Section Nigri Isolates Research Articles

Description and management of Aspergillus section Nigri causing post-harvest bulbs rot of onion

When onions are improperly stored, a post-harvest disease known as black mold of onion bulbs can result in considerable economic losses. Aspergillus section Nigri, one of many species, has been implicated in the development of black mold. In the present study, rot onion bulbs were collected from markets in Qena, Egypt. Thirteen Aspergillus section Nigri isolates were obtained and identified by morphological and molecular characterization. The ochratoxins potential of isolated A. section Nigri was tested, and three isolates were producers at the range of 1.5–15 ppm. For the presence of pks gene, no amplification product was detected. Using the fungal growth inhibition test, the isolates of A. niger were inhibited by eco-friendly materials Cement and Zeolite. Cement exhibited maximum percentage growth inhibition against the tested isolates at 74.7–86.7%. The pathogenicity activity of the A. niger isolates was tested by inoculation of healthy onion bulbs, other onion bulbs covered with Cement and Zeolite before inoculation by A. niger was used. The two treatments significantly reduced bulbs rot disease of onion than untreated bulbs. Seven and nine isolates showed 0% rot on covered bulbs by Cement and Zeolite, respectively as compared with inoculated onions, which exhibited rot ranging from 55 to 80%. Using eco-friendly materials with efficiency against post-harvest bulbs rot of onion was evaluated in this study.

Invasive Factors Recognition in Aspergillus Section Nigri Isolates from Patient and Environmental Samples in the Centre Region, Cameroon

Background: Aspergillus section Nigri species are invasive opportunistic pathogens, seen in individuals with various immune disorders. The invasive capacity involves the production of varieties of enzymes such as lipases, phospholipase, proteases and hyaluronidase. The determination of proteinase, phospholipase, esterase and biofilm production in patient and environmental isolates approve the pathogenic strength of the species.
 Aims: To evaluate the invasive capacity of Aspergillus section Nigri isolates from patients and environmental samples.
 Methods: Our study is cross sectional and experimental, performed at the outpatient clinic of the otorhinolaryngology department of Central and University teaching hospital during a period of 12 months from March 2018 to February 2019. To determine the invasive capacity of Aspergillus section Nigri species, 400 samples were evaluated in the study (that is; 250 from patients and 150 samples from environment). Patient samples and hospital environment samples were evaluated by standard phenotypic methods for detecting of Proteinase, phospolipase, esterase and biofilm. The variables were statistically analyzed using Chi-square test of independent and SPSS (Version 16.0).
 Results: The isolates recovered from the patient sample shows maximum invasive capacity as compared to the environmental isolates, that is for 44 isolates; 42 isolates showed proteinase activity and biofilm production, followed by phospholipase activity 36, and then esterase 32.The isolates recovered from the hospital environment also showed the production of the various invasive factors, that is for 16 isolates; 15 isolates showed biofilm production, followed by proteinase activity 6, phospholipase 5 and esterase 4.The disparities of the invasive capacity in patient and environment isolates virulence were statistically significant for proteinase, phospholipase and esterase ( that is; p-value <0.05). Majority the isolates recovered from patients and the environment were potential producers of biofilm.
 Conclusion: The isolates recovered from patients sample showed high invasive capacity as compare to the isolates recovered from the environment. This highlights the implications of phospholipase enzyme, proteinase enzyme, esterase enzyme and biofilm used by Aspergillus section Nigri isolates as means of survival in the host system.

Diversity and ochratoxin A-fumonisin profile of black Aspergilli isolated from grapes in China

Aspergillus spp. are a common contaminant of grapes and a major source of mycotoxins. China is the largest producer of grape in the world now, however, the toxigenicAspergillus population on grape in this country is still largely unknown. In this study, a total of 345 strains were isolated from grapes of 13 main grapevine producing regions in China. Based on calmodulin gene sequences, eight species withinAspergillus sectionNigri were identified. Among them,Aspergillus tubingensis (48.7%) was predominant, followed byAspergillus welwitschiae (20.6%) andAspergillus aculeatinus (11%). Average of contamination level was up to 64.19%, and we found the occurrence of sectionNigri species on the surface of fresh grapes was significantly influenced by the climate (P<0.05). The subtropical monsoon climate showed the highest fungal detection rate (72.45%), followed by the temperate monsoon climate (49.82%), and the lowest frequency was found in the temperate continental climate (37.23%). Regarding mycotoxin-producing capacity, 4.4% of the total tested sectionNigri isolates (137) were positive for ochratoxin A (OTA) production and 59.6% were fumonisin B2 (FB2) producers. Of those,Aspergillus carbonarius was the main OTA producer andA. welwitschiae andAspergillus niger were the main FB2 producers with different toxigenic ability. Our results highlight the potential risk of OTA and FB2 contamination byA. carbonarius andA. welwitschiae on grape in China, respectively; management strategies should be considered for preventing and reducing the toxigenicAspergillus and its mycotoxins.

Genotypic identification of ochratoxigenic Aspergilli that contaminated beef luncheon and their protease activity

Twenty-six fungal species belonging to 10 genera were collected from 40 beef luncheon samples marketed in the Qena city on Czapek–Dox agar at 28 °C. A. section Nigri and A. flavus were the most prevalent species among isolated fungi; they were contaminating 65% and 50% of the luncheon samples. According to the phylogenetic analysis using β-tubulin gene, the selected A. section Nigri was identified as A. niger and A. tubingensis. All selected isolates belonging to A. niger and A. tubingensis showed positive results for the presence of the PKS gene. Using VICAM fluorometer, the average level of ochratoxin A was found to range from 4.1 to 7.1 and 4.6 to 8.2 ppm for A. tubingensis and A. niger, respectively. All Aspergillus section Nigri isolates were protease producers except two isolates belonging to A. tubingensis. A significant difference was observed in protease production between A. tubingensis and A. niger (P = 0.005); the most active protease producers were AnL 12 and 19 (A. niger) and AtL 3 and 4 (A. tubingensis) were weak producers.

Species identification, antifungal susceptibility, and clinical feature association of Aspergillus section Nigri isolates from the lower respiratory tract.

Species of Aspergillus section Nigri are generally identified by molecular genetics approaches, whereas in clinical practice, they are classified as A. niger by their morphological characteristics. This study aimed to investigate whether the species of Aspergillus section Nigri isolated from the respiratory tract vary depending on clinical diagnosis. Forty-four Aspergillus section Nigri isolates isolated from the lower respiratory tracts of 43 patients were collected from February 2012 to January 2017 at the National Hospital Organization (NHO) Tokyo National Hospital. Species identification was carried out based on β-tubulin gene analysis. Drug susceptibility tests were performed according to the Clinical and Laboratory Standards Institute (CLSI) M38 3rd edition, and the clinical characteristics were retrospectively reviewed. A. welwitschiae was isolated most frequently, followed by A. tubingensis. More than half of the A. tubingensis isolates exhibited low susceptibility to azoles in contrast to only one A. welwitschiae isolate. Approximately three quarters of the patients from whom A. welwitschiae was isolated were diagnosed with colonization, whereas more than half the patients from whom A. tubingensis was isolated were diagnosed with chronic pulmonary aspergillosis (CPA). More attention needs to be given to the drug choice for patients with CPA with Aspergillus section Nigri infection because A. tubingensis, which was found to be frequently azole-resistant, was the most prevalent in these patients.

Species identification, antifungal susceptibility, and clinical feature association of Aspergillus section Nigri isolates from the lower respiratory tract.

Species of Aspergillus section Nigri are generally identified by molecular genetics approaches, whereas in clinical practice, they are classified as A. niger by their morphological characteristics. This study aimed to investigate whether the species of Aspergillus section Nigri isolated from the respiratory tract vary depending on clinical diagnosis. Forty-four Aspergillus section Nigri isolates isolated from the lower respiratory tracts of 43 patients were collected from February 2012 to January 2017 at the National Hospital Organization (NHO) Tokyo National Hospital. Species identification was carried out based on β-tubulin gene analysis. Drug susceptibility tests were performed according to the Clinical and Laboratory Standards Institute (CLSI) M38 3rd edition, and the clinical characteristics were retrospectively reviewed. A. welwitschiae was isolated most frequently, followed by A. tubingensis. More than half of the A. tubingensis isolates exhibited low susceptibility to azoles in contrast to only one A. welwitschiae isolate. Approximately three quarters of the patients from whom A. welwitschiae was isolated were diagnosed with colonization, whereas more than half the patients from whom A. tubingensis was isolated were diagnosed with chronic pulmonary aspergillosis (CPA). More attention needs to be given to the drug choice for patients with CPA with Aspergillus section Nigri infection because A. tubingensis, which was found to be frequently azole-resistant, was the most prevalent in these patients.

Diversity of Aspergillus section Nigri on the surface of Vitis labrusca and its hybrid grapes

This study investigated the presence of Aspergillus species belonging to Aspergillus section Nigri on Vitis labrusca and its hybrid grapes grown in Brazil. The ability of the fungi isolates to produce ochratoxin A (OTA) and fumonisin B2 (FB2) as well as the presence of these mycotoxins in the grapes were also studied. Eighty-eight samples were collected from the main grape producing states in Brazil: Rio Grande do Sul (n=30), Pernambuco (n=21), São Paulo (n=21) and Paraná (n=16). The highest average contamination level by A. section Nigri occurred on the grapes from Pernambuco (66.3%). A total of 2042 A. section Nigri isolates was analyzed and clustered in three groups according to morphology characterization: A. section Nigri uniseriate (79.3%), A. niger “aggregate” (18.3%) and A. carbonarius (2.4%). In order to precisely identify the Aspergillus species, two hundred and forty-eight strains were subjected to DNA sequencing. Among the A. section Nigri uniseriate group, the following species were found: A. japonicus, A. uvarum, A. brunneoviolaceus, A. aculeatus and A. labruscus. Within the A. niger “aggregate”, the following species were found: A.niger sensu stricto, A. welwitschiae and A. vadensis. Regarding mycotoxin-production capacity, 3.2% of the total A. section Nigri isolates (2042) were positive for OTA production and from A. niger “aggregate” (373) tested, 42.1% were FB2 producers. However, none of the 88 grape samples were contaminated with these mycotoxins.

Fumonisin-production by Aspergillus section Nigri isolates from Japanese Foods and Environments.

Fumonisins are well known as mycotoxins produced by various Fusarium species. Recently Aspergillus niger has been reported to be a fumonisin B2 (FB2) producer. Aspergillus niger is a member of Aspergillus section Nigri. Members of this section are common food contaminants and are also distributed widely in the environment. This study aimed to determine 1) optimum culture conditions of A. niger for fumonisin production including growth medium, temperature and incubation period and 2) fumonisin production among isolates of Aspergillus section Nigri and closely related species isolated from Japanese food and environmental samples. Growth on Czapek yeast extract broth +5% NaCl (CYBS) at 28°C for 7 days resulted in the highest levels of FB2 production as determined by quantitative LC-MS/MS of culture extracts. Sixty-two isolates were collected from various foods in domestic markets as well as from soil and air. The isolates principally separated into two groups; A. niger and A. luchuensis/A. piperis/A. tubingensis, following molecular phylogenetic analysis. ELISA using the tip culture method was shown to be suitable for screening of the fumonisin-producing strains. Phylogenic analysis of Aspergillus section Nigri isolates from food and environmental samples indicated that fumonisin producing strains could be grouped into the A. niger clade. Nineteen of 35 (54%) isolates classified as A. niger were FB2 producers. The current study suggests that FB2-producing A. niger are distributed throughout several regions of Japan.

English

Section Nigri is among the most important from the genus Aspergillus, since it possesses economical and biotechnological properties. Its identification is considered quite hard and complex. Due to this fact, Aspergillus taxonomy has been carried out by morphological, biochemical and molecular data. Morphological characterization besides molecular analyses was performed to properly identify Aspergillus section Nigri. A set of 42 Aspergillus section Nigri isolates were obtained from Brazilian Atlantic Rainforest. From these isolates, 16.7% originated from leaf litter layer and 83.3%, from soil. The isolates were divided into three different groups according to analyzed characteristics. 26 were identified as Aspergillus aculeatus, 12 as Aspergillus aculeatinus and 4 belonged to a group called “Aspergillus niger Aggregate”, considered as biseriate. Key words: Fungi, taxonomy, morphological identification, polymerase chain reaction (PCR), ITS.

Aislamiento de cepas de Aspergillus sección Nigri en la yerba mate comercializada en Posadas (Misiones, Argentina) y evaluación de su potencial ocratoxigénico

The objectives of the present work were to investigate the isolation frequency of genus Aspergillus in canchada yerba mate (YMCH) and elaborated yerba mate (YME) (Ilex paraguariensis) and the proportion of section Nigri isolates, as well as to determine ochratoxin A production by Aspergillus species section Nigri. Three hundred twenty eightAspergillus strains from 20 samples of YMCH and 1306 Aspergillus strains from 36 samples of YME were isolated; of the total, 279 from the first group of strains and 1215 from the latter group, belonged to section Nigri. For the detection of ochratoxin A production, the strains were cultivated on Czapeck yeast extract agar and the toxin was detected by thin layer chromatography under UV light. Uniserate species predominance was observed in the 1494 strains of Aspergillus section Nigri obtained (Aspergillus japonicus var. japonicus and Aspergillus japonicus var. aculeatus), whereas none of the strains analysed showed ochratoxin A production in vitro at the detection level of the methodology employed.

Transformation of zearalenone to zearalenone-sulfate by Aspergillus spp.

The primary goal of this research was to assess the biotransformation of zearalenone (ZEA), an oestrogenic mycotoxin, into ZEA-sulfate by some Aspergillus section Nigri isolates. A. niger isolates were shown to be able to convert ZEA after 72 h of incubation at different ZEA concentrations (5 to 150 µg/ml). The product formula corresponding to ZEA-sulfate was determined by accurate mass measurement. This conjugate was shown to be less oestrogenic than ZEA using a MCF-7 proliferation assay. This study demonstrated that A. niger has the ability to transform ZEA over a broad range of ZEA concentrations (5 to 150 µg/ml) and that sulfonation could lead to a less toxic compound. These results are significant as little is known about the ability of fungi, and especially A. niger, to detoxify ZEA by sulfonation. This study could lead to a way of detoxifying feed naturally contaminated with mycotoxins.

Occurrence of ochratoxin A producing fungi in wine and table grapes in Israel

A 3-year survey was conducted to assay the number of Aspergillus Section Nigri isolates and in vitro ochratoxin A (OTA) production capacity in 10 vineyards in Israel. The survey included field sampling of two wine cultivars, ‘Sauvignon Blanc’ and ‘Cabernet Sauvignon’ as well as the table grape cultivar ‘Superior’. A total of 2114 isolates were analyzed and of those 161 isolates were shown to produce OTA. The major finding was that Aspergillus carbonarius (336 tested strains) is the most consistent producer of OTA, with approximately 35% of the isolates identified as positive in vitro. In comparison, 3.1% of other isolates from the Aspergillus niger aggregate (of 1432 strains) produced OTA in vitro. In contrast, none of the 346 tested strains with a uniseriate head morphology produced OTA. The incidence of infected berries was very low before veraison, while at harvest, this frequency was twice as high. In general, the composition of black Aspergilli did not differ during berry development. Generally, more OTA-producing isolates were isolated from the surface of table grapes cv. ‘Superior’ compared to ‘Sauvignon Blanc’. None of the samples collected at harvest contained traces of OTA in the juice. This study shows that grapes in Israel are contaminated with ochratoxigenic species which represent a risk of OTA contamination.

Occurrence of Ochratoxigenic Fungi and Ochratoxin A in Green Coffee from Different Origins

Fungal infection and ochratoxin A (OTA) contamination were determined in green coffee samples from different origins, in which OTA-producing fungi were also identified. About 72% of the beans analysed by direct plating presented fungal infection, including species of Aspergillus, Penicillium and Rhizopus. The genus Aspergillus was presented in more than 90% of infected coffee beans. Aspergillus ochraceus and Aspergillus section Nigri isolates represented 2.8 and 65.4%, respectively from the total number of isolates from the coffee beans. The capacity to produce OTA was determined in 260 isolates of A. section Nigri and 19 of A. ochraceus by the agar plug method, giving positive results for 6% of the A. section Nigri isolates and 16% of the A. ochraceus. OTA production was analysed by high performance liquid chromatography. OTA contamination of green coffee beans was analysed by enzyme immunoassay. OTA levels in all samples analysed were above the limit of detection (0.6 mg/kg), with a mean OTA concentration of 6.7 mg/kg.