金黄色葡萄球菌杀白细胞素ED的研究进展

杀白细胞素ED(leukocidin ED,LukED)是金黄色葡萄球菌产生的双组分成孔杀白细胞素之一,由共转录于一条mRNA的lukE和lukD两个基因编码。LukED可与趋化因子受体CCR5结合以杀伤巨噬细胞、T细胞和树突细胞,或与中性粒细胞、单核细胞和自然杀伤(natural kiler,NK)细胞上的表面受体CXCR1/2结合以促进金黄色葡萄球菌的致病性及系统性感染宿主的死亡。此外,LukED还可结合Duffy 抗原趋化因子受体,使裂解红细胞释放血红蛋白,促进细菌的铁吸收和生长繁殖。LukED的表达受双组分信号转导系统附属基因调节子--毒素抑制子(Agr-Rot)通路和转录调节子RpiRc、SpoVG的调控。lukED基因在金黄色葡萄球菌中广泛流行,与金黄色葡萄球菌所致血流感染、脓疱病及抗生素相关性腹泻密切相关。这些进展对了解LukED的表达调控机制、临床意义及其在细菌致病机制中的作用,开发新的金黄色葡萄球菌感染抗毒素治疗药物具有重要意义     

In vitro inhibitory effects of farnesol and interactions between farnesol and antifungals against biofilms of Candida albicans resistant strains

Antifungal resistance is a serious problem in clinical infections. Farnesol, which is a potential antifungal agent against biofilms formed by Candida albicans resistant strains (a fluconazole-resistant isolate derived from SC5314 and two clinical Candida resistant isolates), was investigated in this study. The inhibitory effects of farnesol on biofilms were examined by XTT assay. The morphological changes and biofilm thicknesses were analyzed by scanning electron microscopy and confocal laser scanning microscopy, respectively. Additionally, the checkerboard microdilution method was used to investigate the interactions between farnesol and antifungals (fluconazole, amphotericin B, caspofungin, itraconazole, terbinafine and 5-flurocytosine) against biofilms. The results showed decreased SMICs of farnesol and thinner biofilms in the farnesol-treated groups, indicating that farnesol inhibited the development of biofilms formed by the resistant strain. Furthermore, there were synergistic effects between farnesol and fluconazole/5-flurocytosine, while there were antagonistic effects between farnesol and terbinafine/itraconazole, respectively, on the biofilms formed by the resistant strains.     

Inhibitory effects of food additives derived from polyphenols on staphylococcal enterotoxin A production and biofilm formation by Staphylococcus aureus

In this study, we examined the inhibitory effects of 14 food additives derived from polyphenol samples on staphylococcal enterotoxin A (SEA) production and biofilm formation by Staphylococcus aureus. Tannic acid AL (TA), Purephenon 50 W (PP) and Polyphenon 70A (POP) at 0.25 mg/mL and Gravinol®-N (GN), Blackcurrant polyphenol AC10 (BP), and Resveratrol-P5 (RT) at 1.0 mg/mL significantly decreased SEA production by S. aureus C-29 (p < 0.05). TA, GN, BP, and RT significantly inhibited the expression of the sea gene in S. aureus C-29 (p < 0.05), while suppression attempts by PP and POP proved unsuccessful. After result analysis, it can be derived that TA, GN, BP, and RT inhibit the production of SEA. Of the six samples, each one significantly inhibited biofilm formation (p < 0.05). Food additives derived from polyphenols have viability to be used as a means to inhibit the enterotoxin production and control the biofilm formation of foodborne pathogens.     

Mutations of the β‐tubulin gene fragments from carbendazim‐resistant isolates of Pestalotiopsis sp. causing strawberry leaf blight in Chiang Mai,Thailand

Screening of field isolates of Pestalotiopsis sp. from strawberry leaf blight in Thailand identified 56 carbendazim‐resistant isolates. Of 56 isolates, 39 highly resistant (HR) phenotypes grew well on PDA amended with carbendazim even at ≥500 mg/L. Isolates with carbendazim‐resistant phenotype had a conspicuous mutation at particular sites in the beta‐tubulin (β‐tubulin) gene sequence. A β‐tubulin encoding gene from this pathogen was cloned and sequenced. Analysis of the β‐tubulin gene in highly resistant (HR) isolates showed a substitution at codon 79 and 102 from serine (AGT) to lysine (AAA) and valine (GTA) to alanine (GCA), respectively. The detection of such point mutations in the β‐tubulin gene allows the rapid screening to detect carbendazim‐resistant isolates in the field.     

The evaluations of 99mTc cyclopentadienyl tricarbonyl triphenyl phosphonium cation for multidrug resistance

A triphenylphosphonium cation, [^99mTc]Technetium cyclopentadienyltricarbonyl-6-hexanoyl-triphenylphosphonium cation ([^99mTc]3) was prepared to target multidrug resistance (MDR). The radiotracer was evaluated in the MDR-negative MCF-7 and MDR-positive MCF-7/ADR cell lines in vitro, as well as animal models in vivo. [^99mTc]3 was proofed to be a substrate of P-glycoprotein and multidrug resistant protein 1, and showed a higher accumulation in the MDR-negative MCF-7 cells compared to ^99mTc-sestamibi in vitro. The MCF-7 tumor-to-MCF-7/ADR tumor ratio of [^99mTc]3 was ～3 at 1 h p.i. in the biodistribution study. These results demonstrated the capability of the radiotracer to detect multidrug resistance in tumor cells.     

Recent advancements in the development of anti-tuberculosis drugs

Modern chemotherapy has significantly improved patient outcomes against drug-sensitive tuberculosis. However, the rapid emergence of drug-resistant tuberculosis, together with the bacterium’s ability to persist and remain latent present a major public health challenge. To overcome this problem, research into novel anti-tuberculosis targets and drug candidates is thus of paramount importance. This review article provides an overview of tuberculosis highlighting the recent advances and tools that are employed in the field of anti-tuberculosis drug discovery. The predominant focus is on anti-tuberculosis agents that are currently in the pipeline, i.e. clinical trials.     

The structural basis for inhibition of the classical and lectin complement pathways by S. aureus extracellular adherence protein

The extracellular adherence protein (Eap) plays a crucial role in pathogenesis and survival of Staphylococcus aureus by inhibiting the classical and lectin pathways of complement. We have previously shown that Eap binds with nanomolar affinity to complement C4b and disrupts the initial interaction between C4b and C2, thereby inhibiting formation of the classical and lectin pathway C3 pro‐convertase. Although an underlying mechanism has been identified, the structural basis for Eap binding to C4b is poorly understood. Here, we show that Eap domains 3 and 4 each contain a low‐affinity, but saturable binding site for C4b. Taking advantage of the high lysine content of Eap, we used a zero‐length crosslinking approach to map the Eap binding site to both the α′‐ and γ‐chains of C4b. We also probed the C4b/Eap interface through a chemical footprinting approach involving lysine modification, proteolytic digestion, and mass spectrometry. This identified seven lysines in Eap that undergo changes in solvent exposure upon C4b binding. We found that simultaneous mutation of these lysines to either alanine or glutamate diminished C4b binding and complement inhibition by Eap. Together, our results provide insight into Eap recognition of C4b, and suggest that the repeating domains that comprise Eap are capable of multiple ligand‐binding modes.     

Co‐expression of GR79 EPSPS and GAT yields herbicide‐resistant cotton with low glyphosate residues

Glyphosate‐resistant (GR) crops have been adopted on a massive scale by North and South American farmers. Currently, about 80% of the 120 million hectares of the global genetically modified (GM) crops are GR crop varieties. However, the adoption of GR plants in China has not occurred at the same pace, owing to several factors including, among other things, labour markets and the residual effects of glyphosate in transgenic plants. Here, we report the co‐expression of codon‐optimized forms of GR79 EPSPS and N‐acetyltransferase (GAT) genes in cotton. We found five times more resistance to glyphosate with 10‐fold reduction in glyphosate residues in two pGR79 EPSPS‐pGAT co‐expression cotton lines, GGCO2 and GGCO5. The GGCO2 line was used in a hybridization programme to develop new GR cottons. Field trials at five locations during three growing seasons showed that pGR79‐pGAT transgenic cotton lines have the same agronomic performance as conventional varieties, but were USD 390‐495 cheaper to produce per hectare because of the high cost of conventional weed management practices. Our strategy to pyramid these genes clearly worked and thus offers attractive promise for the engineering and breeding of highly resistant low‐glyphosate‐residue cotton varieties.