Current Microbiology最新文献

The present study investigates the antibacterial potential of fatty acid methyl esters (FAMEs) from the cyanobacterial species Neowestiellopsis persica, isolated from Meghalaya, a north-eastern state in India. Given the growing threat of antibiotic resistance, this study explores an alternative source of bioactive compounds from cyanobacteria to combat bacterial pathogens such as Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus. The cyanobacterial species Neowestiellopsis persica was cultured under controlled laboratory conditions, followed by the extraction of fatty acid methyl esters (FAMEs). The extract was then screened for antimicrobial activity using Kirby-Bauer disc diffusion assays, demonstrating significant inhibition of bacterial growth, particularly against Staphylococcus aureus with a zone of inhibition of 22 ± 1 mm. Minimum inhibitory concentration (MIC) tests further supported the antibacterial efficacy of the extract with Staphylococcus aureus and Klebsiella pneumoniae exhibiting the lowest minimum inhibitory concentrations of 2.5 ± 0 mg/mL. Gas chromatography-mass spectrometry (GC-MS) analysis identified four key bioactive compounds which were subsequently evaluated through in silico molecular docking studies. The docking results revealed promising interactions between the bioactive compounds notably heptacosanoic acid, 25-methyl,-methyl ester with PBP2a protein of Staphylococcus aureus with the lowest binding energy of -6.49 ± 0.560 kcal/mol, suggesting potential for developing new antimicrobial agents. Additionally, the drug-likeness and toxicity of the compounds were assessed using in silico tools, supporting the potential for these compounds as viable candidates for future antibacterial drug development.

Magnesium is an essential mineral involved in more than 300 enzymatic reactions, including protein synthesis, neuromuscular function, and blood pressure regulation. Recent studies have highlighted the role of probiotics, beneficial microorganisms in the human gut, in enhancing mineral absorption. However, the interaction between magnesium and probiotic strains remains poorly understood. This study aimed to investigate the capacity of Lacticaseibacillus rhamnosus ATCC 53,103 to uptake and internalize magnesium ions, using MgSO₄ as a supplementation source. The bacterium was cultivated in MRS medium with varying concentrations of MgSO₄ (0, 0.1444, 0.722, and 1.444 g/L) over seven days. Quantitative analysis revealed that at 0.722 g/L MgSO₄, intracellular magnesium accumulation peaked at 0.7 mg/dL by Day 3, representing a 7-fold increase compared to the control (0.1 mg/dL). Scanning and transmission electron microscopy indicated essential morphological changes, including ruffled cell surfaces and enhanced ribosomal visibility. These findings suggest that L. rhamnosus can internalize magnesium under enriched conditions, supporting its potential as a microbial carrier for nutribiotic applications. This work contributes to the growing field of mineral-microbe interactions and may inform the development of probiotic-based strategies to improve magnesium bioaccessibility in the human gut.

Device- and mucosa-associated candidiasis is difficult to cure because Candida biofilms shield cells from antifungals, leading to relapse and device failure. Standard treatment decisions are still largely guided by planktonic susceptibility tests, which poorly predict the drug exposure needed to clear mature biofilms. Here we synthesize evidence that natural-compound adjuvants can dismantle key biofilm defenses and outline design rules to rationalize biofilm-aware combination therapy. Across Candida albicans, non-albicans species and Candida auris, the most reproducible adjuvant effects fell into three themes: (1) reprogramming adhesion and morphogenesis, (2) disrupting membrane sterol homeostasis, and (3) weakening the extracellular matrix and efflux-mediated tolerance. When paired with standard antifungals, these actions frequently increase killing of established biofilms and reduce the exposures required for eradication. Local delivery approaches that concentrate actives at mucosal surfaces or device interfaces (nano- or surface-directed formulations) further improve intrabiofilm exposure while limiting systemic toxicity. We conclude that translation will require standardized biofilm assays, species-stratified testing and tighter links between biofilm pharmacology and clinically achievable exposure. The framework presented here is intended to help prioritize natural adjuvants and combinations most likely to benefit device-associated and mucosal candidiasis.

This study demonstrates the green synthesis of silver nanoparticles (AgNPs) using Stevia rebaudiana (Bertoni) Bertoni leaf extract and endophytic fungus Aspergillus versicolor strain PSFNRO-2. The synthesized nanoparticles exhibited favorable physicochemical properties, including nanoscale dimensions and crystalline structure, as confirmed by spectroscopic and microscopic analysis. Comprehensive bioactivity evaluations revealed that the endophyte-derived AgNPs possessed superior antimicrobial, antioxidant, antidiabetic, and cytotoxic properties compared to plant extract-synthesized nanoparticles. Notably, the endophyte-mediated AgNPs demonstrated significantly enhanced antibacterial efficacy against Pseudomonas aeruginosa and exhibited strong inhibitory effects on α-amylase activity, indicating potential antidiabetic properties. Phytochemical screening identified a diverse array of bioactive compounds, including flavonoids, phenolic acids, tannins, terpenoids, and steviol glycosides, which functioned synergistically as reducing/capping agents, as well as direct antimicrobial contributors. These phytochemicals work in concert with silver ions to induce oxidative stress, disrupt microbial membranes, and inhibit the growth of pathogens through multiple mechanisms. The findings highlight endophyte-mediated green synthesis as a promising biotechnological approach for producing potent therapeutic nanoparticles. This work represents the first comprehensive evaluation of AgNPs biosynthesized using Aspergillus versicolor PSFNRO-2 from Stevia rebaudiana (Bertoni) Bertoni, demonstrating their potential as sustainable alternatives to conventional antimicrobial and pharmaceutical agents.

Koi (Cyprinus rubrofuscus) is a world-famous ornamental fish known for its unique characteristics and economic value. This species is susceptible to various infections, leading to high mortality and morbidity rates. In this study, bacterial pathogens isolated from naturally diseased koi were identified as belonging mainly to the genera Aeromonas and Proteus through comprehensive characterisation and molecular identification. Experimental infections with Proteus sp. closely related to Proteus vulgaris (vulgaris/hauseri complex) showed some clinical signs very similar to those in naturally infected koi, suggesting that Proteus sp. in this study is a possible pathogen in addition to Aeromonas, indicating a potential co-infection. The median lethal dose (LD50) for Proteus sp. was determined to be 1.7 × 10⁸ CFU/mL, with histopathological analysis showing changes such as fusions, lymphocyte aggregation, and necrosis in the kidney and liver. The bacterium was found to be sensitive to various antibiotics, suggesting that broad-spectrum antibiotics may be effective in treating the pathogen. This study represents the isolation of Proteus sp. closely related to P. vulgaris (vulgaris/hauseri complex) from koi and provides valuable insights for the prevention and management of related disease outbreaks. The study on bacterial infections in koi fish, particularly the isolation and characterization of Aeromonas species alongside Proteus sp., highlights significant implications for koi health management. The findings underscore the pathogenicity, potential for coinfection, and the susceptibility of Proteus sp. to broad-spectrum antibiotics, providing key understanding for disease outbreak management in ornamental koi populations.

Dengue and associated complications are spreading to non-endemic regions of Pakistan. Vector control, the foremost and widely adopted strategy for managing dengue has been implemented through various measures in Pakistan. Biological control through the use of Wolbachia, a bacterium naturally present in various insect genera, including Aedes, has demonstrated promising results globally. In this study we collected Aedes species and investigated its microbiomes with a particular focus on identifying the endosymbiont Wolbachia. Mosquitoes were collected via Gravitraps in the Peshawar region of Pakhtunkhwa province in the northwest of Pakistan. The identity of the mosquitoes was initially confirmed through morphological characters followed by molecular identification using species-specific Cytochrome oxidase I (COI) primers. The DNA from female Ae. aegypti and Ae. albopictus was further subjected to 16 S rRNA sequencing. The hypervariable regions V3/V4 of 16 S rRNA were used for sequencing using the paired-end Illumina MiSeq platform. The phylogenetic analysis of the COI gene in our samples demonstrated similarity to Aedes species previously documented in Pakistan. In comparative analysis of the microbiomes, Ae. albopictus was found to harbor 921 bacterial species, while Ae. aegypti only had 239 species. The metagenomic analysis revealed single-strain Wolbachia pipientis infection in Ae. aegypti, while Ae. albopictus harbored a double-strain infection involving a supergroup A strain (referred to as Wolbachia pipientis in 16 S EzBioCloud database) and a supergroup B strain (referred to as Wolbachia bourtzisii in16S EzBioCloud database).

The ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) are key multidrug-resistant organisms increasingly recognized outside clinical settings. Their persistence in wastewater raises concerns regarding the efficacy of conventional treatment processes and the dissemination of antimicrobial resistance. This study aimed to detect and quantify ESKAPE pathogens in wastewater treatment plants (WWTPs) and downstream environments using agar-based enumeration and real-time PCR (RT-PCR). Culture methods detected all targeted species, with Enterobacter spp. being most abundant and A. baumannii least prevalent. RT-PCR quantified four species (E. faecium, S. aureus, K. pneumoniae, and A. baumannii), identifying K. pneumoniae as dominant. Both approaches revealed higher concentrations in influents that declined after treatment, although RT-PCR indicated elevated downstream levels, suggesting incomplete removal. The highest removal efficiency (100%) was observed for S. aureus and A. baumannii in WWTPs B and J, and the lowest (54.1%) for S. aureus in WWTP K. Integrating culture and molecular methods improved detection sensitivity and provided complementary insights. These results demonstrate that conventional treatment may not fully eliminate ESKAPE pathogens and underscore the need to include them in wastewater-based surveillance for antimicrobial resistance monitoring.

The nitrogen-fixing bacterium Kosakonia radicincitans GXGL-4A can produce siderophore to sequester iron, which is essential for survival and bacteriostasis. In this investigation, a mutant, M246-2, resulting from Tn5 insertion mutagenesis of the strain GXGL-4A, was found to have lost the ability to synthesize siderophores. Whole-genome sequencing of the mutant M246-2 revealed that the insertion site is within the nucleotide sequence of the guaA gene encoding glutamine-hydrolyzing guanosine monophosphate (GMP) synthase. The deletion of the guaA gene (∆guaA) resulted in the loss of the ability to produce siderophores in the strain GXGL-4A and a significant slowdown in the bacterial growth curve. Moreover, the intracellular GMP contents in the strains M246-2 and ∆guaA were statistically significantly reduced compared to the wild-type strain GXGL-4A. The bacterial functional complementation and guaA gene deletion experiments revealed that the guaA gene modulated the siderophore synthesis in the strain GXGL-4A. The results of differential transcriptome analysis showed that the transcription levels of genes related to the siderophore synthesis in the mutant M246-2 had no significant changes compared to the wild-type strain GXGL-4A, suggesting that the guaA gene may modulate the siderophore synthesis of the strain GXGL-4A through a complex mechanism at the non-transcriptional level.

The clinical management of Nakaseomyces glabratus is becoming increasingly difficult because of its intrinsic and acquired resistance to multiple antifungal drugs, particularly azoles. This situation highlights the urgent need for new antifungal agents. In this study, the antifungal efficacy and toxicity profile of an organometallic compound, named FE1, was evaluated in the in vivo model Galleria mellonella infection model. Larvae were inoculated with a standardized suspension of N. glabratus CBS138 and treated with FE1 or fluconazole at different concentrations (0.4, 4.0, and 20 mg/kg). Survival and fungal burden (CFU/larva) were monitored at defined time points post-inoculation (24, 120 and 360 h). The results obtained in this study show that the model of N. glabratus infection in G. mellonella is suitable to evaluate toxicity, antifungal efficacy and evolution of the infection in response to antifungal treatments. In this context, compound FE1 showed significant antifungal activity, superior to that of fluconazole in parameters evaluated, such as survival and fungal burden, while melanization was monitored as a qualitative visual indicator of infection progression. The dose-dependent response observed in both survival and CFU/larva reduction assays, together with the complete protection in the groups treated with 20 mg/kg FE1 suggests a high therapeutic potential of this compound against N. glabratus infections.