A contribuição das bombas de efluxo QacA e Smr para a multirresistência em Staphylococcus aureus

RESUMO: O efluxo de compostos antimicrobianos é um mecanismo importante na multirresistência em bactérias. Bombas de efluxo codificadas em plasmídeos, como a QacA e a Smr, estão implicadas na susceptibilidade reduzida a biocidas, geralmente utilizados na prevenção e controlo de infecções nosocomiais, incluindo as causadas por estirpes de Staphylococcus aureus resistentes à meticilina (MRSA). Neste trabalho pretendeu-se avaliar a relevância de QacA e Smr no perfil de susceptibilidade dos isolados clínicos MRSA SM39 e SM52, que transportam os plasmídeos pSM39 e pSM52 com os determinantes qacA e smr, respectivamente. A actividade de efluxo das estirpes SM39 e SM39 curada (sem pSM39) e das estirpes SM52 e RN4220:pSM52 (estirpe susceptível RN4220 transformada com pSM52) foi caracterizada por: (1) determinação da concentração mínima inibitória (CMI) de biocidas, corantes e antibióticos, na ausência e presença dos inibidores de efluxo tioridazina, clorpromazina, verapamil e reserpina; e (2) fluorometria em tempo-real. A determinação de CMIs demonstrou que a actividade de efluxo mediada por QacA e Smr está envolvida na susceptibilidade reduzida aos biocidas e corantes testados, que incluíram o brometo de hexadeciltrimetilamónio, a cetrimida, o cloreto de benzalcónio, a berberina, o cloreto de dequalínio, a pentamidina e o brometo de etídeo. Os ensaios fluorométricos confirmaram a elevada actividade de efluxo presente nas estirpes com os genes qacA ou smr. A determinação de CMIs para antibióticos β-lactâmicos em conjunto com o teste da nitrocefina revelou a presença simultânea do gene qacA e de uma β-lactamase no plasmídeo pSM39. Este trabalho evidencia a importância das bombas de efluxo QacA e Smr na resistência a biocidas em estirpes MRSA e na sobrevivência destas estirpes em ambiente hospitalar e na comunidade, para além de destacar a questão da potencial co-resistência entre biocidas e antibióticos.--------------- ABSTRACT: Drug efflux has become an important cause of multidrug resistance (MDR) in bacteria. Plasmid-encoded MDR efflux pumps, such as QacA and Smr, are implicated in reduced susceptibility to biocides, generally used in the prevention and control of nosocomial infections, including the ones caused by methicillin-resistant Staphylococcus aureus (MRSA). In this work, we aimed to evaluate the relevance of QacA and Smr to the susceptibility profile of the clinical MRSA isolates SM39 and SM52, which harbor the plasmids pSM39 and pSM52 that carry the determinants qacA and smr, respectively. Efflux activity of strain SM39 and its plasmid-free counterpart, SM39 cured, SM52 and RN4220:pSM52 (susceptible strain RN4220 transformed with pSM52) was characterized by: (1) determination of minimum inhibitory concentration (MIC) of biocides, dyes and antibiotics, in the absence and presence of the efflux inhibitors thioridazine, chlorpromazine, verapamil and reserpine; and (2) real-time fluorometry. MIC determination showed that QacA and Smr mediated efflux was involved in the reduced susceptibility profile to the biocides and dyes tested, which included hexadecyltrymethylammonium bromide, cetrimide, benzalkonium chloride, berberine, dequalinium chloride, pentamidine and ethidium bromide. Fluorometric assays confirmed the higher efflux activity present in strains harboring qacA or smr genes. Moreover, MIC determination for β-lactam antibiotics together with the nitrocefin test confirmed the presence of a β-lactamase in the plasmid carried by SM39 strain, pSM39. This work highlights the relevance of QacA and Smr to the biocide resistance in MRSA strains, and consequently to their survival and maintenance in the hospital environment and in the community. Furthermore, the presence of a β-lactamase and qacA determinants in the the same plasmid reinforces the question of the potencial biocide/antibiotic co-resistance in MRSA strains.

Ankylosing spondylitis: genomic and functional characterization of candidate genes and their repercussion in clinical practice

RESUMO: Introdução: A espondilite anquilosante (EA) é uma doença inflamatória crónica caracterizada pela inflamação das articulações sacroilíacas e da coluna. A anquilose progressiva motiva uma deterioração gradual da função física e da qualidade de vida. O diagnóstico e o tratamento precoces podem contribuir para um melhor prognóstico. Neste contexto, a identificação de biomarcadores, assume-se como sendo muito útil para a prática clínica e representa hoje um grande desafio para a comunidade científica. Objetivos: Este estudo teve como objetivos: 1 - caracterizar a EA em Portugal; 2 - investigar possíveis associações entre genes, MHC e não-MHC, com a suscetibilidade e as características fenotípicas da EA; 3 - identificar genes candidatos associados a EA através da tecnologia de microarray. Material e Métodos: Foram recrutados doentes com EA, de acordo com os critérios modificados de Nova Iorque, nas consultas de Reumatologia dos diferentes hospitais participantes. Colecionaram-se dados demográficos, clínicos e radiológicos e colhidas amostras de sangue periférico. Selecionaram-se de forma aleatória, doentes HLA-B27 positivos, os quais foram tipados em termos de HLA classe I e II por PCR-rSSOP. Os haplótipos HLA estendidos foram estimados pelo algoritmo Expectation Maximization com recurso ao software Arlequin v3.11. As variantes alélicas dos genes IL23R, ERAP1 e ANKH foram estudadas através de ensaios de discriminação alélica TaqMan. A análise de associação foi realizada utilizando testes da Cochrane-Armitage e de regressão linear, tal como implementado pelo PLINK, para variáveis qualitativas e quantitativas, respetivamente. O estudo de expressão génica foi realizado por Illumina HT-12 Whole-Genome Expression BeadChips. Os genes candidatos foram validados usando qPCR-based TaqMan Low Density Arrays (TLDAs). Resultados: Foram incluídos 369 doentes (62,3% do sexo masculino, com idade média de 45,4 ± 13,2 anos, duração média da doença de 11,4 ± 10,5 anos). No momento da avaliação, 49,9% tinham doença axial, 2,4% periférica, 40,9% mista e 7,1% entesopática. A uveíte anterior aguda (33,6%) foi a manifestação extra-articular mais comum. Foram positivos para o HLA-B27, 80,3% dos doentes. Os haplótipo A*02/B*27/Cw*02/DRB1*01/DQB1*05 parece conferir suscetibilidade para a EA, e o A*02/B*27/Cw*01/DRB1*08/DQB1*04 parece conferir proteção em termos de atividade, repercussão funcional e radiológica da doença. Três variantes (2 para IL23R e 1 para ERAP1) mostraram significativa associação com a doença, confirmando a associação destes genes com a EA na população Portuguesa. O mesmo não se verificou com as variantes estudadas do ANKH. Não se verificou associação entre as variantes génicas não-MHC e as manifestações clínicas da EA. Foi identificado um perfil de expressão génica para a EA, tendo sido validados catorze genes - alguns têm um papel bem documentado em termos de inflamação, outros no metabolismo da cartilagem e do osso. Conclusões: Foi estabelecido um perfil demográfico e clínico dos doentes com EA em Portugal. A identificação de variantes génicas e de um perfil de expressão contribuem para uma melhor compreensão da sua fisiopatologia e podem ser úteis para estabelecer modelos com relevância em termos de diagnóstico, prognóstico e orientação terapêutica dos doentes. -----------ABSTRACT: Background: Ankylosing Spondylitis (AS) is a chronic inflammatory disorder characterized by inflammation in the spine and sacroiliac joints leading to progressive joint ankylosis and in progressive deterioration of physical function and quality of life. An early diagnosis and early therapy may contribute to a better prognosis. The identification of biomarkers would be helpful and represents a great challenge for the scientific community. Objectives: The present study had the following aims: 1- to characterize the pattern of AS in Portuguese patients; 2- to investigate MHC and non-MHC gene associations with susceptibility and phenotypic features of AS and; 3- to identify candidate genes associated with AS by means of whole-genome microarray. Material and Methods: AS was defined in accordance to the modified New York criteria and AS cases were recruited from hospital outcares patient clinics. Demographic and clinical data were recorded and blood samples collected. A random group of HLA-B27 positive patients and controls were selected and typed for HLA class I and II by PCR-rSSOP. The extended HLA haplotypes were estimated by Expectation Maximization Algorithm using Arlequin v3.11 software. Genotyping of IL23R, ERAP1 and ANKH allelic variants was carried out with TaqMan allelic discrimination assays. Association analysis was performed using the Cochrane-Armitage and linear regression tests as implemented in PLINK, for dichotomous and quantitative variables, respectively. Gene expression profile was carried out using Illumina HT-12 Whole-Genome Expression BeadChips and candidate genes were validated using qPCR-based TaqMan Low Density Arrays (TLDAs). Results: A total of 369 patients (62.3% male; mean age 45.4±13.2 years; mean disease duration 11.4±10.5 years), were included. Regarding clinical disease pattern, at the time of assessment, 49.9% had axial disease, 2.4% peripheral disease, 40.9% mixed disease and 7.1% isolated enthesopathic disease. Acute anterior uveitis (33.6%) was the most common extra-articular manifestation. 80.3% of AS patients were HLA-B27 positive. The haplotype A*02/B*27/Cw*02/DRB1*01/DQB1*05 seems to confer susceptibility to AS, whereas A*02/B*27/Cw*01/DRB1*08/DQB1*04 seems to provide protection in terms of disease activity, functional and radiological repercussion. Three markers (two for IL23R and one for ERAP1) showed significant single-locus disease associations. Association of these genes with AS in the Portuguese population was confirmed, whereas ANKH markers studied did not show an association with AS. No association was seen between non-MHC genes and clinical manifestations of AS. A gene expression signature for AS was established; among the fourteen validated genes, a number of them have a well-documented inflammatory role or in modulation of cartilage and bone metabolism. Conclusions: A demographic and clinical profile of patients with AS in Portugal was established. Identification of genetic variants of target genes as well as gene expression signatures could provide a better understanding of AS pathophysiology and could be useful to establish models with relevance in terms of susceptibility, prognosis, and potential therapeutic guidance.

Electrochemical characterization of Dps, a DNA-protecting protein

Dissertação para obtenção do Grau de Mestre em Biotecnologia

Impacto da infiltração e afluência de águas pluviais na rede de saneamento

A existência de contribuições significativas de águas de infiltração e de águas pluviais nas redes de drenagem de águas residuais urbanas, motivaram a realização deste trabalho. Este estudo foi realizado no sistema de saneamento de Gondomar, utilizando os registos de caudais e qualidade das águas residuais em quatro estações de tratamento de águas residuais, durante quatro anos. O principal objectivo deste trabalho foi estimar as afluências de infiltração e precipitação ao sistema de saneamento e a identificação dos subsistemas críticos. Concluiu-se que a percentagem de volume excedente é cerca de 30% nos anos com maior ocorrência de precipitação. O propósito deste estudo foi também apresentar soluções para este problema, incluindo técnicas de inspecção e reparação dos elementos de drenagem, as quais foram definidas para os subsistemas identificados como críticos, Freixo e Rio Tinto. No Freixo mostrou-se importante a inspecção dos colectores, ramais e câmaras de visita, uma vez que o caudal afluente a este subsistema é muito superior ao esperado e a água residual apresenta-se diluída. Em Rio Tinto evidenciou-se como prioritária a detecção e eliminação de ligações abusivas, dado que são frequentes as ocorrências de exfiltração, com danos significativos. Para além das técnicas de detecção apresentadas considera-se que é necessário manter a monitorização de caudais e recipitação nos subsistemas, e se possível com registo contínuo ao longo do dia. Para a quantificação de precipitação é sugerida a utilização de três udómetros, de forma a permitir estabelecer com maior exactidão, a relação entre as contribuições pluviais e o caudal afluente. São apresentadas propostas, que incluem além de inspecções, ensaios e reparações, como um ponto de partida para a recolha de informação para actualização do adastro, com vista a uma futura aplicação da modelação matemática de previsão do comportamento destes subsistemas.

Evaluation of dengue NS1 antigen detection for diagnosis in public health laboratories, São Paulo State, 2009

The present work evaluated the diagnostic accuracy of detection of Dengue NS1 antigen employing two NS1 assays, an immunochromatographic assay and ELISA, in the diagnostic routine of Public Health laboratories. The results obtained with NS1 assay were compared with virus isolation and, in a subpopulation of cases, they were compared with the IgM-ELISA results obtained with convalescent samples. A total of 2,321 sera samples were analyzed by one of two NS1 techniques from March to October 2009. The samples were divided into five groups: groups I, II and III included samples tested by NS1 and virus isolation, and groups IV and V included patients with a first sample tested by NS1 and a second sample tested by IgM-ELISA. Sensitivity, specificity, positive and negative predictive values, Kappa Index and Kappa Concordance were calculated. The results showed that NS1 testing in groups I, II and III had high sensitivity (98.0%, 99.5% and 99.3%), and predictive values and Kappa index between 0.9 - 1.0. Groups IV and V only had Kappa Concordance calculated, since the samples were analyzed according to the presence of NS1 antigen or IgM antibody. Concordance of 92.1% was observed when comparing the results of NS1-negative samples with IgM-ELISA. Based on the findings, it is possible to suggest that the tests for NS1 detection may be important tools for monitoring the introduction and spread of Dengue serotypes.

First isolation of dengue 4 in the state of São Paulo, Brazil, 2011

We report the first isolation of Dengue virus 4 (DENV-4) in the state of São Paulo, from two patients - one living in São José do Rio Preto and the other one in Paulo de Faria, both cities located in the Northwest region of the state. The virus isolations were accomplished in the clone C6/36 Aedes albopictus cell line, followed by indirect immunofluorescence assays, performed with type-specific monoclonal antibodies that showed positive reactions for DENV-4. The results were confirmed by Nested RT-PCR and Real-Time RT-PCR assays. The introduction of DENV-4 in a country that already has to deal with the transmission of three other serotypes increases the possibility of the occurrence of more severe cases of the disease. The importance of early detection of dengue cases, before the virus spreads and major outbreaks occur, should be emphasized.

Rickettsia parkeri: a Rickettsial pathogen transmitted by ticks in endemic areas for spotted fever rickettsiosis in southern Uruguay

At first Rickettsia conorii was implicated as the causative agent of spotted fever in Uruguay diagnosed by serological assays. Later Rickettsia parkeri was detected in human-biting Amblyomma triste ticks using molecular tests. The natural vector of R. conorii, Rhipicephalus sanguineus, has not been studied for the presence of rickettsial organisms in Uruguay. To address this question, 180 R. sanguineus from dogs and 245 A. triste from vegetation (flagging) collected in three endemic localities were screened for spotted fever group (SFG) rickettsiosis in southern Uruguay. Tick extracted DNA pools were subjected to PCR using primers which amplify a fragment of the rickettsial gltA gene. Positive tick DNA pools with these primers were subjected to a second PCR round with primers targeting a fragment of the ompA gene, which is only present in SFG rickettsiae. No rickettsial DNA was detected in R. sanguineus. However, DNA pools of A. triste were found to be positive for a rickettsial organism in two of the three localities, with prevalences of 11.8% to 37.5% positive pools. DNA sequences generated from these PCR-positive ticks corresponded to R. parkeri. These findings, joint with the aggressiveness shown by A. triste towards humans, support previous data on the involvement of A. triste as vector of human infections caused by R. parkeri in Uruguay.

High prevalence of the simultaneous excretion of polyomaviruses JC and BK in the urine of HIV-infected patients without neurological symptoms in São Paulo, Brazil

OBJECTIVE: To evaluate the prevalence of the urinary excretion of BKV and JCV in HIV-infected patients without neurological symptoms. METHODS: Urine samples from HIV-infected patients without neurological symptoms were tested for JC virus and BK virus by PCR. Samples were screened for the presence of polyomavirus with sets of primers complementary to the early region of JCV and BKV genome (AgT). The presence of JC virus or BK virus were confirmed by two other PCR assays using sets of primers complementary to the VP1 gene of each virus. Analysis of the data was performed by the Kruskal-Wallis test for numerical data and Pearson or Yates for categorical variables. RESULTS: A total of 75 patients were included in the study. The overall prevalence of polyomavirus DNA urinary shedding was 67/75 (89.3%). Only BKV DNA was detected in 14/75 (18.7%) urine samples, and only JCV DNA was detected in 11/75 (14.7%) samples. Both BKV and JCV DNA were present in 42/75 (56.0%) samples. CONCLUSION: In this study we found high rates of excretion of JCV, BKV, and simultaneous excretion in HIV+ patients. Also these results differ from the others available on the literature.

Strategies of the African swine fever virus to manipulate innate immunity

Dissertation presented to obtain the Ph.D degree in Biology

PARASITOLOGICAL AND MOLECULAR DIAGNOSIS IN EXPERIMENTAL Strongyloides venezuelensis INFECTION

Strongyloides venezuelensis is a parasitic nematode of rats which is frequently used as a model to study human and animal strongyloidiasis. The aim of this study was to evaluate the correlation between parasitological and molecular diagnosis in Strongyloides venezuelensis infection. PCR assays were used to detect S. venezuelensis DNA in fecal samples obtained from experimentally infected Rattus norvegicus. The results showed a higher sensitivity of the PCR assay in detecting the infection compared to parasitological methods.

Evaluation of three different DNA extraction methods from blood samples collected in dried filter paper in Plasmodium subpatent infections from the Amazon region in Brazil

Asymptomatic Plasmodium infection is a new challenge for public health in the American region. The polymerase chain reaction (PCR) is the best method for diagnosing subpatent parasitemias. In endemic areas, blood collection is hampered by geographical distances and deficient transport and storage conditions of the samples. Because DNA extraction from blood collected on filter paper is an efficient method for molecular studies in high parasitemic individuals, we investigated whether the technique could be an alternative for Plasmodium diagnosis among asymptomatic and pauciparasitemic subjects. In this report we compared three different methods (Chelex®-saponin, methanol and TRIS-EDTA) of DNA extraction from blood collected on filter paper from asymptomatic Plasmodium-infected individuals. Polymerase chain reaction assays for detection of Plasmodium species showed the best results when the Chelex®-saponin method was used. Even though the sensitivity of detection was approximately 66% and 31% for P. falciparum and P. vivax, respectively, this method did not show the effectiveness in DNA extraction required for molecular diagnosis of Plasmodium. The development of better methods for extracting DNA from blood collected on filter paper is important for the diagnosis of subpatent malarial infections in remote areas and would contribute to establishing the epidemiology of this form of infection.

Produção de Biodiesel em reator de ultrassons

A contínua subida dos preços dos combustíveis fósseis tradicionais aliada à crescente pressão por parte de várias instituições mundiais para uma política “verde” no que diz respeito aos combustíveis, levam a um aumento da procura dos biocombustíveis e é neste contexto que surge o biodiesel como um dos principais intervenientes. O biodiesel pode ser definido como um derivado éster monoalquílico de ácidos gordos de cadeia longa proveniente de fontes renováveis como óleos vegetais ou gorduras animais e que apresenta características semelhantes ao diesel de petróleo, podendo ser utilizado sem qualquer problema em motores de ignição por compressão. Este trabalho apresenta como principal objetivo o estudo da aplicação da tecnologia de ultrassons na produção de biodiesel. Foi utilizado neste trabalho como matéria-prima um óleo doméstico usado. Este óleo foi previamente filtrado sendo depois analisado o seu índice de acidez para avaliar o seu teor em ácidos gordos livres. O valor obtido para o índice de acidez do óleo foi de 1,91 mg KOH/g, um valor relativamente baixo permitindo a sua utilização sem ser necessário um tratamento inicial via esterificação para diminuir a acidez do mesmo. Foram realizados três ensaios de reação independentes, o primeiro recorrendo ao método tradicional de produção de biodiesel através de transesterificação e recorrendo a agitação mecânica e aquecimento, o segundo utilizando uma sonda de ultrassons com a potência de 500 W e um terceiro ensaio de reação utilizando uma sonda de ultrassons de 2000 W. Em todas as reações foi utilizada uma proporção de 1:5 de óleo usado e metanol e 0,5 % (em relação á massa de óleo utilizada) de catalisador metilato de sódio. Todas as alíquotas recolhidas durante os ensaios foram analisadas através de cromatografia gasosa de modo a determinar o conteúdo em ésteres presente em cada uma delas. A reação convencional teve uma duração total de 150 minutos e decorreu a uma temperatura de 65ºC e a agitação constante de 500 rpm. Ao longo da reação foram retiradas alíquotas de cerca de 25 ml, que foram tratadas de imediato e posteriormente analisadas de modo a estudar-se o comportamento da reação ao longo do tempo. A percentagem de ésteres metílicos no biodiesel obtida ao fim de 90 minutos foi de 81,3%. Em seguida realizou-se uma reação utilizando uma sonda de ultrassons de 500 W de potência mergulhada num recipiente reacional devidamente isolado com uma rolha de cortiça de modo a minimizar as perdas de metanol por evaporação. O tempo total de reação foi de 90 minutos e foram-se retirando alíquotas de cerca de 25 ml para acompanhar o desenrolar da reação, tendo-se obtido uma percentagem de ésteres metílicos de 85,9% ao fim dos 90 minutos. Foi realizada por fim um terceiro ensaio de reação utilizando uma sonda de 2000 W com uma duração total de 90 minutos, tendo-se obtido resultados pouco satisfatórios (77,7%), provavelmente devido a algum problema operacional relacionado com a sonda de ultrassons utilizada ou devido a uma geometria do reator pouco eficiente. Os produtos resultantes da reação convencional e da reação utilizando a sonda de ultrassons de 500 W, assim como o óleo utilizado como matéria-prima foram caracterizados em termos de índice de acidez, densidade a 15ºC e viscosidade a 40ºC.

High-Content Analysis of Breast Cancer Using Single-Cell Deep Transfer Learning

High-content analysis has revolutionized cancer drug discovery by identifying substances that alter the phenotype of a cell, which prevents tumor growth and metastasis. The high-resolution biofluorescence images from assays allow precise quantitative measures enabling the distinction of small molecules of a host cell from a tumor. In this work, we are particularly interested in the application of deep neural networks (DNNs), a cutting-edge machine learning method, to the classification of compounds in chemical mechanisms of action (MOAs). Compound classification has been performed using image-based profiling methods sometimes combined with feature reduction methods such as principal component analysis or factor analysis. In this article, we map the input features of each cell to a particular MOA class without using any treatment-level profiles or feature reduction methods. To the best of our knowledge, this is the first application of DNN in this domain, leveraging single-cell information. Furthermore, we use deep transfer learning (DTL) to alleviate the intensive and computational demanding effort of searching the huge parameter's space of a DNN. Results show that using this approach, we obtain a 30% speedup and a 2% accuracy improvement.

SEROLOGICAL SURVEY OF Ehrlichia SPECIES IN DOGS, HORSES AND HUMANS: ZOONOTIC SCENERY IN A RURAL SETTLEMENT FROM SOUTHERN BRAZIL

SUMMARY The aims of this study were to determine the seroprevalence of Ehrlichia spp. and risk factors for exposure in a restricted population of dogs, horses, and humans highly exposed to tick bites in a Brazilian rural settlement using a commercial ELISA rapid test and two indirect immunofluorescent assays (IFA) with E. canis and E. chaffeensis crude antigens. Serum samples from 132 dogs, 16 horses and 100 humans were used. Fifty-six out of 132 (42.4%) dogs were seropositive for E. canis. Dogs > one year were more likely to be seropositive for E. canis than dogs ≤ one year (p = 0.0051). Ten/16 (62.5%) and 8/16 (50%) horses were seropositive by the commercial ELISA and IFA, respectively. Five out of 100 (5%) humans were seropositive for E. canis and E. chaffeensis. Rhipicephalus sanguineus (n = 291, 97.98%) on dogs and Amblyomma cajennense (n = 25, 96.15%) on horses were the most common ticks found. In conclusion, anti-Ehrlichia spp. antibodies were found in horses; however, the lack of a molecular characterization precludes any conclusion regarding the agent involved. Additionally, the higher seroprevalence of E. canis in dogs and the evidence of anti-Ehrlichia spp. antibodies in humans suggest that human cases of ehrlichiosis in Brazil might be caused by E. canis, or other closely related species.

APPLICATION OF 6-NITROCOUMARIN AS A SUBSTRATE FOR THE FLUORESCENT DETECTION OF NITROREDUCTASE ACTIVITY IN Sporothrix schenckii

Introduction Sporothrix schenckii is a thermal dimorphic pathogenic fungus causing a subcutaneous mycosis, sporotrichosis. Nitrocoumarin represents a fluorogenic substrate class where the microbial nitroreductase activity produces several derivatives, already used in several other enzyme assays. The objective of this study was the analysis of 6-nitrocoumarin (6-NC) as a substrate to study the nitroreductase activity in Sporothrix schenckii. Methods Thirty-five samples of S. schenckii were cultivated for seven, 14 and 21 days at 35 °C in a microculture containing 6-nitrocoumarin or 6-aminocoumarin (6-AC) dissolved in dimethyl sulfoxide or dimethyl sulfoxide as a negative control, for posterior examination under an epifluorescence microscope. The organic layer of the seven, 14 and 21-day cultures was analyzed by means of direct illumination with 365 nm UV light and by means of elution on G silica gel plate with hexane:ethyl acetate 1:4 unveiled with UV light. Results All of the strains showed the presence of 6-AC (yellow fluorescence) and 6-hydroxylaminocoumarin (blue fluorescence) in thin layer chromatography, which explains the green fluorescence observed in the fungus structure. Conclusion The nitroreductase activity is widely distributed in the S. schenckii complex and 6-NC is a fluorogenic substrate of easy access and applicability for the nitroreductase activity detection.