exhibited antibiotic activity against at least one Gram-positive or yeast strain and were classified within the genera Lysobacter, Streptomyces, Pseudomonas, Brevundimonas and Bacillus. These findings underscore the highly diverse nature of cave microbiota and their significant biotechnological potential, particularly in the production of antibiotic compounds.

Design and Evaluation of Pyridinyl Sulfonyl Piperazine LpxH Inhibitors with Potent Antibiotic Activity Against Enterobacterales

Design and Evaluation of Pyridinyl Sulfonyl Piperazine LpxH Inhibitors with Potent Antibiotic Activity Against Enterobacterales

Molecular Docking and Antibacterial Activity of Campesterol Derivatives Against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa Multiresistant Strains.

This work describes the evaluation the potentiating activity of antibiotics by campesterol (1) and its derivatives (2-11) against multiresistant strains of Staphylococcus aureus 10, Escherichia coli 06 and Pseudomonas aeruginosa 24 employing the microdilution test. When subjected to the in vitro potentiating activity bioassay, all compounds showed a potentiating effect associated with norfloxacin against E. coli and P. aeruginosa with a reduction in the MIC of the antibiotic of up to 75 %. These compounds also reduced the MIC of gentamicin by 37 % to 87 % in S. aureus and E. coli. Additionally, molecular docking studies were conducted to gain a deeper understanding of the interactions between the appropriate proteins and the most effective compounds (2, 4, 9, and 10 against E. coli; 1, 2, 3, 5, 8, and 9 against S. aureus), including antibiotics. This paper registers for the first time the in vitro and in silico studies on the action of compounds 1-11 in antibiotic potentiation.

Effect of nanoemulsion loaded with macela (Achyrocline satureioides) on the ultrastructure of Staphylococcus aureus and the modulating activity of antibiotics

Nanoformulations with herbal actives for treating bovine mastitis present an alternative for controlling bacterial infections in the emerging scenario of antimicrobial resistance. In this study, we investigated macela (Achyrocline satureioides) nanoemulsion (NE-ML), a formulation developed for the treatment of bovine mastitis (registered under Brazilian patent application BR 10 2021 008630 0), in the context of its bactericidal mechanism(s) of action and potential synergism with commercial antimicrobials. The effect of NE-ML on the integrity and cell permeability of Staphylococcus aureus was evaluated by measuring the electrical conductivity of bacterial suspensions exposed to different concentrations of NE-ML and by assessing the release of cellular constituents. Damage to bacterial ultrastructures was analyzed by transmission electron micrographs. The synergism of NE-ML with beta-lactam antibiotics and aminoglycosides was evaluated by the checkerboard test method against S. aureus (n = 6). The relative electrical conductivity of the bacterial solution gradually increased over time, reaching high values after exposure to 1xMIC (52.3%) and 2xMIC (75.34%) of NE-ML. Total proteins were detected in the bacterial suspensions exposed to NE-ML, increasing in concentration over exposure time (p &amp;lt; 0.05). Through bacterial micrographs, we observed that exposure to NE-ML (1xMIC) affected the integrity of the plasma membrane with invaginations in the cytosolic region and alterations in the cell wall. The increase in NE-ML concentration resulted in greater damage to the ultrastructure of S. aureus with changes in bacterial cell division patterns. When NE-ML was combined with the beta-lactam antimicrobials, the interaction was indifferent, indicating no modulation of antimicrobial resistance. In contrast, when combined with the aminoglycoside, a synergistic interaction did occur. These general findings suggest that the bactericidal action of NE-ML begins in the plasma membrane, causing alterations in its permeability and integrity, and extends to the cell wall, cytoplasm, and cell division. Although synergy was restricted to the aminoglycoside by destabilizing the bacterial cell membrane, this suggests that NE-ML can induce the entry of other actives, potentially reducing their therapeutic doses. Understanding the mechanism of action of this new nanoformulation is certain to drive pharmacological advances, broaden the perspective of its in vivo use, and improve the treatment of bovine mastitis.

Pseudomonas rhodesiae HAI-0804 suppresses Pythium damping off and root rot in cucumber by its efficient root colonization promoted by amendment with glutamate

Plant diseases caused by soil-borne fungi and oomycetes significantly reduce yield and quality of many crops in the agricultural systems and are difficult to control. We herein examine Pseudomonas rhodesiae HAI-0804, a bacterial biological control agent that was originally developed for control of bacterial diseases on the surface of vegetables, and assessed its efficacy at controlling soil-borne diseases caused by oomycetes. Strain HAI-0804 did not exhibit detectable antibiotic activity toward Pythium ultimum, a causal agent of damping-off and root rot; however, it effectively protected against Pythium damping-off and root rot in cucumber. Exogenous glutamate enhanced the efficacy of biocontrol, the production of siderophore pyoverdine, root colonization in cucumber plants, and the ratio of biofilm formation to planktonic cells. The epiphytic fitness of strain HAI-0804 appears to contribute to plant protection efficacy against a broad spectrum of pathogens for both above-ground plant parts and the rhizosphere.

Production of Antibiotics from Endophyte Fungi Isolates of Bidara Plants (Ziziphus mauritina L.) Isolates Codes IFAZ-6, IFBZ-6, IFDZ-8 With Variations in Carbon Sources

Research has been carried out on antibiotic production from endophytic fungal isolates coded IFAZ-6, IFBZ-6, and IFDZ-8 from bidara plants (Ziziphus mauritina L.) with variations in carbon sources. This research aims to determine antibiotic production with variations in carbon sources. The first stage was the purification of each selected endophytic fungal isolate. The endophytic fungal isolate was inoculated into the fermentation medium using a variety of carbon sources, namely glucose, fructose, and galactose for 21 days. The antibiotic activity was carried out using the agar diffusion method against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli bacteria. The results obtained showed that the glucose carbon source was better in producing antibiotic compounds than the galactose carbon source in endophytic fungal isolates coded IFAZ-6, the glucose carbon source was better in producing antibiotic compounds than the fructose and galactose sources in endophytic fungal isolates coded IFBZ-6, and the fructose carbon source is better at producing antibiotic compounds than the galactose source in endophytic fungal isolates coded IFDZ-8.

Phage-derived polysaccharide depolymerase potentiates ceftazidime efficacy against Acinetobacter baumannii pneumonia via low-serum-dependent mechanisms

The emergence of multidrug-resistant Acinetobacter baumannii (MDR-AB), which most commonly manifests as pneumonia, has posed significant clinical challenges and called for novel treatment strategies. Phage depolymerases, which degrade bacterial surface carbohydrates, have emerged as potential antimicrobial agents. However, their preclinical application is limited to systemic infections due to their dependency on serum-mediated bacterial killing. To extend the treatment paradigm of depolymerase to low-serum lung infections, we explored the feasibility of applying phage depolymerase to potentiate antibiotic efficacy in controlling MDR-AB pneumonia. Using a model depolymerase, Dpo71, we observed that it could effectively potentiate antibiotic efficacy against MDR-AB2 bacteria in low-serum conditions mimicking lung milieu but showed no adjuvant effect in serum-free conditions. Unprecedentedly, we reported this low-serum-dependent mechanism that polysaccharide-degrading enzyme Dpo71 exposed bacteria to serum-induced membrane permeabilization and oxidative phosphorylation pathway inhibition, leading to a weakened ATP-dependent efflux pump and strengthened ROS-induced membrane permeabilization. These joint effects facilitated antibiotic (ceftazidime, CFZ) binding, ultimately exerting bactericidal effects. Resultantly, the bacterial load in the lungs of the Dpo71-CFZ combination group was significantly reduced compared with the Dpo71-alone and CFZ-alone groups. Overall, this study unravels the low-serum-dependent mechanisms by which depolymerase potentiated antibiotic efficacy, highlighting its potential as a novel strategy to enhance antibiotic activity against severe pneumonia.

The role of tranexamic acid for infection prevention after fracture fixation

Despite the measures employed, fracture-related infections remain a concern after fracture fixation worldwide. Recently, the role of tranexamic acid as a protective drug against postsurgical infections in joint replacement and orthopedic trauma surgery has been proposed, where tranexamic acid has been associated with less surgical wounds complications and infectious complications including periprosthetic joint infection. The mechanism through which tranexamic acid exerts a protective effect against peri-implant infection is still the subject of debate. Although some authors hypothesize an indirect effect inhibiting the formation of postoperative hematoma, there are several studies that show a direct antibacterial effect of the drug against the capacity of bacterial aggregation, even avoiding biofilm formation, favoring the immune response of the host and the action of antibiotics. The purpose of this narrative review is to show the current role of tranexamic acid in orthopedic trauma, specifically its relationship with the prevention of infections related to implants.

Liposomal formulation with thiazolic compounds against bacterial efflux pumps

This study aimed to evaluate the effects of liposome-encapsulated eugenol-based thiazolic derivatives against efflux pump-carrying bacteria. The Minimum Inhibitory Concentration (MIC) was determined to evaluate the antibacterial activity and antibiotic potentiation against Pseudomonas aeruginosa and Staphylococcus aureus, as well as to analyze the inhibition of efflux pumps in S. aureus strains 1199B and K2068 in the ethidium bromide assay. The direct antibacterial activity analysis showed no clinically relevant results since the compounds presented MICs ≥1024 µg/mL. Regarding the analysis of antibiotic potentiation against multidrug-resistant (MDR) strains of S. aureus, compound LF16 reduced norfloxacin MIC from 128 µg/mL to 64 µg/mL. All associated with gentamicin caused a significant antibiotic MIC reduction. None of the compounds could potentate the activity of norfloxacin against P. aeruginosa. However, all of them potentiated the activity of gentamicin against the same strain. Only the LF 26 caused a significant MIC reduction in the ethidium bromide assay, suggesting efflux inhibition in the S. aureus 1199B strain. Similar results were observed with the K2068 strain. Observing antibiotic MIC reduction S. aureus strains carrying the NorA and MepA proteins brought additional evidence of efflux pump inhibition. Our results indicate that while eugenol-based thiazoles didn’t exhibit direct activity, they can potentiate the antibiotics activity against MDR strains of P. aeruginosa and S. aureus. Among them, compound LF 26 potentiated the inhibitory effects of ethidium bromide and antibiotics against S. aureus strains carrying the NorA and MepA proteins, indicating a potential role of this class of compounds as efflux pump inhibitors.

Synergistic potential of Leu10-teixobactin and cefepime against multidrug-resistant Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a significant Gram-positive opportunistic pathogen behind many debilitating infections. β-lactam antibiotics are conventionally prescribed for treating S. aureus infections. However, the adaptability of S. aureus in evolving resistance to multiple β-lactams contributed to the persistence and spread of infections, exemplified in the emergence of methicillin-resistant S. aureus (MRSA). In the present study, we investigated the efficacies of the synthetic teixobactin analogue, Leu10-teixobactin, combined with the penicillinase-resistant cephalosporin cefepime against MRSA strains. The Leu10-teixobactin and cefepime combination exerted synergism against most strains tested in broth microdilution assay. Time-kill profiles showed that both Leu10-teixobactin and cefepime predominantly exhibited synergistic activity, with > 2.0-log10CFU decrease compared to monotherapy at 24 h. Moreover, biofilm assays revealed a significant inhibition of biofilm production in ATCC™43300 cells treated with sub-MICs of Leu10-teixobactin and cefepime. Subsequent electron microscopy studies showed more extensive damage with the combination therapy compared to monotherapies, including aberrant bacterial morphology, vesicle formation and substantial lysis, indicating combined damage to the cell wall. Quantitative real-time PCR revealed marked perturbation of genes mecA, sarA, atlA, and icaA, substantiating the apparent mode of combined antibacterial action of both antibiotics against peptidoglycan synthesis and initial biofilm production. Hence, the study highlights the prospective utility of the Leu10-teixobactin-cefepime combination in treating MRSA infections via β-lactam potentiation.

Bactericidal versus bacteriostatic antibacterials: clinical significance, differences and synergistic potential in clinical practice.

Antibacterial activity can be classified as either bactericidal or bacteriostatic, using methods such as the MBC/MIC ratio and time-kill curves. However, such categorization has proven challenging in clinical practice, as these definitions only apply under specific laboratory conditions, which may differ from clinical settings. Several factors, such as the specific bacteria or infectious medium, can affect the action of antibiotics, with many antibacterials exerting both activities. These definitions have also led to the belief that bactericidal antibacterials are superior to bacteriostatic, especially in more severe cases, such as endocarditis, neutropenia and bacteraemia. Additionally, current dogma dictates against the combination of bactericidal and bacteriostatic antibacterials in clinical practice, due to potential antagonism. This review aimed to assess the differences in antibacterial activity of bactericidal and bacteriostatic antibacterials based on in vitro and in vivo studies and examine their antagonistic or synergistic effects. Our findings show that specific bacteriostatic agents, such as linezolid and tigecycline, are clinically non-inferior to bactericidals in multiple infections, including pneumonia, intra-abdominal infections, and skin and soft tissue infections. Studies also support using several bacteriostatic agents as salvage therapies in severe infections, such as neutropenic fever and endocarditis. Additionally, not all combinations of bacteriostatic and bactericidal agents appear to be antagonistic, with many combinations, such as linezolid and rifampicin, already being used. The findings should be interpreted with caution, as most evidence is from observational studies and there is a need for randomized controlled trials to assess their effectiveness and combinations, especially within the context of rising antimicrobial resistance.

Unlocking Nitrofurantoin: Understanding Molecular Mechanisms of Action and Resistance in Enterobacterales.

Antimicrobial resistance (AMR) is a global health crisis that has already claimed millions of lives and is projected to affect millions more unless urgent action is taken. Effective control of AMR requires the correct choice and dosage of antibiotics, as well as robust surveillance and research. Understanding the mechanisms of antibiotic action and the emergence of resistance phenotypes along with their genotypes is essential. This knowledge, combined with insights into resistance prevalence and spread, empowers clinicians to propose alternative therapies. Nitrofurantoin, a 70-year-old antibiotic, remains effective for the treatment of uncomplicated lower UTIs. Preventing emergence and spread of nitrofurantoin resistant superbugs would preserve the efficacy of this antibiotic which is crucial for ongoing and future AMR efforts. Nitrofurantoin resistance evolves slowly, leading to low prevalence compared to other antibiotics. However, it is often linked with extensive drug resistance, complicating treatment outcomes. Even a minor percentage of nitrofurantoin-resistant bacteria can cause significant clinical challenges due to irreversible evolution. While detailed study of these mechanisms can guide the development of strategies to combat nitrofurantoin resistance, early detection of resistant infections is critical for saving lives. The current review aims to provide a comprehensive analysis of nitrofurantoin's mechanisms of action, resistance evolution, prevalence, and resistance prediction. Our goal is to offer valuable insights for researchers and clinicians to enhance nitrofurantoin use and address the challenges posed by AMR.

Tridentate N-donor Schiff base metal Complexes: Synthesis, Characterization, computational Studies, and assessment of biomedical applications in cancer Therapy, Helicobacter pylori Eradication, and COVID-19 treatment

A unique Schiff base ligand (BCA), 4-(2-((1E,2E)-1-(2-(p-tolyl)hydrazono)propan-2-ylidene)hydrazinyl)quinazoline, was synthesized and complexed with Mn [II], Co [II], Cu [II, and Cd [II] ions, with 1,10-Phenanthroline (PHN) as an auxiliary ligand. The unique Schiff base ligand BCA and its metal complexes were characterized using multiple analytical techniques, including elemental analysis, UV–visible spectroscopy, FT-IR, mass spectrometry, and conductometric measurements. These methods provided detailed insights into the compounds’ structural and electronic properties. Density Functional Theory (DFT) computations complemented the experimental data, elucidating electronic configuration stability, HOMO-LUMO energy gaps, chemical hardness, and dipole moments. The computational results confirmed the distorted octahedral structure of the complexes. Antimicrobial testing against various bacterial and fungal strains revealed that the Cd (II) complex exhibited the highest activity, with inhibition zones ranging from 19.7 ± 0.6 mm to 35.0 ± 1.0 mm, surpassing the activity of standard antibiotics in some cases. Notably, the compounds displayed significant efficacy against Helicobacter pylori, with the Cd (II) complex showing an inhibition zone of 32.67 ± 0.58 mm and a minimum inhibitory concentration (MIC) of 7.8 μg/ml. Anticancer properties were evaluated against MCF-7 (Breast carcinoma) cells, with the [(BCA)(PHN)Cd(H2O)].2Cl·2H2O complex demonstrating superior activity (IC50 = 29.97 μg/ml) compared to the free ligand (IC50 = 183.96 μg/ml) and other metal complexes. Notably, the Cd(II) complex showed reduced cytotoxicity towards normal VERO cells, suggesting potential selectivity for cancer cells. Molecular docking simulations evaluated the complexes’ binding interactions with protein targets associated with Helicobacter pylori, MCF cancer cells, and the COVID-19 virus. The main objective of this research was to design and synthesize a unique Schiff base ligand and its new corresponding Ternary metal complexes and then investigate their potential medical applications. Specifically, the study aimed to evaluate the compounds’ effectiveness as antibiotics, antitumor agents, and possible treatments for COVID-19.

Differential frequency of persister cells in clinically derived isolates of Pseudomonas aeruginosa after exposure to cefiderocol and ceftolozane/tazobactam.

Bacterial persistence is a phenomenon whereby a subpopulation of bacteria survive high concentrations of an active antibiotic in the absence of phenotypic alterations. Persisters are associated with chronic and recurrent infections for pathogens including Pseudomonas aeruginosa. Understanding persister profiles of newer antibiotics such as cefiderocol and ceftolozane/tazobactam against P. aeruginosa is warranted as these agents generally target difficult-to-treat infections. Persister formation was assessed using in vitro assays against nine clinical P. aeruginosa isolates exposed to cefiderocol or ceftolozane/tazobactam. Quantitative persister assays were performed using a stationary phase of bacteria challenged with 10-fold MIC drug concentrations. Persisters were quantitated as the percent persisters at 24 h and the log ratio (LR) difference in AUC for cfu for each antibiotic alone compared with growth control. The tolerance disc test (TDtest) was used to qualitatively detect persisters. Percent persisters at 24 h was lower with cefiderocol compared with ceftolozane/tazobactam for six of the nine tested isolates. Eight of the nine isolates had higher reduction in LR for cefiderocol groups, suggesting an overall higher and more rapid bacterial reduction in cefiderocol groups. For cefiderocol, five of the nine tested isolates lacked regrowth after replacement with glucose disc, suggesting no persistence via the TDtest. For ceftolozane/tazobactam, three isolates lacked persister formation. Cefiderocol resulted in less bacterial persistence relative to ceftolozane/tazobactam against nine clinical P. aeruginosa isolates. Cefiderocol's siderophore mechanism may be advantageous over ceftolozane/tazobactam through enhanced anti-persister effects. Clinical correlation of these findings is warranted as persisters can lead to antibiotic resistance and treatment failure.

Evaluation of the Antibacterial Activity of Antibiotics with different Antibacterial Mechanisms using Electrochemical Signals of Heat‐Treated Escherichia Coli

AbstractElectrochemistry with purines as indicators may be a promising new method for antibiotic activity testing. However, the traditional electrochemical detection method (S‐LSV) requires a long accumulation time for purines and has low signal intensity. High‐temperature treatment of bacterial samples may significantly enhance the signal intensity and speed of detection. However, this process may also impact the structure and metabolism of bacteria. Further research is necessary to determine how electrochemical signals respond to antibiotic antibacterial activity. In this paper, the electrochemical detection method based on heat‐treated Escherichia coli (E. coli, H‐LSV) was used to investigate the effects of 11 antibiotics with four different antibacterial mechanisms on the electrochemical behavior of E. coli. The results showed that compared to the S‐LSV, the electrochemical signal of E. coli detected by the H‐LSV increased by 362%, and showed a strong linear relationship with bacterial counts up to 1.88×108 CFU/mL, with a detection limit of 1.15×106 CFU/mL. The electrochemical signal consistently correlated with changes in viable E. coli counts following treatment with the four different antibacterial mechanisms. HPLC analysis further confirmed that the changes in purine contents in bacteria after antibiotic treatment were consistent with the trends in electrochemical signals. The evaluation of antibiotic antibacterial ability by H‐LSV showed good consistency with results from plate counting and turbidity methods, but was closer to the results of plate counting. The inhibition rates of antibiotics on E. coli detected by H‐LSV and S‐LSV also showed high consistency, indicating that short‐term high‐temperature treatment of E. coli did not affect the response of the bacterium to the inhibitory activity of antibiotics.

Chemical Profile, Antibacterial and Toxicological Study of Asparagus setaceus (KUNTH)

Objective: The objective of this work was to obtain the chemical profile and verify the biological activities of ethanolic extract from the leaves of Asparagus setaceus. Method: The extract was obtained with cold ethanol and the classes of secondary metabolites were identified with specific reagents. The antibacterial assays were performed using the microdilution method against the standard bacteria, Gram +: Sthaphylococcus aureus, Streptococcus mutans and Enterococcus faecalis and Gram -: Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoneae and two multidrug-resistant strains: Escherichia coli 27 and Staphylococcus aureus 358 and the resistance modulation assay was performed using aminoglycoside and beta- lactam antibiotics. Toxicity was tested against the microcrustacean Artemia salina (Leach) ranging in concentrations from 10 to 500 μg/mL Results and Discussion: The ethanolic extract of Asparagus setaceus (EEAS) indicated the presence of phenols, condensed tannins, anthocyanins, anthocyanidins, flavones, flavonols, xanthones, chalcones, aurones, flavononols, catechins, leukoanthocyanidins, flavones and saponins. The EEAS presented CL50 of 90.22 μg/ mL. The microbial assay showed inhibition for standard strains of Gram + and Gram bacteria - but in the multidrug-resistant strains it showed clinically non-signific results. For the modulation of antibiotic action against bacterial strains, EEAS presented both synergistic and antagonistic action, with the synergistic action being more expressive on benzylpenicillin, amikacin and gentamicin in front of Escherichia coli 27. The aminoglycoside antibiotics showed synergistic activity on all bacteria tested. Research Implications: Given the results, it was found that the ethanolic extract of the leaves of Asparagus setaceus (Kunth) disp of chemical and biological properties that can contribute to the elaboration of therapeutic resources against inflammatory and bacterial infectious processes. Keywords: Antibacterial Assay, Secondary Metabolites, Modulation, Asparagus setaceus.

The activity of hydrolytic enzymes and antibiotics against biofilms of bacteria isolated from industrial-scale cooling towers

BackgroundCooling towers (CTs) are crucial to myriad industrial processes, supporting thermal exchange between fluids in heat exchangers using water from lakes and rivers as coolant. However, CT water can sometimes introduce microbial contaminants that adhere to and colonize various surfaces within the CT system. These microorganisms can form biofilms, significantly hindering the system’s thermal exchange efficiency. Current treatment strategies employ oxidizing biocides to prevent microbial growth. However, despite their affordability, they do not eliminate biofilms effectively and can lead to corrosive damage within the system. Herein, we aim to devise an anti-biofilm strategy utilizing hydrolytic enzymes (such as α-amylase, glucoamylase, pectin-lyase, cellulase, protease, and DNase) alongside antibiotics (including meropenem, ciprofloxacin, gentamicin, erythromycin, chloramphenicol, and ceftriaxone) to combat microbial growth and biofilm formation in cooling systems.ResultsAll enzymes reduced the development of the biofilms significantly compared to controls (p < 0.05). The polysaccharidases exhibited biomass reduction of 90%, except for pectin-lyase (80%), followed by DNAse and protease at 43% and 49%, respectively. The antibiotics reduced the biofilms of 70% of isolates in concentration of > 2 mg/mL. The minimal biofilm eradication concentration (MBEC) lower than 1 mg/mL was detected for some 7-day-old sessile isolates. The enzymes and antibiotics were also used in combination against biofilms using the modified Chequerboard method. We found six synergistic combinations, with Fractional inhibitory concentrations (FIC) < 0.5, out of the ten tested. In the presence of the enzymatic mixture, MBECs presented a significant decrease (p < 0.05), at least 4-fold for antibiotics and 32-fold for enzymes. Moreover, we characterized high molecular weight (> 12 kDa) exopolysaccharides (EPS) from biofilms of ten isolates, and glycosyl composition analysis indicated a high frequency of glucose, mannose, erythrose, arabinose, and idose across isolates EPS contrasting with rhamnose, allose, and those carbohydrates, which were detected in only one isolate.ConclusionThe synergistic approach of combining enzymes with antibiotics emerges as a highly effective and innovative strategy for anti-biofilm intervention, highlighting its potential to enhance biofilm management practices.