Dihydroisocoumarins produced by Diaporthe cf. heveae LGMF1631 inhibiting citrus pathogens.

Citrus black spot (CBS) and post-bloom fruit drop (PFD), caused by Phyllosticta citricarpa and Colletotrichum abscissum, respectively, are two important citrus diseases worldwide. CBS depreciates the market value and prevents exportation of citrus fruits to Europe. PFD under favorable climatic conditions can cause the abscission of flowers, thereby reducing citrus production by 80%. An ecofriendly alternative to control plant diseases is the use of endophytic microorganisms, or secondary metabolites produced by them. Strain LGMF1631, close related to Diaporthe cf. heveae 1, was isolated from the medicinal plant Stryphnodendron adstringens and showed significant antimicrobial activity, in a previous study. In view of the potential presented by strain LGMF1631, and the absence of chemical data for secondary metabolites produced by D. cf. heveae, we decided to characterize the compounds produced by strain LGMF1631. Based on ITS, TEF1, and TUB phylogenetic analysis, strain LGMF1631 was confirmed to belong to D. cf. heveae 1. Chemical assessment of the fungal strain LGMF1631 revealed one new seco-dihydroisocoumarin [cladosporin B (1)] along with six other related, already known dihydroisocoumarin derivatives and one monoterpene [(-)-(1S,2R,3S,4R)-p-menthane-1,2,3-triol (8)]. Among the isolated metabolites, compound 5 drastically reduced the growth of both phytopathogens in vitro and completely inhibited the development of CBS and PFD in citrus fruits and flowers. In addition, compound 5 did not show toxicity against human cancer cell lines or citrus leaves, at concentrations higher than used for the inhibition of the phytopathogens, suggesting the potential use of (-)-(3R,4R)-cis-4-hydroxy-5-methylmellein (5) to control citrus diseases.

Vochysiamides A and B: Two new bioactive carboxamides produced by the new species Diaporthe vochysiae.

Endophytic fungi have been considered a rich source for bioactive secondary metabolites with novel chemical structures. A high diverse group of endophytes, isolated from different medicinal plants, belongs to the genus Diaporthe. In a previously study performed by our group the crude extract of strain LGMF1583 showed considerable antibacterial activity mainly against Gram-negative bacteria. Based on ITS phylogeny analysis, strain LGMF1583 was identified as belonging to Diaporthe genus and may represent a new species. In the present study, we described the new species Diporthe vochysiae based on multilocus phylogeny analysis and morphological characteristics. The species name refers to the host, from which strain LGMF1583 was isolated, the medicinal plant Vochysia divergens. In view of the biotechnological potential of strain LGMF1583, we have also characterized the secondary metabolites produced by D. vochysiae. Chemical assessment of the D. vochysiae LGMF1583 revealed two new carboxamides, vochysiamides A (1) and B (2), in addition to the known metabolite, 2,5-dihydroxybenzyl alcohol (3). In the biological activity analysis, vochysiamide B (2) displayed considerable antibacterial activity against the Gram-negative bacterium Klebsiella pneumoniae (KPC), a producer of carbapenemases, MIC of 80 µg/mL. Carbapenemases are considered a major antimicrobial resistance threat, and infections caused by KPC have been considered a public health problem worldwide, and new compounds with activity against this bacterium are nowadays even more required.

ERG11 gene polymorphisms and susceptibility to fluconazole in candida isolates from diabetic and kidney transplant patients

Abstract INTRODUCTION: Candidiasis is the most frequent opportunistic mycosis in humans and can cause mortality, particularly in immunodeficient patients. One major concern is the increasing number of infections caused by drug-resistant Candidas trains, as these cannot be efficiently treated with standard therapeutics. The most common mechanism of fluconazole resistance in Candida is mutation of ERG11, a gene involved in the biosynthesis of ergosterol, a compound essential for cell integrity and membrane function. METHODS: Based on this knowledge, we investigated polymorphisms in the ERG11 gene of 3 Candida species isolated from immunocompromised and immunocompetent patients. In addition, we correlated the genetic data with the fluconazole susceptibility profile of the Candida isolates. RESULTS: A total of 80 Candida albicans, 8 Candida tropicalis and 6 Candida glabrata isolates were obtained from the saliva of diabetic, kidney transplant and immunocompetent patients. Isolates were considered susceptible to fluconazole if the minimum inhibitory concentration was lower than 8 μg/mL. The amino acid mutations F105L, D116E, K119N, S137L, and K128T were observed in C. albicans isolates, and T224C and G263A were found in C. tropicalis isolates. CONCLUSIONS: Despite the high number of polymorphisms observed, the mutations occurred in regions that are not predicted to interfere with ergosterol synthesis, and therefore are not related to fluconazole resistance.

Analysis of the genetic diversity of Candida isolates obtained from diabetic patients and kidney transplant recipients

Yeasts of the genus Candida have high genetic variability and are the most common opportunistic pathogenic fungi in humans. In this study, we evaluated the genetic diversity among 120 isolates of Candida spp. obtained from diabetic patients, kidney transplant recipients and patients without any immune deficiencies from Paraná state, Brazil. The analysis was performed using the ITS1-5.8S-ITS2 region and a partial sequence of 28S rDNA. In the phylogenetic analysis, we observed a consistent separation of the species C. albicans, C. dubliniensis, C. glabrata, C. tropicalis, C. parapsilosis, C. metapsilosis and C. orthopsilosis, however with low intraspecific variability. In the analysis of the C. albicans species, two clades were formed. Clade A included the largest number of isolates (91.2%) and the majority of isolates from GenBank (71.4%). The phylogenetic analysis showed low intraspecific genetic diversity, and the genetic polymorphisms between C. albicans isolates were similar to genetic divergence found in other studies performed with isolates from Brazil. This low genetic diversity of isolates can be explained by the geographic proximity of the patients evaluated. It was observed that yeast colonisation was highest in renal transplant recipients and diabetic patients and that C. albicans was the species most frequently isolated.

Seleção de cepas de Staphylococcus aureus, ß-lactamase positiva portadoras do gene mecA / Seletion of Staphylococcus aureus, ß-lactamase positive strains with mecA gene

Um dos maiores problemas de Saúde Pública das últimas décadas foi o agravamento da resistência a antimicrobianos; a qual em estafilococos é resultado de genes cromossômicos que codificam modificações no receptor de ação dos lactâmicos, as proteínas ligadoras de penicilinas (PBPs), havendo a produção PBPs a, essa modificação é devido ao gene mecA, onde uma seqüência de DNA de origem não estafilocócica é incorporado ao cromossomo. O Objetivo do presente estudo foi avaliar o perfil de resistência dos Staphylococcus aureus a, β-lactâmicos em uruculturas, devido a presença de gene mecA. A metodologia consistiu, em semear a urina no meio BP. Após o crescimento realizou-se provas bioquímicas para identificação de S. aureus (Gram, catalase e coagulase); após a confirmação, realizou-se o antibiograma com oxacilina 1µg, considerando resistentes halos menores que 13 mm, para confirmar o gene mecA, inoculou-se as colônias resistentes em meio MH, com oxacilina à 6µg/mL. Foi considerado positivo o crescimento microbiano. Com os resultados foi possível isolar 388 colônias, sendo 36 ,β-lactamases positiva, resistentes a oxacilina, ou seja, 9,27%, dessas 69,44% (26 colônias) foram identificadas como portadoras do gene mecA, a qual sugere a probabilidade de transferência horizontal de genes entre espécies distintas.