Mycelial inhibitory effects of antagonistic fungi, plant essential oils and propolis against five phytopathogenic Fusarium species

Fusarium spp. are considered as one of the most devastating plant pathogenic fungi worldwide. In this study, the effect of essential oil (EO) of Mentha longifolia, M. spicata, Achillea sp. and Foeniculum vulgare, ethanolic extract of Propolis (EEP), and Trichoderma harzianum T447 and T. hamatum T622 was investigated against five phytopathogenic Fusarium species. The results showed that the fungal species, the type of EO, and concentrations play a substantial role in inhibiting the mycelial growth of Fusarium spp. GC-MS analysis of the EOs showed that the piperitone oxide and cis-piperitone oxide were found as the main components of M. longifolia. Our results also revealed that EEP possessed the growth inhibitory effect against Fusarium spp. It was observed that the extracellular secretions of T. harzianum T447 showed very high inhibition against the fungi. Our results highlighted the need for further research to apply them as a safe alternative to the chemical pesticides.

Key Global Actions for Mycotoxin Management in Wheat and Other Small Grains

Mycotoxins in small grains are a significant and long-standing problem. These contaminants may be produced by members of several fungal genera, including Alternaria, Aspergillus, Fusarium, Claviceps, and Penicillium. Interventions that limit contamination can be made both pre-harvest and post-harvest. Many problems and strategies to control them and the toxins they produce are similar regardless of the location at which they are employed, while others are more common in some areas than in others. Increased knowledge of host-plant resistance, better agronomic methods, improved fungicide management, and better storage strategies all have application on a global basis. We summarize the major pre- and post-harvest control strategies currently in use. In the area of pre-harvest, these include resistant host lines, fungicides and their application guided by epidemiological models, and multiple cultural practices. In the area of post-harvest, drying, storage, cleaning and sorting, and some end-product processes were the most important at the global level. We also employed the Nominal Group discussion technique to identify and prioritize potential steps forward and to reduce problems associated with human and animal consumption of these grains. Identifying existing and potentially novel mechanisms to effectively manage mycotoxin problems in these grains is essential to ensure the safety of humans and domesticated animals that consume these grains.

Antifungal activity of TiO2/AgBr nanocomposites on some phytopathogenic fungi

TiO2/AgBr composites were synthesized by a simple ultrasonic strategy. Various instruments such as SEM, EDX, XRD, and FT-IR were exploited to investigate their characteristics. Antifungal activities of the as-obtained samples were assessed through the inactivation of Fusarium graminearum in the spore suspension method and mycelial growth inhibition of F. graminearum, Botrytis cinerea, and Sclerotinia sclerotiorum in the microdilution method. The results represented that the TiO2/AgBr samples possess higher antifungal activities on F. graminearum spores than the pure TiO2. The sample with 20 wt% silver bromide represented the highest inhibitory effect on the growth of F. graminearum so that all fungal spores were degraded in the initial times of the treatment process. The inactivation of fungal spores after 60 min was 35.2%, 97.8%, 98.9%, and 98.7%, in respect, for 5, 10, 20, and 30 weight percent of AgBr in the binary nanocomposites, while the inhibition rate was 13.4% for the pure TiO2. With increasing ultrasound irradiation time for more than 30 min, the inactivation rate constant decreased. It was also found that the antifungal activity of the nanocomposites without calcination was higher than those of the calcined materials. Considering the antifungal potential against phytopathogenic fungi and advantages such as simple synthesis and eco-friendly nature, it seems that TiO2/AgBr nanocomposites can be used instead of synthetic chemicals after additional field investigations and mass production.

Trichothecenes in Cereal Grains - An Update

Trichothecenes are sesquiterpenoid mycotoxins produced by fungi from the order Hypocreales, including members of the Fusarium genus that infect cereal grain crops. Different trichothecene-producing Fusarium species and strains have different trichothecene chemotypes belonging to the Type A and B class. These fungi cause a disease of small grain cereals, called Fusarium head blight, and their toxins contaminate host tissues. As potent inhibitors of eukaryotic protein synthesis, trichothecenes pose a health risk to human and animal consumers of infected cereal grains. In 2009, Foroud and Eudes published a review of trichothecenes in cereal grains for human consumption. As an update to this review, the work herein provides a comprehensive and multi-disciplinary review of the Fusarium trichothecenes covering topics in chemistry and biochemistry, pathogen biology, trichothecene toxicity, molecular mechanisms of resistance or detoxification, genetics of resistance and breeding strategies to reduce their contamination of wheat and barley.

Fusarium spp. in Loggerhead Sea Turtles (Caretta caretta): From Colonization to Infection

With the aim of evaluating the presence of Fusarium spp. in sea turtles with and without lesions and assessing the risk factors favoring colonization and/or infection, 74 loggerhead sea turtles (Caretta caretta) admitted to rescue and rehabilitation clinics in Italy were analyzed. The study compared 31 individuals with no apparent macroscopic lesions and 43 individuals with macroscopic lesions. Shell and skin samples were analyzed using Calcofluor white with 10% potassium hydroxide, standard histopathological examination, and fungal cultures. Fusarium spp. were isolated more frequently from animals with superficial lesions (39%) than from those with no macroscopic lesions (16%). Isolates from animals with superficial lesions were Fusarium solani species complex (FSSC) lineages haplotypes 9, 12, and 27 (unnamed lineages), FSSC-2 (Fusarium keratoplasticum), Fusarium oxysporum (27%), and Fusarium brachygibbosum (3%). In contrast, only F. solani haplotypes 9 and 12 were isolated from animals with no macroscopic lesions. The presence of lesions was identified as a risk factor for the occurrence of Fusarium spp. Of the 74 animals, only 7 (9.5%) scored positive on microscopic examination with Calcofluor, and histological examination of those 7 animals revealed necrosis, inflammatory cells, and fungal hyphae in the carapace and skin. The results of this study suggest that fusariosis should be included in the differential diagnosis of shell and skin lesions in sea turtles. Direct examination using Calcofluor and potassium hydroxide was not useful to diagnose the infection. Histopathological examination and fungal culture should be performed to ensure correct treatment and infection control.

Discriminating Healthy Wheat Grains from Grains Infected with Fusarium graminearum Using Texture Characteristics of Image-Processing Technique, Discriminant Analysis, and Support Vector Machine Methods

Among agricultural plants, wheat, with valuable foodstuffs such as proteins, vitamins, and minerals, provides about 25% of the world’s food calories. Hence, providing its health conditions and quality is of great importance. One of the most important wheat diseases that causes a lot of damages to this product is Fusarium head blight (FHB). In most areas, the causal agent of disease is Fusarium graminearum. This disease not only decreases product quality and efficiency but also has harmful effects on humans and animals by mycotoxin production. FHB discrimination requires experimental work in special conditions and also experts, but these facilities may not be available at customs and other related grain health testing centers. In this study, discriminating healthy wheat grains and the grains infected with F. graminearum was performed with an image-processing technique, an accurate, rapid, and nondestructive method. First, healthy and infected wheat grains were selected, and then digital images of samples were prepared in randomized mass method using cameras and lightening chamber. Then using the image-processing technique, a total of 21 texture characteristics were obtained for each grain. Discrimination and classification of healthy and infected grains were done with 100% accuracy using extracted texture characteristics and two techniques mentioned above. The results of this research could be helpful in the development of automatic devices for rapid discrimination of healthy grains and grains infected with F. graminearum, one of the most destructive wheat diseases.

Geographic distribution of phylogenetic species of the Fusarium graminearum species complex and their 8-ketotrichothecene chemotypes on wheat spikes in Iran

Isolates of the Fusarium graminearum species complex (FGSC, n = 446) were collected from wheat spikes from northern and western regions of Iran with a history of Fusarium head blight (FHB) occurrences. The trichothecene mycotoxin genotypes/chemotypes, the associated phylogenetic species, and geographical distribution of these isolates were analyzed. Two phylogenetic species, Fusarium asiaticum and F. graminearum, were identified and were found to belong to sequence characterized amplified region (SCAR) groups V and I. Isolates from F. asiaticum species lineage 6 were within SCAR group V, whereas F. graminearum species lineage 7 were of SCAR group I. Of the 446 isolates assayed, 274 were F. asiaticum species predominantly of the nivalenol (NIV) genotype, while other isolates were either deoxynivalenol (DON) plus 3-acetyldeoxynivalenol (3-AcDON) or DON plus 15-acetyldeoxynivalenol (15-AcDON) genotype. Based on Tri7 gene sequences, a new subpopulation of 15-AcDON producers was observed among F. asiaticum strains in which 11-bp repeats were absent in the Tri7 sequences. The trichothecene chemotype was confirmed and quantified by high-performance liquid chromatography (HPLC) in 46 FGSC isolates. Isolates produced NIV (33.4-108.2 μg/g) and DON (64.7-473.6 μg/g) plus either 3-AcDON (51.4-142.4 μg/g) or 15-AcDON (24.1-99.3 μg/g). Among FGSC isolates, F. asiaticum produced the highest levels of trichothecenes. Using BIOCLIM based on the climate data of 20-year during 1994-2014, modelling geographical distribution of FGSC showed that F. asiaticum was restricted to warmer and humid areas with a median value of mean annual temperature of about 17.5 °C and annual rainfall of 658 mm, respectively (P < 0.05). In contrast, F. graminearum (only 15-AcDON producers) was restricted to cooler and drier areas, with a median value of the mean annual temperature of 14.4 °C and an annual rainfall of 384 mm, respectively (P < 0.05). Based on climate parameters at anthesis, the recorded distribution of F. graminearum and F. asiaticum was similar to that based on BIOCLIM parameters. Therefore, geographic differences on the wheat-growing areas in Iran have had a significant effect on distribution of FGSC and their trichothecene chemotypes.

Multiplex Detection of Fusarium Species

Multiplex PCR is a powerful method to detect, identify, and quantify the mycotoxigenic fungus by targeting the amplification of genes associated with mycotoxin production and detection, identification, and quantification of Fusarium species. As compared with uniplex PCR, it has several advantages such as low cost, shortened time, and simultaneous amplification of more than two genes (in only one reaction tube). Here, we describe multiplex PCR-based detection and identification of trichothecene-, zearalenone-, fumonisin-, and enniatin-producing Fusarium species, the use of multiplex PCR in multiplex genotype assay and the use of multiplex TaqMan real-time qPCR.

In vitro resistance of clinical Fusarium species to amphotericin B and voriconazole using the EUCAST antifungal susceptibility method

Susceptibility testing using the EUCAST-AFST method against 39 clinical Fusarium strains consecutively collected from local and invasive infections during the last 10years assessed the in vitro activities of amphotericin B (AmB) and triazole antifungal agents. In addition, the susceptibility pattern of 12 reference strains from the CBS-KNAW Fungal Biodiversity Centre (CBS) was evaluated. In particular Fusarium petroliphilum and F. solani sensu lato were involved in disseminated infections and known for treatment failure. AmB displayed the lowest MICs followed by voriconazole VRC, posaconazole (POC). Itraconazole (ITC) showed high MIC values, displaying in vitro resistance. Clinical isolates were significantly (P <0.05) more resistant to AmB, VRC, and POC, than the CBS reference isolates probably due to previous exposure to antifungal therapy. Resistant profiles to AmB and VRC, which are the currently recommended agents in the guidelines for treatments, and a late diagnosis may be associated with high mortality rate in immunocompromised patients. The present antifungal susceptibility profiles showed that species- and strain-specific differences in antifungal susceptibility exist within Fusarium and that susceptibility testing is important and may improve the prognosis of these infections.

Phylogenetic diversity of human pathogenic Fusarium and emergence of uncommon virulent species

OBJECTIVES

Fusarium species cause a broad spectrum of infections. However, little is known about the etiological agents to the species level. We identified Fusarium species isolated from clinical specimens including those of high risk patients to better understand the species involved in the pathogenesis.

METHODS

A set of 44 Fusarium isolates were identified by two-locus sequence typing using partial sequences of the second largest subunit of RNA polymerase (RPB2) and translation elongation factor 1 alpha (TEF-1α).

RESULTS

The identified species belonged to four species complexes (SC); the most common SC was Fusarium solani (FSSC) (75%), followed by Fusarium oxysporum (FOSC) (4.5%), Fusarium fujikuroi (FFSC) (13.6%), and Fusarium dimerum (FDSC) (6.8%). Sites of infections were nails (n = 19, 43.2%), skin (n = 7, 15.9%), cornea (n = 6, 13.6%), blood (n = 3, 9%), wound (n = 4, 6.8%), burn (n = 2, 4.5%), tissue (n = 2, 4.5%), and urine (n = 1, 2.27%). Fusarium acutatum was rare and seem restricted to the Middle East. Comorbidities associated with invasive infections were hematological malignancy and autoimmune disorders.

CONCLUSIONS

Members of the FSSC predominantly caused cornea, nail and bloodstream infections. Less frequently encountered were the FOSC, FFSC and FDSC. More accurate molecular identification of Fusarium species is important to predict therapeutic outcome and the emergence of these species.

Spectrum of Fusarium infections in tropical dermatology evidenced by multilocus sequencing typing diagnostics

Fusarium species are emerging causative agents of superficial, cutaneous and systemic human infections. In a study of the prevalence and genetic diversity of 464 fungal isolates from a dermatological ward in Thailand, 44 strains (9.5%) proved to belong to the genus Fusarium. Species identification was based on sequencing a portion of translation elongation factor 1-alpha (tef1-α), rDNA internal transcribed spacer and RNA-dependent polymerase subunit II (rpb2). Our results revealed that 37 isolates (84%) belonged to the Fusarium solani species complex (FSSC), one strain matched with Fusarium oxysporum (FOSC) complex 33, while six others belonged to the Fusarium incarnatum-equiseti species complex. Within the FSSC two predominant clusters represented Fusarium falciforme and recently described F. keratoplasticum. No gender differences in susceptibility to Fusarium were noted, but infections on the right side of the body prevailed. Eighty-nine per cent of the Fusarium isolates were involved in onychomycosis, while the remaining ones caused paronychia or severe tinea pedis. Comparing literature data, superficial infections by FSSC appear to be prevalent in Asia and Latin America, whereas FOSC is more common in Europe. The available data suggest that Fusarium is a common opportunistic human pathogens in tropical areas and has significant genetic variation worldwide.

Biogeography of Fusarium graminearum species complex and chemotypes: a review

Differences in the geographic distribution of distinct trichothecene mycotoxins in wheat and barley were first recorded two decades ago. The different toxicological properties of deoxynivalenol (DON), nivalenol (NIV) and their acetylated derivatives require careful monitoring of the dynamics of these mycotoxins and their producers. The phylogenetic species concept has become a valuable tool to study the global occurrence of mycotoxin-producing Fusarium species. This has revolutionised our views on the terrestrial distribution of trichothecene-producing Fusaria in the context of agronomics, climatic conditions, and human interference by the global trade and exchange of agricultural commodities. This paper presents an overview of the dynamics of the different trichothecene-producing Fusarium species as well as their chemotypes and genotypes across different continents. Clearly not one global population exists, but separate ones can be distinguished, sometimes even sympatric in combination with different hosts. A population with more pathogenic strains and chemotypes can replace another. Several displacement events appear to find their origin in the inadvertent introduction of new genotypes into new regions: 3-acetyl-DON-producing F. graminearum in Canada; 3-acetyl-DON-producing F. asiaticum in Eastern China; 15-acetyl-DON F. graminearum in Uruguay; and NIV-producing F asiaticum in the southern United States.

Fatal disseminated infection with Fusarium petroliphilum

Members of the Fusarium solani species complex (FSSC) are causing the majority of the fusariosis in humans. Disseminated fusariosis has a high mortality and is predominantly observed in patients with leukemia. Here, we present the case of a fatal infection by a Fusarium strain with a degenerated phenotype, in a patient with acute lymphatic leukemia. Multiple nasal and skin biopsies as well as blood cultures yielded fungal growth, while in direct and histopathological examination of biopsy material septate hyphae were visible. Initial colonies were white with slimy masses with microconidia reminiscent of Fusarium/Acremonium, but with conidiospore production directly on the hyphae. Multi-locus sequence typing discerned a pionnotal-morphologically degenerated-colony of the recently recognized F. petroliphilum as etiological agent. The culture returned to a typical F. solani species complex morphology only after several weeks of growth in culture. Antifungal susceptibility tests indicate amphotericin B as best drug for this FSSC member rather than any of the azoles or echinocandins.

Molecular Quantification and Genetic Diversity of Toxigenic Fusarium Species in Northern Europe as Compared to Those in Southern Europe

Fusarium species produce important mycotoxins, such as deoxynivalenol (DON), nivalenol (NIV) and T-2/HT-2-toxins in cereals. The highest DON and T-2/HT-2 toxin levels in northern Europe have been found in oats. About 12%-24% of Finnish oat samples in 2012 contained >1.75 mg·kg-1 of DON, which belongs to type B trichothecenes. Fusarium graminearum is the most important DON producer in northern Europe and Asia and it has been displacing the closely related F. culmorum in northern Europe. The 3ADON chemotype of F. graminearum is dominant in most northern areas, while the 15ADON chemotype of F. graminearum is predominating in Central and southern Europe. We suggest that the northern population of F. graminearum may be more specialized to oats than the southern population. Only low levels of F. culmorum DNA were found in a few oat samples and no correlation was found between F. culmorum DNA and DON levels. DNA levels of F. graminearum were in all cases in agreement with DON levels in 2011 and 2012, when DON was measured by gas chromatography-mass spectrometry (GC-MS). When the RIDA®QUICK SCAN kit results (DON) were compared to DNA levels of F. graminearum, the variation was much higher. The homogenization of the oats flour by grinding oats with 1 mm sieve seems to be connected to this variation. There was a significant correlation between the combined T-2 and HT-2 and the combined DNA levels of F. langsethiae and F. sporotrichioides in Finland in 2010-2012.