During the search for natural antibiotics from fungal metabolites, a new cyathane diterpenoid, fragilicine A (1), and three known cyathane diterpenoids, erinacines I, A, and B (2–4) were isolated from the culture broth of Dentipellis fragilis. Chemical structures of 1–4 were determined by analyses of 1D- and 2D-NMR and MS data and by comparisons with data of those reported in the literature. These isolated compounds were assessed for their antimicrobial activities against Bacillus subtilis, B. atrophaeus, B. cereus, Listeria monocytogenes, Fusarium oxysporum, Diaporthe sp., and Rhizoctonia solani. These compounds showed weak antimicrobial activities.

The problematic treatment of infections caused by multiple-resistant Klebsiella, especially in ICU, is the leading cause of prolonged hospitalization and high mortality rates. The use of antibiotics for the prevention of infections is considered unreasonable as it may contribute to the selection of resistant bacteria. In this regard, the development of drugs that will be effective in preventing infection during various invasive procedures is extremely necessary. We have shown that the developed innovative antibacterial compound fluorothiazinone (FT) that suppresses the formation of biofilms is effective in the prevention of a model pneumonia caused by a multi-resistant clinical K. pneumoniae isolate. Prophylactic use followed by treatment with FT in mice with acute pneumonia modulates the local innate immune response without suppressing protective properties in the early stages of infection, while contributing to a decrease in the bacterial load in the organs and preventing lethal pathological changes in the lungs at later stages of K. pneumoniae infection. Further development of such antivirulence drugs and their use will reduce morbidity and mortality in nosocomial infections, as well as reduce the number of antibiotics used.

Two new alkylresorcinols named herein 5’-methoxy-integracins A-B (1-2), two new monomeric alkyl aromatic derivatives 3-(7-hydroxyheptyl)-5-methoxyphenol (5) and 7-(3,5-dihydroxyphenyl) heptyl acetate (6), along with four known compounds including integracins A-B (3-4), 2,4-dihydroxy-6-(8-hydroxyoctyl) benzene (7), and cytosporone B (8) were isolated from the endophytic fungus Cytospora rhizophorae A761. The structures of the four new compounds were elucidated by NMR, HRESIMS data, and electronic circular dichroism (ECD) calculations, whereas the compounds 1 and 2 were disclosed as a class of the natural rare-occurring dimeric alkylresorcinol derivatives. Moreover, the bioassays of the new compounds clarified that compound 1 was a potent inhibitor for the α-glucosidase, and compound 2 showed relatively good activity against the tumor cell lines. It is worth mentioning that the known compound integracin B (4) was first reported to display significant antibacterial activity against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) with MIC values of 6.25 μg ml−1.

Amamine (1), a new isoquinoline alkaloid, was isolated from the culture extract of an actinomycete Kitasatospora sp. HGTA304. The structure of 1 was determined by NMR and MS analyses in combination with UV data. Compound 1 displayed α-glucosidase inhibitory potential (IC50 value of 56 μM) compared with acarbose (IC50 value of 549 μM) as standard.

The prevalence of antimicrobial-resistant Cutibacterium acnes in acne patients has increased owing to inappropriate antimicrobial use. Commensal skin bacteria may play an important role in maintaining the balance of the skin microbiome by producing antimicrobial substances. Inhibition of Cu. acnes overgrowth can prevent the development and exacerbation of acne vulgaris. Here, we evaluated skin bacteria with anti-Cu. acnes activity. Growth inhibition activity against Cu. acnes was tested using 122 strains isolated from the skin of healthy volunteers and acne patients. Comparative genomic analysis of the bacterium with or without anti-Cu. acnes activity was conducted. The anti-Cu. acnes activity was confirmed by cloning an identified gene cluster and chemically synthesized peptides. Cu. avidum ATCC25577 and 89.7% of the Cu. avidum clinical isolates (26/29 strains) inhibited Cu. acnes growth. The growth inhibition activity was also found against other Cutibacterium, Lactiplantibacillus, and Corynebacterium species, but not against Staphylococcus species. The genome sequence of Cu. avidum showed a gene cluster encoding a novel bacteriocin named avidumicin. The precursor protein encoded by avdA undergoes post-translational modifications, supposedly becoming a circular bacteriocin. The anti-Cu. acnes activity of avidumicin was confirmed by Lactococcus lactis MG1363 carrying avdA. The C-terminal region of the avidumicin may be essential for anti-Cu. acnes activity. A commensal skin bacterium, Cu. avidum, producing avidumicin has anti-Cu. acnes activity. Therefore, avidumicin is a novel cyclic bacteriocin with a narrow antimicrobial spectrum. These findings suggest that Cu. avidum and avidumicin represent potential alternative agents in antimicrobial therapy for acne vulgaris.

The study was conceived with the hypothesis that human aerobic gut flora could act as a reservoir of ß-lactamases and contribute to the emergence of ß-lactam resistance by transferring ß-lactamase genes to resident anaerobes. Thus, we studied the repertoire of ß-lactam resistance determinants (ß-lactamases associated with aerobes and anaerobes) in Gram-negative anaerobes. The phenotypic resistance against ß-lactams and the presence of aerobic and anaerobic ß-lactamases were tested in Gram-negative anaerobic isolates (n = 200) by agar dilution method and targeted PCR, respectively. In addition, whole-genome sequencing (WGS) was used to study the ß-lactam resistance determinants in 4/200 multi-drug resistant (MDR) strains. The resistance to ß-lactams was as follows: imipenem (0.5%), cefoxitin (26.5%), and piperacillin–tazobactam (27.5%). None of the isolates showed the presence of ß-lactamases found in aerobic microorganisms. The presence of anaerobic ß-lactamase genes viz. cfiA, cepA, cfxA, cfiAIS [the intact segment containing cfiA gene (350 bp) and upstream IS elements (1.6–1.7 kb)] was detected in 10%, 9.5%, 21.5%, and 0% isolates, respectively. The WGS data showed the presence of cfiA, cfiA4, cfxA, cfxA2, cfxA3, cfxA4, cfxA5 in MDR strains. The study showed a distinct dichotomy in repertoires of ß-lactamases between aerobes and anaerobes.

Three phenazines, 1-methoxyphenazine (1), methyl-6-methoxyphenazine-1-carboxylate (2), 1,6-dimethoxyphenazine (4), and a 2,3-dimethoxy benzamide (3) were isolated from the Streptomyces luteireticuli NIIST-D75, and the antibacterial effects of compounds 1-3, each in combination with ciprofloxacin, were investigated. The in vitro antibacterial activity was assessed by microdilution, checkerboard, and time-kill assay against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhi. According to the checkerboard assay results, each combination of compounds 1, 2 and 3 with ciprofloxacin resulted in a significantly lower minimum inhibitory concentrations (MICs) of 0.02–1.37 µg ml−1, suggesting synergistic combinations by fractional inhibitory concentration index, and displayed bactericidal activity in time-kill kinetics within 48 h. SEM analysis was carried out to determine the changes in morphology in S. aureus and E. coli during treatment with individual combination of ciprofloxacin and compounds (1-3), which revealed drastic changes in the cells such as dent formation, biofilm disruption, cell bursting, and doughnut-like formation, change in surface morphology in S. aureus, and cell elongation, cell burst with ruptured cell, and change in surface morphology in E. coli. Hep G2 cell viability was not affected by the compounds (1-3) that were tested for cytotoxicity up to 250 µM.

Vanitaracin A, an anti-hepatitis B virus polyketide, has been previously isolated from Talaromyces sp. In the present study, we searched for novel compounds in the culture broth obtained from a vanitaracin A-producing fungus under various conditions. Three novel compounds (vanitaracin C, vanitaraphilone A, and 2-hydroxy-4-(hydroxymethyl)-6-methylbenzaldehyde) were isolated, and their structures were determined using spectroscopic methods (1D/2D NMR and MS). In addition, the antiviral spectrum of vanitaracin A was examined by measuring its antiviral activities against rabies virus, Borna disease virus 1, and bovine leukemia virus. This compound exhibited antiviral activity against bovine leukemia virus, which is the causative agent of enzootic bovine leukosis. The anti-bovine leukemia virus effects of other compounds isolated from the vanitaracin A-producing fungus, namely, vanitaracins B and C, vanitaraphilone A, and 2-hydroxy-4-(hydroxymethyl)-6-methylbenzaldehyde, were also evaluated. Vanitaracin B, vanitaraphilone A and 2-hydroxy-4-(hydroxymethyl)-6-methylbenzaldehyde were also found to exhibit activity against bovine leukemia virus. These findings reveal the broad-spectrum antiviral activity of the vanitaracin scaffold and suggest several candidates for the development of anti-bovine leukemia virus drugs.

The multi-drug resistant Staph. aureus strain, Methicillin-resistant Staphylococcus aureus (MRSA), is an emerging pathogen that could penetrate skin cuts and wounds, causing a life-threatening condition. The green biosynthesis of silver nanoparticles with liquorice extract has been demonstrated over several years for anticancer and antioxidant effects, as well as antibacterial effect against both Gram-positive and Gram-negative bacteria. The study was designed to evaluate the synergistic in vivo and in vitro wound healing and anti-MRSA activity of decorated liquorice silver nanoparticles (LD-AgNPs). The LD-AgNPs were prepared by thoroughly mixing diluted liquorice extract with AgNO3 at room temperature. The prepared nanoparticles were characterized by size measurement, IR spectroscopy, TEM imaging, and X-ray diffraction. The in vitro and in vivo antibacterial and wound healing testing were also performed. The obtained LD-AgNPs were spherical in shape and had a hydrodynamic size of about 50.16 ± 5.37 nm. Moreover, they showed potent antibacterial activity against Gram-positive and Gram-negative resistant bacteria, produced a significantly higher level of procollagen type I compared to either liquorice extract or standard silver sulfadiazine, and promoted the wound healing process in rabbits. The formulation of silver nanoparticles with liquorice extract showed synergetic effects in enhancing the treatment of wounds, with significant antibacterial activity against E. coli and MRSA.

Two new naphthohydroquinone derivatives designated iseoic acids A (1) and B (2) and a new symmetrical glycerol bisester of naphthoquinonepropanoic acid designated bisiseoate (3) were isolated from the culture extract of a marine-derived actinomycete Streptomyces sp. DC4-5. The structures of 1–3 were determined by analyzing one- and two-dimensional NMR data and MS analytical data. The absolute configurations were determined by NOESY analysis and the phenylglycine methyl ester (PGME) method for 1 and by considering the structural similarity and biosynthesis for 2 and 3. Compound 3 exhibited modest cytotoxicity against P388 murine leukemia cells with an IC50 value of 19 μM.

In pursuit of novel antibiotics that could curb the growing trend of multidrug resistance by Salmonella typhimurium, a data set of some cephalosporin analogues were subjected to Molecular Docking based virtual screening against a penicillin-binding protein (PBP 1b) of the bacterium to ascertain the binding affinity values of the bioactive ligands against the active sites of the PBP 1b protein target using the AutoDock Vina Software. Three compounds with binding affinity values ranging from −7.8 kcal/mol to −8.2 kcal/mol were selected as the most promising leads. The selected compounds also displayed better potencies against the bacterium when compared with Cefuroxime (binding affinity = −6.4 kcal/mol), a standard β-lactam antibiotic used herein for quality control and assurance. Furthermore, evaluation of the drug-likeness and ADMET properties of the three most promising leads revealed that they possess good oral bioavailability and excellent pharmacokinetic profiles. It is hoped that the findings of this study will provide an excellent template for developing more potent β-lactam antibiotics against Salmonella typhimurium.

Two new antimalarial compounds, named deacetyl fusarochromene (1) and 4′-O-acetyl fusarochromanone (2), were discovered from the static fungal cultured material of Fusarium sp. FKI-9521 isolated from feces of a stick insect (Ramulus mikado) together with three known compounds fusarochromanone (3), 3′-N-acetyl fusarochromanone (4), and 5 (fusarochromene or banchromene). The structures of 1 and 2 were elucidated as new analogs of 3 by MS and NMR analyses. The absolute configurations of 1, 2, and 4 were determined by chemical derivatization. All five compounds showed moderate in vitro antimalarial activity against chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum strains, with IC50 values ranging from 0.08 to 6.35 µM.

Phaeolschidin F (1) was isolated from fruiting bodies of the bitter and toxic mushroom Gymnopilus aeruginosus. Structure analysis by NMR and MS revealed that 1 is a new symmetrical bis(styrylpyrone). A series of anti-oxidant and pro-oxidant tests characterized that 1 is a redox catalyst having more anti-oxidant and less pro-oxidant activities than quercetin.

Simple, rapid, and accurate detection of Fluoroquinolone (FQ) resistance is essential for early initiation of appropriate anti-tuberculosis treatment regimen among rifampicin-resistant tuberculosis (RR-TB). In this study, we developed a new assay, which combines multienzyme isothermal rapid amplification and a lateral flow strip (MIRA-LF), to identify the mutations on codons 90 and 94 of gyrA for detecting levofloxacin (LFX) resistance. Compared to conventional phenotypic drug susceptibility testing, the new assay detected fluoroquinolone resistance with a sensitivity, specificity, and accuracy of 92.4%, 98.5%, and 96.5%, respectively. Thus, these characteristics of the newly developed MIRA-LF assay make it particularly useful and accurate for detecting FQ resistance in Mycobacterium tuberculosis in resource-limited condition.

COVID-19, caused by SARS-CoV-2 infection, is currently among the most important public health concerns worldwide. Although several effective vaccines have been developed, there is an urgent clinical need for effective pharmaceutical treatments for treatment of COVID-19. Ivermectin, a chemical derivative of avermectin produced by Streptomyces avermitilis, is a macrocyclic lactone with antiparasitic activity. Recent studies have shown that ivermectin inhibits SARS-CoV-2 replication in vitro. In the present study, we investigated the in vivo effects of ivermectin in a hamster model of SARS-CoV-2 infection. The results of the present study demonstrate oral administration of ivermectin prior to SARS-CoV-2 infection in hamsters was associated with decreased weight loss and pulmonary inflammation. In addition, the administration of ivermectin reduced pulmonary viral titers and mRNA expression level of pro-inflammatory cytokines associated with severe COVID-19 disease. The administration of ivermectin rapidly induced the production of virus-specific neutralizing antibodies in the late stage of viral infection. Zinc concentrations leading to immune quiescence were also significantly higher in the lungs of ivermectin-treated hamsters compared to controls. These results indicate that ivermectin may have efficacy in reducing the development and severity of COVID-19 by affecting host immunity in a hamster model of SARS-CoV-2 infection.

This study aims to explore the potential targets of bithionol in Staphylococcus aureus.The four bithionol biotinylated probes Bio-A2-1, Bio-A2-2, Bio-A2-3, and Bio-A2-4 were synthesized, the minimal inhibitory concentrations (MICs) of these probes against S. aureus were determined. The bithionol binding proteins in S. aureus were identified through immunoprecipitation and LC-MS/MS with bithionol biotinylated probe. The biotinylated bithionol probes Bio-A2-1 and Bio-A2-3 displayed antibacterial activities against S. aureus. The Bio-A2-1 showed lower MICs than Bio-A2-3, and both with the MIC50/MIC90 at 12.5/12.5 μM against S. aureus clinical isolates. The inhibition rates of bithionol biotinylated probes Bio-A2-1 and Bio-A2-3 on the biofilm formation of S. aureus were comparable to that of bithionol, and were stronger than that of Bio-A2-2 and Bio-A2-4. The biofilm formation of 10 out of 12S. aureus clinical isolates could be inhibited by Bio-A2-1 (at 1/4×, or 1/2× MICs). There are three proteins identified in S. aureus through immunoprecipitation and LC-MS/MS with bithionol biotinylated probe Bio-A2-1: Protein translocase subunit SecA 1 (secA1), Alanine--tRNA ligase (alaS) and DNA gyrase subunit A (gyrA), and in which the SecA1 protein the highest coverage and the most unique peptides. The LYS112, GLN143, ASP213, GLY496 and ASP498 of SecA1 protein act as hydrogen acceptors to form 6 hydrogen bonds with bithionol biotinylated probe Bio-A2-1 by molecular docking analysis. In conclusion, the bithionol biotinylated probe Bio-A2-1 has antibacterial and anti-biofilm activities against S. aureus, and SecA1 was probably one of the potential targets of bithionol in S. aureus.

To further exploit secondary metabolic potential of a minor actinomycete genus Phytohabitans within the family Micromonosporaceae, metabolite profiling by HPLC-UV analysis, combined with 16S rDNA sequence-based phylotyping were attempted on seven Phytohabitans strains available at the public culture collection. The strains were grouped into three clades and each exhibited unique and distinct metabolite profiles, which were highly conserved among strains within the same clade. These results were consistent with previous observations on two other actinomycetes genera, reconfirming species-specificity of secondary metabolite production, which were conventionally thought to be strain-specific. A strain RD003215, belonging to the P. suffuscus clade, produced multiple metabolites, some of which were presumed to be naphthoquinones. Liquid fermentation followed by chromatographic separation of the broth extract led to the discovery of three new pyranonaphthoquinones, designated habipyranoquinones A–C (1–3), and one new isatin derivative, (R)-N-methyl-3-hydroxy-5,6-dimethoxyoxindole (4), along with three known synthetic compounds, 6,8-dihydroxydehydro-α-lapachone (5), N-methyl-5,6-dimethoxyisatin (6), and 5,6-dimethoxyisatin (7). Structures of 1–4 were unequivocally elucidated by NMR, MS, and CD spectral analysis, with assistance of density functional theory-based NMR chemical shift prediction and ECD spectral calculation. Compound 2 displayed antibacterial activity against Kocuria rhizophila and Staphylococcus aureus with MIC 50 µg/mL and cytotoxicity against P388 murine leukemia cells with an IC50 value of 34 µM. Compounds 1 and 4 also showed cytotoxicity against P388 cells with IC50 values of 29 and 14 µM, respectively.

A polyphasic approach was used to determine the taxonomic position of a marine actinomycete, designated isolate CWH03T, which we previously reported to produce new linear azole-containing peptides spongiicolazolicins A and B. Strain CWH03T is mesophilic, neutrophilic, and halotolerant streptomycete that forms spiral spore chains on aerial mycelium. Comparative 16S rRNA gene sequencing showed that CWH03T was most closely related to Streptomyces tirandamycinicus HNM0039T (99.7%), Streptomyces spongiicola HNM0071T (99.4%), ‘Streptomyces marianii’ ICN19T (99.1%) and Streptomyces wuyuanensis CGMCC4.7042T (99.0%). The phylogenetic tree prepared using the 16S rRNA gene, as well as the phylogenomic tree using the genome BLAST distance phylogeny method and 81 core housekeeping genes, respectively, showed that the closest relative of strain CWH03T was S. spongiicola HNM0071T. The average nucleotide identity and digital DNA-DNA hybridization values between strains CWH03T and S. spongiicola HNM0071T were 91.46% and 44.2%, respectively, which were below the thresholds of 96% and 70% for prokaryotic conspecific assignation. The G+C content of the genomic DNA of strain CWH03T was 72.3%. Whole-cell hydrolysates of strain CWH03T contained LL-diaminopimelic acid. The predominant menaquinone was MK-9(H8) (88.3%), and the major fatty acids were iso-C16:0 (28.4%), anteiso-C15:0 (15.0%) and iso-C15:0 (12.9%). The major phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and an unidentified phospholipid. Based on data obtained from phenotypic, phylogenetic, genomic, and chemotaxonomic analyses, strain CWH03T represents a novel species of the genus Streptomyces, for which the proposed name is Streptomyces pacificus sp. nov. The type strain is CWH03T ( = NBRC 114659T = TBRC 15780T).

A new decalin-containing secondary metabolite, wakodecaline C, was isolated from a fungus Pyrenochaetopsis sp. RK10-F058 by screening structurally interesting metabolites based on LC/MS profiling. The structure including the absolute configuration was determined by a combination of spectroscopic methods including NMR and mass spectrometry, chemical reaction, and calculation of ECD spectra. Wakodecaline C has unique structural features containing a tetrahydrofuran-fused decalin skeleton and tetramic acid moiety, which are connected through a double bond. The compound showed moderate cytotoxicity against HL-60 cells and antimalarial activity against the Plasmodium falciparum 3D7 strain.

The use of antibiotics promotes the emergence of resistant bacteria in the patient and the environment. The extent of this well-documented biological relationship is, however, not well characterized at an ecological level. To make good policy around antibiotic use, it is important to understand the empirical connection between usage and resistance. We provide a consistent approach to estimate this relationship using national-level surveillance data. This paper estimates the effect of antibiotic usage on antibiotic resistance using an 11-year panel of data on both usage and resistance for 26 antibiotic–bacteria combinations in 26 European countries. Using distributed–lag models and event-study specifications, we provide estimates of the rate at which increases in antibiotic usage at the national level affect antibiotic resistance nationally and internationally. We also calculate the persistence of resistance and analyze how resistance behaves asymmetrically with respect to increases and decreases in usage. Our analysis finds the prevalence of resistant bacteria increases immediately after usage and continues to increase for at least 4 years after usage. We show that a decrease in usage has little identifiable impact on resistance over the same period. Usage in neighboring countries increases resistance in a country, independent of usage in that country. Trends in usage-related resistance vary across European regions and across bacterial classifications.