Isolation and whole-genome sequencing of a new type of linezolid-resistant Enterococcus faecalis from two cases of infective endocarditis following renal transplantation

Synthesis, Antibacterial and Anthelmintic Activity of Novel 3-(3-Pyridyl)-oxazolidinone-5-methyl Ester Derivatives

In this study, a series of 3-(3-pyridyl)-oxazolidone-5-methyl ester derivatives was synthesized and characterized by 1H NMR, 13C NMR, and LC-MS. The conducted screening antibacterial studies of the new 3-(3-pyridyl)-oxazolidone-5-methyl ester derivatives established that the methyl sulfonic acid esters have broad activity spectrum towards Staphylococcus aureus, Streptococcus pneumoniae, Bacillus subtilis and Staphylococcus epidermidis. Among them, compound 12e has the most potent activity, with an MIC of 16 μg/mL against B.subtilis, and could reduce the instantaneous growth rate of bacteria. Furthermore, molecular docking studies were also simulated for compound 12e to predict the specific binding mode of this compound. In addition, anthelmintic activity of these compounds was also evaluated against adult Indian earthworms (Pheretima posthuman). The results showed that compound 11b had the best effect. These results above can provide experimental reference for the development of novel antibacterial and anthelmintic drugs.

What Does 16S rRNA Gene-Targeted Next Generation Sequencing Contribute to the Study of Infective Endocarditis in Heart-Valve Tissue?

Infective endocarditis (IE) is a severe and life-threatening disease. Identification of infectious etiology is essential for establishing the appropriate antimicrobial treatment and decreasing mortality. The aim of this study was to explore the potential utility of metataxonomics for improving microbiological diagnosis of IE. Here, next-generation sequencing (NGS) of the V3-V4 region of the 16S rRNA gene was performed in 27 heart valve tissues (18 natives, 5 intravascular devices, and 4 prosthetics) from 27 patients diagnosed with IE (4 of them with negative blood cultures). Metataxonomics matched with conventional diagnostic techniques in 24/27 cases (88.9%). The same bacterial family was assigned to 24 cases; the same genus, to 23 cases; and the same species, to 13 cases. In 22 of them, the etiological agent was represented by percentages > 99% of the reads and in two cases, by ~70%. Staphylococcus aureus was detected in a previously microbiological undiagnosed patient. Thus, microbiological diagnosis with 16S rRNA gene targeted-NGS was possible in one more sample than using traditional techniques. The remaining two patients showed no coincidence between traditional and 16S rRNA gene-targeted NGS microbiological diagnoses. In addition, 16S rRNA gene-targeted NGS allowed us to suggest coinfections that were supported by clinical data in one patient, and minority records also verified mixed infections in three cases. In our series, metataxonomics was valid for the identification of the causative agents, although more studies are needed before implementation of 16S rRNA gene-targeted NGS for the diagnosis of IE.

Evaluation of the Anti-Mycobacterial Activity of Newly Synthesized (S)-N-(3-(2-Fluoro-4'-(2-Amino-4-Thiazolyl)Biphenyl-4-Yl)-2-Oxo-1,3-Oxazolidie-5-Ylmethyl) Acetamide Derivative in Vitro and in Mycobacterium marinum-Infected Zebrafish

Through our previous work, we have identified that novel oxazolidinone structures, the biaryloxazolidinone analogues containing a hydrazone moiety, act as promising antibacterial agents against gram-positive bacterial strains. Based on this active structure, in this study, we synthesized a series of novel oxazolidinones and determined their anti-mycobacterial activities in vitro and in Mycobacterium marinum-infected zebrafish. The in vitro anti-mycobacterial assay demonstrated that all of the synthesized compounds have potent efficacy against both H37Rv and clinical mycobacterial isolates. Among all the generated active agents, (S)-N-(3-(2-fluoro-4'-(2-amino-4-thiazolyl)biphenyl-4-yl)-2-oxo-1,3-oxazolidie-5-ylmethyl)acetamide (compound 7), whose in vitro MIC was 10-fold lower than that of linezolid, showed the strongest bactericidal effects, with ~2.2-log reduction of M. marinum load in zebrafish at 10 mg/kg dosage. Other novel oxazolidinones, compounds 9, 12, 16, and 21, exhibited reduction range of 1.1-1.8 log against M. marinum and displayed better efficacy than linezolid. Our results indicate that these identified compounds have the potential to be further developed as novel anti-mycobacterial agents.