An amalgam of pathogenic and beneficial endophytic fungi colonizing four Dendrobium species from Meghalaya,India

Endophytic fungi are known to play an important role in driving the evolution of plants by conferring adaptational advantages to their host through the production of secondary metabolites and phytohormones. In this study, we evaluated the diversity and phylogenetic relationship of endophytic fungal communities from four Dendrobium species viz., Dendrobium chrysanthum, Dendrobium heterocarpum, Dendrobium hookerianum, and Dendrobium longicornu of Meghalaya, India. A total of 51 culturable endophytic fungi were isolated from the four selected orchid species. The isolates were identified based on nuclear large subunit sequences into 33 species. Approximately 91% of the isolates showed affinity to Ascomycetes, while 9% of the isolates showed BLAST search similarity to Basidiomycetes. The most common genera were Trichoderma and Xylaria. The most prevalent genera were Fusarium, which was detected in all the four Dendrobium species followed by Diaporthe, which was present in three Dendrobium species viz., D. chrysanthum, D. hookerianum, and D. heterocarpum. The Shannon index value of endophytic fungal communities was the highest in D. chrysanthum (2.66), while D. longicornu (1) had the highest Evenness index. The present study revealed that endophytic fungi in these orchids are an amalgam of pathogenic and beneficial fungi, which have, at the least, switched their lifestyle to asymptomatic endophyte in their host. To our knowledge, this is the first such report on the diversity of endophytic fungi in the four selected Dendrobium species from Meghalaya, India.     

Cerebral phaeohyphomycosis due to Cladophialophora bantiana in a French Guianese child

We report a case of cerebral phaeohyphomycosis, a fungal brain infection due to a dark (dematiaceous) fungi in a 6-year-old French Guyanese boy. The child presented fever and drowsiness due to several paraventricular brain abscesses. Neurological surgeries were performed to reduce intracranial hypertension and to obtain abscess biopsies. Mycological cultures of intraoperative samples led to the diagnosis of cerebral phaeohyphomycosis due to Cladophialophora bantiana. The patient neurological status deteriorated and remained critical after several weeks of combination antifungal therapy with voriconazole 8 mg/kg/day, liposomal amphotericin B 10 mg/kg/day and flucytosine 200 mg/kg/day. A complete surgical resection was not possible because of multiple small abscesses. A multidisciplinary ethical staff decided on home medical care with palliative ventriculoperitoneal shunt, nasogastric feeding and analgesics. One year later, the patient's neurological condition had improved and cerebral lesions had regressed, while he had not received any antifungal treatment but only traditional medicines. Cerebral phaeohyphomycosis are rare diseases affecting immunocompromised but also apparently non-immunocompromised patients, as in this case. A complete surgical resection is not always possible and mortality rates are high in spite of treatments with a combination of antifungals. The diagnosis may be difficult because of these dematiaceous fungi's slowly growing and their potential pathogenicity for laboratory staff.     

基于高通量测序技术研究药食两用薏苡仁中污染真菌多样性

目的:调查药食两用薏苡仁中污染真菌多样性,为其安全使用提供参考依据。方法:收集薏苡仁样品18批,提取真菌DNA并扩增ITS2序列,基于Illumina MiSeq PE250平台进行高通量测序。结果:共检测到4门18纲44目99科149属的真菌,子囊菌门Ascomycota是最优势菌门,镰刀菌属Fusarium(3.05%~60.32%)是属水平最优势属,其次是曲霉属Aspergillus(2.20%~45.44%)、白僵菌属Beauveria(0.07%~63.21%)、链格孢属Alternaria(0.80%~11.92%)、Arachnomyces(0.03%~39.36%)和青霉属Penicillium(0.24%~8.03%)。此外,共检测到5种潜在产毒真菌,分别是烟曲霉A.fumigatus、土曲霉A.terreus、梨孢镰刀菌F.poae、囊状青霉P.capsulatum和展青霉P.paxilli。结论:高通量测序技术可以快速有效地检测薏苡仁中污染真菌种类,为薏苡仁污染真菌毒素提供风险预警。     

华南地区某眼科医院的感染性角膜炎病原菌谱特征

目的 探讨华南地区某眼科医院感染性角膜炎的病原菌谱及其特点。方法 回顾性系列病例研究。选择2013年7月1日至2017年12月31日在中山大学中山眼科中心进行角膜取材和微生物检测的角膜感染患者3 914例。表面麻醉后刮取病灶边缘的病灶组织,进行细菌、真菌培养及鉴定。培养结果阳性的细菌采用生化比色或质谱进行种属鉴定;真菌依据形态学进行种属鉴定。各季节菌谱阳性率差异比较采用卡方检验。结果 感染性角膜炎患者中,男2 468例（63.1%）,女1 446例（36.9%）,年龄（49.5±16.8）岁。病原菌培养阳性的患者共1 673例（42.7%）,其中单纯细菌749例（44.8%）,单纯真菌849例（50.7%）,混合感染75例（4.5%）。最常见的细菌是葡萄球菌属（20.1%）,其次是假单胞菌属（7.5%）;最常见的真菌是镰刀菌属（25.5%）,其次是曲霉菌属（10.3%）。细菌的阳性率在5-8月明显高于1-2月和9-12月（P<0.05）,真菌的阳性率在5-6月明显低于1-2月和9-12月（P<0.05）。结论 在华南地区一所三甲眼科医院的感染性角膜炎中,真菌感染略高于细菌感染,且细菌和真菌感染存在季节性差异。     

可见光连续环境消毒系统对手术室消毒前后菌群生物气溶胶浓度的影响

目的探讨可见光连续环境消毒系统(CED)对手术室真菌和细菌气溶胶浓度的影响以及与环境因素的相关性。方法以焦作市第二人民医院5间手术室作为研究对象,分别对CED应用前后手术室内生物气溶胶浓度进行检测,并进行真菌和细菌培养,将检测结果进行比较,并与同期检测的消毒前后的室内温度和湿度相关性进行分析。结果消毒前和消毒后强化消毒模式下手术室内细菌、真菌浓度均较常规消毒模式降低,其次术后消毒完成后强化消毒模式下室内相对湿度相比常规消毒降低,差异均有统计学意义(P<0.05)。消毒过程中手术室的相对湿度标准值为(41.12±4.06)%,温度为(23.41±2.07)℃。经Spearman相关分析显示,消毒后真菌和细菌浓度与相对湿度标准值呈正相关(r=0.109,0.107;P=0.034,0.037),与温度无相关性(P>0.05)。结论常规消毒措施上加用可见光连续环境消毒系统能大大降低手术室的菌群生物气溶胶浓度,同时维持室内相对湿度减少细菌和真菌的繁殖。     

Outdoor fungi and child asthma health service attendances

Asthma is a significant global public health issue. Severe asthma exacerbations can be triggered by environmental factors and require medical care from health services. Although it is known that fungal exposure may lead to allergic sensitization, little is understood about its impact on asthma exacerbations. This review aims to examine whether outdoor fungi play a significant role in child asthma exacerbations. Systematic search of seven electronic databases and hand searching for peer‐reviewed studies published in English, up to 31 August 2013. Inclusion criteria were study population aged <18 yr, diagnosis of asthma, attended a health service; outdoor fungi exposure was reported. Quality and risk of bias assessments were conducted. Due to significant heterogeneity, meta‐analysis was not conducted. Of the 1896 articles found, 15 were eligible. Findings were not consistent, possibly due to methodological variations in exposure classifications, statistical methods and inclusion of confounders. Cross‐sectional studies found no or weak associations. All but one time series studies indicated an association that varied between fungal species. Increasing evidence indicates that asthmatic children are susceptible to asthma exacerbations when exposed to outdoor fungal spores. There is limited understanding of the contributions of different fungal species. Research is needed to investigate interactions of outdoor fungi with pollen, air pollutants and respiratory viruses.     

Redistribution of soil water by a saprotrophic fungus enhances carbon mineralization

The desiccation of upper soil horizons is a common phenomenon, leading to a decrease in soil microbial activity and mineralization. Recent studies have shown that fungal communities and fungal-based food webs are less sensitive and better adapted to soil desiccation than bacterial-based food webs. One reason for a better fungal adaptation to soil desiccation may be hydraulic redistribution of water by mycelia networks. Here we show that a saprotrophic fungus (Agaricus bisporus) redistributes water from moist (–0.03 MPa) into dry (–9.5 MPa) soil at about 0.3 cm⋅min⁻¹ in single hyphae, resulting in an increase in soil water potential after 72 h. The increase in soil moisture by hydraulic redistribution significantly enhanced carbon mineralization by 2,800% and enzymatic activity by 250–350% in the previously dry soil compartment within 168 h. Our results demonstrate that hydraulic redistribution can partly compensate water deficiency if water is available in other zones of the mycelia network. Hydraulic redistribution is likely one of the mechanisms behind higher drought resistance of soil fungi compared with bacteria. Moreover, hydraulic redistribution by saprotrophic fungi is an underrated pathway of water transport in soils and may lead to a transfer of water to zones of high fungal activity.Drought is one of the most important and frequent abiotic stresses in terrestrial ecosystems (1). With respect to soil processes, soil desiccation limits microbial activity and decreases soil enzyme activity (2), carbon mineralization (3, 4) and nitrogen mineralization (5). In addition, drought can also alter soil microbial community composition (2, 6).During desiccation and dry periods, soil fungal communities and fungal-based food webs are better adapted to drought than bacterial communities and bacteria-based food webs (7, 8). Bacteria are more strongly restricted than fungi (9), as bacterial activity needs a constant supply of water (10). One reason for the better adaptation of fungi compared with bacteria to low soil water potentials is seen in their strong cell walls, preventing water losses (1). The strength of fungal cell walls can even be enhanced by cross-linking of polymers and thickening under stress. Another reason for the better adaptation of fungi to soil desiccation might be hydraulic redistribution of water by mycelia networks. Hydraulic redistribution is defined as the passive transport of water in soils through organisms along a gradient in soil water potential and was first observed for plant roots (11). Hydraulic redistribution through plant roots improves plant survival and nutrient uptake by extending the life span and activity of roots (12) and by favoring decomposition of soil organic matter (13). Mycorrhiza fungal hyphae can also relocate water along gradients in soil water potential (12, 14–16). In addition, some studies reported the transport of nutrients and water over larger distances (>1 m) by saprotrophic fungal hyphae in nonsoil systems. Further, water leakage from hyphae into dry growth medium was observed (17). The water transport in hyphae was attributed to gradients in osmotic potentials (18–22).Saprotrophic fungi are main regulators of soil nutrient cycling, litter decomposition, and soil respiration due to their specific enzymatic activities (23, 24) and due to the high density of hyphae in soil (up to 800 m⋅g⁻¹ soil) (25), and especially in litter layers. The ability of saprotrophic fungi to distribute water would provide a direct and fast connection between water and nutrient sources in soils that would be hardly accessible to bacteria. This could have an enormous impact on decomposition processes under drought conditions.Here, we show the potential of the saprotrophic fungus Agaricus bisporus for hydraulic redistribution and impact of water redistribution on carbon mineralization in a desiccated soil.     

乌头叶面细菌、真菌DGGE分析条件的建立与优化

目的:筛选并优化适用于分析乌头叶面细菌、真菌多样性的变性梯度凝胶电泳(DGGE)实验条件。方法:采用Touch Down-PCR技术扩增乌头叶面细菌16 S r DNA V3区域和真菌18 S r DNA~5.8 S r DNA序列,利用该扩增产物对乌头叶面细菌、真菌DGGE电泳条件进行优化。采用DGGE垂直电泳法筛选凝胶变性梯度,时间间隔法优化电泳时间。结果:乌头叶面细菌DGGE最佳分析条件为变性剂梯度30%~65%(Gel 10%),电泳温度60℃,电压120 V,电泳时间7 h。乌头叶面真菌DGGE最佳分析条件为变性剂梯度25%~45%(Gel 8%),电泳温度60℃,电压120 V,电泳时间10 h。结论:利用以上优化条件能有效分离乌头叶面细菌16 S r DNA V3区及真菌18 S r DNA~5.8 S r DNA序列,为乌头叶面细菌,真菌的群落结构PCR-DGGE分析提供可靠的技术支撑。     

Oral fungal and bacterial infections in HIV-infected individuals: an overview in Africa

Oral opportunistic infections developing secondary to human immunodeficiency virus (HIV) infection have been reported from the early days of the epidemic and have been classified by both the EC-Clearinghouse and the World Health Organisation (WHO). Among the fungal infections, oral candidiasis, presenting in African HIV-infected patients has been sporadically documented. We review the literature with respect to candidal carriage, oral candidiasis prevalence and the predictive value of oral candidiasis for a diagnosis of underlying HIV disease in African HIV-infected patients. The use of oral candidiasis as a marker of disease progression, the species of yeasts isolated from the oral cavity in Africa and the resistance of the yeasts to antifungal agents and treatment regimens are discussed. Orofacial lesions as manifestations of the systemic mycoses are rarely seen in isolation and few cases are reported in the literature from Africa. In spite of the high incidence of noma, tuberculosis, chronic osteomyelitis and syphilis in Africa, surprisingly there have been very few reported cases of the oral manifestations of these diseases in HIV-positive individuals. Orofacial disease in HIV-infected patients is associated with marked morbidity, which is compounded by malnutrition. The authors indicate specific research areas, initially directed at the most effective management strategies, which would complete data in this important area.