Microbial contributions to bronchial asthma occurrence in children: A metagenomic study

Bronchial asthma, a common chronic respiratory disease in children, is traditionally regarded as a noninfectious disease. Current hypotheses, however, argue that asthma can be caused by microbial infection. We, therefore, hypothesize that a variety of microbes are more commonly found in the sputum of children with asthma, and these microbes may contribute to the occurrence and development of asthma. The present study proposes to use metagenomic approach to explore microbial diversity and to identify the microbial community characteristics of sputum from children with asthma. We found that microbial communities in the sputum of children differed significantly between asthmatics and controls. Kruskal-Wallis testing showed that 16 phyla, 104 genera, and 159 species were significantly downregulated, whereas two phyla including Platyhelminthes phylum and Chordata phylum, two genera including Spirometra genus and Homo sapiens, and the Spirometra erinaceieuropaei species were significantly upregulated in asthma patients compared with controls (P < 0.05). Among them, H. sapiens and S. erinaceieuropaei exhibited 2.3- and 2.0-fold overabundance in asthmatics vs controls, respectively. Meanwhile, metastats assay demonstrated that 31 phyla, 400 genera, and 813 species were significantly downregulated, whereas two phyla, 10 genera, and 16 species were significantly upregulated in asthma patients compared with controls (P < 0.05). Among them, Tetrahymena thermophila and Candidatus Zinderia insecticola exhibited 4.7-fold overabundance in asthmatics vs controls. Our study establishes a link between microbial infection and the mechanisms leading to asthma development, which will be useful for developing novel diagnostic biomarkers and aiding in the prevention and control of asthma.     

致病性葡萄球菌cfr基因介导的多重耐药机制研究进展

葡萄球菌是临床常见致病菌及食源性致病菌,可在食品原料加工、包装及运输过程中污染食品,引起人体多种严重感染,其耐药性的不断增强对公共卫生安全产生了重大的威胁。葡萄球菌中cfr (chloramphenicol-florfenicol resistance)基因编码的甲基转移酶,可引起细菌核糖体RNA的甲基化,从而阻碍或减弱多种化学结构不同的抗生素与肽基转移酶活性中心(peptidyl transferase center,PTC)的结合,导致葡萄球菌多重耐药表型的出现。噁唑烷酮类药物−利奈唑胺是继万古霉素后治疗耐药革兰氏阳性菌所致感染的最后一道防线,cfr基因的出现大大加速了利奈唑胺耐药性的传播。cfr基因广泛分布于多种致病性葡萄球菌中,cfr基因与各类型可转移元件(质粒、转座子和整合相关元件等)密切关联的遗传环境是其广泛传播的结构基础。在cfr基因水平传播的过程中,食源性致病葡萄球菌作为中间者扮演着重要的角色。本文就近年来国内外对致病性葡萄球菌中cfr基因的分布状况、耐药机制、遗传环境、传播机制等进行综述,以期为防控致病性葡萄球菌的传播提供参考,以遏制多重耐药菌的进一步传播。     

Effects of a combination of fibrolytic and amylolytic enzymes on ruminal enzyme activities,bacterial diversity,blood profile and milk production in dairy cows

We hypothesised that adding a combination of fibrolytic and amylolytic enzymes to the diet of early-lactation dairy cows would improve rumen enzyme activity and bacterial diversity, promote energy metabolism, and benefit milk production in cows. Twenty multiparous early-lactation (90 ± 5 d) Holstein cows with similar body conditions were randomly allocated to control (CON, n = 10) and experimental (EXP, n = 10) groups in a completely randomised single-factor design. The CON was fed only a basal total mixed ration diet, and the diet of the EXP was supplemented with a combination of fibrolytic and amylolytic enzymes at 70 g/cow/d (cellulase 3 500 CU/g, xylanase 2 000 XU/g, β-glucanase 17 500 GU/g, and amylase 37 000 AU/g). The experiment lasted 28 days, with 21 days for adaptation and 7 days for sampling. Enzyme addition increased the activity levels of α-amylase and xylanase, and the ammonia-N concentration (P < 0.05) tended to increase the activity of β-glucanase (P = 0.08) in rumen fluid. However, there was no significant difference in the rumen bacterial richness and diversity, phylum (richness > 0.1%) or genus (richness > 1%) composition between the CON and EXP groups (P > 0.05). A tendency of difference was found between CON and EXP (R = 0.22, P = 0.098) in principal component analysis. Ten genera showed different abundances across the CON and EXP groups (linear discriminant analysis effect size, linear discriminant analysis > 2). EXP increased the ratio of albumin to globulin and the concentrations of total cholesterol and low-density lipoprotein cholesterol (P < 0.05) and tended to increase triglycerides (P = 0.09) in blood. Milk yield, 3.5% fat-corrected milk yield and energy-corrected milk yield increased with enzyme supplementation (P < 0.05). The production levels of milk fat and lactose increased, but the percentage of solids, not fat and protein, decreased in EXP (P < 0.05). Although the DM intake was not affected, the feed efficiency tended to increase (P = 0.07) in EXP. In conclusion, dietary supplementation with a mixture of fibrolytic and amylolytic enzymes on multiparous early-lactation dairy cows increased α-amylase and xylanase activity levels in rumen fluid, enhanced milk performance and tended to improve the feed efficiency in cows.     

The role of volatiles in plant communication

Volatiles mediate the interaction of plants with pollinators, herbivores and their natural enemies, other plants and micro‐organisms. With increasing knowledge about these interactions the underlying mechanisms turn out to be increasingly complex. The mechanisms of biosynthesis and perception of volatiles are slowly being uncovered. The increasing scientific knowledge can be used to design and apply volatile‐based agricultural strategies.     

The contribution of tellurite resistance genes to the fitness of Escherichia coli uropathogenic strains

The presence of tellurite resistance gene operons has been reported in several human pathogens despite the fact that tellurium, as well as its soluble salts, are both rare in nature and are no longer in use as antimicrobial agents. We have introduced the cloned terWZA-F genes from an uropathogenic Escherichia coli isolate into another clinical E. coli isolate that was shown to be ter-gene free. The presence of the introduced genes increased the level of potassium tellurite resistance, as well as the level of resistance to oxidative stress mediated by hydrogen peroxide; and prolonged the ability of particular strains to survive in macrophages. We therefore propose that the contribution of tellurite resistance genes to oxidative stress resistance in bacteria is at least one reason for their presence in the genomes of a broad range of pathogenic microorganisms.     

Biofilm formation by avian Escherichia coli in relation to media, source and phylogeny

AIMS: To assess the abilities of 105 avian pathogenic Escherichia coli (APEC) and 103 avian faecal commensal E. coli (AFEC) to form biofilms on a plastic surface and to investigate the possible association of biofilm formation with the phylotype of these isolates. METHODS AND RESULTS: Biofilm production was assessed in 96-well microtitre plates using three different media, namely, M63 minimal medium supplemented with glucose and casamino acids, brain-heart infusion broth, and diluted tryptic soy broth. Avian E. coli are highly variable in their ability to form biofilms. In fact, no strain produced a strong biofilm in all three types of media; however, most (75.7% AFEC and 55.2% APEC) were able to form a moderate or strong biofilm in at least one medium. Biofilm formation in APEC seems to be mostly limited to nutrient deplete media; whereas, AFEC are able to form biofilms in both nutrient deplete and replete media. Also, biofilm formation in E. coli from phylogenetic groups B2, D and B1 was induced by nutrient deplete conditions; whereas, biofilm formation by members of phylogenetic group A was strongest in a rich medium. CONCLUSIONS: Biofilm formation by APEC and phylotypes B2, D and B1 is induced by nutrient deplete conditions, while AFEC are able to form biofilms in both nutrient rich and deplete media. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to investigate biofilm formation by a large sample of avian E. coli isolates, and it provides insight into the conditions that induce biofilm formation in relation to the source (APEC or AFEC) and phylogenetic group (A, B1, B2 and D) of an isolate.     

微生物群体效应信号分子研究进展

微生物细胞通过分泌可溶性小分子控制群体行为,获得生存优势的行为称为群体效应（Quorum sensing）。单细胞微生物利用群体效应获得多细胞生物的功能,从而提高自身在环境中的竞争力。信号分子是微生物发挥群体效应、进行信息交流的关键因子。信号分子普遍存在于各类微生物群体中,其结构、性质与功能存在巨大的种属差异,对信号分子进行全面的研究将有助于更加深入地了解和利用微生物群体效应。本文主要对群体效应信号分子在种类、结构、来源以及功能等方面的研究进展进行介绍。