Toxigenic Species Research Articles

The prevalence of benthic dinoflagellates associated with ciguatera fish poisoning in the central Red Sea

This study confirms the presence of the toxigenic benthic dinoflagellates Gambierdiscus belizeanus and Ostreopsis spp. in the central Red Sea. To our knowledge, this is also the first report of these taxa in coastal waters of Saudi Arabia, indicating the potential occurrence of ciguatera fish poisoning (CFP) in that region. During field investigations carried out in 2012 and 2013, a total of 100 Turbinaria and Halimeda macroalgae samples were collected from coral reefs off the Saudi Arabian coast and examined for the presence of Gambierdiscus and Ostreopsis, two toxigenic dinoflagellate genera commonly observed in coral reef communities around the world. Both Gambierdiscus and Ostreopsis spp. were observed at low densities (<200 cells g−1 wet weight algae). Cell densities of Ostreopsis spp. were significantly higher than Gambierdiscus spp. at most of the sampling sites, and abundances of both genera were negatively correlated with seawater salinity. To assess the potential for ciguatoxicity in this region, several Gambierdiscus isolates were established in culture and examined for species identity and toxicity. All isolates were morphologically and molecularly identified as Gambierdiscus belizeanus. Toxicity analysis of two isolates using the mouse neuroblastoma cell-based assay for ciguatoxins (CTX) confirmed G. belizeanus as a CTX producer, with a maximum toxin content of 6.50±1.14×10−5pg P-CTX-1 eq. cell−1. Compared to Gambierdiscus isolates from other locations, these were low toxicity strains. The low Gambierdiscus densities observed along with their comparatively low toxin contents may explain why CFP is unidentified and unreported in this region. Nevertheless, the presence of these potentially toxigenic dinoflagellate species at multiple sites in the central Red Sea warrants future study on their possible effects on marine food webs and human health in this region.

Differentiation and identification of grape-associated black aspergilli using Fourier transform infrared (FT-IR) spectroscopic analysis of mycelia

The purpose of this study was to evaluate the potential of FT-IR spectroscopy as a high-throughput method for rapid differentiation among the ochratoxigenic species of Aspergillus carbonarius and the non-ochratoxigenic or low toxigenic species of Aspergillus niger aggregate, namely A. tubingensis and A. niger isolated previously from grapes of Greek vineyards. A total of 182 isolates of A. carbonarius, A. tubingensis, and A. niger were analyzed using FT-IR spectroscopy. The first derivative of specific spectral regions (3002–2801cm−1, 1773–1550cm−1, and 1286–952cm−1) were chosen and evaluated with respect to absorbance values. The average spectra of 130 fungal isolates were used for model calibration based on Discriminant analysis and the remaining 52 spectra were used for external model validation. This methodology was able to differentiate correctly 98.8% in total accuracy in both model calibration and validation. The per class accuracy for A. carbonarius was 95.3% and 100% for model calibration and validation, respectively, whereas for A. niger aggregate the per class accuracy amounted to 100% in both cases. The obtained results indicated that FT-IR could become a promising, fast, reliable and low-cost tool for the discrimination and differentiation of closely related fungal species.

Occurrence of Filamentous Fungi in Human Milk, Infant Formula and Milk-Based Products for Young Children Nutrition

The safety of foods (human milk-HM; infant formula-IF; milk-based products-MBPs) aimed for children nutrition (from birth to 5 years old) through filamentous fungi & yeasts were investigated (n = 158). Their analysis followed the ISO 6611: 2004 recommended for total load (isolation & enumeration) in milk and dairy products. The occurrence of filamentous fungi & yeasts was observed in 29, 51 and 60% of the HM (n = 98), IF (n = 45) and MBP (n = 15) samples surveyed. Fungi isolated present counts above 102 CFU/g and yeasts higher (> 104CFU/g). Aspergillus, Penicillium and Thichoderma genera were identified in all the three sample types at percentages of 100/13/9%, 78/11/22% and 32/39/25% for IF, MBP and HM samples, respectively, being Aspergillus the most isolated, especially in the IF samples. Despite deterioration that can cause, the presence of filamentous fungi in HM and other infant foods, can enable mycotoxins production as long as toxigenic species are present which are hazardous for babies.

Mycobiota of Slovak wine grapes with emphasis on aspergillus and penicillium species in the south Slovak wine region

The Southern Slovak wine growing region is warmest part of Slovakia and is suitable for cultivating the grapes for production of wines at high quality. From the eight vineyards were collected 8 samples of wine grapes (white 7, blue 1) during harvesting 2011, 2012 and 2013. The aim of this work was to gain more knowledge about mycobiota on grapes originating from Slovakia, to identify Aspergillus and Penicillium species according to their morphopogy and evaluate the presence of secondary metabolites (also including intracellular and extracellular mycotoxins) produced in in vitro conditions by thin layer chromatography method from fresh grape berries. Fifty wine grapes per bunch (approximately 7 - 8 berries per plate) that showed no symptoms were randomly selected on Dichloran Rose Bengal Chloramphenicol agar medium. The plates were then incubated aerobically at 25 ±1 °C for 5 to 7 days in the dark. Of these samples were identified 17 genera. One hundred percent of samples were colonies by the genus Penicillium and 75% by the genus Aspergillus. During the survey, 135 isolates belonging to 9 Penicillium species (P. aurantiogriseum, P. canescens, P. citrinum, P. crustosum, P. decumbens, P. expansum, P. funiculosum, P. chrysogenum and P. purpurogenum) and 26 isolates belonging to 3 Aspergillus species (A. clavatus, A. flavus and A. section Nigri) were isolated and identified from exogenous contamination. The main occurring penicillium species of the samples were P. expansum (37.5% Fr), followed P. citrinum, P. chrysogenum and P. crustosum (25% Fr). The main occurring aspergillus species of the samples were A. section Nigri (62.5%). Eight potentially toxigenic species were tested for their toxigenic ability. It was confirmed the production of various mycotoxins such as aflatoxin B1, citrinin, patulin, cyclopiazonic acid, penitrem A and roquefortin C. Out of 34 strains, 56% produced at least one mycotoxin.

Pseudo-nitzschia simulans sp. nov. (Bacillariophyceae), the first domoic acid producer from Chinese waters

The genus Pseudo-nitzschia has attracted attention because of production of the toxin, domoic acid (DA), causing Amnesic Shellfish Poisoning (ASP). Pseudo-nitzschia blooms occur frequently in Chinese coastal waters, and DA has been detected in several marine organisms, but so far no Pseudo-nitzschia strains from Chinese waters have been shown to produce DA. In this study, monoclonal Pseudo-nitzschia strains were established from Chinese coastal waters and examined using light microscopy, electron microscopy and molecular markers. Five strains, sharing distinct morphological and molecular features differentiating them from other Pseudo-nitzschia species, represent a new species, Pseudo-nitzschia simulans sp. nov. Morphologically, the taxon belongs to the P. pseudodelicatissima group, cells possessing a central nodule and each stria comprising one row of poroids. The new species is characterized by the poroid structure, which typically comprises two sectors, each sector located near opposite margins of the poroid. The production of DA was examined by liquid chromatography tandem mass spectrometry (LC–MS/MS) analyses of cells in stationary growth phase. Domoic acid was detected in one of the five strains, with concentrations around 1.05–1.54 fg cell−1. This is the first toxigenic diatom species reported from Chinese waters.

Causality of an extreme harmful algal bloom in Monterey Bay, California, during the 2014–2016 northeast Pacific warm anomaly

AbstractAn ecologically and economically disruptive harmful algal bloom (HAB) affected much of the northeast Pacific margin in 2015, during a prolonged oceanic warm anomaly. Caused by diatoms of the genus Pseudo‐nitzschia, this HAB produced the highest particulate concentrations of the biotoxin domoic acid (DA) ever recorded in Monterey Bay, California. Bloom inception followed strong upwelling during the spring transition, which introduced nutrients and eliminated the warm anomaly locally. Subsequently, moderate and intermittent upwelling created favorable conditions for growth and accumulation of HAB biomass, which was dominated by a highly toxigenic species, P. australis. High cellular DA concentrations were associated with available nitrogen for DA synthesis coincident with silicate exhaustion. This nutrient influence resulted from two factors: (1) disproportionate depletion of silicate in upwelling source waters during the warm anomaly, the most severe depletion observed in 24 years, and (2) silicate uptake by the dense diatom bloom.

Fungal contamination in green coffee beans samples: A public health concern

ABSTRACTStudies on the microbiology of coffee cherries and beans have shown that the predominant toxigenic fungal genera (Aspergillus and Penicillium) are natural coffee contaminants. The aim of this study was to investigate the distribution of fungi in Coffea arabica L. (Arabica coffee) and Coffea canephora L. var. robusta (Robusta coffee) green coffee samples obtained from different sources at the pre-roasting stage. Twenty-eight green coffee samples from different countries of origin (Brazil, Timor, Honduras, Angola, Vietnam, Costa Rica, Colombia, Guatemala, Nicaragua, India, and Uganda) were evaluated. The fungal load in the contaminated samples ranged from 0 to 12330 colony forming units (CFU)/g, of which approximately 67% presented contamination levels below 1500 CFU/g, while 11% exhibited intermediate contamination levels between 1500 and 3000 CFU/g. Contamination levels higher than 3000 CFU/g were found in 22% of contaminated coffee samples. Fifteen different fungi were isolated by culture-based methods and Aspergillus species belonging to different sections (complexes). The predominant Aspergillus section detected was Nigri (39%), followed by Aspergillus section Circumdati (29%). Molecular analysis detected the presence of Aspergillus sections Fumigati and Circumdati. The% coffee samples where Aspergillus species were identified by culture-based methods were 96%. Data demonstrated that green coffee beans samples were contaminated with toxigenic fungal species. Since mycotoxins may be resistant to the roasting process, this suggests possible exposure to mycotoxins through consumption of coffee. Further studies need to be conducted to provide information on critical points of coffee processing, such that fungal contamination may be reduced or eliminated and thus exposure to fungi and mycotoxins through coffee handling and consumption be prevented.

Gene expression as a good indicator of aflatoxin contamination in dry-cured ham

Aspergillus flavus and Aspergillus parasiticus are mould species producers of aflatoxins (AFs) and may grow on dry-cured ham during the ripening process. In this study, the influence of different water activity (aw) and temperatures on the temporal relative expression of three genes involved in AFs biosynthesis and their relationship with AFs production on dry-cured ham-based medium were evaluated. In general, the regulatory aflR and aflS genes showed similar expression patterns, and the expression of the structural aflP gene was much higher than that obtained for aflR and aflS genes. Regarding A. flavus, a decrease of aw regardless of temperature caused an increase of the expression of the regulatory aflR and aflS genes. Concerning A. parasiticus, the highest and lowest expression values of the regulatory aflR and aflS genes were found at 0.95 aw and 0.85 aw, respectively. The expression of the structural aflP gene of both species was stimulated at low temperature and aw. The PCA analysis indicated that both toxigenic species showed a strong correlation between the relative expression of the aflR and aflS genes and the concentration of AFs under conditions which simulate dry-cured ham ripening. This suggests that an early detection of the expression of regulatory genes can be a good indicator of possible AFs contamination of dry-cured ham through ripening.

Rathayibacter toxicus, Other Rathayibacter Species Inducing Bacterial Head Blight of Grasses, and the Potential for Livestock Poisonings.

Rathayibacter toxicus, a Select Agent in the United States, is one of six recognized species in the genus Rathayibacter and the best known due to its association with annual ryegrass toxicity, which occurs only in parts of Australia. The Rathayibacter species are unusual among phytopathogenic bacteria in that they are transmitted by anguinid seed gall nematodes and produce extracellular polysaccharides in infected plants resulting in bacteriosis diseases with common names such as yellow slime and bacterial head blight. R. toxicus is distinguished from the other species by producing corynetoxins in infected plants; toxin production is associated with infection by a bacteriophage. These toxins cause grazing animals feeding on infected plants to develop convulsions and abnormal gate, which is referred to as "staggers," and often results in death of affected animals. R. toxicus is the only recognized Rathayibacter species to produce toxin, although reports of livestock deaths in the United States suggest a closely related toxigenic species may be present. A closely related but undescribed species, Rathayibacter sp. EV, originally isolated from Ehrharta villosa var. villosa in South Africa, is suspected of producing toxin. Many of the diseases caused by Rathayibacter species occur in arid areas and the extracellular polysaccharide they produce is believed to aid in their survival between crops. For example, R. "agropyri" was isolated from infected plant material after being stored for 50 years in a herbarium. Similarly, the anguinid vectors associated with these bacteria form seed galls in infected plants and are capable of surviving for very long periods of time under dry conditions. The addition of R. toxicus to the list of Select Agents has raised concern over its potential introduction and a realization that current diagnostic methods are inadequate to distinguish among Rathayibacter species. In addition, little is known about the Rathayibacter species and their seed gall nematode vectors present in the United States.

Cyanobacterial dynamics and toxins concentrations in Lake Alto Flumendosa, Sardinia, Italy

Seasonal blooms of cyanobacteria (CB) are a typical feature of Lake Alto Flumendosa (Sardinia, Italy). The waters of this lake are used for drinking water supply, for agricultural and industrial uses, and fish farming activities. Since cyanotoxins are not monitored in edible organisms, diet could be a relevant route of human exposure. CB also represent a threat for the health of wild and domestic animals that use lake water for beverage. Therefore, to characterize the CB community and assess the risk for human and animal population, CB dynamic, mcyB+ fraction, and microcystins (MCs) concentration have been followed monthly for 18 months, in three stations. Results confirmed the presence of several toxigenic species. Planktothrix rubescens dominated between August 2011 and April 2012 (3.5×106 cells L-1), alternating with Woronichinia naegeliana (8×106 cells L-1) and Microcystis botrys (9×105 cells L-1). Dolichospermum planctonicum was always present at low densities (104 cells L-1). MCs were detected, at values well below the 1 µg L-1 threshold of WHO for drinking water. The molecular analysis of mcyB gene for P. rubescens indicated the presence of a persistent toxic population (average 0.45 mcyB/16S rDNA). Highly significant linear regressions were found between P. rubescens and the sum of the demethylated MC variants, and between M. botrys and the sum of MC-LR and MC-LA, also when co-occurring, suggesting that these two species were responsible for different MC patterns production. The regression lines indicated a quite stable MC cell quota. However, in some spotted samples very different values were obtained for both MC concentrations and cell quota (from 10-fold lower to 30-40-fold higher than the ‘average’) showing an unexpected significant variability in the rate of toxin production. The relatively low cell densities during the monitoring period is consistent with the low-to absent MC contamination level found in trout muscle; however, the analytical method was affected by low recovery, probably due to MC-protein binding. Our results show that, during the study period, no risk of exposure for the human and animal population occurred. However, the persistence of a complex CB community characterised by a significant toxic fraction suggests the need for periodic monitoring activity. Particularly, the hidden deep summer P. rubescens blooms, located where water is taken for drinking water supply, and M. botrys, able to produce the most toxic MC variants with high cell quota, should be kept under control. The documentation and interpretation of sudden changes in toxins concentrations deserve special attention. This is particularly relevant in proximity of fish farming plants and water catchment sites.

Inter and intra-specific growth and domoic acid production in relation to nutrient ratios and concentrations in Pseudo-nitzschia: phosphate an important factor

The factors responsible for inducing the synthesis of toxins and responses from toxic phytoplankton blooms remain unclear. In this study we compare the influence of genotypic (at both the intra and interspecific levels) and environmental factors (nutrient concentration and ratio) on growth (in terms of cell densities) and domoic acid (DA) production in three Pseudo-nitzschia species: P. australis, P.pungens and P.fradulenta. A strong phosphate effect was detected. More precisely, a low initial concentration in phosphate, even at high initial nitrogen and silicate concentrations, induced the highest DA concentrations and the lowest cell densities in all strains/species studied. In contrast, a low initial concentration of nitrogen and silicate combined, with a higher phosphate concentration resulted in low cell densities, but without high DA production. Inter-species effects were also observed in DA production, where P. australis represented the most toxigenic species of all. Intra-specific variations were only moderate, except for a recently isolated P. australis strain, suggesting the influence of time since isolation on the physiology and DA production of Pseudo-nitzschia species. Overall, the lack of strong interaction between environmental and genotypic factors showed that the various genotypes investigated did not extensively diverge in their ability to respond (in terms of DA production and cell densities) to contrasting nutrient supply.

Microbial detoxification of eleven food and feed contaminating trichothecene mycotoxins

BackgroundContamination of agricultural commodities with multiple trichothecene mycotoxins, produced by toxigenic Fusarium species, is a food safety issue, which greatly affects grain production and marketing worldwide. Importantly, exposure to multiple trichothecenes may increase toxicity in animals due to their synergistic and/or additive effects. To address the problem this study aimed to achieve a novel biological trait capable of detoxifying various food and feed contaminating trichothecenes under aerobic and anaerobic conditions and wide range of temperatures.ResultsA highly enriched microbial consortium (called DX100) capable of transforming eleven trichothecenes to significantly less toxic de-epoxy forms was achieved after prolonged incubation of soil microbial culture with 200 μg/mL deoxynivalenol (DON). DX100 demonstrated de-epoxidation activity under aerobic and anaerobic conditions, a greater range of temperatures and around neutral pH. The consortium contains 70% known and 30% unknown bacterial species, dominated by Stenotrophomonas species. Probably novel bacteria including strains of Stenotrophomonas and Alkaliphilus-Blautia species complex could be involved in aerobic and anaerobic de-epoxidation of trichothecenes, respectively. DX100 showed rapid and stable activity by de-epoxidizing 100% of 50 μg/mL deoxynivalenol at 48 h of incubation and retaining de-epoxidation ability after 100 subcultures in mineral salts broth (MSB). It was able to de-epoxidize high concentration of DON (500 μg/mL), and transformed ten more food contaminating trichothecenes into de-epoxy forms and/or other known/unknown compounds. Microbial de-epoxidation rate increased with increasing trichothecene concentrations in the broth media, suggesting that DX100 maintains a robust trichothecene detoxifying mechanism. Furthermore, the nature of microbial de-epoxidation reaction and inhibition of the reaction by sodium azide and the finding that bacterial cell culture lysate retained activity suggests that certain cytoplasmic reductases may be responsible for the de-epoxidation activity.ConclusionsThis study reports the enrichment procedure for obtaining an effective and stable microbial consortium DX100 capable of de-epoxidizing several food contaminating trichothecene mycotoxins. DX100, which has de-epoxidation ability under wide range of conditions, represents a unique enzymatic source which has great industrial potential for reducing contamination of foods/feeds with multiple trichothecenes, and minimizing their synergistic/additive cytotoxic effects on consumer health.

Electrochemical identification of toxigenic fungal species using solid-state voltammetry strategies

An electrochemical methodology for the characterization of mycotoxin-producing fungal species from the genera Aspergillus and Fusarium using solid-state voltammetry is described. Upon attachment of fungal colony microsamples to glassy carbon electrodes in contact with aqueous acetate buffer, characteristic voltammetric signals mainly associated to the oxidation of polyphenolic metabolites are recorded. The possibility of fungi-localized electrochemical processes was assessed by means of electron microscopy and field emission scanning electrochemical microscopy coupled to the application of oxidative potential inputs. Using pattern recognition methods, the determined voltammetric profiles were able to discriminate between mycotoxin-producing fungi from different sections and to identify selected toxigenic species of the Aspergillus and Fusarium genera isolated from grapes and cereals.

Prevalence of mycotoxins in foods and decontamination

Toxigenic fungi can colonize crops and may accumulate bioactive substances in the infected products. These compounds, called mycotoxins, occur widely in nature and pose a great risk to human and animal health. The most relevant toxigenic fungal species belong to the genera Aspergillus , Penicillium , Alternaria and Fusarium . Mycotoxins are produced naturally in many agricultural crops. They can accumulate in food commodities in the field, after harvest, and during storage. Most of the important mycotoxins are resistant to most forms of food and feed processing. Several efforts are made to reduce mycotoxins in raw materials and processed food, both in pre-harvest stages inhibiting production of the toxins in the field, and in post-harvest by remediation strategies, reducing mycotoxin concentration in commodities.

Characterization of Gambierdiscus lapillus sp. nov. (Gonyaulacales, Dinophyceae): a new toxic dinoflagellate from the Great Barrier Reef (Australia).

Gambierdiscus is a genus of benthic dinoflagellates found worldwide. Some species produce neurotoxins (maitotoxins and ciguatoxins) that bioaccumulate and cause ciguatera fish poisoning (CFP), a potentially fatal food-borne illness that is common worldwide in tropical regions. The investigation of toxigenic species of Gambierdiscus in CFP endemic regions in Australia is necessary as a first step to determine which species of Gambierdiscus are related to CFP cases occurring in this region. In this study, we characterized five strains of Gambierdiscus collected from Heron Island, Australia, a region in which ciguatera is endemic. Clonal cultures were assessed using (i) light microscopy; (ii) scanning electron microscopy; (iii) DNA sequencing based on the nuclear encoded ribosomal 18S and D8-D10 28S regions; (iv) toxicity via mouse bioassay; and (v) toxin profile as determined by Liquid Chromatography-Mass Spectrometry. Both the morphological and phylogenetic data indicated that these strains represent a new species of Gambierdiscus, G.lapillus sp. nov. (plate formula Po, 3', 0a, 7″, 6c, 7-8s, 5‴, 0p, 2″″ and distinctive by size and hatchet-shaped 2' plate). Culture extracts were found to be toxic using the mouse bioassay. Using chemical analysis, it was determined that they did not contain maitotoxin (MTX1) or known algal-derived ciguatoxin analogs (CTX3B, 3C, CTX4A, 4B), but that they contained putative MTX3, and likely other unknown compounds.

Plankton resting stages in recent sediments of Haifa port, Israel (Eastern Mediterranean) - Distribution, viability and potential environmental consequences

Resting stages of plankton were sampled in the surficial sediments in the port of Haifa, Israel, on the eve of a major port enlargement project. We recorded the structure of the assemblages and examined their relationship with different environments within the port. Our findings reveal a remarkably high diversity coupled with low density and the highest number of oligotrich ciliate cyst types recorded from marine sediments. Near the eutrophic and highly polluted zone of the Kishon estuary ciliates were more abundant than elsewhere in the port, whereas dinoflagellates' abundance was reduced, and these trends held true both for full and empty cysts. Some harmful or potentially toxic species, such as Scrippsiella acuminata, were widespread in the port. The toxigenic species include Alexandrium minutum, Gymnodinium uncatenatum and Lingulodinium polyedrum. Active cells of the unarmoured, bloom-forming Akashiwo sanguinea were identified in the cultures obtained from the incubated sediments.

Suppressive Effect of Trichoderma spp. on toxigenic Fusarium species.

The aim of the present study was to examine the abilities of twenty-four isolates belonging to ten different Trichoderma species (i.e., Trichoderma atroviride, Trichoderma citrinoviride, Trichoderma cremeum, Trichoderma hamatum, Trichoderma harzianum, Trichoderma koningiopsis, Trichoderma longibrachiatum, Trichoderma longipile, Trichoderma viride and Trichoderma viridescens) to inhibit the mycelial growth and mycotoxin production by five Fusarium strains (i.e., Fusarium avenaceum, Fusarium cerealis, Fusarium culmorum, Fusarium graminearum and Fusarium temperatum). Dual-culture bioassay on potato dextrose agar (PDA) medium clearly documented that all of the Trichoderma strains used in the study were capable of influencing the mycelial growth of at least four of all five Fusarium species on the fourth day after co-inoculation, when there was the first apparent physical contact between antagonist and pathogen. The qualitative evaluation of the interaction between the colonies after 14 days of co-culturing on PDA medium showed that ten Trichoderma strains completely overgrew and sporulated on the colony at least one of the tested Fusarium species. Whereas, the microscopic assay provided evidence that only T. atroviride AN240 and T. viride AN255 formed dense coils around the hyphae of the pathogen from where penetration took place. Of all screened Trichoderma strains, T. atroviride AN240 was also found to be the most efficient (69-100% toxin reduction) suppressors of mycotoxins (deoxynivalenol, 3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol, nivalenol, zearalenone, beauvericin, moniliformin) production by all five Fusarium species on solid substrates. This research suggests that T. atroviride AN240 can be a promising candidate for the biological control of toxigenic Fusarium species.

Screening of Bacterial and Fungal Biota Associated with Oreochromis niloticus in Lake Manzala and Its Impact on Human Health

In this study fish samples were investigated for Bacteria and Fungi, in fish parts, such as intestine, gills and skin. Bacterial counts of Total viable bacteria (T.V.B) reached more than 9.5 × 105 cfu and faecal coliforms (F.C) reached 1.2 × 105 cfu. Different species were identified, Using API technology. Escherichia coli comes first by being recording thirty number case of isolation constituting 36%, it followed by Proteus mirabilis which is represented by twenty four number case of isolation accounting for 30%. Other taxa viz: Klebsiella pneumonia, Citrobacter freundii, Providencia stuartii and Erwinia sp. came next according to their case number of isolation, they represented only by 7%. They showed different antibiotics with different inhibitory concentrations, resistance pattern to gentamycin 10 μg, Penicillin G, tetracycline 30 μg, Ampicillin 10 μg, Ampicillin 30 μg, chloramphenicol (C) 30 μg, Rifampicin 25 μg, Streptomycin 5 μg, cefotaxime 15 μg. Mycological investigation revealed the presence of variety of fungal species, particularly, toxigenic species, such as, Aspergillus spp, Penicillium spp and Fusarium spp. These results are indication of the spoilage of fishes which caught from Lake Manzala and are risky for human consumption and hazardous to human health in this important area of Egypt, due to the high pollution condition of Lake Manzala.

Screening and Identification of Yeasts Antagonistic to Pathogenic Fungi Show a Narrow Optimal pH Range for Antagonistic Activity.

Microbes have evolved ways of interference competition to gain advantage over their ecological competitors. The use of secreted antagonistic compounds by yeast cells is one of the prominent examples. Although this killer behavior has been thoroughly studied in laboratory yeast strains, our knowledge of the antagonistic specificity of killer effects in nature remains limited. In this study, yeast strains were collected from various niches and screened for antagonistic activity against one toxin-sensitive strain of Saccharomyces cerevisiae and three pathogenic fungi. We demonstrate that some strains with antagonistic activity against these pathogenic fungi can be found in antagonist culture tests. These yeasts were identified as members of Trichosporon asahii, Candida stellimalicola, Wickerhamomyces anomalus, Ustilago esculenta, Aureobasidium pullulans, and Pichia kluyveri. The results indicated that the antagonistic activity of these killer yeasts has a narrow optimal pH range. Furthermore, we found that the antagonistic activity of some species is strain-dependent.

Characterization and pathogenicity of Fusarium proliferatum andFusarium verticillioides, causal agents of Fusarium ear rot of corn

Fusarium ear rot is a significant disease of corn caused by several toxigenic Fusarium species including Fusarium proliferatum and Fusarium verticillioides. Forty-one Fusarium isolates were recovered from corn with Fusarium ear rot disease symptoms collected from Peninsular Malaysia. Isolates were classified into three described species known as F. proliferatum, F. verticillioides, and F. solani. Based on sexual compatibility test, four isolates from F. proliferatum (MATD-1) were crossed-fertile with tester isolate F. proliferatum D024853 (MATD-2), producing perithecia in the presence of ascospores. Meanwhile, the isolates from F. verticillioides (MATA-2) were crossed with tester isolate F. verticillioides A00149 (MATA-1), but were found producing 11 isolates with barren perithecia and three infertile isolates, whereas in 11 isolates of F. verticillioides (MATA-1), seven isolates produced barren perithecia with four nonfertile isolates. In the pathogenicity test, all isolates were found pathogenic and displayed disease symptoms with variation in severity. The highest disease severity index value was observed in F. proliferatum B68c at 4.67, which was obtained in an updated report on the mating type of F. verticillioides and F. proliferatum isolated from Fusarium ear rot disease.