1-Hydroxyanthraquinone exhibited antibacterial activity by regulating glutamine synthetase of Staphylococcus xylosus as a virulence factor

A comprehensive review on genomic insights and advanced technologies for mastitis prevention in dairy animals

Mastitis is a multi-etiological disease that significantly impacts milk production and reproductive efficiency. It is highly prevalent in dairy populations subjected to intensive selection for higher milk yield and where inbreeding is common. The issue is amplified by climate change and poor hygiene management, making disease control challenging. Key obstacles include antibiotic resistance, maximum residue levels, horizontal gene transfer, and limited success in breeding for resistance. Predictive genomics offers a promising solution for mastitis prevention by identifying genetic traits linked with susceptibility to mastitis. This review compiles the research and findings on genomics and its allied approaches, such as pan-genomics, epigenetics, proteomics, and transcriptomics, for diagnosing, understanding, and treating mastitis. In dairy production, artificial intelligence (AI), particularly deep learning (DL) techniques like convolutional neural networks (CNNs), has demonstrated significant potential to enhance milk production and improve farm profitability. It highlights the integration of advanced technologies like machine learning (ML), CRISPR, and pan-genomics to improve our knowledge of mastitis epidemiology, pathogen evolution, and the development of more effective diagnostic, preventive and therapeutic strategies for dairy herds. Genomic advancements provide critical insights into the complexities of mastitis, offering new avenues for understanding its dynamics. Integrating these findings with key predisposing factors can drive targeted prevention and more effective disease management.

Antibacterial activity of natural flavones against bovine mastitis pathogens: in vitro, SAR analysis, and computational study

Bovine mastitis is a worldwide disease affecting dairy cattle and causes major economic losses in the dairy industry. Recently, the emergence of microbial resistance to the current antibiotics complicates the treatment protocol which necessitates antibiotic stewardship and further research to find new active compounds. Recently, phytobiotics have gained interest in being used as an alternative to antibiotics in the poultry industry as an antibiotic stewardship intervention. This study evaluated the in vitro antibacterial activity of 16 flavonoids against bovine mastitis pathogens. Two flavones: 2-(4-methoxyphenyl)chromen-4-one (1) and 2-(3-hydroxyphenyl)chromen-4-one (4) showed inhibition of the growth of Klebsiella oxytoca with MIC values range (25-50 µg mL- 1) followed by a structure-activity relationship (SAR) study indicating that the presence of a hydroxyl group at C-3` or methoxy at C-4` increases the activity against Klebsiella oxytoca while the presence of hydroxyl group at C-7 decreases the activity. Furthermore, a structure-based drug development approach was applied using several in silico tools to understand the interactions of active flavones at the active site of the DNA gyrase protein. Compound (4) showed a higher docking score than quercetin (standard) which is known to have antibacterial activity by inhibiting the DNA gyrase. In addition, the structure-based pharmacophores of compound (4) and quercetin showed similar pharmacophoric features and interactions with DNA gyrase. Based on our findings, compounds (1) and (4) are promising for further study as potential anti-microbial phytochemicals that can have a role in controlling bovine mastitis as well as to investigate their mechanism of action further.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-024-00253-w.

Tannic acid inhibits Escherichia coli biofilm formation and underlying molecular mechanisms: Biofilm regulator CsgD

Biofilms often engender persistent infections, heightened antibiotic resistance, and the recurrence of infections. Therefor, infections related to bacterial biofilms are often chronic and pose challenges in terms of treatment. The main transcription regulatory factor, CsgD, activates csgABC-encoded curli to participate in the composition of extracellular matrix, which is an important skeleton for biofilm development in enterobacteriaceae. In our previous study, a wide range of natural bioactive compounds that exhibit strong affinity to CsgD were screened and identified via molecular docking. Tannic acid (TA) was subsequently chosen, based on its potent biofilm inhibition effect as observed in crystal violet staining. Therefore, the aim of this study was to investigate the specific effects of TA on the biofilm formation of clinically isolated Escherichia coli (E. coli). Results demonstrated a significant inhibition of E. coli Ec032 biofilm formation by TA, while not substantially affecting the biofilm of the ΔcsgD strain. Moreover, deletion of the csgD gene led to a reduction in Ec032 biofilm formation, alongside diminished bacterial motility and curli synthesis inhibition. Transcriptomic analysis and RT-qPCR revealed that TA repressed genes associated with the csg operon and other biofilm-related genes. In conclusion, our results suggest that CsgD is one of the key targets for TA to inhibit E. coli biofilm formation. This work preliminarily elucidates the molecular mechanisms of TA inhibiting E. coli biofilm formation, which could provide a lead structure for the development of future antibiofilm drugs.

Ion-Induced Nanoarchitectonics for Anthraquinone Single Crystals with Enhanced Fluorescence Properties

Recently, bioinspired fluorescent materials have drawn ever-increasing attention due to their ecofriendliness and easy accessibility. Herein, we demonstrate that anthraquinone/metal ion coordination complexes can form well-defined crystals and possess obvious fluorescence enhancement properties. The fluorescence quantum yields of anthraquinone/metal ion assemblies are more than 2 orders of magnitude compared to those of anthraquinone assemblies. The electronic structures of the first excited singlet states of anthraquinone/metal ion molecules are obtained, and the mechanism of the fluorescence enhancement is elucidated. Such photoluminescent anthraquinone/metal ion crystals can be considered as efficient phosphors in fabricating light-emitting diodes. This work provides a simple route for the development of highly efficient natural fluorescent materials.

In Silico and In Vitro Identification of 1,8-Dihydroxy-4,5-dinitroanthraquinone as a New Antibacterial Agent against Staphylococcus aureus and Enterococcus faecalis

Increasing rates of bacterial resistance to antibiotics are a growing concern worldwide. The search for potential new antibiotics has included several natural products such as anthraquinones. However, comparatively less attention has been given to anthraquinones that exhibit functional groups that are uncommon in nature. In this work, 114 anthraquinones were evaluated using in silico methods to identify inhibitors of the enzyme phosphopantetheine adenylyltransferase (PPAT) of Staphylococcus aureus, Enterococcus faecalis, and Escherichia coli. Virtual screenings based on molecular docking and the pharmacophore model, molecular dynamics simulations, and free energy calculations pointed to 1,8-dihydroxy-4,5-dinitroanthraquinone (DHDNA) as the most promising inhibitor. In addition, these analyses highlighted the contribution of the nitro group to the affinity of this anthraquinone for the nucleotide-binding site of PPAT. Furthermore, DHDNA was active in vitro towards Gram-positive bacteria with minimum inhibitory concentration (MIC) values of 31.25 µg/mL for S. aureus and 62.5 µg/mL for E. faecalis against both antibiotic-resistant isolates and reference strains but was ineffective against E. coli. Experiments on kill-time kinetics indicated that, at the tested concentrations, DHDNA produced bacteriostatic effects on both Gram-positive bacteria. Overall, our results present DHDNA as a potential PPAT inhibitor, showing antibacterial activity against antibiotic-resistant isolates of S. aureus and E. faecalis, findings that point to nitro groups as key to explaining these results.

Molecular Mechanism of Staphylococcus xylosus Resistance Against Tylosin and Florfenicol

Purpose

Drug resistance presents an ever-increasing global public health threat that involves all major microbial pathogens and antimicrobial drugs. Strains that are resistant to multiple drugs pose severe clinical problems and cost lives. However, systematic studies on cross-resistance of Staphylococcus xylosus have been missing.

Methods

Here, we investigated various mutations in the sequence of ribosomal proteins involved in cross-resistance. To understand this effect on a molecular basis and to further elucidate the role of cross-resistance, we computationally constructed the 3D model of the large ribosomal subunit from S. xylosus as well as its complexes with both tylosin and florfenicol. Meanwhile, all-atom molecular dynamics simulations was used. In addition, the regulation of protein networks also played an essential role in the development of cross-resistance in S. xylosus.

Results

We discovered that the minimum inhibitory concentration against both tylosin and florfenicol of the mutant strain containing the insertion L22 97KRTSAIN98 changed dramatically. Further, we found that unique structural changes in the β-hairpin of L22 played a central role in this variant in the development of antibiotic resistance in S. xylosus. The regulation of protein networks also played an essential role in the development of cross-resistance in S. xylosus.

Conclusion

Our work provides insightful views into the mechanism of S. xylosus resistance that could be useful for the development of the next generation of antibiotics.

Biofilm Research in Bovine Mastitis

Bovine mastitis is one of the most important diseases in the dairy industry and has detrimental impact on the economy and welfare of the animals. Further, treatment failure results in increased antibiotic use in the dairy industry, as some of these mastitis cases for unknown reasons are not resolved despite standard antibiotic treatment. Chronic biofilm infections are notoriously known to be difficult to eradicate with antibiotics and biofilm formation could be a possible explanation for mastitis cases that are not resolved by standard treatment. This paper reviews the current literature on biofilm in bovine mastitis research to evaluate the status and methods used in the literature. Focus of the current research has been on isolates from milk samples and investigation of their biofilm forming properties in vitro. However, in vitro observations of biofilm formation are not easily comparable with the in vivo situation inside the udder. Only two papers investigate the location and distribution of bacterial biofilms inside udders of dairy cows with mastitis. Based on the current knowledge, the role of biofilm in bovine mastitis is still unclear and more in vivo investigations are needed to uncover the actual role of biofilm formation in the pathogenesis of bovine mastitis.

The Active Ingredients Identification and Antidiarrheal Mechanism Analysis of Plantago asiatica L. Superfine Powder

Plantago asiatica L. is a natural medicinal plant that has been widely used for its various pharmacological effects such as antidiarrheal, anti-inflammatory, and wound healing. This study aims to explore the antidiarrheal active ingredients of Plantago asiatica L. that can be used as quality markers to evaluate P. asiatica L. superfine powder (PSP). Molecular docking experiment was performed to identify the effective components of P. asiatica L., which were further evaluated by an established mouse diarrhea model. Na+/K+-ATPase and creatine kinase (CK) activities and the Na+/K+ concentrations were determined. The gene expression of ckb and Atp1b3 was detected. PSP was prepared and evaluated in terms of the tap density and the angle of repose. The structures of PSPs of different sizes were measured by infrared spectra. The active ingredient contents of PSPs were determined by HPLC. The results indicated that the main antidiarrheal components of P. asiatica L. were luteolin and scutellarein that could increase the concentration of Na+ and K+ by upregulating the activity and gene level of CK and Na+/K+-ATPase. In addition, luteolin and scutellarein could also decrease the volume and weight of small intestinal contents to exert antidiarrheal activity. Moreover, as the PSP size decreased from 6.66 to 3.55 μm, the powder tended to be amorphous and homogenized and of good fluidity, the content of active compounds gradually increased, and the main structure of the molecule remained steady. The optimum particle size of PSP with the highest content of active components was 3.55 μm, and the lowest effective dose for antidiarrhea was 2,000 mg/kg. Therefore, the antidiarrheal active ingredients of PSP were identified as luteolin and scutellarein that exert antidiarrheal activity by binding with Na+/K+-ATPase. PSP was successfully prepared and could be used as a new dosage form for the diarrhea treatment.