Burkholderia cepacia complex taxon K : where to split?

The objective of the present study was to provide an updated classification for Burkholderia cepacia complex (Bcc) taxon K isolates. A representative set of 39 taxon K isolates were analyzed through multilocus sequence typing (MLST) and phylogenomic analyses. MLST analysis revealed the presence of at least six clusters of sequence types (STs) within taxon K, two of which contain the type strains of Burkholderia contaminans (ST-102) and Burkholderia lata (ST-101), and four corresponding to the previously defined taxa Other Bcc groups C, G, H and M. This clustering was largely supported by a phylogenomic tree which revealed three main clades. Isolates of B. contaminans and of Other Bcc groups C, G, and H represented a first clade which generally shared average nucleotide identity (ANI) and average digital DNA-DNA hybridization (dDDH) values at or above the 95–96% ANI and 70% dDDH thresholds for species delineation. A second clade consisted of Other Bcc group M bacteria and of four B. lata isolates and was supported by average ANI and dDDH values of 97.2 and 76.1% within this clade and average ANI and dDDH values of 94.5 and 57.2% toward the remaining B. lata isolates (including the type strain), which represented a third clade. We therefore concluded that isolates known as Other Bcc groups C, G, and H should be classified as B. contaminans, and propose a novel species, Burkholderia aenigmatica sp. nov., to accommodate Other Bcc M and B. lata ST-98, ST-103, and ST-119 isolates. Optimized MALDI-TOF MS databases for the identification of clinical Burkholderia isolates may provide correct species-level identification for some of these bacteria but would identify most of them as B. cepacia complex. MLST facilitates species-level identification of many taxon K strains but some may require comparative genomics for accurate species-level assignment. Finally, the inclusion of Other Bcc groups C, G, and H into B. contaminans affects the phenotype of this species minimally and the proposal to classify Other Bcc group M and B. lata ST-98, ST-103, and ST-119 strains as a novel Burkholderia species is supported by a distinctive phenotype, i.e., growth at 42°C and lysine decarboxylase activity

Synthesized mercaptopropyl nanoporous resins in DGT probes for determining dissolved mercury concentrations

3-Mercaptopropyl functionalized SBA-15 (SH-SBA) and 3-mercaptopropyl functionalized ethenylene bridged periodic mesoporous organosilica (SH-PMO) were included in a Diffusive Gradients in Thin film (DGT) probe and compared to similar commercially available resins also containing thiol functional groups, such as Sumichelate Q10R (SQR) and 3-mercaptopropyl functionalized silica gel (SH-KG), and also to the Chelex-100 resin for the determination of labile Hg concentrations. An agarose gel was used as the diffusive gel because the classic polyacrylamide gel shows more than 20% of Hg adsorption. According to our results, the Chelex-100 resin presents a much lower affinity for Hg than the thiol based resins. The non-linear accumulation profile of mercury with time for the Chelex-100 resin makes it in fact impossible to use Fick's law for estimating the diffusion coefficient of Hg. The 4 other resins all show a linear accumulation profile of Hg with time. Although the highest accumulation rate is observed for SH-PMO followed by SQR, SH-SBA and SH-KG, these values do not differ very much

Antibacterial activity of a lectin‐like B

&lt;p&gt;Bacteriocins of the LlpA family have previously been characterized in the γ-proteobacteria Pseudomonas and Xanthomonas. These proteins are composed of two MMBL (monocot mannose-binding lectin) domains, a module predominantly and abundantly found in lectins from monocot plants. Genes encoding four different types of LlpA-like proteins were identified in genomes from strains belonging to the Burkholderia cepacia complex (Bcc) and the Burkholderia pseudomallei group. A selected recombinant LlpA-like protein from the human isolate Burkholderia cenocepacia AU1054 displayed narrow-spectrum genus-specific antibacterial activity, thus representing the first functionally characterized bacteriocin within this β-proteobacterial genus. Strain-specific killing was confined to other members of the Bcc, with mostly Burkholderia ambifaria strains being susceptible. In addition to killing planktonic cells, this bacteriocin also acted as an antibiofilm agent.&lt;/p&gt;</p

Antibacterial activity of a lectin-like Burkholderia cenocepacia protein.

&lt;p&gt;Bacteriocins of the LlpA family have previously been characterized in the γ-proteobacteria Pseudomonas and Xanthomonas. These proteins are composed of two MMBL (monocot mannose-binding lectin) domains, a module predominantly and abundantly found in lectins from monocot plants. Genes encoding four different types of LlpA-like proteins were identified in genomes from strains belonging to the Burkholderia cepacia complex (Bcc) and the Burkholderia pseudomallei group. A selected recombinant LlpA-like protein from the human isolate Burkholderia cenocepacia AU1054 displayed narrow-spectrum genus-specific antibacterial activity, thus representing the first functionally characterized bacteriocin within this β-proteobacterial genus. Strain-specific killing was confined to other members of the Bcc, with mostly Burkholderia ambifaria strains being susceptible. In addition to killing planktonic cells, this bacteriocin also acted as an antibiofilm agent.&lt;/p&gt;</p

Thiazolidinedione derivatives as novel agents against Propionibacterium acnes biofilms

AIMS: The aim of the present study was to determine the effect of two thiazolidinedione derivatives on Propionibacterium acnes biofilm formation in vitro and to assess their effect on the susceptibility of P. acnes biofilms towards antimicrobials. METHODS AND RESULTS: The compounds were shown to have a moderate to strong antibiofilm activity when used in subinhibitory concentrations. These compounds do not affect P. acnes attachment but lead to increased dispersal of biofilm cells. This dispersal results in an increased killing of the P. acnes biofilm cells by conventional antimicrobials. CONCLUSION: The antibiofilm effect and the effect on biofilm susceptibility of the thiazolidinedione-derived quorum sensing inhibitors were clearly demonstrated. SIGNIFICANCE AND IMPACT OF THE STUDY: Propionibacterium acnes infections are difficult to treat due to the presence of biofilms at the infection site and the associated resistance towards conventional antimicrobials. Our results indicate that these thiazolidinedione derivatives can be promising leads used for the treatment of P. acnes infections and as anti-acne drugs