Antimicrobial and antibiofilm effects of essential fatty acids against clinically isolated vancomycin-resistant Enterococcus faecium.

Introduction: Enterococcus faecium is a leading cause of hospital-acquired infections, which has become a serious public health concern. The increasing incidence of vancomycin-resistant E. faecium (VRE-fm) raises an urgent need to find new antimicrobial agents as a complement to traditional antibiotics. The study aimed to evaluate the antimicrobial and antibiofilm activity of essential fatty acids (EFAs) against VRE-fm, and further explore the molecular mechanism of the antibiofilm activity of EFAs. Method: The microdilution broth method was used for antimicrobial susceptibility testing with traditional antibiotics and EFAs, including α-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), linoleic acid (LOA), γ-linolenic acid (GLA), and arachidonic acid (AA). The effect of EFAs on cell morphology of VRE-fm was investigated by scanning electron microscopy. The crystal violet method was used to evaluate the antibiofilm activities of EFAs against VRE-fm. Furthermore, the expression of biofilm-related genes (acm, atlA, esp, and sagA) of VRE-fm isolates under the action of GLA was analyzed using quantitative reverse transcription PCR (qRT-PCR) assay. Results: VRE-fm isolates were highly resistant to most traditional antibiotics, only highly susceptible to quinupristin-dalfopristin (90.0%), tigecycline (100%), and linezolid (100%). EPA, DHA, and GLA exhibited excellent antimicrobial activity. The MIC50/90 of EPA, DHA, and GLA were 0.5/1, 0.25/0.5, and 0.5/1 mM, respectively. SEM imaging showed that strain V27 adsorbed a large number of DHA molecules. Furthermore, all EFAs exhibited excellent inhibition and eradication activities against VRE-fm biofilms. The biofilm inhibition rates of EFAs ranged from 45.3% to 58.0%, and eradication rates ranged from 54.1% to 63.4%, against 6 VRE-fm isolates with moderate biofilm formation ability. GLA exhibited remarkable antibiofilm activity against VRE-fm isolates. The qRT-PCR analysis showed that GLA could significantly down-regulate the expression of the atlA gene (P < 0.01) of VRE-fm. Conclusion: DHA showed the strongest antibacterial activity, while GLA showed the strongest antibiofilm effect among the EFAs with antibacterial activity. Our novel findings indicate that the antibiofilm activity of GLA may be through down-regulating the atlA gene expression in VRE-fm. Therefore, DHA and GLA had the potential to be developed as therapeutic agents to treat infections related to multiple antimicrobial-resistant E. faecium.

Corrigendum: Molecular epidemiology and comparative genomics of carbapenemase-producing Escherichia coli isolates from 19 tertiary hospitals in China from 2019 to 2020.

[This corrects the article DOI: 10.3389/fmicb.2023.1056399.].

Molecular epidemiology and comparative genomics of carbapenemase-producing Escherichia coli isolates from 19 tertiary hospitals in China from 2019 to 2020.

Background: The clinical use of carbapenems is facing challenges due to increased carbapenemase-producing Escherichia coli (CP-EC) infections over the past decade. Meanwhile, whole-genome sequencing (WGS) is an important method for bacterial epidemiological research. We aim to provide more gene-based surveys to explore the genomics and occurrence of CP-EC in China. Methods: A total of 780 Escherichia coli isolates were collected by the China Antimicrobial Resistance Surveillance Trial (CARST) from 2019 to 2020. An antibacterial susceptibility test was performed by using the agar dilution method. CP-EC were detected by the modified carbapenem inactivation method (mCIM), EDTA-modified carbapenem inactivation method (eCIM), and polymerase chain reaction (PCR). Homology analysis was performed by multilocus sequence typing (MLST). A conjugation experiment was performed to verify the transferability of plasmids carrying carbapenemase genes. WGS was conducted to explore the gene-environment of the carbapenemase gene. Result: Of the 780 Escherichia coli isolates, 31 isolates were insensitive to carbapenem with a rate of 4%. Among them, 13 CP-EC isolates had transferability of the bla NDM gene. These isolates belonged to nine distinct sequence types (STs), with some correlation. We found that two (2/13, 15.4%) of the CP-EC isolates that were collected from blood specimens were highly pathogenic and also showed high transferability of the bla NDM gene. In addition, eight (8/13, 61.5%) of the CP-EC isolates were found to be multidrug-resistant. Conclusion: With the increasing use of carbapenem, CP-EC isolates accounted for nearly half of the total carbapenem-insensitive Escherichia coli isolates. Our findings highlight the urgent need to pay attention to CP-EC isolates in bloodstream infections and ESBL-producing CP-EC isolates. Based on the One Health concept, we suggest various measures, including the development of bacterial vaccines, antibiotic management, and establishment of better medical environments, to avoid the outbreak of CP-EC.

Molecular detection of Nocardia: development and application of a real-time PCR assay in sputum and bronchoalveolar lavage fluid samples.

The diagnosis of pulmonary nocardiosis remains challenging. Rapid detection of Nocardia is of primary importance for early diagnosis and precise treatment of nocardiosis. In this study, our objective was to develop and validate a new TaqMan real-time PCR (qPCR) assay for rapidly detecting Nocardia spp. in respiratory samples. Based on published sequence data, primers in a conserved region of the 16S rRNA gene and a probe within that region that was specific for Nocardia were designed. The distinction effect of the qPCR assay was assessed between Nocardia and other respiratory-associated bacteria. Furthermore, the specificity and sensitivity of the assay were evaluated in respiratory clinical samples (n = 205), compared to the results of 16S rRNA gene amplicon sequencing and clinical diagnosis. The qPCR assay exhibited high specificity, sensitivity, repeatability, and reproducibility. The limit of detection of standard plasmid DNA was 3 × 102 copies/mL. Additionally, the qPCR assay was applied to the direct detection of 205 clinical respiratory samples. The specificity and sensitivity of the qPCR were all 100% compared to 16S rRNA gene amplicon sequencing, as well as 98.4% and 100% compared to clinical diagnosis respectively. The qPCR yielded results within 3 h of sample processing, compared to several days for culture, significantly reducing turnaround time. The results suggest that the new qPCR assay developed in this study provides reliable and rapid detection of Nocardia spp. in the respiratory tracts and is expected to reduce the time required for diagnosing and treating nocardiosis.

In-situ modified biosynthetic crystals with lanthanum for fluoride removal based on microbially induced calcium precipitation: Characterization, kinetics, and mechanism.

In this research, in-situ modified biosynthetic crystals with lanthanum (BC-La) were synthesized based on anaerobic microbially induced calcium precipitation (MICP) and investigated its capacity for groundwater defluoridation under various operational conditions. The kinetic and thermodynamic models were simulated to explore the effect of the material on the removal of fluoride ion (F-) under various parameters (pH, initial concentration of F-, and temperature). BC-La had the maximum F- adsorption capacity of 10.92 mg g-1 and 96.66% removal efficiency. The pseudo-second-order kinetic model and Langmuir isotherm model were the best kinetic and isotherm models for F- removal from BC-La, which indicated that F- were mainly spontaneously removed through chemisorption and adsorption processes. The specific surface area was 54.26 m2 g-1 and the average pore size was 9.0670 nm. BC-La mainly contained LaCO3OH, LaPO4, CaCO3, Ca5 (PO4)3OH, and F- was mainly removed through ion exchange with the material surface. Moreover, OH-, PO43-, and CO32- significantly influenced the F- removal. This work suggested a novel method for in-situ modification of anaerobic biosynthetic crystals, which improved the defluoridation effect of traditional biosynthetic crystals, increased the stability of the BC-La and allowed to remove F- from groundwater consistently.

Novel Plasmid-Mediated tet(X5) Gene Conferring Resistance to Tigecycline, Eravacycline, and Omadacycline in a Clinical Acinetobacter baumannii Isolate.

A novel, plasmid-mediated, high-level tigecycline resistance tet(X) gene variant, tet(X5), was detected in a clinical Acinetobacter baumannii isolate from China in 2017. Tet(X5) shows 84.5% and 90.5% amino acid identity to Tet(X3) and Tet(X4), respectively, with similar binding sites and a comparable affinity for tetracyclines. The tet(X5)-containing plasmid could only be transferred to A. baumannii via electrotransformation. This report follows the recent study describing the identification of tet(X3) and tet(X4).

Multiscale imaging of colitis in mice using confocal laser endomicroscopy, light-sheet fluorescence microscopy, and magnetic resonance imaging.

The objective of our study is to develop a multimodality approach by combining magnetic resonance imaging (MRI) and optical imaging methods to assess acute murine colitis at the macro- and microscopic level. In vivo MRI is used to measure the cross-sectional areas of colons at the macroscopic level. Dual-color confocal laser endomicroscopy (CLE) allows in vivo examination of the fluorescently labeled epithelial cells and microvessels in the mucosa with a spatial resolution of ∼1.4 µm during ongoing endoscopy. To further validate the structural changes of the colons in three-dimensions, ex vivo light-sheet fluorescence microscopy (LSFM) is applied for in-toto imaging of cleared colon sections. MRI, LSFM, and CLE findings are significantly correlated with histological scoring (p < 0.01) and the inflammation-associated activity index (p < 0.01). Our multimodality imaging technique permits visualization of mucosa in colitis at different scales, which can enhance our understanding of the pathogenesis of inflammatory bowel diseases.