Folia microbiologica最新文献

The increase in the prevalence of carbapenem-resistant Klebsiella pneumoniae strains (CRKP) has led to higher mortality and hospitalization of patients in health care facilities. This study investigates the resistance in CRKP, highlighting the involvement of carbapenemases, extended-spectrum β-lactamases (ESBLs), and AmpC β-lactamases, alongside the contribution of ompK35 and ompK36 porin genes in diminished antibiotic susceptibility. In the present study, 44 CRKP isolates were obtained from clinical samples, and antimicrobial susceptibility of isolates was determined. The presence of ESBLs, carbapenemase, and AmpC β-lactamases was identified through phenotypic testing. The ompK35 and ompK36 genes were identified using the polymerase chain reaction (PCR) technique, while their expression levels were evaluated through quantitative real-time PCR (q-PCR). ESBLs, carbapenemases, and AmpC β-lactamases were identified in 75%, 84%, and 13.6% of the isolates, respectively. The ompK35 was detected in 59.1% and ompK36 was detected in 56.8% of the CRKP isolates. A decresing in the expression of ompK35 and ompK36 was associated with elevated minimum inhibitory concentrations (MICs) for cefotaxime and cefepime, although no correlation was observed with imipenem. The high prevalence of ESBLs and carbapenemase production and the decreased expression of ompK35 and ompK36 correlated with decreased susceptibility to cefepime and cefotaxime, highlighting the co-exist of different of mechanisms resistance in CRKP. These results emphasize the necessity for continued surveillance and developing specific therapeutic strategies to tackle CRKP infections effectively.

The main aim of this study was to evaluate the optimum conditions for extracting the total reducing sugar content for bioethanol production using spirulina algae. The spirulina algae was pretreated using microwave-assisted acid hydrolysis, and the parameters were optimized using response surface methodology (RSM). The selected independent parameters were microwave power (250-350 W), sulfuric acid concentration (1-7%), and time duration (1-5 min). The results showed that a maximum reducing sugar concentration of 3.8 mg/mL was produced at optimum conditions. ANOVA and R-squared (R²) value (99.87%) show the model was significant (p value is < 0.0001). Additionally, a study on optimization and modeling was conducted utilizing response surface methodology (RSM) as well as artificial neural networks (ANN) to evaluate the impact of temperature (30-40 °C), concentration of inoculum (1-5 g/L), and fermentation duration (12-45 h). This comparative assessment showed that the highest ethanol concentration of 1.824 g/L was achieved under optimal conditions of 30 °C, 5 g/L inoculum concentration, and 28.5 h duration, as determined by the high-performance liquid chromatography method. Finally, it is suggested that the RSM approach demonstrated superior performance with a higher R² value (97.42%), p value is < 0.0001 (significant), and a lower mean square error (MSE) of 0.0065 compared to the ANN model.

The growing emergence of antibiotic resistance has prompted the World Health Organization to include Escherichia coli on its list of global priority pathogens, highlighting the urgent need for new therapeutic strategies. This study was designed to isolate and characterize phage(s) against multidrug-resistant (MDR) E. coli and to evaluate their potential for inhibiting biofilms. Phages were isolated from hospital sewage and screened against 18 prophage-free clinical MDR E. coli isolates. Two phages, R8 and R9, were selected for further characterization. Their host range, efficiency of plating, one-step growth curve, and morphology were determined via transmission electron microscopy. The biofilm inhibitory efficacy of each phage, both individually and as a two-phage cocktail, was quantified using a microtiter plate assay. Two isolated bacteriophages, R8 and R9, belonging to the class Caudoviricetes, were identified. Both phages demonstrated a lytic spectrum against 38.8% of the tested MDR isolates. They exhibited short latent periods (20-22 min), with R9 displaying a significantly larger burst size (300 PFU/cell) than R8 (130 PFU/cell). Notably, phage R9, when applied alone, showed significantly superior biofilm inhibition compared to both phage R8 and the phage cocktail across various MOIs. The relatively broad host range, short latent phase, suitable burst size, and biofilm inhibitory effect demonstrate the potential of both phages-especially R9-for further analysis and consideration as candidates for therapeutic applications.

A bacterium, Kalamiella piersonii, first identified from the ISS, later reclassified as Pantoea piersonii has emerged as an opportunistic pathogen of global clinical relevance. It was initially predicted to be nonpathogenic; however, subsequent reports have shown it to be associated with human infections, capable causing bacteremia, and sepsis across different patient populations. The genome of P. piersonii encodes several virulence genes involved in adhesion, invasion, and colonization, enabling its successful infection in diverse body sites. Given its environmental resilience, metabolic adaptability, and pathogenic potential, P. piersonii represents an under-recognized but important emerging pathogen. The frequent misidentification of Pantoea species due to limitation in the existing routine clinical diagnostic methods may contribute to rise of AMR due to non-specific antibiotic use. This underscores the need to compile existing knowledge on this pathogen that can support the development of accurate identification tools. This will help in better surveillance to prevent its spread and mitigate the global AMR burden to achieve the sustainable developmental goal.

Bacterial biofilm formation plays a critical role in the pathogenicity and virulence of Pseudomonas aeruginosa posing a significant threat to human health. Previously, the uncharacterized P. aeruginosa gene PA2798, was identified as a contributor to its resistance to antibiofilm peptide. However, the functional role of PA2798 and the underlying mechanisms by which it regulates biofilm formation and virulence factor production remain largely unexplored. In this study, a PA2798-deficient mutant (PAO1∆PA2798) was constructed, and aminoglycosides minimum inhibitory concentrations (MICs) were measured to assess the effect of PA2798 on antibiotic susceptibility. In addition, both in vitro phenotypic assays and in vivo experiments in chronic and acute lung infection mice models were performed to evaluate the role of PA2798 in bacterial biofilm associated infection and its potential as an antimicrobial target. Results demonstrated that deletion of PA2798 led to fourfold decreases in MICs for gentamicin, amikacin, tobramycin and netilmicin, and was accompanied by reduced biofilm biomass and virulence factor production in PAO1∆PA2798. Moreover, compromised cellular integrity, reduced bacterial activity, and impaired bacterial motility were observed in PAO1∆PA2798. Simultaneously, mice infected with this mutant strain were observed with the reduction of bacterial colonization and improved survival in both chronic and acute in vivo models. Conclusively, our findings support a role for PA2798 in aminoglycoside resistance, biofilm formation and virulence factor production in P. aeruginosa, highlighting its potential as a target for therapeutic intervention in biofilm-associated infections.

Urinary tract infections (UTIs) are predominantly caused by Escherichia coli, and the rise of multidrug-resistant strains poses major clinical challenges. Colicin-producing E. coli have attracted interest for their competitive advantage in microbial ecosystems and their potential role as natural antimicrobial agents. Seven E. coli isolates from UTI patients were examined using classical phenotypic assays (Gram staining, biochemical characterization) and molecular tools (16S rRNA sequencing, PCR, and real-time PCR). The colicin N gene (cna) was screened using specific primers. Sequencing results were confirmed through BLAST alignment, and phylogenetic relationships were assessed. Antimicrobial properties of colicin extracts were tested against Staphylococcus aureus, Proteus vulgaris, and Bacillus subtilis using disc diffusion assays. Four isolates carried the cna gene, confirming their colicin-producing ability. Sequence analysis revealed 98.7-99% similarity with reference E. coli strains, while phylogenetic mapping showed close clustering with Shigella spp. Colicin extracts displayed dose-dependent inhibition zones (8-24 mm) against the tested pathogens. All isolates were sensitive to commonly used antibiotics, indicating no compromise in drug susceptibility. This study provides molecular and functional confirmation of colicin N production among clinical E. coli strains from UTIs. The demonstrated antibacterial activity, along with preserved antibiotic susceptibility, underscores the therapeutic promise of colicin-producing strains. Further work should focus on colicin purification, expanded antimicrobial testing, and potential synergistic applications with conventional antibiotics.

Due to their vast chemical diversity, natural products derived from medicinal plants, whether as standardized extracts or isolated compounds, hold significant promise for new drug discovery. This study focused on the application of various analytical techniques, including phytochemical screening, extraction, isolation, and characterization of bioactive constituents from Angelica glauca extracts. The antibacterial properties of these isolated compounds were evaluated using the disk diffusion method against respiratory pathogens such as Staphylococcus aureus (MTCC 1144), Streptococcus pneumoniae (MTCC 655), Streptococcus pyogenes (MTCC 442), Pseudomonas aeruginosa (MTCC 2474), and Klebsiella pneumoniae (MTCC 4030). Findings revealed that the methanolic extract of A. glauca contains three primary bioactive compounds: n-hexacosane, stigmasterol, and 6,7-dimethoxycoumarin. Additionally, the extract was rich in alkaloids, flavonoids, glycosides, steroids, saponins, and tannins. Among the isolated compounds, 6,7-dimethoxycoumarin demonstrated the strongest antibacterial activity against S. aureus (17.0 ± 0.97 mm), outperforming n-hexacosane and stigmasterol. These results highlight the therapeutic potential of these compounds in treating respiratory infections and suggest their suitability as candidates for developing new antimicrobial agents. Future research will aim to formulate novel drugs based on these promising bioactive molecules.

The wide spread of opportunistic fungal infections among several immunocompromised patients has become a major health concern. A surge in the prevalence of multi drug resistant pathogenic fungi mainly Candida and Aspergillus sp. to current antifungals has lead scientists to search for new lead compounds which can address the issues of emerging fungal infections. Majority of the antifungals used currently are less effective against these pathogens and scenario of developing resistance to azoles is also a major concern. The marine environment has become a greatest treasure house for a large number of bioactive compounds due to its extreme habitat. Several bioactive compounds have been extracted and characterized from marine sources. Nevertheless, identification of antifungal compounds from marine sources especially from marine actinobacteria is less investigated so far. The existing antifungal compounds have several limitations like toxicity, poor biocompatibility and low efficacy. Hence, the development of novel antifungal compounds from marine actinobacteria with greater potency can be an attractive solution to fight this hurdle of fungal infections. From active investigation and studies reported so far, antifungal compounds from marine actinobacteria have been addressed in this review. In addition to that, this review also focuses on actinobacteria mediated nanoparticles in the treatment of opportunistic fungal infections. Nanoparticles can be a promising approach in antifungal therapy due to their nanoscale size and surface properties which enhances treatment efficacy through disruption of fungal cell membranes. Therefore, marine antifungal compounds along with the application of nanotechnology hope to contribute better solutions to opportunistic fungal infections.

Lead (Pb) contamination is a critical environmental concern that adversely affects plant growth and development. This study investigates the potential of ZnFe₂O₄ nanoparticles (NPs) and plant growth-promoting rhizobacteria to alleviate Pb-induced phytotoxicity in Vigna radiata (mung bean). Seeds were subjected to 30 µM Pb stress alone or in combination with ZnFe₂O₄ NPs and PGPR. Germination parameters including germination percentage, mean germination time, and germination index were significantly impaired under Pb stress, whereas co-application of ZnFe₂O₄ NPs and PGPR restored these traits, resulting in improved and timely seedling emergence. Vegetative growth parameters such as shoot and root length, fresh and dry biomass, and leaf area were notably reduced under Pb exposure. However, the integrated use of ZnFe₂O₄ NPs and PGPR significantly improved plant height (by 29.4%), root length (33.8%), and leaf area (27.9%) compared to Pb-stressed plants. Similarly, fresh and dry biomass values showed marked recovery, indicating improved water and nutrient uptake efficiency in treated plants. Anatomical analysis revealed severe structural damage in Pb-stressed leaves, including reduced epidermal thickness, disrupted mesophyll tissue, and decreased stomatal dimensions. The application of ZnFe₂O₄ NPs and PGPR markedly ameliorated these anatomical deformities, enhancing epidermal integrity, vascular bundle organization, and stomatal morphology. Notably, stomatal length and guard cell dimensions were restored closer to control levels. Overall, the synergistic effect of ZnFe₂O₄ NPs and PGPR substantially mitigated Pb toxicity and promoted normal germination, vegetative development, and anatomical structure in Vigna radiata, suggesting a viable strategy for cultivating crops in contaminated soils.

Nontuberculous mycobacteria (NTM) cause difficult-to-treat pulmonary infections due to their high antimicrobial resistance. Among them, the Mycobacterium abscessus complex (MABC) is a major pathogen characterized by prolonged treatment courses and low success rates. This study investigated the combination effects of the antimicrobials bedaquiline (BDQ) and clarithromycin (CLA) with the efflux pump inhibitors (EPIs) verapamil (VP) and berberine (BER) in clinical MABC isolates. Nineteen MABC strains isolated from respiratory samples were analyzed using the checkerboard method, and fractional inhibitory concentration index (FICI) values were calculated to determine synergistic, indifferent, or antagonistic interactions. Subspecies identification and genotypic resistance profiles were assessed using the GenoType NTM-DR assay. Of the isolates, 84.2% were identified as M. abscessus subsp. abscessus, 10.5% as M. abscessus subsp. massiliense, and 5.26% as M. abscessus subsp. bolletii. While no rrl (acquired macrolide resistance) or rrs (aminoglycoside resistance) mutations were detected, a functional erm41 (inducible macrolide resistance) gene was found in 73.6% of isolates. Synergistic effects were observed at rates of 84.2% for BDQ/VP, 57.9% for CLA/VP, 5.26% for BDQ/BER, and 31.5% for CLA/BER, with no antagonism identified. The BDQ/VP combination showed significantly greater synergy than BDQ/BER (p < 0.0005) and was superior to CLA/VP (p < 0.0005). Combinations with VP demonstrated significantly lower FICI values (p < 0.0005). Median fold increases in antimicrobial activity were four-fold with VP and two-fold with BER. In conclusion, the BDQ/VP combination emerged as the most effective regimen. These results highlight the synergistic potential of EPI-antimicrobial combinations and may inform the development of new therapeutic strategies for NTM infections.