Changes In Bacterial Morphology Research Articles

Bactericidal and biofilm eradication efficacy of a fluorinated benzimidazole derivative, TFBZ, against methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) is a major inducement of nosocomial infections and its biofilm formation render the high tolerance to conventional antibiotics, which highlights the requirement to develop new antimicrobial agents urgently. In this study, we identified a fluorinated benzimidazole derivative, TFBZ, with potent antibacterial efficacy toward planktonic MRSA (MIC = 4μg/mL, MBC = 8μg/mL) and its persistent biofilms (≥99%, MBEC = 8μg/mL). TFBZ manifested significant irreversible time-dependent killing against MRSA as characterized by diminished cell viability, bacterial morphological change and protein leakage. Furthermore, the results from CBD devices, crystal violet assay in conjunction with live/dead staining and scanning electron microscopy confirmed that TFBZ was capable of eradicating preformed MRSA biofilms with high efficiency. Simultaneously, TFBZ reduced the bacterial invasiveness and exerted negligible hemolysis and cytotoxicity toward mammalian cells, which ensuring the robust therapeutic effect on mouse skin abscess model. The transcriptome profiling and quantitative RT-PCR revealed that a set of encoding genes associated with cell adhesion, biofilm formation, translation process, cell wall biosynthesis was consistently downregulated in MRSA biofilms upon exposure to TFBZ. In conclusion, TFBZ holds promise as a valuable candidate for therapeutic applications against MRSA chronic infections.

Evaluation of the in vitro effects of concentrations of antibiotics on three Enterobacteriaceae isolates

Due to the misuse and overuse of antibiotics, bacteria are now exposed to sub-minimum inhibitory concentrations (sub-MICs) of antibiotics in various environments. In recent years, exposure of bacteria to sub-MICs of antibiotics has led to the widespread emergence of antibiotic-resistant bacteria. In this study, three bacterial species from the Enterobacteriaceae family (Raoultella ornithinolytica, Pantoea agglomerans and Klebsiella quasivariicola) were isolated from water. The antibiotic susceptibility of these bacteria to 16 antibiotics was then investigated. The effects of sub-MICs of four selected antibiotics (kanamycin, chloramphenicol, meropenem, and ciprofloxacin) on the growth, biofilm formation, surface polysaccharide production, siderophore production, morphology, and expression of the translational/transcriptional regulatory transformer gene rfaH of these bacteria were analysed. The MICs of kanamycin, chloramphenicol, meropenem, and ciprofloxacin were determined to be 1, 2, 0.03 and 0.03 µg/mL for R. ornithinolytica; 0.6, 6, 0.03 and 0.05 µg/mL for P. agglomerans; and 2, 5, 0.04 and 0.2 µg/mL for K. quasivariicola. The growth kinetics and biofilm formation ability decreased for all three isolates at sub-MICs. The surface polysaccharides of R. ornithinolytica and P. agglomerans increased at sub-MICs. There was no significant change in the siderophore activities of the bacterial isolates, with the exception of MIC/2 meropenem in R. ornithinolytica and MIC/2 kanamycin in K. quasivariicola. It was observed that the sub-MICs of meropenem and ciprofloxacin caused significant changes in bacterial morphology. In addition, the expression of rfaH in R. ornithinolytica and K. quasivariicola increased with the sub-MICs of the selected antibiotics.

Insights into the antimicrobial effects of tafenoquine against Enterococcus and its biofilms.

The purpose of this study is to assess the in vitro antimicrobial and anti-biofilm effects of the anti-protozoal agent tafenoquine (TAF) on Enterococcus and elucidate its underlying mode of action. The present work investigated the susceptibility of TAF on 3 type strains and 11 clinical isolates of enterococci. The results indicated that TAF exhibited powerful antimicrobial activity against both of Enterococcus faecalis and Enterococcus faecium with minimum inhibitory and bactericidal concentrations ranging from 8 to 16µg ml-1. Meanwhile, biofilm inhibition and eradication assays showed that TAF exhibited potent anti-biofilm activity against E. faecalis ATCC 29212 and E. faecium ATCC 19434. Ultra-microscopic observations revealed significant changes in bacterial morphology and structure caused by TAF, particularly for the disruption of plasma membrane. Mechanistic investigations also revealed that TAF altered both membrane permeability and potential while also impacting adenosine triphosphate production as well as reactive oxygen species generation. In addition, no detectable cytotoxicity of TAF on human cells was observed at concentrations near the minimal inhibitory concentration. In summary, this study confirmed that TAF could effectively inhibit Enterococcus as well as its biofilm formation.

Rapid and high accurate identification of Escherichia coli active and inactivated state by hyperspectral microscope imaging combing with machine learning algorithm

Rapid identification of the active state of foodborne bacteria is crucial for ensuring the safety and quality control of food or pharmaceutical products. In this study, a combination of hyperspectral microscope imaging (HMI) and machine learning algorithm is employed for the identification of active state of Escherichia coli (E. coli). Hyperspectral microscope images of live, 100 ℃ heat inactivation and 121 ℃ high-pressure inactivation of E. coli are collected in wavelength range of 370–1060 nm. Savitzky-Golay (SG) smoothing combing with normalization is used for spectra preprocessing. And principal component analysis (PCA) is employed for spectral dimension reduction. Four different regions of interest (ROIs), including the entire bacterial cell ROI (cell), the outer cell wall ROI (cell_r), the membrane structure ROI (cell_w) formed by the cell wall and cell membrane, and the central of the cell ROI (cell_cy), are extracted and used as model input variables to investigate the influence on the modeling results. Five model algorithms, support vector machines (SVM), random forests (RF), k-nearest neighbors (KNN) algorithms, discriminant analysis (DA) classifiers, and long short-term memory (LSTM) neural networks are used and compared. Modeling results with spectral data of cell_r perform better than those with other ROIs. Accuracy of the models with data of the cell_r ROI are as follows: 79.78% for SVM, 95.11% for RF, 91.33% for KNN, 98.22% for DA, and 93.78% for LSTM. DA achieves the highest classification accuracy. The results show that high-temperature inactivation induces changes in bacterial tissue and morphology, resulting in certain spectral differences among bacteria in three different states. The combination of hyperspectral microscope imaging and machine learning algorithm can provide an effective method for identification of active and inactive states of E. coli. Furthermore, the model, constructed with the data of cell_r ROI, exhibits the best performance in identification.

Mechanism of Synergistic Photoinactivation Utilizing Curcumin and Lauric Arginate Ethyl Ester against Escherichia coli and Listeria innocua.

This study investigated the mechanism of how lauric arginate ethyl ester (LAE) improves the photoinactivation of bacteria by curcumin after diluting the 100 µmol/L stock curcumin-LAE micelle solution to the concentration used during the treatment based on the curcumin concentration. The photoinactivation of bacteria was conducted by irradiating the 1 µmol/L curcumin-LAE solution containing cocktails of Escherichia coli and Listeria innocua strains (7 log CFU/mL) for 5 min with UV-A light (λ = 365 nm). The changes in solution turbidity, curcumin stability, and bacterial morphology, viability, and recovery were observed using SEM, TEM, and live/dead cell assays. The study found that LAE enhances the photoinactivation of bacteria by increasing the permeability of cell membranes which could promote the interaction of reactive oxygen species produced by photosensitized curcumin with the cell components. The combination of curcumin and LAE was demonstrated to be more effective in inhibiting bacterial recovery at pH 3.5 for E. coli, while LAE alone was more effective at pH 7.0 for L. innocua.

Sub-inhibitory concentrations of ceftriaxone induce morphological alterations and PIA-independent biofilm formation in Staphylococcus aureus

The exposure of bacteria to sub-inhibitory concentrations of antibiotics is of biological significance since it can occur in vivo under many circumstances, including low-dose treatment, poor adherence to a regimen, poor drug penetration, drug-drug interactions, and antibiotic resistance of the pathogen. In this study, we investigated the effects of subinhibitory concentrations of four antibiotics: ampicillin, ceftriaxone, gentamicin, and norfloxacin, which are commonly used in clinical settings and on cell morphology and biofilm formation in Staphylococcus aureus as one of the leading causes of nosocomial and biofilm-associated infections. Nine clinical S. aureus biofilm-producing isolates and two known biofilm-producing reference strains, S. aureus ATCC 29213 and S. aureus ATCC 6538, were used in this study. Sub-MICs of beta-lactam antibiotics (ampicillin and ceftriaxone) significantly induced biofilm formation in S. aureus ATCC 29213 and S. aureus ATCC 6538 and in six clinical isolates out of the nine selected isolates when compared with the antibiotic-free control group (P < 0.05), with an approximately 2- to 2.5-fold increase. Gentamicin and norfloxacin induced biofilms in S. aureus ATCC 29213 and S. aureus ATCC 6538, while gentamicin and norfloxacin induced biofilms only in three and two of the nine tested isolates, respectively (P < 0.05). The chemical nature of the biofilm matrix produced by half the MIC of ceftriaxone in the six isolates that showed increased biofilm was all non-polysaccharide in composition (PIA-independent). Gene expression of biofilm-encoding genes atl and sarA in biofilms of the two tested strains (S. aureus ATCC 6538) and clinical strain (S. aureus 16) showed a significant upregulation after exposure to half MIC of ceftriaxone. Additionally, the bacterial cell morphological changes in planktonic cells caused by half MIC of ceftriaxone were evaluated by scanning electron microscopy, which demonstrated a significant cell enlargement when compared with the antibiotic-free control (P < 0.05), and some deformed cells were also noticed. In S. aureus clinical isolates, sub-MICs of ampicillin, ceftriaxone, gentamicin, and norfloxacin may stimulate substantial production of biofilm, which could have important clinical significance and make infection treatment challenges. Further, in vivo research is needed to fully comprehend how sub-MIC of antibiotics can affect biofilm formation in clinical settings. Additionally, more research is required to reveal the clinical implications of the morphological alterations in S. aureus brought on by exposure to ceftriaxone at concentrations below its MIC.Graphical

Phage-induced bacterial morphological changes reveal a phage-derived antimicrobial affecting cell wall integrity.

In a looming post-antibiotic era, antibiotic alternatives have become key players in the combat against pathogens. Although recent advances in genomic research allow scientists to fully explore an organism's genome in the search for novel antibacterial molecules, laborious work is still needed in order to dissect each individual gene product for its antibacterial activity. Here, we exploited phage-induced bacterial morphological changes as anchors to explore and discover a potential phage-derived antimicrobial embedded in the phage genome. We found that, upon vibriophage KVP40 infection, Vibrio parahaemolyticus exhibited morphological changes similar to those observed when treated with mecillinam, a cell wall synthesis inhibitor, suggesting the mechanism of pre-killing that KVP40 exerts inside the bacterial cell upon sieging the host. Genome analysis revealed that, of all the annotated gene products in the KVP40 genome that are involved in cell wall degradation, lytic transglycosylase (LT) is of particular interest for subsequent functional studies. A single-cell morphological analysis revealed that heterologous expression of wild-type KVP40-LT induced similar bacterial morphological changes to those treated with the whole phage or mecillinam, prior to cell burst. On the contrary, neither the morphology nor the viability of the bacteria expressing signal-peptide truncated- or catalytic mutant E80A- KVP40-LT was affected, suggesting the necessity of these domains for the antibacterial activities. Altogether, this research paves the way for the future development of the discovery of phage-derived antimicrobials that is guided through phage-induced morphological changes.

Discovery of tryptanthrin analogues bearing F and piperazine moieties as novel phytopathogenic antibacterial and antiviral agents.

Plant bacterial infections and plant viruses seriously affect the yield and quality of crops. Based on the various activities of tryptanthrin, a series of tryptanthrin analogues bearing F and piperazine moieties were designed, synthesized, and evaluated for their biological activities against three plant bacteria and tobacco mosaic virus (TMV). Bioassay results indicated that compounds 6a-6l displayed excellent antibacterial activities in vitro and 6a-6c and 6g exhibited better antiviral activities against TMV than commercial ribavirin. In particular, 6b showed the most effect on Xanthomonas oryzae pv. oryzae (Xoo) with a half-maximal effective concentration (EC50 ) of 1.26 μg mL-1 , compared with the commercial pesticide bismerthiazol (BT; EC50 = 34.3 μg mL-1 ) and thiodiazole copper (TC; EC50 = 73.3 μg mL-1 ). Meanwhile, 6a also had the best antiviral activity at 500 μg mL-1 for curative, protection, and inactivation purposes, compared with ribavirin in vivo. Compound 6b could cause changes in bacterial morphology, induce the accumulation of reactive oxygen species, promote apoptosis of bacterial cells, inhibit the formation of biofilm, and block the growth of Xoo cells. Proteomic analysis revealed major differences in the bacterial secretory system pathways T2SS and T6SS, which inhibited membrane transport. Molecular docking revealed that 6a and 6g could interact with TMV coat protein preventing virus assembly. These results suggest that tryptanthrin analogues bearing F and piperazine moieties could be promising candidate agents for antibacterial and antiviral use in agricultural production. © 2023 Society of Chemical Industry.

Assessing the Potential of Gallic Acid and Methyl Gallate to Enhance the Efficacy of β-Lactam Antibiotics against Methicillin-Resistant Staphylococcus aureus by Targeting β-Lactamase: In Silico and In Vitro Studies.

Methicillin-resistant Staphylococcus aureus (MRSA), a global health concern, has prompted research into antibiotic adjuvants as a potential solution. Although our group previously reported the enhancing effects of gallic acid (GA) and methyl gallate (MG) on penicillin G activity against MRSA, the synergistic potential with other β-lactam antibiotics and the underlying mechanism have not been fully explored. Therefore, this study primarily aimed to investigate the antibacterial synergism with β-lactam antibiotics through disc diffusion, checkerboard, and time-kill assays. The β-lactamase inhibition was also examined through both molecular modeling and in vitro experiments. Additionally, bacterial morphology changes were studied using a scanning electron microscopy (SEM). The results revealed that both GA and MG exhibited anti-MRSA activity and showed indifferent effects when combined with β-lactam antibiotics against methicillin susceptible S. aureus (MSSA). Interestingly, MG demonstrated synergism with only the β-lactamase-unstable antibiotics against MRSA with the lowest fractional inhibitory concentration (FIC) indexes of ≤3.75. However, GA and MG exhibited weak β-lactamase inhibition. Furthermore, GA, MG, and the combination with ampicillin induced the morphological changes in MRSA, suggesting a possible mechanism affecting the cell membrane. These findings suggest that MG could potentially serve as an adjunct to β-lactam antibiotics to combat MRSA infections.

Persistent ciprofloxacin exposure induced the transformation of Klebsiella pneumoniae small colony variant into mucous phenotype

IntroductionSmall colony variant (SCV) is a bacterial phenotype closely related to persistent and recurrent infections. SCVs are mutations that occur within bacterial populations, resulting in a change in bacterial morphology and the formation of small colonies. This morphological change may enhance bacterial resistance to antibiotics and contribute to persistent and recurrent infections.MethodsWe isolated Klebsiella pneumoniae (KPN) and its SCV from a child with recurrent respiratory tract infections. KPN and SCV were treated with subinhibitory concentrations of antibiotics. growth curves, serum resistance experiments, macrophage phagocytosis experiments and whole genome sequencing were used to characterize KPN and SCV.ResultsAfter treating KPN and SCV with subinhibitory concentrations of antibiotics, we found that ciprofloxacin induced the SCV transition to the mucoid phenotype. We found that the growth of mucoid Klebsiella pneumoniae was significantly slower than maternal strain and SCV though growth curves. Serum resistance experiments showed that mucoid strains had significantly higher serum resistance compared to maternal strain and SCV. Macrophage phagocytosis experiments revealed that SCV had significantly higher intracellular survival rates compared to maternal strain and mucoid strains. Differential gene analysis of three strains revealed that the mucoid strain contained DNA polymerase V subunit UmuC gene on the plasmid, while the SCV strain had an additional IcmK family IV secretion protein on its plasmid.DiscussionOur study showed the SCV of KPN changed to a mucoid colony when exposed to subinhibitory concentrations of ciprofloxacin. The higher resistance of serum of mucoid colonies was possibly related to the UmuC gene, while the increased intracellular survival of SCV may be related to the IcmK family type IV secretion proteins.

The depsidones from marine sponge-derived fungus Aspergillus unguis IB151 as an anti-MRSA agent: Molecular docking, pharmacokinetics analysis, and molecular dynamic simulation studies

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging nosocomial pathogen among hospitalized patients, with high morbidity and mortality rates. The discovery of a novel antibacterial is urgently needed to address this resistance problem. The present study aims to explore the antibacterial potential of three depsidone compounds: 2-clorounguinol (1), unguinol (2), and nidulin (3), isolated from the marine sponge-derived fungus Aspergillus unguis IB1, both in vitro and in silico. The antibacterial activity of all compounds was evaluated by calculating the Minimum inhibitory concentration (MIC) and Minimum bactericidal concentration (MBC) against MRSA using agar diffusion and total plate count methods, respectively. Bacterial cell morphology changes were studied for the first time using scanning electron microscopy (SEM). Molecular docking, pharmacokinetics analysis, and molecular dynamics simulation were performed to determine possible protein–ligand interactions and the stability of the targeting penicillin-binding protein 2a (PBP2a) against 2-clorounguinol (1). The research findings indicated that compounds 1 to 3 exhibited MIC and MBC values of 2 µg/mL and 16 µg/mL against MRSA, respectively. MRSA cells displayed a distinct shape after the addition of the depsidone compound, as observed in SEM. According to the in silico study, 2-chlorounguinol exhibited the highest binding-free energy (BFE) with PBP2a (-6.7 kcal/mol). For comparison, (E)-3-(2-(4-cyanostyryl)-4-oxoquinazolin-3(4H)-yl) benzoic acid inhibits PBP2a with a BFE less than −6.6 kcal/mol. Based on the Lipinski's rule of 5, depsidone compounds constitute a class of compounds with good pharmacokinetic properties, being easily absorbed and permeable. These findings suggest that 2-chlorounguinol possesses potential antibacterial activity and could be developed as an antibiotic adjuvant to reduce antimicrobial resistance.

Sialic acid catabolism contributes to Vibrio mimicus virulence

Vibrio mimicus is an emerging pathogen primarily associated with catfish vibriosis. Infectious caused by V. mimicus in aquatic animals have been characterized by a short infection course and high mortality rate, resulting in significant economic losses. The utilization of sialic acid has been shown to be correlated with bacterial virulence, particularly in highly sialylated environments. In this study, we investigated virulence-determining phenotypes of V. mimicus strain SCCF01 (WT) and the sialic acid catabolism (SaCS) defect strain ΔSaCS, and revealed their potential molecular connections by comparative proteomics analysis. Our results showed that abrogation of sialic acid catabolism ability resulted in bacterial morphological changes, a decrease in biofilm formation, but an increase in cell adherence ability. Animal experiments confirmed that SaCS contributes to V. mimicus pathogenicity, as the LD50 of ΔSaCS strain was 27-fold lower compared to WT strain. Proteomics analysis revealed that differentially expressed proteins between the culture supernatants of WT and ΔSaCS were mainly enriched in pentose phosphate pathway, purine metabolism and bacterial chemotaxis. The ΔSaCS lacked several extracellular proteins and virulence factors, providing additional explanation for its attenuating effect.

Quaternized carbon dots with enhanced antimicrobial ability towards Gram-negative bacteria for the treatment of acute peritonitis caused by E. coli.

Infections caused by Gram-negative bacteria still pose a clinical challenge. Although nanomaterials have been developed for antibacterial treatments, a systematic evaluation of the mechanisms and intervention models of antibacterial materials toward Gram-negative bacteria is still lacking. Herein, antibacterial quaternized carbon dots (QCDs) were synthesized via a one-step melting method using anhydrous citric acid and diallyl dimethyl ammonium chloride (DDA). The QCDs exhibited effective broad-spectrum antibacterial activity and enhanced inhibitory ability towards Gram-negative bacteria. The antibacterial mechanism of the QCDs with respect to Gram-negative bacteria was investigated through the characterization of bacterial morphology changes, the absorption modes of the QCDs on bacteria, and the potential generation of reactive oxygen species by the QCDs. The QCDs showed low toxicity in different cells, and did not cause hemolysis. The QCDs were administered via intraperitoneal injection to treat acute peritonitis in mice infected with E. coli. Routine blood examination, magnetic resonance imaging, and pathological analysis were undertaken and it was found that, similar to the positive control group treated with gentamicin sulfate, the QCDs exhibited a therapeutic effect that eliminated infection and inflammation. This study explores a controllable synthetic strategy for the synthesis of active carbon dots with antibacterial activity, a material that is a promising candidate for new treatments of Gram-negative bacterial infections.

Scattering angle resolved optical coherence tomography measures morphological changes in Bacillus subtilis colonies.

An unmet need is recognized for early detection and diagnosis of neurological diseases. Many psychological markers emerge years after disease onset. Mitochondrial dysfunction and corresponding neurodegeneration occur before onset of large-scale cell and tissue pathology. Early detection of subcellular morphology changes could serve as a beacon for early detection of neurological diseases. This study is on bacterial colonies, Bacillus subtilis, which are similar in size to mitochondria. This study investigates whether morphological changes can be detected in Bacillus subtilis using scattering angle resolved optical coherence tomography (SAR-OCT). The SAR-OCT was applied to detect scattering angle distribution changes in Bacillus subtilis. The rod-to-coccus shape transition of the bacteria was imaged, and the backscattering angle was analyzed by recording the distribution of the ratio of low- to medium angle scattering (L/M ratio). Bacillus orientation at different locations in colonies was analytically modeled and compared with SAR-OCT results. Significant differences in the distribution of backscattering angle were observed in Bacillus subtilis transitioning from rod-to-coccus shapes. In Bacillus subtilis, the -parameter of the Burr distribution of the SAR-OCT-derived L/M ratio was significantly smaller in coccus compared with rod-shaped bacteria. SAR-OCT-derived L/M ratio varied with bacterial position in the colony and is consistent with predicted orientations from previous studies. Study results support the potential of utilizing SAR-OCT to detect bacterial morphological changes.

Combination of high-frequency ultrasound with propyl gallate for enhancing inactivation of bacteria in water and apple juice

This study evaluated a combination of high-frequency ultrasound (HFU, 1 MHz, 1.6 W/cm2).and a food-grade antioxidant, propyl gallate (PG, 10 mM), to enhance inactivation rates of Listeria innocua and Escherichia coli O157:H7 in water and clarified apple juice. Treatment times ranged from 5 to 20 min. The study also assessed the potential mechanisms of synergistic interactions based on an evaluation of changes in bacterial permeability, morphology, and intracellular oxidative stress. Within 15 min of treatment time, HFU + PG significantly (reduced by 5.5 log CFU/mL, P < 0.05) decreased the bacterial load of both L. innocua and E. coli O157:H7 from an initial inoculum of 6.5 log CFU/mL in both water and clarified apple juice. Overall, L. innocua demonstrated significantly higher resistance to inactivation than E. coli O157:H7 using a combination of HFU + PG. The synergistic antimicrobial activity of HFU+ PG resulted in enhanced membrane damage and oxidative stress induction in bacteria compared to the individual treatments of HFU or PG alone. Industrial relevanceThis study evaluates the synergistic combination of high frequency ultrasound and the food grade antioxidant propyl gallate for non-thermal processing of liquids. The results illustrate significant (>5 log CFU) and rapid inactivation (∼15 min) of inoculated model Gram positive and Gram negative bacteria in apple juice using a synergistic combination of propyl gallate and high frequency ultrasound. The synergistic interactions result in enhanced membrane damage and oxidative stress induction in bacteria. These results illustrate potential of the synergistic non-thermal thermal processing method for processing liquid beverages. Further studies are required for evaluating the scale up and optimization of the novel processing technology and enhancement in quality attributes of beverages.

Inactivation efficacy and mechanisms of atmospheric cold plasma on Alicyclobacillus acidoterrestris: Insight into the influence of growth temperature on survival.

The bactericidal effect of dielectric barrier discharge-atmospheric cold plasma (DBD-ACP, 20, and 30 kV) against Alicyclobacillus acidoterrestris on the saline solution and apple juice was investigated. Results show that DBD-ACP is effective for the inactivation of A. acidoterrestris by causing significant changes in cell membrane permeability and bacterial morphology. The effect of culture temperatures on the resistance of A. acidoterrestris to DBD-ACP was also studied. A. acidoterrestris cells grown at 25°C had the lowest resistance but it was gradually increased as the culture temperature was increased (25–45°C) (p < 0.05). Moreover, results from Fourier transform infrared spectroscopy (FT-IR) and Gas Chromatography-Mass Spectrometer (GC-MS) analysis showed that the increase in the culture temperature can gradually cause the decreased level of cyclohexaneundecanoic acid in the cell membrane of A. acidoterrestris (p < 0.05). In contrast, cyclopentaneundecanoic acid, palmitic acid, and stearic acid showed an increasing trend in which the fluidity of the bacterial cell membrane decreased. This study shows a specific correlation between the resistance of A. acidoterrestris and the fatty acid composition of the cell membrane to DBD-ACP.

Anti-biofilm activity of chlorhexidine-releasing elastomerics against dental microcosm biofilms

ObjectiveTo evaluate the anti-biofilm activity of chlorhexidine-releasing elastomerics (CRE) developed to prevent biofilm-related diseases in orthodontic patients, using dental microcosm biofilms. MethodsElastomerics coated with one of two solutions (CRE 1 and 2) were attached to bovine enamel specimens. Uncoated elastomerics were used for negative (distilled water [DW]) and positive (0.1% chlorhexidine [CHX]) control groups. After saliva inoculation on the surface of the specimen for biofilm formation, DW and CRE groups were treated with DW, and the positive control group was treated with CHX twice a day for 5 min. After 7 days of biofilm formation, colony-forming units (CFUs, total and aciduric bacteria), red/green (R/G) ratio, biofilm thickness, live/dead cell ratio, and bacterial morphology in the biofilms were evaluated. Enamel demineralization was evaluated by fluorescence loss (ΔF). ResultsThe CFUs of total and aciduric bacteria and R/G ratios in the CRE groups were significantly lower than those in the DW group with a reduction by 13%, 13%, and 19%, respectively (p < 0.05). The CFUs of total bacteria was significantly lower in the CRE groups than in the 0.1% CHX group (p < 0.05). Among the CRE groups, only CRE 1 exhibited a significantly reduced biofilm thickness of 54% compared to the DW group (p < 0.05) and apparent changes in bacterial morphology. ΔF in the CRE groups was significantly higher by 36% compared to that in the DW group (p < 0.05). ConclusionsCREs exhibited anti-biofilm and demineralization-inhibiting effect. Particularly, CRE 1 using dichloromethane as the solvent was most effective against biofilms. Clinical significanceChlorhexidine-releasing elastomerics exhibited increased anti-biofilm and demineralization-inhibiting effect compared to 0.1% chlorhexidine mouthwash. Therefore, it is possible to prevent biofilm-related diseases simply and effectively by applying chlorhexidine-releasing elastomerics to orthodontic patients.

Reactivity Differences Enable ROS for Selective Ablation of Bacteria

AbstractAn effective strategy to engineer selective photodynamic agents to surmount bacterial‐infected diseases, especially Gram‐positive bacteria remains a great challenge. Herein, we developed two examples of compounds for a proof‐of‐concept study where reactive differences in reactive oxygen species (ROS) can induce selective ablation of Gram‐positive bacteria. Sulfur‐replaced phenoxazinium (NBS‐N) mainly generates a superoxide anion radical capable of selectively killing Gram‐positive bacteria, while selenium‐substituted phenoxazinium (NBSe‐N) has a higher generation of singlet oxygen that can kill both Gram‐positive and Gram‐negative bacteria. This difference was further evidenced by bacterial fluorescence imaging and morphological changes. Moreover, NBS‐N can also successfully heal the Gram‐positive bacteria‐infected wounds in mice. We believe that such reactive differences may pave a general way to design selective photodynamic agents for ablating Gram‐positive bacteria‐infected diseases.

Reactivity Differences Enable ROS for Selective Ablation of Bacteria.

An effective strategy to engineer selective photodynamic agents to surmount bacterial-infected diseases, especially Gram-positive bacteria remains a great challenge. Herein, we developed two examples of compounds for a proof-of-concept study where reactive differences in reactive oxygen species (ROS) can induce selective ablation of Gram-positive bacteria. Sulfur-replaced phenoxazinium (NBS-N) mainly generates a superoxide anion radical capable of selectively killing Gram-positive bacteria, while selenium-substituted phenoxazinium (NBSe-N) has a higher generation of singlet oxygen that can kill both Gram-positive and Gram-negative bacteria. This difference was further evidenced by bacterial fluorescence imaging and morphological changes. Moreover, NBS-N can also successfully heal the Gram-positive bacteria-infected wounds in mice. We believe that such reactive differences may pave a general way to design selective photodynamic agents for ablating Gram-positive bacteria-infected diseases.

Isolation and Identification of Polyphenols From Fresh Sweet Sorghum Stems and Their Antibacterial Mechanism Against Foodborne Pathogens.

As a C4 energy crop widely planted all over the world, sweet sorghum is mainly used in sugar making and brewing. Fresh sweet sorghum stalks contain many natural ingredients that have antioxidant properties and can significantly inhibit the growth of foodborne pathogens. In this study, the polyphenols in sweet sorghum were extracted by acid ethanol and ion precipitation, and the types of polyphenols were determined by HPLC-MS. The polyphenol content in fresh sweet sorghum stalks was 5.77 mg/g after process optimization with 18 types of phenolic acids identified. The extract had a total antioxidant capacity of 9.4 μmol Trolox/mL. Polyphenol extract of sweet sorghum displayed antibacterial activity against Staphylococcus aureus, Escherichia coli, Listeria spp., and Salmonella spp. The extract increased the conductivity of cell suspensions by destroying the membrane structure, resulting in leakage of cell electrolytes. Changes in bacterial morphology and internal structure were indicated. The data describe an optimized process to extract polyphenols from sweet sorghum stalks and the methodology to identify the major components within the extract. The data provide a novel option for the comprehensive utilization of fresh sweet sorghum stalks.