Taxonomic and Metabolite Diversities of Moss-Associated Actinobacteria from Thailand

Actinobacteria are a group of ecologically important bacteria capable of producing diverse bioactive compounds. However, much remains unknown about the taxonomic and metabolic diversities of actinobacteria from many geographic regions and ecological niches. In this study, we report the isolation of actinobacteria from moss and moss-associated rhizosphere soils in Thailand. Among the 89 isolates analyzed for their bioactivities, 86 strains produced indole-3-acetic acid (IAA, ranging from 0.04 to 59.12 mg/L); 42 strains produced hydroxamate type of siderophore; 35 strains produced catecholate type of siderophore; 21 strains solubilized tricalcium phosphate; and many strains exhibited antagonistic activities against one to several of the seven selected plant, animal, and human pathogens. Overall, actinobacteria from the rhizosphere soil of mosses showed greater abilities to produce IAA and siderophores and to solubilize tricalcium phosphate than those from mosses. Among these 89 isolates, 37 were analyzed for their 16S rRNA gene sequences, which revealed their diverse phylogenetic distributions among seven genera, Streptomyces, Micromonospora, Nocardia, Actinoplanes, Saccharothrix, Streptosporangium, and Cryptosporangium. Furthermore, gas chromatography-mass spectrometry analyses of ethyl acetate crude extracts of three selected isolates with inhibitory effects against a methicillin-resistant Staphylococcus aureus strain revealed diverse metabolites with known antimicrobial activities. Together, our results demonstrate that actinobacteria from mosses in Thailand are taxonomically diverse and capable of producing a range of metabolites with plant-growth-promoting and microbial pathogen-inhibiting potentials.

Toxicity, Monitoring, and Biodegradation of Cypermethrin Insecticide: A Review

Cypermethrin insecticide is widely used to prevent and control pest and crop diseases though, its residues have caused significant damage to the environment and living organisms. Microbial remediation becomes a popular approach to counter the toxicity of cypermethrin in both aquatic as well as terrestrial life. Cypermethrin can be effectively degraded to nontoxic compounds by bacterial and fungal strains. Various bacterial and fungal strains such as Ochrobactrum lupini DG-S-01, Bacillus sp. strain SG2, Azoarcus indigens strain HZ5, Streptomyces aureus strain HP-S-01, and Aspergillus oryzae M-4 are used for the cypermethrin degradation. Extensive usage of cypermethrin has caused problems such as surface water contamination, reduced fertility of the soil, detrimental effects on soil microbiota and non-targeted species. Due to environmental concerns associated with the cypermethrin in groundwater and food products, there is a crucial need to develop economical, rapid, and reliable techniques that can be used for field applications. An in-depth understanding of cypermethrin is explored in this review paper and possible solutions to mitigate its environmental toxicity are suggested.

Investigating Pathogenicity and Virulence of Staphylococcus pettenkoferi: An Emerging Pathogen

Staphylococcus pettenkoferi is a coagulase-negative Staphylococcus identified in 2002 that has been implicated in human diseases as an opportunistic pathogenic bacterium. Its multiresistant character is becoming a major health problem, yet the pathogenicity of S. pettenkoferi is poorly characterized. In this study, the pathogenicity of a S. pettenkoferi clinical isolate from diabetic foot osteomyelitis was compared with a Staphylococcus aureus strain in various in vitro and in vivo experiments. Growth kinetics were compared against S. aureus, and bacteria survival was assessed in the RAW 264.7 murine macrophage cell line, the THP-1 human leukemia monocytic cell line, and the HaCaT human keratinocyte cell line. Ex vivo analysis was performed in whole blood survival assays and in vivo assays via the infection model of zebrafish embryos. Moreover, whole-genome analysis was performed. Our results show that S. pettenkoferi was able to survive in human blood, human keratinocytes, murine macrophages, and human macrophages. S. pettenkoferi demonstrated its virulence by causing substantial embryo mortality in the zebrafish model. Genomic analysis revealed virulence factors such as biofilm-encoding genes (e.g., icaABCD; rsbUVW) and regulator-encoding genes (e.g., agr, mgrA, sarA, saeS) well characterized in S. aureus. This study thus advances the knowledge of this under-investigated pathogen and validates the zebrafish infection model for this bacterium.

The Persistence of Staphylococcus aureus in Pressure Ulcers: A Colonising Role

Decubitus pressure ulcers (PU) are a major complication of immobilised patients. Staphylococcus aureus is one of the most frequently detected microorganisms in PU samples; however, its persistence and role in the evolution of these wounds is unknown. In this study, we analysed S. aureus strains isolated from PU biopsies at inclusion and day 28. Eleven S. aureus (21.1%) were detected in 52 patients at inclusion. Only six PUs (11.5%) continued to harbour this bacterium at day 28. Using a whole genome sequencing approach (Miseq®, Illumina), we confirmed that these six S. aureus samples isolated at D28 were the same strain as that isolated at inclusion, with less than 83 bp difference. Phenotypical studies evaluating the growth profiles (Infinite M Mano, Tecan®) and biofilm formation (Biofilm Ring Test®) did not detect any significant difference in the fitness of the pairs of S. aureus. However, using the Caenorhabditis elegans killing assay, a clear decrease of virulence was observed between strains isolated at D28 compared with those isolated at inclusion, regardless of the clinical evolution of the PU. Moreover, all strains at inclusion were less virulent than a control S. aureus strain, i.e., NSA739. An analysis of polymicrobial communities of PU (by metabarcoding approach), in which S. aureus persisted, demonstrated no impact of Staphylococcus genus on PU evolution. Our study suggested that S. aureus presented a colonising profile on PU with no influence on wound evolution.

PCN-224 Nanoparticle/Polyacrylonitrile Nanofiber Membrane for Light-Driven Bacterial Inactivation

Increasing issues of pathogen drug resistance and spreading pose a serious threat to the ability to treat common infectious diseases, which encourages people to explore effective technology to meet the challenge. Photodynamic antibacterial inactivation (aPDI) is being explored for inactivating pathogens, which could be used as a novel approach to prevent this threat. Here, porphyrin-embedded MOF material (PCN-224) with photodynamic effect was synthesized, then the PCN-224 nanoparticles (NPs) were embedded into PAN nanofibers with an electrospinning process (PAN-PCN nanofiber membrane). On the one hand, polyacrylonitrile (PAN) nanofibers help to improve the stability of PCN-224 NPs, which could avoid their leakage. On the other, the PAN nanofibers are used as a support material to load bactericidal PCN-224 NPs, realizing recycling after bacterial elimination. An antibacterial photodynamic inactivation (aPDI) study demonstrated that the PAN-PCN 0.6% nanofiber membrane processed 3.00 log unit elimination towards a E. coli bacterial strain and 4.70 log unit towards a S. aureus strain under illumination. A mechanism study revealed that this efficient bacterial elimination was due to singlet oxygen (1O2). Although the materials are highly phototoxic, an MTT assay showed that the as fabricated nanofiber membranes had good biocompatibility in the dark, and the cell survival rates were all above 85%. Taken together, this work provided an application prospect of nanofibers with an aPDI effect to deal with the issues of pathogen drug resistance and spreading.

Characterisation and Molecular Analysis of an Unusual Chimeric Methicillin Resistant Staphylococcus Aureus Strain and its Bacteriophages

In the context of microarray-based epidemiological typing of the clonal organism Staphylococcus aureus/MRSA, a strain was identified that did not belong to known clonal complexes. The molecular analysis by microarray-based typing yielded signals suggesting that it was a mosaic or hybrid strain of two lineages. To verify this result, the isolate was sequenced with both, short-read Illumina and long-read Nanopore technologies and analysed in detail. This supported the hypothesis that the genome of this strain, ST6610-MRSA-IVg comprised of segments originating from two different clonal complexes (CC). While the backbone of the strain’s genome, i.e., roughly 2 megabases, belongs to CC8, a continuous insert of 894 kb (approx. 30% of the genome) originated from CC140. Beside core genomic markers in the normal succession and orientation, this insert also included the mecA gene, coding for PbP2a and causing methicillin resistance, localised on an SCCmec IVg element. This particular SCCmec type was also previously observed in CC140 MRSA from African countries. A second conspicuous observation was the presence of the trimethoprim resistance gene dfrG within on a prophage that occupied an attachment site normally used by Panton-Valentine Leucocidin phages. This observation could indicate a role of large-scale chromosomal recombination in the evolution of S. aureus as well as a role of phages in the dissemination of antibiotic resistance genes.

Phytochemical analysis and antimicrobial and antioxidant activities of Hen-riettea succosa (Aubl.) DC. leaves

Henriettea succosa is a tree species consumed in abundance by birds, however, there is no report on its phytochemical profile and biological activity. This study performed the phytochemical screening and the antimicrobial and antioxidant potential of H. succosa leaves. The hexane (Hex), ethyl acetate (AcOEt) and methanol (MeOH) extracts of the leaves were evaluated for chemical composition by Thin Layer Chromatography and spectrophotometric analysis; the antimicrobial activity was determined by the Minimum Inhibitory Concentration (MIC) and Minimum Microbicide Concentration (MMC); antioxidant activity was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, determination of the reducing power and the phosphomolybdenum complex reduction assay. The photoprotor action of the extracts was also evaluated. The results showed a higher content of phenolic compounds (444.08 ± 0.020 mg EAG/g) and tannins (414.37 ± 0.16 mg EAG/g) in the MeOH extract, which was effective against Staphylococcus aureus and Serratia marcescens, with MIC of 1 mg/ ml and CMM of 2 mg/ml. The MIC and MMC of AcOEt for Micrococcus luteus was 1 mg/mL, this was also considered the minimum concentration necessary for the Hex extract to act on the S. aureus strain. The MeOH extract showed greater antioxidant activity by the DPPH (79.09%) and reducing power (327.2 ± 0.00 mg EAA/g) methods, while the AcOEt extract showed greater activity by the phosphomolybdenum method (40.5%). However, none of the extracts showed a photoprotective effect against UV radiation. In summary, this study revealed that the leaves of H. succosa have secondary metabolites with bactericidal potential, in addition to antioxidant action.

Complete Genome Sequence of the Methicillin-Resistant Staphylococcus aureus Strain SQL1/USA300, Used for Testing the Antimicrobial Properties of Clay Phyllosilicates and Customized Aluminosilicates

Methicillin-resistant Staphylococcus aureus (MRSA) is a Gram-positive bacterium that causes community-acquired and health care-acquired infections. We previously demonstrated that clay phyllosilicates and customized aluminosilicates display antimicrobial activity against the MRSA strain SQL1. The SQL1 annotated genome reveals a USA300 lineage and contributes critical knowledge of the MRSA virulence factors associated with tissue infection.