Search Results (787)

Acinetobacter baumannii emerged as one of the most important pathogens for the development of new antimicrobials due to the worldwide detection of isolates resistant to all commercial antibiotics, especially in nosocomial infections. Biofilm formation enhances A. baumannii survival by impairing antimicrobial action, being an important target for new antimicrobials. Fluopsin C (FlpC) is an organocupric secondary metabolite with broad-spectrum antimicrobial activity. This study aimed to evaluate the antibiofilm activity of FlpC in established biofilms of extensively drug-resistant A. baumannii (XDRAb) and the effects of its combination with polymyxin B (PolB) on planktonic cells. XDRAb susceptibility profiles were determined by Vitek 2 Compact, disk diffusion, and broth microdilution. FlpC and PolB interaction was assessed using the microdilution checkerboard method and time–kill kinetics. Biofilms of XDRAb characterization and removal by FlpC exposure were assessed by biomass staining with crystal violet. Confocal Laser Scanning Microscopy was used to determine the temporal removal of the biofilms using DAPI, and cell viability using live/dead staining. The minimum inhibitory concentration (MIC) of FlpC on XDRAb was 3.5 µg mL⁻¹. Combining FlpC + PolB culminated in an additive effect, increasing bacterial susceptibility to both antibiotics. FlpC-treated 24 h biofilms reached a major biomass removal of 92.40 ± 3.38% (isolate 230) using 7.0 µg mL⁻¹ FlpC. Biomass removal occurred significantly over time through the dispersion of the extracellular matrix and decreasing cell number and viability. This is the first report of FlpC’s activity on XDRAb and the compound showed a promissory response on planktonic and sessile cells, making it a candidate for the development of a new antimicrobial product. Full article

We analyzed the whole genome sequences (WGS) and antibiograms of 35 Enterobacter isolates, including E. hormaechei and E. asburiae, and the recently described E. bugandensis, E. kobei, E. ludwigii, and E. roggenkampii species. Isolates were obtained from human blood and urinary tract infections in patients in the United States. Our goal was to understand the genetic diversity of antimicrobial resistance genes and virulence factors among the various species. Thirty-four of 35 isolates contained an AmpC class bla_ACT allele; however, the E. roggenkampii isolate contained bla_MIR-5. Of the six Enterobacter isolates resistant to ertapenem, imipenem, and meropenem, four harbored a carbapenemase gene, including bla_KPC or bla_NDM. All four isolates were mCIM-positive. The remaining two isolates had alterations in ompC genes that may have contributed to the resistance phenotype. Interpretations of cefepime test results were variable when disk diffusion and automated broth microdilution results were compared due to the Clinical Laboratory and Standards Institute use of the “susceptible dose-dependent” classification. The diversity of the bla_ACT alleles paralleled species identifications, as did the presence of various virulence genes. The classification of recently described Enterobacter species is consistent with their resistance gene and virulence gene profiles. Full article

AISI 316L austenitic stainless steel superficially modified by the solid nitriding technique was investigated at different nitriding times (2, 4, 6, 8, 12 and 24 h) and at 450 °C. The microstructural characterization was conducted using scanning electron microscopy (SEM) analysis and X-ray diffraction analyses, finding the presence of Fe_2–3N, Fe₄N and Cr₂N, among others. The mechanical behavior of the modified surfaces was carried out by developing hardness profiles and relating it with the nitride layer thickness evaluated using scanning electron microscopy (SEM), obtaining layers up to 70 µm wide. The nitrogen diffusion produced species above and below the surface sample with a transformation from the austenitic phase to an expanded austenite (γ_N) phase, which is responsible for producing an increase in hardness of up to 1200 HV in the samples treated at 24 h, which is four times higher than the untreated steels. Wear evaluations of the obtained layers were performed using a pin-on-disk system under zero lubrication, indicating that the samples with 12 and 24 h of treatment present the best wear resistance promoted by an oxidative–adhesive mechanism. The obtained results are positively comparable with those of the ion nitriding technique but with a lower implementation cost. Full article

Herein, we introduce a simple precipitation method for preparing graphene oxide–silver nanoparticle (GO/AgNP) composites, utilizing Calendula officinalis (C. officinalis) seed extract as both a reducing and stabilizing agent. Our research combines the sustainable preparation of graphene oxide (GO) with the green synthesis of silver nanoparticles (AgNPs), aiming to explore the potential of the obtained composite as a novel antibacterial material. To establish a benchmark, the synthesis was also performed using sodium citrate, a conventional reducing agent. The resultant GO/AgNP composites were characterized through several analytical techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy, X-ray diffraction (XRD), infrared (IR) spectroscopy, and ultraviolet–visible (UV-vis) spectroscopy, confirming the successful functionalization of GO with AgNPs. The antibacterial effectiveness of the composites was systematically assessed against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), with nanoparticle concentrations spanning from 0 to 250 µg/mL, utilizing mostly disk diffusion and colony-forming unit (CFU) count assays. The AgNPs were characterized by a size range of 15–50 nm. Notably, the GO/AgNP composite prepared using C. officinalis seed extract demonstrated superior antibacterial activity at all tested concentrations, outperforming both pure GO and the GO/AgNP composite prepared with sodium citrate. The most pronounced antibacterial effect was observed at a concentration of 32.0 µg/mL. Therefore, this innovative synthesis approach may offer a valuable contribution to the development of new therapeutic agents to combat bacterial infections, suggesting further exploration into antibacterial coatings or potential drug development. Full article

Edible films based on biopolymers are used to protect food from adverse environmental factors. However, their ample use may be hindered by some challenges to their mechanical and antimicrobial properties. Despite this, in most cases, increasing their mechanical properties and antibacterial activity remains a relevant challenge. To solve this problem, a possible option is to fill the biopolymer matrix of films with a functional filler that combines high reinforcing and antibacterial properties. In this work, biocomposite films based on a mixture of chitosan and cassava starch were filled with a hybrid filler in the form of bentonite clay particles loaded with ginger essential oil (GEO) in their structure with varied concentrations. For this purpose, GEO components were intercalated into bentonite clay interlayer space using a mechanical capture approach without using surface-active and toxic agents. The structure and loading efficiency of the essential oil in the obtained hybrid filler were analyzed by lyophilization and laser analysis of dispersions, ATR-FTIR spectroscopy, thermogravimetry, and X-ray diffraction analysis. The filled biocomposite films were analyzed using ATR-FTIR spectroscopy, optical and scanning electron spectroscopy, energy dispersive spectroscopy, mechanical analysis under tension, and the disk diffusion method for antibacterial activity. The results demonstrated that the tensile strength, Young’s modulus, elongation at the break, and the antibacterial effect of the films increased by 40%, 19%, 44%, and 23%, respectively, compared to unfilled film when the filler concentration was 0.5–1 wt.%. Full article

Objectives: To develop a system for the rapid detection of Acinetobacter baumannii 173-p1 antibiotic resistance (to ensure reliable fixation of bacteria on a cantilever without losing their nanomotion, to show that nanomotion is due to bacterial metabolism, to compare the nanomotion of bacteria in suspension form and inside of the biofilms), to study the sensitivity/resistance of A. baumannii 173-p1 to antibiotics (lincomycin, ceftriaxone and doxycycline) using the oscillation method of atomic force microscopy and to evaluate the sensitivity and speed of the method in comparison with the classical disk diffusion method. Methods: The oscillation mode of atomic force microscopy, scanning electron microscopy and the classical disk diffusion method were used for a complex parallel study of A. baumannii 173-p1 antibiotic resistance, which included testing of fixing agents (poly-L-lysine, rosin and fibronectin), comparison of bacterial metabolism in a set of media (normal saline solution, meat-peptone broth and lysogeny broth) and assessment of antibiotic sensitivity/resistance per se. Results: A method for express testing of Acinetobacter baumannii antibiotic resistance using AFM was developed; it is shown that bacterial nanomotion directly correlates with bacteria metabolic activity and that bacterial nanomotion is more easily detected in suspension form, rather than in biofilms. Conclusion: The express testing method gave results that are completely comparable with the classical disk diffusion test and with the results of morphology studies by the SEM method, but it significantly exceeded them in speed, allowing a conclusion to be made on the sensitivity/resistance of bacteria less than an hour after the start of the diagnostics. Full article

Momentum diffusion and kinetic energy transfer in turbomachinery have always been significant issues, with a considerable impact on the performance of the bladeless Tesla turbine. This radial turbine shows high potential for various energy applications, such as Organic Rankine Cycle or combined heat and power systems. Analyzing the flow inside the gap between the corotating disks of the Tesla turbine presents challenges due to several factors, including submillimeter length scales, variations in flow cross-section, interactions of body forces arising from rotation with turbulence, interactions between the turbine’s inlet nozzles and rotor, and moving walls. General design parameters, e.g., number of nozzles, also pose a challenge in order to achieve the full potential of this turbine. In this research, two different variants of the supply system are considered with six and forty nozzles. To minimize computational expenses, a portion of the entire domain is considered. The flow in each domain, consisting of one inlet nozzle and a segment of one gap between the disks, is examined to reveal the complexity of flow structures and their impact on the Tesla turbine performance. Large Eddy Simulation (LES) with the Smagorinsky subgrid-scale model is used to verify the results of the k-ω Shear-Stress Transport (SST) turbulence model in the first case study with six nozzles. Analyzing the results indicates that the k-ω SST model provides valuable insights with appropriate accuracy. The second case study, with forty nozzles, is simulated using the k-ω SST turbulence model. The research compares flow structure, flow parameters, and their impact on the system’s performance. From the comparison between the k-ω SST turbulence model and LES simulation, it was observed that although the k-ω SST model slightly overestimates the general parameters and damps fluctuations, it still provides valuable insights for assessing flow structures. Additionally, the mesh strategy is described, as the LES requirements make this simulation computationally expensive and time-consuming. The overall benefits of this method are discussed. Full article

Shiga toxin-producing E. coli (STEC) are considered important zoonotic pathogens of great economic significance, associated with diarrhea, hemolytic uremic syndrome (HUS), hemorrhagic colitis (HC), and death in humans. This study aimed to investigate the distribution of various STEC virulence gene markers and antimicrobial susceptibility (AST) profiles associated within E. coli isolates from the recto-anal mucosal swabs (RAMSs) of slaughtered cattle and buffaloes in Islamabad, Pakistan. The RAMSs (n = 200) were analyzed using multiplex PCR for the presence of stx1, stx2, eae, and ehxA genes. Samples that were positive for one or more of the virulence genes were inoculated with Sorbitol MacConkey agar (SMAC) for isolation of STEC. The isolates were further analyzed for the presence of virulence genes using multiplex PCR. Of the 200 RAMS, 118 (59%) were positive for one or more virulence genes. E. coli isolates (n = 18) with one or more virulence genes were recovered from the 118 positive samples. The DNA of the isolates positive for one or more virulent genes was extracted and subjected to whole genome sequencing using Illumina. Analysis of the WGS data indicated that the E. coli isolates could be differentiated into 11 serotypes. Most E. coli isolates (13/18; 72.2%) carried five genes (stx1, stx2, Iha, iss, and IpfA) in various combinations. In addition to these five genes, other virulence genes identified in these isolates were espI, ireA, espP, exhA, epeA, mcmA, mch, ast, celB, eilA, katP, and capU. The AST was performed using the Kirby–Bauer disk diffusion test. The study indicated that all the isolates were resistant to rifampicin and a significant proportion of the isolates were MDR. A wide range of antimicrobial resistance genes (ARGs) were detected among the isolates, reflecting the complex nature of resistance mechanisms. The study results indicate that cattle and buffaloes slaughtered in Islamabad might be the carriers of antimicrobial resistant STEC of zoonotic significance, thus representing a source of human infection. Full article

Enterococcus faecalis and E. faecium are opportunistic pathogens commonly found in the microbiota of humans and other animals as well as in the environment. This article presents the results of antimicrobial susceptibility testing using phenotypic methods (broth microdilution and standardized disk diffusion) on selected clinical, food, and wastewater isolates of E. faecalis and E. faecium. The isolates were divided into subgroups based on their sensitivity to the following antibiotics: vancomycin (VAN) and ciprofloxacin (CIP), and biocides triclosan (TCL) and chlorhexidine (CHX). The study also investigated in vitro virulence factors, including biofilm formation ability, cell surface hydrophobicity (CSH) and β-hemolysis, to explore aspects of pathogenesis. In our study, regardless of the isolation source, VAN-resistant (VAN-R) and CIP-resistant (CIP-R) E. faecalis and E. faecium were detected. The highest proportion of CIP-R strains was found among clinical isolates of E. faecalis and E. faecium, with clinical E. faecium also showing the highest proportion of VAN-R strains. But the highest proportion of VAN-R E. faecalis strains was found in wastewater samples. The highest TCL MIC₉₀ values for E. faecalis were found in wastewater isolates, while for E. faecium, the highest TCL MIC₉₀ values were observed in food isolates. The highest CHX MIC₉₀ values for both E. faecalis and E. faecium were identified in clinical specimens. The results obtained for E. faecalis did not indicate differences in TCL MIC and CHX MIC values with respect to sensitivity to VAN and CIP. Higher CHX MIC₅₀ and CHX MIC₉₀ values were obtained for CIP-R and VAN-R E. faecium. Among the tested isolates, 97.75% of the E. faecalis isolates produced biofilm, while 72.22% of the E. faecium isolates did so as well. In biofilm-forming strength categories III and IV, statistically significantly higher proportions of CIP-susceptible (CIP-S) and VAN-susceptible (VAN-S) E. faecalis were determined. In category III, there is no statistically significant difference in E. faecium CIP sensitivity. In category IV, we had a significantly higher proportion of CIP-R strains. On the other hand, the association between the moderate or strong category of biofilm formation and E. faecium VAN susceptibility was not significant. E. faecalis isolated from wastewater had a CSH index (HI) ≥ 50%, categorizing them as “moderate”, while all the other strains were categorized as “low” based on the CSH index. Among the E. faecalis isolates, cell surface hydrophobicity indices differed significantly across isolation sources. In contrast, E. faecium isolates showed similar hydrophobicity indices across isolation sources, with no significant difference found. Moreover, no correlation was found between the enterococcal cell surface hydrophobicity and biofilm formation in vitro. After anaerobic incubation, β-hemolytic activity was confirmed in 19.10% of the E. faecalis and 3.33% of the E. faecium strains. Full article

Colletotrichum boninense is the main pathogenic fungus causing leaf spot disease in Sorghum sudangrass hybrids, which seriously impairs its quality and yield. In order to find an efficient and green means of control, this study used the agar disk diffusion method to screen for a fungicide with the strongest inhibitory effect on C. boninense from among several bacteria, fungi, and chemicals. Then, the changes in the plant’s antioxidant system and metabolic levels after treatment were used to compare the three means of control. The lowest inhibitory concentration of Zalfexam was 10 mg/mL, at which point C. boninense did not grow, and the inhibition rates of Bacillus velezensis (X7) and Trichoderma harzianum were 33.87–51.85% and 77.86–80.56%, respectively. Superoxide dismutase (SOD) and chitinase were up-regulated 2.43 and 1.24 folds in the Trichoderma harzianum group (M group) and SOD activity was up-regulated 2.2 folds in the Bacillus velezensis group (X7 group) compared to the control group (CK group). SOD, peroxidase (POD), and chitinase activities were elevated in the Zalfexam group (HX group). The differential metabolites in different treatment groups were mainly enriched in amino acid metabolism and production, flavonoid production, and lipid metabolism pathways. Compared with the diseased plants (ZB group), the M, X7, HX, and CK groups were co-enriched in the tryptophan metabolic pathway and glutamate–arginine metabolic pathway, and only the CK group showed a down-regulation of the metabolites in the two common pathways, while the metabolites of the common pathways were up-regulated in the M, X7, and HX groups. In addition, the salicylic acid–jasmonic acid pathway and ascorbic acid–glutathione, which were unique to the M group, played an important role in helping Sorghum sudangrass hybrids to acquire systemic resistance against stress. This study fills the gap in the control of Colletotrichum boninene, which causes leaf spot disease in Sorghum sudangrass hybrids. This paper represents the first reported case of biological control for leaf spot disease in Sorghum sudangrass hybrids and provides a reference for the control of leaf spot disease in Sorghum sudangrass hybrids as well as other crops infected with Colletotrichum boninense. Full article

The aim of the present work was to genetically characterise cefotaxime-resistant enterobacteria isolated from community carriers in Bulgaria. In total, 717 faecal samples from children and adults in five medical centres in Sofia, Pleven and Burgas were examined. Antimicrobial susceptibility was evaluated by the disk diffusion method. bla_ESBL or plasmidic AmpC (pAmpC) genes were detected by PCR and sequencing. MLST and ERIC-PCR were used to detect clonal relatedness. Among the faecal samples, 140 cefotaxime-resistant enterobacteria were found. The most frequently detected species was Escherichia coli (77.9%, 109/140 samples), followed by Klebsiella pneumoniae (7.9%, 11/140). Among the isolates, bla_CTX-M-15 (37.1%) was predominant, followed by bla_CTX-M-3 (19.2%), bla_CTX-M-14 (10%), and bla_CTX-M-27 (4.3 %). Genes encoding pAmpC were observed in 11.4% (bla_DHA-1, 16/140) and in 1.4% (bla_CMY-2, 2/140). The frequency of ESBL and pAmpC producers among the subjects was 14.6% and 2.5%, respectively. No carbapenem-resistant isolates were found. Four main clonal complexes (CC131, CC10, CC38, and CC155) were detected among E. coli isolates. The most common type was ST131, phylogroup B2 (16.5%). The increased frequency of ESBL- and pAmpC-producing enterobacteria in the community is a prerequisite for treatment failures of the associated infections and a good background for further studies. Full article

As bloodstream infections and associated septic shock are common causes of mortality in hospitals, rapid antibiotic susceptibility testing (AST) performed directly on positive blood cultures is needed to implement an efficient therapy in clinical settings. We evaluated the Reveal^® rapid AST system on a collection of 197 fully characterized carbapenem-resistant Enterobacterales, including 177 carbapenemase producers (CPE) spiked in blood culture bottles. The clinical categorization based on the Minimal Inhibitory Concentration (MIC) determination of eighteen antimicrobial molecules was compared to the clinical categorization based on the disk diffusion assay as a reference. The Reveal AST system provided results within a mean time to result of 5 h. Overall, the categorical agreement (CA) between the two techniques was 94.1%. The rates of very major errors (VMEs), major errors (MEs) and minor errors (mEs) were 3.8%, 3.7% and 5.6%, respectively. Imipenem was the antimicrobial with the lowest CA rate (78.7%), with rates of 15% VMEs and 10.7% MEs, but the performances were better when considering only the non-CPE category (CA of 89%). On this resistant collection of Enterobacterales with numerous acquired β-lactamases, the Specific Reveal assay proved to be useful for a rapid determination of AST compatible with a quick adaptation of the patient’s antimicrobial treatment. Full article

Enteropathogenic Escherichia coli (EPEC) are pathogens associated with gastrointestinal illnesses. Dogs and cats can harbor EPEC, and antimicrobial resistance may impair necessary treatments. This study characterized E. coli strains from dogs and cats, focusing on phylogroup classification, virulence factors, and antimicrobial resistance profiles. Ninety-seven E. coli isolates from fecal samples of 31 dogs and 3 cats were obtained from a private diagnostic laboratory in Botucatu, Brazil, from March to October 2021. The antimicrobial susceptibility was assessed using the disk diffusion method. Polymerase chain reaction (PCR) was employed to screen for bla_CTX-M and genes encoding virulence factors, as well as to classify the isolates into phylogroups. Twenty isolates were positive for intimin encoding gene eae and, consequently, these isolates were classified as EPEC (20.62%). Notably, 5.1% (5/97) of the isolates exhibited extended-spectrum β-lactamase (ESBL) production and 13.4% (13/97) were identified as multidrug-resistant bacteria. Phylogroups A and B2 were the most prevalent, comprising 29.9% (29/97) and 26.8% (26/97) of the bacterial isolates, respectively. This characterization highlights the prevalence of EPEC in domestic animals, emphasizing the potential risk they pose to public health and highlighting the urgency of responsible antimicrobial use in veterinary practices and the important role of laboratories in the surveillance of pathogenic multidrug-resistant bacteria. Full article

Due to the extremely low Reynolds number, the mixing of substances in laminar flow within microfluidic channels primarily relies on slow intermolecular diffusion, whereas various rapid reaction and detection requirements in lab-on-a-chip applications often necessitate the efficient mixing of fluids within short distances. This paper presents a magnetic pillar-shaped particle fabrication device capable of producing particles with planar shapes, which are then utilized to achieve the rapid mixing of multiple fluids within microchannels. During the particle fabrication process, a degassed PDMS chip provides self-priming capabilities, drawing in a UV-curable adhesive-containing magnetic powder and distributing it into distinct microwell structures. Subsequently, an external magnetic field is applied, and the chip is exposed to UV light, enabling the mass production of particles with specific magnetic properties through photo-curing. Without the need for external pumping, this chip-based device can fabricate hundreds of magnetic particles in less than 10 min. In contrast to most particle fabrication methods, the degassed PDMS approach enables self-priming and precise dispensing, allowing for precise control over particle shape and size. The fabricated dual-layer magnetic particles, featuring fan-shaped blades and disk-like structures, are placed within micromixing channels. By manipulating the magnetic field, the particles are driven into motion, altering the flow patterns to achieve fluid mixing. Under conditions where the Reynolds number in the chip ranges from 0.1 to 0.9, the mixing index for substances in aqueous solutions exceeds 0.9. In addition, experimental analyses of mixing efficiency for fluids with different viscosities, including 25 wt% and 50 wt% glycerol, reveal mixing indices exceeding 0.85, demonstrating the broad applicability of micromixers based on the rapid rotation of magnetic particles. Full article

This systematic review and meta-analysis compile the in vitro antimicrobial efficacy of lactic acid bacteria (LAB) supernatants against three common pathogenic bacteria found in dairy products: Salmonella spp., L. monocytogenes, and Staphylococcus aureus. After screening and analysis of full papers, identified by searches in PubMed, Scopus, and Web of Science databases, thirty-nine studies were regarded as relevant, and a total of 510 observations were recorded. The effects of moderators on inhibition diameters were assessed by adjusting three pathogen-specific meta-regression models. Results showed that, in general terms, strains from the Enterococcus genus displayed the highest inhibition values against L. monocytogenes (15.90 ± 2.138 mm), whereas Lacticaseibacillus strains were more effective against S. aureus (11.89 ± 0.573 mm). The well diffusion test outperformed the spot and disk diffusion tests, and more acidic LAB supernatants resulted in higher measurements of inhibition diameters (p < 0.001). Meta-regression models incorporating LAB genus, pathogen concentration, and incubation time explained 33.8%, 52.3%, and 19.8% of the total variance in inhibition diameters for L. monocytogenes, Salmonella spp., and S. aureus, respectively. None of the three models showed evidence of publication bias. This meta-regression study demonstrated that LAB strains present in dairy products possess a variable capacity to inhibit any of the three foodborne pathogens. Overall, L. monocytogenes was found to exhibit greater susceptibility than Salmonella spp. and S. aureus; thus, the antilisterial capacity of the selected LAB strains could be exploited in developing biocontrol strategies for cheese-making. Full article