Análisis de los cambios en la epidemiología de las infecciones micóticas invasivas / Analysis of changes in epidemiology of invasive fungal infections

Las infecciones micóticas invasivas (IMI) constituyen una importante causa de morbimortalidad, en especial en los pacientes con factores de riesgo subyacentes (neutropenia, quimioterapia, trasplante, sida). Las especies de los géneros Candida y Aspergillus representan aun las causas relevantes de IMI, pero otros organismos están adquiriendo importancia creciente. Han surgido especies del género Aspergillus menos sensibles a los antifúngicos y se ha encontrado resistencia a los azólicos, especialmente en Aspergillus fumigatus. Asimismo, las infecciones debidas a especies de los géneros Trichosporon, Fusarium y Glomeromycota (antes llamado Zygomycetes) se han incrementado y se asocian con altas tasas de mortalidad. Algunas de estas infecciones emergentes se presentan como brotes durante el tratamiento con nuevos antifúngicos, como las equinocandinas o los azólicos. La incidencia, gravedad y pronóstico de las IMI dependen de manera acentuada del organismo causal, el estado del paciente, el nivel de inmunosupresión y la localización geográfica. El diagnóstico precoz y el reconocimiento de estos cambios epidemiológicos son críticos para la atención de los pacientes.

Biocontrol potential of salinity tolerant mutants of Trichoderma harzianum against Fusarium oxysporum

A exposição de uma cepa selvagem de Trichoderma harzianum à irradiação gama induziu dois mutantes tolerantes a sal (Th50M6 e Th50M11). Em condições salinas, os dois mutantes foram muito superiores à cepa selvagem em relação à velocidade de multiplicação, esporulação e eficiência contra Fusarium oxysporum, o agente causador da doença wilt do tomate. Os mutantes tolerantes foram capazes de multiplicação e esporulação em meio de cultura contendo NaCl até 69 mM. Em comparação à cepa selvagem, os dois mutantes possuíam conteúdo mais elevado de prolina e hidroxiprolina, conteúdo de sódio superior ao de potássio, cálcio ou magnésio e conteúdo elevado de fenóis totais. A análise eletroforética das proteínas totais solúveis no mutante Th50M6 apresentou bandas diferentes acumuladas em resposta a NaCl 69 mM. Os resultados também indicaram que os mutantes produzem alguns metabólitos ativos como quitinases, celulases, b-galactosidades e antibióticos como tricodermina, gliotoxina e gliovirina. Os mutantes de Trichoderma reduziram significativamente a incidência da doença e melhoraram o rendimento e o conteúdo de minerais do tomate tanto em condições salinas como não-salinas e também em condições naturais e de infestação. Quando comparados à cepa selvagem, os mutantes de Trichoderma foram também mais eficientes em diminuir o crescimento de F. oxysporum na rizosfera.A densidade populacional de ambos mutantes na rizosfera excedeu muito a da cepa selvagem.

Biocontrol of root and crown rot in tomatoes under greenhouse conditions using Trichoderma harzianum and Paenibacillus lentimorbus: additional effect of solarization

Trichoderma harzianum 650 (Th650) and Paenebacillus lentimorbus 629 (Pl629) selected earlier for their ability to control Rhizoctonia solani, Fusarium solani and F. oxysporum in vitro, were applied alone or combined with solarization (summer assay) and/or with methyl bromide (MeBr) (summer and winter assays) to a soil with a high inoculum level, for the control of tomato root rot caused by the complex F. oxysporum f. sp. lycopersici - Pyrenochaeta lycopersici - Rhizoctonia solani. Evaluations were also performed independently for root damage caused by P. lycopersici, and also for R. solani in the summer assay. MeBr decreased tomato root damage caused by the complex from 88.7 percent to 21.2 percent and from 78.4 percent to 35.7 percent in the summer and in the winter assay, respectively. None of the bio-controllers could replace MeBr in the winter assay, but Th650 and Pl629 reduced root damage caused by this complex in the summer assay. Treatments with bio-controllers were improved by their combination with solarization in this season. Independent evaluations showed that the positive control of Th650 towards R. solani and the lack of effect on P. lycopersici correlates well with the endochitinase pattern expressed by Th650 in response to these phytopathogens. Root damage caused by R. solani can be controlled at a similar level as it does MeBr in summer assays, thus representing an alternative to the use of this chemical fungicide for the control of this phytopathogen.

Screening and in vitro production of diplodiatoxin from the isolates of Stenocarpella maydis and its toxigenic effect on bacterial strains.

Stenocarpella maydis from different maize growing regions in South Africa were collected and screened for the presence of diplodiatoxin. The presence of diplodiatoxin in these isolates was detected by thin layer chromatography and further confirmed by atomic pressure chemical ionization mass spectrometry. Samples containing diplodiatoxin showed a strong positive ion at m/z=307. MC34, MC35, MC43 and MC50 isolates of Potchefstroom region produced high amount of diplodiatoxin, whereas some of the isolates from Potchefstroom (D72, D74, D78, D79 and D80) and Cedara (CH3 and U3H) regions did not contain diplodiatoxin. Experiments were conducted to optimize in vitro production of diplodiatoxin using the isolate MC 43. A varied range of pH (3.0 to 5.0) and various culture media viz., PDB, CME, CLM and MSM were tested. Growth of mycelium and production of diplodiatoxin was maximum in PDB media at pH 4.5 and it was observed that diplodiatoxin was produced in detectable quantity in the cultures older than 6 weeks in this media. Further, diplodiatoxin was isolated and purified from 8-weeks-old cultures of MC43 isolate and confirmed by nuclear mass resolution. The standard and the compound purified showed similar NMR spectrum. Sixty-gram (fresh weight) mycelium yielded 19.52 mg of diplodiatoxin. Effect of diplodiatoxin on the growth of various bacterial strains in agar-gelled LB media was studied. They showed different range of tolerance to diplodiatoxin. The increasing order of tolerance to diplodiatoxin was Stenocarpella maydis < B. cereus < B. subtulus < P. fluorescense < E. coli. Further, the effect of different concentrations (4.88-49.70 microg/mL) of diplodiatoxin on the growth of S. aureus in LB liquid media was studied. Presence of diplodiatoxin in the media reduced cell growth as compared to the control thus, confirming anti-bacterial activity of diplodiatoxin.

Metabolitos con actividad antiviral aislados de Curvularia pallescens / Antiviral activity metabolites isolated from Curvularia pallescens

The strain BAFC 2336 of Curvularia pallescens is a hyphomycete isolated from internal fungi present in leaves and stems of Baccharis coridifolia. Three compounds designated B, D1 and D2 which inhibited the replication of vesicular stomatitis virus (VSV) and herpes simplex virus type 1 (HSV-1) in tissue cultures were isolated from fluid cultures of Curvularia pallescens. The purification procedure of the compounds consisted first in an organic solvent extraction followed by chromatography through a silica gel column. Fractions eluted from the column with antiviral activity were pooled and then subjected to thin layer chromatography (TLC) in silica gel plates. Three isolated bands were recognized with Rf of 0.63, 0.36 y 0.33 for B, D1 and D2, respectively. The chromatographic characteristics of the isolated metabolites were determined by TLC and HPLC and their chemical structure by means of spectroscopic methods. Analysis of the data obtained indicated that compound D2 (MW: 280 Da) is identical with Brefeldin A a macrolide with antiviral activity isolated from other fungi but not reported to be present in Curvularia pallescens. Compound D1 is similar in structure to compound D2; however, the low amount obtained after purification unabled us to obtain complete structural characterization. Compound B (MW: 332 Da) has an aromatic ring and a chemical structure related to curvularins, a generic name for certain metabolites from Curvularia. This compound appears to be a novel compound with antiviral potency similar to Brefeldin A, but less toxic.

Amylolytic activity of humicola sp

The thermophylic and cellulolytic fungus Humicola sp. secretes amylases in the liquid culture medium. This activity is induced by starch, maltose and cellobiose. Glucose impairs accumlation of amylolitic activity in the culture medium. The enzyme hydrolyzes starch, maltose and pullulan to glucose as the endproduct