Current Microbiology最新文献

The escalating threat of antimicrobial resistance (AMR) necessitates the development of innovative therapeutic approaches. This study reports the green synthesis of magnesium oxide nanoparticles (MgO-NPs) using Citrullus colocynthis extract, a medicinal plant rich in bioactive compounds, as a sustainable alternative to conventional antibiotics. The synthesized MgO-NPs were characterized by UV-Vis spectroscopy (absorption peak at 250 nm), XRD (cubic crystalline structure, 15-25 nm size), SEM-EDX (agglomerated spherical morphology, Mg/O ratio 2.6:1), and FTIR (Mg-O vibration at 860 cm^- 1). The nanoparticles exhibited potent, dose-dependent antibacterial activity against multidrug-resistant (MDR) Staphylococcus aureus [MIC: 35.3 ± 2.1 µg/ml (0.0353 ± 0.0021 mg/ml); MBC: 97.1 ± 3.5 µg/ml (0.0971 ± 0.0035 mg/ml)] and Escherichia coli [MIC: 47.5 ± 4.2 µg/ml (0.0475 ± 0.0042 mg/ml); MBC: 105.5 ± 6.8 µg/ml (0.1055 ± 0.0068 mg/ml)], with a bactericidal mode of action (MBC/MIC ≤ 4). Remarkably, MgO-NPs restored susceptibility to β-lactam antibiotics (ceftazidime and penicillin) in resistant strains, demonstrating synergistic effects. Antifungal activity of MgO-NPs against Candida albicans (17.3 ± 0.7 mm) and Aspergillus niger (14.4 ± 0.8 mm) at a concentration of 10 mg/ml was also observed. Phytochemical analysis revealed solvent-dependent bioactive constituents in C. colocynthis, with aqueous extracts rich in tannins/phenolics and methanolic extracts rich in flavonoids/terpenoids. This is the first report demonstrating the restoration of antibiotic susceptibility by MgO-NPs synthesized from C. colocynthis extract.

Myroides odoratimimus is an emerging opportunistic pathogen increasingly implicated in infections across human and animal populations. We previously reported the first outbreak of pneumonia in post-weaning piglets associated with M. odoratimimus, marking a significant shift in its recognized host range. The affected swine herd exhibited co-infection with Porcine Circovirus types 2 and 3 (PCV2 and PCV3), likely contributing to proliferative dermatitis and nephropathy syndrome (PDNS), reproductive abnormalities and immunosuppression. This study presents the genomic characterization of a multidrug-resistant strain (M. odoratimimus pgdne) isolated during the outbreak. Whole-genome sequencing revealed multiple antimicrobial resistance determinants-including the chromosomally encoded blaMUS-1 metallo-β-lactamase-and several virulence-associated factors. Genotype-phenotype correlation demonstrated strong concordance. Phylogenetic analysis (distance method, 1,000 bootstrap replicates) showed close relatedness with human isolates, suggesting zoonotic potential. These findings underscore the pathogenic capacity of M. odoratimimus in immunocompromised animal hosts and highlight its relevance to public health and thereby reinforces the need for integrated One Health-based surveillance and control strategies targeting emerging multidrug-resistant pathogens.

Ensuring plant resilience is crucial for maintaining global food security amidst a changing climate. Leveraging the multitude of microorganisms in different environmental conditions appears to be a promising and sustainable approach to boosting agricultural productivity. However, understanding the legacy of microbial bioinoculants in agroecosystems remains a challenging issue, thereby hampering their widespread applicability and acceptance. This review offers an in-depth insight into the intricacies of designing effective bioinoculants, orchestrated by an understanding of the ecological contexts that drive their success. Furthermore, this article emphasizes the importance of adopting a holistic approach to designing effective bioinoculants, thereby enhancing their application in agriculture.

The present study reports the presence of thymoquinone (TQ), a promising benzoquinone compound, in the lichen Dirinaria frostii (strain DF_MSCBU, NCBI-accession no. PP955960), collected from Similipal National Park, India. The extract of D. frostii was subjected to GCMS analysis and detected the presence of thymoquinone. Further, purification of the TQ fraction was carried out using HPLC against a standard thymoquinone reference. FTIR analysis identified the key functional groups. In addition, Nuclear Magnetic Resonance (¹H NMR and ¹³C NMR) spectroscopy was performed to determine the structure and composition of the molecule. The purified TQ was then used for antibacterial assays against pathogenic bacteria Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Vibrio cholerae following the MIC method showed pathogen inhibition at different incubation time, of both Gram +ve and Gram -ve bacteria. Thymoquinone showed significant bactericidal activity compared to the standard antibiotics azithromycin, streptomycin, and erythromycin in a dose-dependent manner. This study demonstrates occurrence of thymoquinone from D. frostii as a novel finding and opens new possibilities for its therapeutic applications in the future.

Biofilm formation and the activity of efflux pumps are major contributors to antibiotic resistance in clinical strains of Pseudomonas aeruginosa and significantly enhance the pathogenicity of this bacterium. Functionalization of metal nanoparticles with plant-derived flavonoids, particularly when combined with conventional antibiotics, represents a promising strategy for overcoming antimicrobial resistance. In the present study, we investigated the synergistic inhibitory effects of quercetin-functionalized magnetic nanoparticles (Fe₃O₄@SiPr@Quercetin NPs) in combination with ciprofloxacin against ciprofloxacin-resistant clinical isolates of P. aeruginosa. Ciprofloxacin-resistant isolates were collected from hospitals and diagnostic laboratories in Tehran Province, Iran. The synthesized nanoparticles exhibited a spherical morphology with an average diameter of 165 nm. Synergistic antibacterial activity of the functionalized nanoparticles combined with ciprofloxacin was evaluated using the checkerboard assay. The most pronounced reduction in biofilm formation, was observed in strains treated with the nanoparticle-ciprofloxacin combination, with inhibition rates ranging from 18.9 ± 1.13% to 90.05 ± 5.72%. Time-kill curve analysis further demonstrated that Fe₃O₄@SiPr@Quercetin in combination with ciprofloxacin produced a more rapid bactericidal effect, reducing bacterial counts to 5.87-4.72 log CFU/mL after 8 h of treatment. Moreover, quantitative real-time PCR (qPCR) analysis revealed significant downregulation of genes associated with efflux pumps (mexA, mexB, oprM, mexX, and mexY) and virulence factors (pelA, algD, pslA, and exoS) in the clinical isolate treated with ½ minimum inhibitory concentration (MIC) of Fe₃O₄@SiPr@Quercetin in combination with ½ MIC of ciprofloxacin, compared with treatment with ciprofloxacin alone. Collectively, these findings indicate that quercetin-functionalized magnetic nanoparticles may serve as a promising adjunctive therapeutic strategy for combating ciprofloxacin-resistant P. aeruginosa infections.

Colorectal cancer (CRC), the third most common malignancy worldwide, arises from a complex interplay of genetic, environmental, and microbial factors. Enterotoxigenic Bacteroides fragilis (ETBF) promotes CRC progression by secreting metalloprotease toxins, such as fragilysin (B. fragilis toxin, BFT), which disrupt intestinal epithelial barrier integrity, activate proinflammatory pathways (e.g., NF-κB), and drive carcinogenesis. Conversely, probiotics such as Lactobacillus helveticus may help attenuate inflammation and tumorigenesis. This study assessed the anti-inflammatory effects of heat-killed L. helveticus and its cell-free supernatant (CFS) on ETBF-induced inflammation in Caco-2 human intestinal epithelial cells. Cells were exposed to purified BFT (1 ng/mL) to induce inflammation, then treated with heat-killed L. helveticus (0.5 mg/mL) or CFS (0.5 mg/mL) for 48 h. Gene expression of cytokines (IL-1β, IL-8, IL-10) and NF-κB was quantified via quantitative reverse transcription polymerase chain reaction (qRT-PCR). ETBF significantly upregulated NF-κB (4-fold; p = 0.0007) and induced morphological disruptions. Treatments upregulated anti-inflammatory IL-10 (2-fold and 5-fold, respectively; p = 0.002 each) and reduced proinflammatory IL-8 (p = 0.005 and p = 0.002), with no change in IL-1β (p > 0.05). Treated cells showed restored morphology, indicating reduced inflammation and cytotoxicity. These findings illustrate the potential of non-viable L. helveticus to modulate inflammation, possibly via NF-κB inhibition and postbiotic metabolites. Future research should investigate strain-specific mechanisms, in vivo efficacy, and expanded cytokine profiles to optimize interventions.

A novel aerobic, Gram-stain-positive, non-motile, non-spore-forming, short rod-shaped strain X10-3^T, was isolated from Daihai Lake, Inner Mongolia, China. The strain formed circular, smooth, transparent, orange-colored colonies with convex elevation and entire margins, which measured approximately 1.0-4.0 mm in diameter after 48 h of incubation on Luria-Bertani agar at 32 °C. The strain was able to grow at pH levels between 6.5 and 9.0 (optimal at 7.5-8.0), temperatures from 4 to 40 °C (optimal at 37 °C), and in 0-13% (optimal at 2-3%, w/v) NaCl. The complete genome of strain X10-3^T comprises 3,244,194 bp with a DNA G + C content of 45.9%. Phylogenetic analysis revealed the closest relationship to members of the genus Planococcus, showing 16S rRNA gene sequence similarities of 99.2% with P. salinarum DSM 23820^T, 98.8% with P. wigleyi Sa1BUA13^T, 98.6% with P. koreense JG07^T, and 98.6% with P. halotolerans SCU63^T. The average nucleotide identity between strain X10-3^T and the species within the genus Planococcus fell below the species delineation thresholds of 95%, and the digital DNA-DNA hybridization values were lower than 70%. Chemotaxonomic analysis revealed that the predominant cellular fatty acids of strain X10-3^T were anteiso-C_15:0 and C_16:1 ω7c alcohol. The primary cellular polar lipids included phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol, while the predominant isoprenoid quinones were menaquinone-8 and menaquinone-7. Based on these comprehensive analyses, strain X10-3^T represents a new species of the genus Planococcus, for which the name Planococcus daihaiensis sp. nov. is proposed. The type strain is X10-3^T (= CGMCC 1.60163^T = KCTC 43688^T).