Activation studies with amines and amino acids of the α-carbonic anhydrase from the pathogenic protozoan Trypanosoma cruzi

The activation of a α-class carbonic anhydrase (CAs, EC 4.2.1.1) from Trypanosoma cruzi (TcCA) was investigated with the best known classes of activators, the amino acids and aromatic/heterocyclic amines. The best TcCA activators were l-/d-DOPA and 4-amino-l-phenylalanine, which had activation constants in the range of 0.38–0.83?µM. Low micromolar activators were also l-/d-Trp, l-/d-Tyr, l-Gln, histamine and serotonin (K_As of 1.79–4.92?µM), whereas l-/d-His, l-/d-Phe and l-Asp were less effective activators (K_As of 6.39–18.7?µM). Amines such as dopamine, pyridyl-alkylamines, aminoethyl-piperazine or l-adrenaline, were devoid of activating effects on TcCA. Since the role of autacoids as many of these compounds investigated here is not known for the life cycle of T. cruzi, our work provides new tools for further investigations of factors connected with this protozoan pathogen infection.     

Effects of disease resistance genes on Rhizobium symbiosis in an annual legume

Summary The evolution of disease resistance in plants may be constrained if genes conferring resistance to pathogens interfere with plant responses toward other, nonpathogenic organisms. To test for such effects, we compared symbiotic nitrogen fixation in Amphicarpaea bracteata plants that differed at a major locus controlling resistance to the pathogen Synchytrium decipiens. Both resistant and susceptible plant genotypes nodulated successfully and grew significantly better in the presence of Rhizobium, although growth enhancement by Rhizobium was altered by different levels of nitrate fertilization. Plants homozygous for disease resistance achieved 2% higher growth than susceptible homozygotes across all treatments, but this difference was not significant. Resistant and susceptible plant genotypes did not differ in the mean number of nodules formed per plant or in nodule diameter. However, there was highly significant variation among replicate families within each disease resistance category for both nodulation characteristics. These results imply that genetic variation exists among A. bracteata plants both for diease resistance and for traits affecting symbiotic nitrogen fixation. However, there were no evident pleiotropic effects of disease resistance genes on the plant-Rhizobium symbiosis.     

Pathogen removal in farm-scale psychrophilic anaerobic digesters processing swine manure

This study assessed the efficiency of commercial-scale psychrophilic anaerobic digestion in sequencing batch reactors (PADSBRs) for pathogen removal from pig manure. The impact of treatment cycle length and of hydraulic flow regimes on pathogen removal efficiency was investigated. Two conventionally operated SBRs (BR1 and BR2) and two SBRs simultaneously fed during the draw step (BR3 and BR4) were monitored over a two-year period. PADSBRs significantly decreased the concentration of coliforms, Salmonella, Campylobacter spp., and Y. enterocolitica, respectively from about 10⁶, 10³ CFU g⁻¹, 10³, and 10⁴ CFU g⁻¹ to undetectable levels in most samples. Densities of the gram-positive Clostridium perfringens and Enterococcus spp. remained high (10⁵ CFU g⁻¹) in the digesters throughout treatment. The PADSBRs maintained the same level of pathogen removal when the treatment cycle length was reduced from 2 to 1 week. Mass balances on volatile fatty acids (VFAs) revealed short-circuits of inlet flow respectively averaging 6.3% and 6.4% for BR3 and BR4, significantly reducing the overall performance of these reactors regarding pathogens removal. The results obtained in this study show the ability of low temperature anaerobic digestion to remove or significantly reduce indicator and pathogen concentration from raw pig manure.     

Sex differences in the anatomical locations of human body scarification and tattooing as a function of pathogen prevalence

Pathogen prevalence can affect human mate selection because pathogen severity limits the number of high-quality pathogen-resistant mates. This creates a selection pressure to fashion mechanisms to identify and select pathogen-resistant mates. Gangestad and Buss have suggested that attractiveness indicates pathogen resistance. Humans in many instances enhance their attractiveness by using permanent body markings, such as tattooing and scarification. We hypothesized that as pathogen severity increases, so should permanent marking of body areas that are attended to for evaluating attractiveness and mate quality. Females were predicted to scarify their breasts and stomachs (due to the stomach being a component of waist-to-hip ratio), both indicative of youthfulness and fertility. Males were predicted to scarify those body parts indicative of sexual maturity and strength, such as the face, shoulders, and arms. Cross-cultural data revealed that pathogen prevalence predicts female stomach scarification independent of polygyny, famine, and social class stratification. The relationship between scarification of body parts and pathogen prevalence was not evident for males. These findings, based upon between-society comparisons, suggest that stomach scarification could act as a signal of female mate quality in societies that encounter a high prevalence of pathogens.     

Targeting chemokines: Pathogens can,why can’t we?

Chemoattractant cytokines, or chemokines, are the largest sub-family of cytokines. About 50 distinct chemokines have been identified in humans. Their principal role is to stimulate the directional migration of leukocytes, which they achieve through activation of their receptors, following immobilization on cell surface glycosaminoglycans (GAGs). Chemokine receptors belong to the G protein-coupled 7-transmembrane receptor family, and hence their identification brought great promise to the pharmaceutical industry, since this receptor class is the target for a large percentage of marketed drugs. Unfortunately, the development of potent and efficacious inhibitors of chemokine receptors has not lived up to the early expectations. Several approaches to targeting this system will be described here, which have been instrumental in establishing paradigms in chemokine biology. Whilst drug discovery programs have not yet elucidated how to make successful drugs targeting the chemokine system, it is now known that certain parasites have evolved anti-chemokine strategies in order to remain undetected by their hosts. What can we learn from them?     

Use of selected bacteria and yeast to protect gnotobiotic Artemia against different pathogens

To evaluate the potential probiotic effect of two bacterial strains towards Artemia cultured in different gnotobiotic conditions, challenge tests were performed with a virulent Vibrio campbellii or with an opportunistic Vibrio proteolyticus strain. For that purpose, three feed sources (different isogenic Saccharomyces cerevisiae mutant strains) were chosen, yielding distinct Artemia culture performances. Both bacterial strains, selected from previous well-performing Artemia cultures, were able to protect against the opportunistic V. proteolyticus, while, generally, these bacteria could not protect Artemia against V. campbellii. The quality of the feed provided (in the form of the isogenic mnn9 yeast mutant) to Artemia had a stronger influence on nauplii protection against the opportunistic and the virulent Vibrio than the addition of beneficial bacteria. This feed has a higher nutritional value for Artemia, but contains also more cell wall bound β-glucans and chitin. Data suggest that the change in the cell wall composition, rather than the overall better nutritional value, of the mnn9 strain is responsible for the protection against both Vibrios.     

中山地区小儿血培养病原菌分布及耐药性分析

目的了解中山地区小儿血培养病原菌分布及其常见病原菌对抗生素的耐药情况。方法对2008年至2009年南方医科大学附属中山市博爱医院新生儿科、儿科住院患儿进行血培养,应用BacT/ALERT 3D全自动血培养仪进行检测,阳性菌株用VITEK-32全自动微生物分析仪进行菌株鉴定及药敏试验。结果 4 647例小儿血培养共检出病原菌316株,总阳性率为6.8%;革兰阳性菌258株(81.6%),其中凝固酶阴性葡萄球菌(CNS)209株(66.1%);革兰阴性菌55株(17.4%),以大肠埃希菌14株(4.4%)和肺炎克雷伯菌12株(3.8%)为主。革兰阳性菌对青霉素G耐药率高达93.4%,其次为氨苄西林/舒巴坦(82.9%)、苯唑西林(82.3%),耐药率均在80%以上。耐甲氧西林金黄色葡萄球菌(MRSA)占25%,耐甲氧西林凝固酶阴性葡萄球菌(MRSCN)占82.3%。未检出对万古霉素、利奈唑胺和呋喃妥因耐药的菌株。革兰阴性菌中大肠埃希菌、肺炎克雷伯菌ESBLs的检出率分别为50%和33%,这些菌株对头孢哌酮/舒巴坦、丁胺卡那霉素、左旋氧氟沙星和亚胺培南的敏感率分别为91.7%、100%、92.9%、100%,表现了较低耐药率。结论本地区小儿血培养病原菌以革兰阳性菌为主,且表现为多重耐药。     

食源性致病菌风险排名方法

综述食品风险排名的相关概念及其在风险评估中的重要性,探讨发达国家进行风险分析的方法与经验,其中致病菌风险排名的研究因病原菌的动态性和宿主特异性而呈现出独特的挑战性。重点详细探讨美国对食源性致病菌排名的创新方法——专家组启发法,此法作为弥补数据不足和不确定性的手段,结合传统的＂自上而下＂和＂自下而上＂方法,可以为风险管理者提供了更全面更有效的食源性致病菌风险排名。     

2009年度宁波市妇儿医院主要病原菌的临床分布及耐药性分析

目的了解宁波市妇儿医院主要病原菌的临床分布及耐药性分析。方法血液培养采用法国生物梅里埃公司的BacT/Alert3D,菌株鉴定采用法国生物梅里埃公司的VITEK 60分析仪,药敏试验采用K-B法,纸片扩散确证试验检测ESBLs。结果前10位细菌构成比依次是大肠埃希菌(13.4%)、白色念珠菌(8.7%)、阴道加德纳菌(7.8%)、表皮葡萄球菌(6.9%)、金黄色葡萄球菌(5.6%)、肺炎克雷伯菌(4.9%)、鲍曼复合醋酸钙不动杆菌(3.9%)、粪肠球菌(D群)(3.1%)、铜绿假单胞菌(2.7%)和溶血葡萄球菌(2.0%)。大肠埃希菌539株中产ESBLs阳性率为52.5%,肺炎克雷伯菌195株中产ESBLs阳性率为45.2%。大肠埃希菌主要分离于尿液,其次是脓液/切口。肺炎克雷伯菌在痰及咽拭子中所占比例最高。46株铜绿假单胞菌和11株鲍曼复合醋酸钙不动杆菌对亚胺培南耐药。结论对产ESBLs的肺炎克雷伯菌和大肠埃希菌、耐甲氧西林金黄色葡萄球菌(MRSA)和耐甲氧西林凝固酶阴性葡萄球菌(MRCNS)、耐亚胺培南的鲍曼复合醋酸钙不动杆菌和铜绿假单胞菌,应加强隔离预防,控制在医院内的扩散,减少耐药菌株产生。     

呼吸道感染临床实验室检查标本的评价

急性呼吸道感染(RTIs)是临床常见多发病,其病原体对抗生素耐药率的增加对诊断微生物学构成了严峻的挑战。临床微生物室对感染病原体的检出率较低,一般只有50%,且不同部位感染所采集的标本,其结果差异很大。本研究将评述呼吸道感染实验室检查标本采集的影响因素和常见病原体肺炎链球菌、流感嗜血杆菌、肺炎支原体、卡他莫拉菌、肺炎衣原体、嗜肺性军团病杆菌、呼吸道病毒、尿抗原试验的临床意义。