Journal of Applied Microbiology最新文献

Aims: We aim to detect beta-lactamase-producing Citrobacter sedlakii from horses and compare the genomic characteristics with isolates from humans.

Methods and result: We characterized phenotypically and genotypically nine C. sedlakii isolates from the feces of horses and then compared them to human-derived isolates using whole genome sequencing and phylogenomic methods. Seven isolates (7/9) were ampicillin-resistant, while at least one isolate was resistant to ceftriaxone, gentamicin, meropenem, and streptomycin. All nine isolates were carriers of the chromosomal-mediated blaSED-1  beta-lactamase gene, which confers resistance to ampicillin. One isolate was positive for the mcr-9 gene that confers resistance to colistin, and another isolate had the aac(6')-lid gene that confers resistance to aminoglycosides. Seven isolates (7/9) were carriers of genes that confer metal resistance to copper, silver, and arsenic. Phylogenetically, two horse-derived isolates clustered together with two human-derived isolates from the NDARO database.

Conclusion: The results from our study provide insight into the antimicrobial susceptibility of C. sedlakii in horses, which was previously lacking, and the specific beta-lactamase gene mediating resistance.

Aims: We aimed to investigate the molecular mechanisms underlying the survival of Mycobacterium abscessus when faced with antibiotic combination therapy. By conducting evolution experiments and whole-genome sequencing (WGS), we sought to identify genetic variants associated with stress response mechanisms, with a particular focus on drug survival and resistance.

Methods and results: We conducted evolution experiments on M. abscessus, exposing the bacteria to a combination therapy of amikacin and rifabutin. Genetic mutations associated with increased antibiotic survival and altered susceptibility were subsequently identified by WGS. We focused on mutations that contribute to stress response mechanisms and tolerance. Of particular interest was a novel frameshift mutation in MAB_3509c, a gene of unknown function within the upstream open reading frame of whiB7. A MAB_3509c knockout mutant was constructed, and expression of downstream drug resistance genes was assessed by RT-qPCR. Mutation of MAB_3509c results in increased RNA levels of whiB7 and downstream stress response genes such as eis2, which is responsible for aminoglycoside resistance.

Conclusion: Our findings demonstrate the importance of whiB7 in the adaptive stress response in M. abscessus. Moreover, our results highlight the complexity of M. abscessus adapting to drug stress and underscore the need for further research.

Aims: Staphylococcus aureus, a high-priority pathogen proclaimed to cause infections ranging from mild to life-threatening, presents significant challenges in treatment. New therapies can be developed quicker using open drug discovery platforms offering a distinct approach to expedite the development of innovative antibacterial and anti-biofilm therapeutics. This study set out to address these issues by finding new uses for current medications to find compounds that are effective against S. aureus.

Methods and results: In this study, we screened the global priority health box, launched by Medicines for Malaria Ventures containing 240 compounds, for their effectiveness against S. aureus. MMV1795508, MMV1542799, MMV027331, MMV1593278, and MMV1804559 showed potential antibacterial activity at 10 µM concentration. These compounds underwent further evaluation for their ability to clear intracellular bacteria, disrupt biofilm formation, and eradicate existing biofilms. MMV1804559 demonstrated strong efficacy across all tested parameters, achieving 94% inhibition of intracellular bacteria, 79.19% disruption of biofilm cells, and 66.18% inhibition of biofilm formation. Scanning electron microscopy revealed notable membrane perforations and blebbing in MMV1804559-treated cells, indicating its impact on bacterial membranes. Gene expression analysis of cells treated with MMV1804559 showed downregulation of clfA and clfB genes, critical for biofilm formation. Additionally, docking studies confirmed the binding affinity of MMV1804559 with clfA, supported by favorable docking scores, MM/GBSA binding energy, and increased hydrogen bond interactions in the binding pocket, suggesting clfA as a target for MMV1804559.

Conclusions: MMV1804559 could serve as a potential therapy for S. aureus by targeting biofilm development and cell adhesion processes.

Aims: Nanoemulsions based on plant essential oils have shown promise as alternatives against fungal pathogens by increasing the solubility and bioavailability of the active compounds of essential oils, which can improve their efficacy and safety. In the present study, we aimed to prepare and characterize nanoemulsions of Lippia origanoides essential oil, and analyze their antifungal activity against C. albicans in planktonic and biofilm form. Additionally, we sought to verify their cytotoxicity.

Methods and results: Alginate nanoemulsions were prepared with different concentrations of essential oil, sunflower oil, and surfactant to investigate ideal formulations regarding stability and antifungal efficiency. The results showed the nanoemulsions remained stable for longer than 60 days, with acidic pH, particle sizes ranging from 180.17 ± 6.86 nm to 497.85 ± 253.50 nm, zeta potential from -60.47 ± 2.25 to -43.63 ± 12, and polydispersity index from 0.004 to 0.622. The photomicrographs revealed that the addition of sunflower oil influenced the formation of the particles, forming nanoemulsions. The antifungal results of the essential oil and nanoemulsions showed that the MIC ranged from 0.078 to 0.312 mg ml-1. The nanoemulsions were more effective than the free essential oil in eradicating the biofilm, eliminating up to 89.7% of its mass. With regard to cytotoxicity, differences were found between the tests with VERO cells and red blood cells, and the nanoemulsions were less toxic to red blood cells than the free essential oil.

Conclusions: These results show that nanoemulsions have antifungal potential against strains of C. albicans in planktonic and biofilm forms.

Aims: Limosilactobacillus reuteri ZJ625 and Ligilactobacillus salivarius ZJ614 are potential probiotic bacteria. The mechanisms of enhanced benefits by muti-strain probiotics are yet fully understood. We elucidated the influence of co-culturing on the metabolite profiles of Limosilactobacillus reuteri ZJ625 and Ligilactobacillus salivarius ZJ614 to decipher the impacts of co-culturing on metabolic interactions between the strains.

Methods and results: Limosilactobacillus reuteri ZJ625 and Ligilactobacillus salivarius ZJ614 were grown in single and co-cultures in defined media. Bacterial cell metabolites were extracted at the mid-stationary growth phase and analysed using two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC-TOFMS). Mass-spectral data were preprocessed and analysed using unsupervised and supervised methods based on the group allocations. A total of 1387 metabolites were identified, with 18.31% significant metabolites (P < 0.05) and 10.17% differential metabolites (P < 0.05, variable importance on projection > 1). The differential metabolites identified include arabinofuranose, methyl-galactoside, N-acetylglutamic acid, phosphoric acid, and decanoic acid. The metabolites impacted carbohydrate and amino-sugar metabolism.

Conclusion: Co-culturing of Limosilactobacillus reuteri ZJ625 and Ligilactobacillus salivarius ZJ614 influenced the metabolite profiles of the strains and impacted metabolic/biosynthetic pathways, indicating cell-to-cell interactions between the strains.

Aims: This study continues our previous investigation of the intrinsic degradation of phosphogypsum (PG) by indigenous microorganisms on amending adequate nutrients. We aim to unravel the intricate mechanisms involved in PG biotransformation by a bacterial consortium.

Methods and results: We isolated and characterized seven multi-metal-resistant bacterial strains from a nutrient-amended PG-contaminated microcosm and identified them through 16S rRNA gene sequencing. Primarily aerobic, Gram-positive chemolithotrophs, these strains demonstrated significant heavy metal uptake and PG degradation potential. Further analysis revealed that all strains produced carbonic anhydrase (CA), while six also produced urease, which may facilitate microbial-induced carbonate precipitation. Microstructural and elemental analysis using scanning electron microscopy-energy-dispersive X-ray and X-Ray Diffraction (XRD) confirmed the PG bio-transformation, indicating substantial increases in carbonate concentrations and reductions in sulfate levels.

Conclusions: The consortium, composed of seven urease- and CA-producing bacterial strains, effectively degraded PG, transforming it from an acidic to an alkaline state and significantly enhancing CO2 sequestration.

Aims: This study aimed to investigate the antibacterial and anti-inflammatory effects of the antimicrobial peptide Microcin C7 for Porphyromonas gingivalis-associated diseases.

Methods and results: Reverse-phase high-performance liquid chromatography revealed that Microcin C7 could remain 25.5% at 12 h in saliva. At a concentration of <10 mg ml-1, Microcin C7 showed better cytocompatibility, as revealed by a hemolysis test and a subchronic systemic toxicity test. Moreover, the minimum inhibitory concentration and minimum bactericidal concentration of Microcin C7 were analyzed using a broth microdilution method, bacterial growth curve, scanning electron microscopy, and confocal laser microscopy and determined to be 0.16 and 5 mg ml-1, respectively. Finally, in a rat model, 5 mg ml-1 Microcin C7 showed better performance in decreasing the expression of inflammatory factors (IL-1β, IL-6, IL-8, and TNF-α) and alveolar bone resorption than other concentrations.

Conclusions: Microcin C7 demonstrated favorable biocompatibility, antibacterial activity, and anti-inflammatory effect, and could decrease the alveolar bone resorption in a rat model, indicating the promising potential for clinical translation and application on P. gingivalis-associated diseases.

Aims: Klebsiella pneumoniae is a Gram-negative bacterium that can colonize, penetrate, and cause infections at several human anatomical locations. The emergence of hypervirulent K. pneumoniae and its ability to evade the immune system and develop antibiotic resistance has made it a key concern in the healthcare industry. The hypervirulent variants are increasingly involved in community-acquired infections. Therefore, it is pertinent to understand the biofilm formation potential among the clinical isolates.

Methods and results: We acquired 225 isolates of K. pneumoniae from the Department of Microbiology, Symbiosis University Hospital and Research Centre (SUHRC), Pune, India, over 1 year from March 2022 to March 2023, and evaluated antimicrobial susceptibility, hypermucoviscous phenotype, virulence, and antimicrobial-resistant gene distribution in K. pneumoniae isolates and established a correlation between antimicrobial resistance and integrons. Most isolates were strong biofilm formers (76%). The isolates harbored one or more carbapenemase/beta-lactamase-encoding gene combinations. Hypermucoviscous (HMKP) isolates had considerably greater positive rates for iutA, magA, K2 serotype, rmpA, and rmpA2 than non-HMKP isolates. Isolates carrying integrons (43%) showed significantly more antibiotic resistance.

Conclusion: The study reveals spread of strong biofilm formers with extensive virulence and antimicrobial-resistant genes, and integrons responsible for multidrug resistance among the clinical isolates of K. pneumoniae in Pune, India, posing a threat to the public health and necessitating close surveillance, accurate diagnosis, control, and therapeutic management of infections.

Aims: A wide range of vector control programmes rely on the efficient production and release of male mosquito. Asaia bacteria are described as potential symbionts of several mosquito species but their relationship with Aedes aegypti has never been rigorously tested. Here, we aimed to quantify the benefits of three Asaia species on host development in Ae. aegypti, and the ability of these bacteria to form a stable symbiotic association with growing larvae.

Methods and results: In order to disentangle direct and indirect effects of Asaia inoculation on host development, experiments used insects with an intact microbiome and those reared in near-aseptic conditions, while we characterized bacterial communities and Asaia densities with culture dependent and independent methods (16S rRNA amplicon sequencing). Neonate larvae were inoculated with Asaia spp. for 24 h, or left as uninoculated controls, all were reared on sterile food. Aseptic larvae were produced by surface sterilization of eggs. Although all Asaia were transient members of the gut community, two species accelerated larval development relative to controls. The two mutualistic species had lasting impacts on the larval microbiome, largely by altering the relative abundance of dominant bacteria, namely Klebsiella and Pseudomonas. Axenic larvae were dominated by Asaia when inoculated with this species but showed slower development than conventionally reared insects, indicating that Asaia alone could not restore normal development.

Conclusions: Our results reveal Asaia as a poor mutualist for Ae. aegypti, but with a species-specific positive effect on improving host performance mediated by interactions with other bacteria.

Bacteriocins, natural antimicrobial peptides produced by bacteria, present eco-friendly, non-toxic, and cost-effective alternatives to traditional chemical antimicrobial agents in the food industry. This review provides a comprehensive update on the classification of bacteriocins in food preservation. It highlights the significant industrial potential of pediocin-like and two-peptide bacteriocins, emphasizing chemical synthesis methods like Fmoc-SPPS to meet the demand for bioactive bacteriocins. The review details the mode of action, focusing on mechanisms such as transmembrane potential disruption and pH-dependent effects. Furthermore, it addresses the limitations of bacteriocins in food preservation and explores the potential of nanotechnology-based encapsulation to enhance their antimicrobial efficacy. The benefits of nanoencapsulation, including improved stability, extended antimicrobial spectrum, and enhanced functionality, are underscored. This understanding is crucial for advancing the application of bacteriocins to ensure food safety and quality.