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Aflatoxins are potent Aspergillus mycotoxins that contaminate food and feed, thereby impacting health and trade. Biopesticides with atoxigenic A. flavus as active ingredients are used to reduce aflatoxin contamination in crops. The mechanism of aflatoxin biocontrol is primarily attributed to competitive exclusion but sometimes aflatoxin is reduced by greater amounts than can be explained by displacement of aflatoxin-producing fungi on the crop. Objectives of this study were to 1) evaluate the ability of atoxigenic A. flavus genotypes to degrade aflatoxin B1 (AFB1) and 2) characterize impacts of temperature, time, and nutrient availability on AFB1 degradation by atoxigenic A. flavus. Aflatoxin-contaminated maize was inoculated with atoxigenic isolates in three separate experiments that included different atoxigenic genotypes, temperature, and time as variables. Atoxigenic genotypes varied in aflatoxin degradation, but all degraded AFB1 > 44% after seven days at 30°C. The optimum temperature for AFB1 degradation was 25-30°C which is similar to the optimum range for AFB1 production. In a time-course experiment, atoxigenics degraded 40% of AFB1 within three days, and 80% of aflatoxin was degraded by day 21. Atoxigenic isolates were able to degrade and utilize AFB1 as a sole carbon source in a chemically defined medium, but quantities of AFB1 degraded declined as glucose concentrations increased. Degradation may be an additional mechanism through which atoxigenic A. flavus biocontrol products reduce aflatoxin contamination pre- and/or post-harvest. Thus, selection of optimal atoxigenic active ingredients can include assessment of both competitive ability in agricultural fields and their ability to degrade aflatoxins.
Lourena A Maxwell; Kenneth Callicott; Ranajit Bandyopadhyay; Hillary Laureen Mehl; Marc Joel Orbach; Peter Cotty. Degradation of aflatoxin B1 by atoxigenic Aspergillus flavus biocontrol agents. Plant Disease 2021, 1 .
AMA StyleLourena A Maxwell, Kenneth Callicott, Ranajit Bandyopadhyay, Hillary Laureen Mehl, Marc Joel Orbach, Peter Cotty. Degradation of aflatoxin B1 by atoxigenic Aspergillus flavus biocontrol agents. Plant Disease. 2021; ():1.
Chicago/Turabian StyleLourena A Maxwell; Kenneth Callicott; Ranajit Bandyopadhyay; Hillary Laureen Mehl; Marc Joel Orbach; Peter Cotty. 2021. "Degradation of aflatoxin B1 by atoxigenic Aspergillus flavus biocontrol agents." Plant Disease , no. : 1.
Iron is an essential component for growth and development. Despite relative abundance in the environment, bioavailability of iron is limited due to oxidation by atmospheric oxygen into insoluble ferric iron. Filamentous fungi have developed diverse pathways to uptake and use iron. In the current study, a putative iron utilization gene cluster (IUC) in Aspergillus flavus was identified and characterized. Gene analyses indicate A. flavus may use reductive as well as siderophore-mediated iron uptake and utilization pathways. The ferroxidation and iron permeation process, in which iron transport depends on the coupling of these two activities, mediates the reductive pathway. The IUC identified in this work includes six genes and is located in a highly polymorphic region of the genome. Diversity among A. flavus genotypes is manifested in the structure of the IUC, which ranged from complete deletion to a region disabled by multiple indels. Molecular profiling of A. flavus populations suggests lineage-specific loss of IUC. The observed variation among A. flavus genotypes in iron utilization and the lineage-specific loss of the iron utilization genes in several A. flavus clonal lineages provide insight on evolution of iron acquisition and utilization within Aspergillus section Flavi. The potential divergence in capacity to acquire iron should be taken into account when selecting A. flavus active ingredients for biocontrol in niches where climate change may alter iron availability.
Bishwo N. Adhikari; Kenneth A. Callicott; Peter J. Cotty. Conservation and Loss of a Putative Iron Utilization Gene Cluster among Genotypes of Aspergillus flavus. Microorganisms 2021, 9, 137 .
AMA StyleBishwo N. Adhikari, Kenneth A. Callicott, Peter J. Cotty. Conservation and Loss of a Putative Iron Utilization Gene Cluster among Genotypes of Aspergillus flavus. Microorganisms. 2021; 9 (1):137.
Chicago/Turabian StyleBishwo N. Adhikari; Kenneth A. Callicott; Peter J. Cotty. 2021. "Conservation and Loss of a Putative Iron Utilization Gene Cluster among Genotypes of Aspergillus flavus." Microorganisms 9, no. 1: 137.
Aflatoxins (AF) are hepatocarcinogenic metabolites produced by several Aspergillus species. Crop infection by these species results in aflatoxin contamination of cereals, nuts, and spices. Etiology of aflatoxin contamination is complicated by mixed infections of multiple species with similar morphology and aflatoxin profiles. The current study investigates variation in aflatoxin production between two morphologically similar species that co-exist in West Africa, A. aflatoxiformans and A. minisclerotigenes. Consistent distinctions in aflatoxin production during liquid fermentation were discovered between these species. The two species produced similar concentrations of AFB1 in defined media with either urea or ammonium as the sole nitrogen source. However, production of both AFB1 and AFG1 were inhibited (p < 0.001) for A. aflatoxiformans in a yeast extract medium with sucrose. Although production of AFG1 by both species was similar in urea, A. minisclerotigenes produced greater concentrations of AFG1 in ammonium (p = 0.039). Based on these differences, a reliable and convenient assay for differentiating the two species was designed. This assay will be useful for identifying specific etiologic agents of aflatoxin contamination episodes in West Africa and other regions where the two species are sympatric, especially when phylogenetic analyses based on multiple gene segments are not practical.
Pummi Singh; Hillary L. Mehl; Marc J. Orbach; Kenneth A. Callicott; Peter J. Cotty. Phenotypic Differentiation of Two Morphologically Similar Aflatoxin-Producing Fungi from West Africa. Toxins 2020, 12, 656 .
AMA StylePummi Singh, Hillary L. Mehl, Marc J. Orbach, Kenneth A. Callicott, Peter J. Cotty. Phenotypic Differentiation of Two Morphologically Similar Aflatoxin-Producing Fungi from West Africa. Toxins. 2020; 12 (10):656.
Chicago/Turabian StylePummi Singh; Hillary L. Mehl; Marc J. Orbach; Kenneth A. Callicott; Peter J. Cotty. 2020. "Phenotypic Differentiation of Two Morphologically Similar Aflatoxin-Producing Fungi from West Africa." Toxins 12, no. 10: 656.
Aflatoxin contamination of groundnut and maize infected by Aspergillus section Flavi fungi is common throughout Senegal. The use of biocontrol products containing atoxigenic Aspergillus flavus strains to reduce crop aflatoxin content has been successful in several regions, but no such products are available in Senegal. The biocontrol product Aflasafe SN01 was developed for use in Senegal. The four active ingredients of Aflasafe SN01 are atoxigenic A. flavus genotypes native to Senegal and distinct from active ingredients used in other biocontrol products. Efficacy tests on groundnut and maize in farmers’ fields were carried out in Senegal during the course of 5 years. Active ingredients were monitored with vegetative compatibility analyses. Significant (P < 0.05) displacement of aflatoxin producers occurred in all years, districts, and crops. In addition, crops from Aflasafe SN01-treated fields contained significantly (P < 0.05) fewer aflatoxins both at harvest and after storage. Most crops from treated fields contained aflatoxin concentrations permissible in both local and international markets. Results suggest that Aflasafe SN01 is an effective tool for aflatoxin mitigation in groundnut and maize. Large-scale use of Aflasafe SN01 should provide health, trade, and economic benefits for Senegal. [Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .
L. A. Senghor; Alejandro Ortega-Beltran; J. Atehnkeng; K. A. Callicott; P. J. Cotty; R. Bandyopadhyay. The Atoxigenic Biocontrol Product Aflasafe SN01 Is a Valuable Tool to Mitigate Aflatoxin Contamination of Both Maize and Groundnut Cultivated in Senegal. Plant Disease 2020, 104, 510 -520.
AMA StyleL. A. Senghor, Alejandro Ortega-Beltran, J. Atehnkeng, K. A. Callicott, P. J. Cotty, R. Bandyopadhyay. The Atoxigenic Biocontrol Product Aflasafe SN01 Is a Valuable Tool to Mitigate Aflatoxin Contamination of Both Maize and Groundnut Cultivated in Senegal. Plant Disease. 2020; 104 (2):510-520.
Chicago/Turabian StyleL. A. Senghor; Alejandro Ortega-Beltran; J. Atehnkeng; K. A. Callicott; P. J. Cotty; R. Bandyopadhyay. 2020. "The Atoxigenic Biocontrol Product Aflasafe SN01 Is a Valuable Tool to Mitigate Aflatoxin Contamination of Both Maize and Groundnut Cultivated in Senegal." Plant Disease 104, no. 2: 510-520.
Aspergillus flavus has long been considered to be an asexual species. Although a sexual stage was recently reported for this species from in vitro studies, the amount of recombination ongoing in natural populations and the genetic distance across which meiosis occurs is largely unknown. In the current study, genetic diversity, reproduction and evolution of natural A. flavus populations endemic to Kenya were examined. A total of 2744 isolates recovered from 629 maize-field soils across southern Kenya in two consecutive seasons were characterized at 17 SSR loci, revealing high genetic diversity (9-72 alleles/locus and 2140 haplotypes). Clonal reproduction and persistence of clonal lineages predominated, with many identical haplotypes occurring in multiple soil samples and both seasons. Genetic analyses predicted three distinct lineages with linkage disequilibrium and evolutionary relationships among haplotypes within each lineage suggesting mutation-driven evolution followed by clonal reproduction. Low genetic differentiation among adjacent communities reflected frequent short distance dispersal.
Md-Sajedul Islam; Kenneth A. Callicott; Charity Mutegi; Ranajit Bandyopadhyay; Peter J. Cotty. Aspergillus flavus resident in Kenya: High genetic diversity in an ancient population primarily shaped by clonal reproduction and mutation-driven evolution. Fungal Ecology 2018, 35, 20 -33.
AMA StyleMd-Sajedul Islam, Kenneth A. Callicott, Charity Mutegi, Ranajit Bandyopadhyay, Peter J. Cotty. Aspergillus flavus resident in Kenya: High genetic diversity in an ancient population primarily shaped by clonal reproduction and mutation-driven evolution. Fungal Ecology. 2018; 35 ():20-33.
Chicago/Turabian StyleMd-Sajedul Islam; Kenneth A. Callicott; Charity Mutegi; Ranajit Bandyopadhyay; Peter J. Cotty. 2018. "Aspergillus flavus resident in Kenya: High genetic diversity in an ancient population primarily shaped by clonal reproduction and mutation-driven evolution." Fungal Ecology 35, no. : 20-33.
To identify predominant isolates for potential use as biocontrol agents, Aspergillus flavus isolates collected from soils of almond, pistachio and fig orchard in the Central Valley of California were tested for their membership to 16 atoxigenic vegetative compatibility groups (VCGs), including YV36, the VCG to which AF36, an atoxigenic isolate commercialized in the United States as biopesticide, belongs. A surprisingly large proportion of isolates belonged to YV36 (13.3%, 7.2% and 6.6% of the total almond, pistachio and fig populations, respectively), while the percentage of isolates belonging to the other 15 VCGs ranged from 0% to 2.3%. In order to gain a better insight into the structure and diversity of atoxigenic A. flavus populations and to further identify predominant isolates, seventeen SSR markers were then used to genetically characterize AF36, the 15 type-isolates of the VCGs and 342 atoxigenic isolates of the almond population. There was considerable genetic diversity among isolates with a lack of differentiation among micro-geographical regions or years. Since isolates sharing identical SSR profiles from distinct orchards were rare, we separated them into groups of at least 3 closely-related isolates from distinct orchards that shared identical alleles for at least 15 out of the 17 loci. This led to the identification of 15 groups comprising up to 24 closely-related isolates. The group which contained the largest number of isolates were members of YV36 while five groups were also found to be members of our studied atoxigenic VCGs. These results suggest that these 15 groups, and AF36 in particular, are well adapted to various environmental conditions in California and to tree crops and, as such, are good candidates for use as biocontrol agents.
Adeline Picot; Mark Doster; Md-Sajedul Islam; Kenneth Callicott; Alejandro Ortega-Beltran; Peter Cotty; Themis Michailides. Distribution and incidence of atoxigenic Aspergillus flavus VCG in tree crop orchards in California: A strategy for identifying potential antagonists, the example of almonds. International Journal of Food Microbiology 2018, 265, 55 -64.
AMA StyleAdeline Picot, Mark Doster, Md-Sajedul Islam, Kenneth Callicott, Alejandro Ortega-Beltran, Peter Cotty, Themis Michailides. Distribution and incidence of atoxigenic Aspergillus flavus VCG in tree crop orchards in California: A strategy for identifying potential antagonists, the example of almonds. International Journal of Food Microbiology. 2018; 265 ():55-64.
Chicago/Turabian StyleAdeline Picot; Mark Doster; Md-Sajedul Islam; Kenneth Callicott; Alejandro Ortega-Beltran; Peter Cotty; Themis Michailides. 2018. "Distribution and incidence of atoxigenic Aspergillus flavus VCG in tree crop orchards in California: A strategy for identifying potential antagonists, the example of almonds." International Journal of Food Microbiology 265, no. : 55-64.
To assess frequencies of the Aspergillus flavus atoxigenic vegetative compatibility group (VCG) YV36, to which the biocontrol agent AF36 belongs, in maize-growing regions of Mexico. Over 3,500 Aspergillus flavus isolates recovered from maize agroecosystems in four Mexican states during 2005 through 2008 were subjected to vegetative compatibility analyses based on nitrate nonutilizing mutants. Results revealed that 59 (1.6%) isolates belong to VCG YV36. All 59 isolates had the MAT1-2 idiomorph at the mating-type locus and the SNP in the polyketide synthase gene that confers atoxigenicity. Additional degradation of the aflatoxin gene cluster was detected in three isolates. Microsatellite loci analyses revealed low levels of genetic diversity and no linkage disequilibrium within VCG YV36. The VCG to which the biocontrol agent AF36 belongs, YV36, is also native to Mexico. The North America Free Trade Agreement should facilitate adoption of AF36 for use by Mexico in aflatoxin prevention programs. An USEPA registered biocontrol agent effective at preventing aflatoxin contamination of crops in the US, is also native to Mexico. This should facilitate the path to registration of AF36 as the first biopesticide for aflatoxin mitigation of maize in Mexico. Economic and health benefits to the population of Mexico should result once aflatoxin mitigation programs based on AF36 applications are implemented.
Alejandro Ortega‐Beltran; Lisa C. Grubisha; Kenneth Callicott; Peter J. Cotty. The vegetative compatibility group to which the US biocontrol agent Aspergillus flavus AF 36 belongs is also endemic to Mexico. Journal of Applied Microbiology 2016, 120, 986 -998.
AMA StyleAlejandro Ortega‐Beltran, Lisa C. Grubisha, Kenneth Callicott, Peter J. Cotty. The vegetative compatibility group to which the US biocontrol agent Aspergillus flavus AF 36 belongs is also endemic to Mexico. Journal of Applied Microbiology. 2016; 120 (4):986-998.
Chicago/Turabian StyleAlejandro Ortega‐Beltran; Lisa C. Grubisha; Kenneth Callicott; Peter J. Cotty. 2016. "The vegetative compatibility group to which the US biocontrol agent Aspergillus flavus AF 36 belongs is also endemic to Mexico." Journal of Applied Microbiology 120, no. 4: 986-998.
The report presents a rapid, inexpensive and simple method for monitoring indels with influence on aflatoxin biosynthesis within Aspergillus flavus populations. PCR primers were developed for 32 markers spaced approximately every 5 kb from 20 kb proximal to the aflatoxin biosynthesis gene cluster to the telomere repeat. This region includes gene clusters required for biosynthesis of aflatoxins and cyclopiazonic acid; the resulting data were named cluster amplification patterns (CAPs). CAP markers are amplified in four multiplex PCRs, greatly reducing the cost and time to monitor indels within this region across populations. The method also provides a practical tool for characterizing intraspecific variability in A. flavus not captured with other methods. Aflatoxins, potent naturally-occurring carcinogens, cause significant agricultural problems. The most effective method for preventing contamination of crops with aflatoxins is through use of atoxigenic strains of Aspergillus flavus to alter the population structure of this species and reduce incidences of aflatoxin producers. Cluster amplification pattern (CAP) is a rapid multiplex PCR method for identifying and monitoring indels associated with atoxigenicity in A. flavus. Compared to previous techniques, the reported method allows for increased resolution, reduced cost, and greater speed in monitoring the stability of atoxigenic strains, incidences of indel mediated atoxigenicity and the structure of A. flavus populations.
Kenneth Callicott; Peter J. Cotty. Method for monitoring deletions in the aflatoxin biosynthesis gene cluster of Aspergillus flavus with multiplex PCR. Letters in Applied Microbiology 2014, 60, 60 -65.
AMA StyleKenneth Callicott, Peter J. Cotty. Method for monitoring deletions in the aflatoxin biosynthesis gene cluster of Aspergillus flavus with multiplex PCR. Letters in Applied Microbiology. 2014; 60 (1):60-65.
Chicago/Turabian StyleKenneth Callicott; Peter J. Cotty. 2014. "Method for monitoring deletions in the aflatoxin biosynthesis gene cluster of Aspergillus flavus with multiplex PCR." Letters in Applied Microbiology 60, no. 1: 60-65.
In order to gain insight into the causal agents of aflatoxin contamination of maize in Italy, populations of Aspergillus flavus on maize produced in the most affected area were characterized. Forty-six percent of A. flavus, isolated from maize kernels collected in 5 districts of northern Italy between 2003 and 2010, were unable to produce detectable levels of aflatoxins. The genetic diversity of the population was assessed by analysis of vegetative compatibility groups (VCGs) and presence or absence of several aflatoxin biosynthesis genes. Forty-eight VCGs were identified through complementation between nitrate non-utilizing mutants. Twenty-five VCGs contained only atoxigenic isolates, and the remaining 23 only aflatoxin producers. Members of the largest atoxigenic VCG (IT6) were found in 4 of the 5 districts sampled. Six deletion patterns of genes in the aflatoxin biosynthesis gene cluster were detected. No deletions in the cluster were detected for twelve atoxigenic isolates and 10 had the entire cluster deleted. One isolate had a deletion pattern only seen once before in Nigeria. The basis for initial selection of endemic atoxigenic strains of A. flavus for biological control of aflatoxin contamination of maize in Italy is provided.
Antonio Mauro; Paola Battilani; Kenneth Callicott; Paola Giorni; Amedeo Pietri; Peter J. Cotty. Structure of an Aspergillus flavus population from maize kernels in northern Italy. International Journal of Food Microbiology 2013, 162, 1 -7.
AMA StyleAntonio Mauro, Paola Battilani, Kenneth Callicott, Paola Giorni, Amedeo Pietri, Peter J. Cotty. Structure of an Aspergillus flavus population from maize kernels in northern Italy. International Journal of Food Microbiology. 2013; 162 (1):1-7.
Chicago/Turabian StyleAntonio Mauro; Paola Battilani; Kenneth Callicott; Paola Giorni; Amedeo Pietri; Peter J. Cotty. 2013. "Structure of an Aspergillus flavus population from maize kernels in northern Italy." International Journal of Food Microbiology 162, no. 1: 1-7.
Humans and animals are exposed to aflatoxins, toxic carcinogenic fungal metabolites, through consumption of contaminated food and feed. Aspergillus flavus, the primary causal agent of crop aflatoxin contamination, is composed of phenotypically and genotypically diverse vegetative compatibility groups (VCGs). Molecular data suggest that VCGs largely behave as clones with certain VCGs exhibiting niche preference. VCGs vary in aflatoxin‐producing ability, ranging from highly aflatoxigenic to atoxigenic. The prevalence of individual VCGs is dictated by competition during growth and reproduction under variable biotic and abiotic conditions. Agronomic practices influence structures and average aflatoxin‐producing potentials of A. flavus populations and, as a result, incidences and severities of crop contamination. Application of atoxigenic strains has successfully reduced crop aflatoxin contamination across large areas in the United States. This strategy uses components of the endemic diversity to alter structures of A. flavus populations and improve safety of food, feed, and the overall environment.
Hillary Mehl; Ramon Jaime; Kenneth Callicott; Claudia Probst; Nicholas P. Garber; Alejandro Ortega-Beltran; Lisa Grubisha; Peter J. Cotty. Aspergillus flavusdiversity on crops and in the environment can be exploited to reduce aflatoxin exposure and improve health. Annals of the New York Academy of Sciences 2012, 1273, 7 -17.
AMA StyleHillary Mehl, Ramon Jaime, Kenneth Callicott, Claudia Probst, Nicholas P. Garber, Alejandro Ortega-Beltran, Lisa Grubisha, Peter J. Cotty. Aspergillus flavusdiversity on crops and in the environment can be exploited to reduce aflatoxin exposure and improve health. Annals of the New York Academy of Sciences. 2012; 1273 (1):7-17.
Chicago/Turabian StyleHillary Mehl; Ramon Jaime; Kenneth Callicott; Claudia Probst; Nicholas P. Garber; Alejandro Ortega-Beltran; Lisa Grubisha; Peter J. Cotty. 2012. "Aspergillus flavusdiversity on crops and in the environment can be exploited to reduce aflatoxin exposure and improve health." Annals of the New York Academy of Sciences 1273, no. 1: 7-17.
Aflatoxin contamination of crops is a world-wide problem. Lethal aflatoxicosis of humans has been associated with maize produced in Kenya for over three decades. The S strain morphotype of Aspergillus flavus was identified as the primary cause of aflatoxin contamination events occurring between 2004 and 2006 in Kenya. Because the S strain was first described in the U.S., it was suggested that the agent causing lethal levels of aflatoxins was introduced to Kenya with maize. DNA sequence comparisons among 68 S strain isolates from Kenya, the Americas, Asia, and Australia suggest the Kenyan isolates are distinct from those causing aflatoxin contaminations in the U.S. Analyses of 4.06 kb representing three loci from distinct chromosomes indicate that most S strain isolates from the U.S. resolved into a clade distinct from one containing the 30 Kenyan isolates. S strain isolates from Kenya were more closely related to the recently described species A. minisclerotigenes than to A. flavus. Furthermore, failure of the Kenyan isolates to produce G aflatoxins was attributed to a previously undescribed deletion in the cypA gene, suggesting that different deletion events led to loss of G aflatoxin production in S strain isolates from the U.S. and Kenya. Thus, although the Kenyan isolates have S strain morphology and produce large quantities of only B aflatoxins like A. flavus S strain isolates, these isolates are phylogenetically divergent from those described from other regions. The molecular characteristics of the Kenyan S strain isolates described herein are valuable tools to identify and track these highly aflatoxigenic fungi.
C. Probst; Kenneth Callicott; P. J. Cotty. Deadly strains of Kenyan Aspergillus are distinct from other aflatoxin producers. European Journal of Plant Pathology 2011, 132, 419 -429.
AMA StyleC. Probst, Kenneth Callicott, P. J. Cotty. Deadly strains of Kenyan Aspergillus are distinct from other aflatoxin producers. European Journal of Plant Pathology. 2011; 132 (3):419-429.
Chicago/Turabian StyleC. Probst; Kenneth Callicott; P. J. Cotty. 2011. "Deadly strains of Kenyan Aspergillus are distinct from other aflatoxin producers." European Journal of Plant Pathology 132, no. 3: 419-429.
Aspergillus flavus K49 secreted at least two xylanase activities when grown on a medium containing larch (wood) xylan as a sole carbon source. Enzyme activity was assayed using an agar medium containing Remazol Brilliant Blue R conjugated oat spelt xylan as substrate. Crude enzyme preparations were inhibited by Hg(+2), with an ED(50) of 17.5 mM and maximum inhibition of 83% at 50 mM. A concentrated sample of A. flavus K49 xylanase preparation was subjected to gel filtration chromatography on a P-30 column. A small protein peak coinciding with the major peak of xylanase activity was separated from the other secreted fungal proteins. An additional peak of xylanase activity was observed in fractions containing multiple fungal proteins. Analysis by denaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of fractions containing the smaller molecular weight xylanase revealed a major and minor protein band in the vicinity of 14 kD. Analysis of these same fractions by acidic native PAGE revealed a single band. Confirmation of identity for the isolated xylanase was provided by isolation of a protein band from a SDS-PAGE gel, followed by trypsin digestion/analysis by tandem mass spectrometry. Comparison of the peptide library derived from this protein band with sequence data from the A. oryzae genomic data base provided a solid match with an endo-1,4-β-xylanase, XlnA. This identification is consistent with a low molecular weight protein associated with the major xylanolytic activity. XlnA may be a highly mobile (diffusible), plant wall hemicellulose degrading factor with significant activity during plant infection.
Jay E. Mellon; Peter J. Cotty; Kenneth A. Callicott; Hamed Abbas. Identification of a Major Xylanase from Aspergillus flavus as a 14-kD Protein. Mycopathologia 2011, 172, 299 -305.
AMA StyleJay E. Mellon, Peter J. Cotty, Kenneth A. Callicott, Hamed Abbas. Identification of a Major Xylanase from Aspergillus flavus as a 14-kD Protein. Mycopathologia. 2011; 172 (4):299-305.
Chicago/Turabian StyleJay E. Mellon; Peter J. Cotty; Kenneth A. Callicott; Hamed Abbas. 2011. "Identification of a Major Xylanase from Aspergillus flavus as a 14-kD Protein." Mycopathologia 172, no. 4: 299-305.
To examine whether there is a relationship between the degree of Campylobacter contamination observed in product lots of retail Icelandic broiler chicken carcasses and the incidence of human disease, 1,617 isolates from 327 individual product lots were genetically matched (using the flaA short variable region [SVR[) to 289 isolates from cases of human campylobacteriosis whose onset was within approximately 2 weeks from the date of processing. When there was genetic identity between broiler isolates and human isolates within the appropriate time frame, a retail product lot was classified as implicated in human disease. According to the results of this analysis, there were multiple clusters of human disease linked to the same process lot or lots. Implicated and nonimplicated retail product lots were compared for four lot descriptors: lot size, prevalence, mean contamination, and maximum contamination (as characterized by direct rinse plating). For retail product distributed fresh, Mann-Whitney U tests showed that implicated product lots had significantly ( P = 0.0055) higher mean contamination than nonimplicated lots. The corresponding median values were 3.56 log CFU/carcass for implicated lots and 2.72 log CFU/carcass for nonimplicated lots. For frozen retail product, implicated lots were significantly ( P = 0.0281) larger than nonimplicated lots. When the time frame was removed, retail product lots containing Campylobacter flaA SVR genotypes also seen in human disease had significantly higher mean and maximum contamination numbers than lots containing no genotypes seen in human disease for both fresh and frozen product. Our results suggest that cases of broiler-borne campylobacteriosis may occur in clusters and that the differences in mean contamination levels may provide a basis for regulatory action that is more specific than a presence-absence standard.
Kenneth Callicott; Hjördís Harðardóttir; Franklín Georgsson; Jarle Reiersen; Vala Friðriksdóttir; Eggert Gunnarsson; Pascal Michel; Jean-Robert Bisaillon; Karl G. Kristinsson; Haraldur Briem; Kelli L. Hiett; David S. Needleman; Norman J. Stern. Broiler Campylobacter Contamination and Human Campylobacteriosis in Iceland. Applied and Environmental Microbiology 2008, 74, 6483 -6494.
AMA StyleKenneth Callicott, Hjördís Harðardóttir, Franklín Georgsson, Jarle Reiersen, Vala Friðriksdóttir, Eggert Gunnarsson, Pascal Michel, Jean-Robert Bisaillon, Karl G. Kristinsson, Haraldur Briem, Kelli L. Hiett, David S. Needleman, Norman J. Stern. Broiler Campylobacter Contamination and Human Campylobacteriosis in Iceland. Applied and Environmental Microbiology. 2008; 74 (21):6483-6494.
Chicago/Turabian StyleKenneth Callicott; Hjördís Harðardóttir; Franklín Georgsson; Jarle Reiersen; Vala Friðriksdóttir; Eggert Gunnarsson; Pascal Michel; Jean-Robert Bisaillon; Karl G. Kristinsson; Haraldur Briem; Kelli L. Hiett; David S. Needleman; Norman J. Stern. 2008. "Broiler Campylobacter Contamination and Human Campylobacteriosis in Iceland." Applied and Environmental Microbiology 74, no. 21: 6483-6494.
Frequency and numbers of Campylobacter spp. were assessed per freshly processed, contaminated broiler carcass. Campylobacter-positive flocks were identified by cecal sample analysis at slaughter. These flocks had been tested as Campylobacter negative at 4.1 ± 0.9 d prior to slaughter. Levels of contamination were estimated using 2 sampling approaches per carcass: (1) free weep fluids and (2) whole-carcass, 100 mL of distilled water rinses. Estimations of counts were determined by directly plating dilutions of weeps and rinses onto Campy-Cefex agar and incubating the plates at 41.5°C under microaerobic atmosphere. Confirmation was provided by latex agglutination to quantify levels per milliliter of weep and per 100 mL of rinse. Thirty-two slaughter groups (∼20 carcasses per group) were compared from 2003 to 2004. The Campylobacter-positive weep frequency was 84.8%, whereas the frequency for rinse samples was 74.4% (P < 0.001). Enumeration of Campylobacter spp. on positive samples ranged from 0.70 to 6.13 log10 cfu/mL of weep (geometric mean of 2.84) and from 2.30 to 7.72 log10 cfu/100 mL of rinse (geometric mean of 4.38). The correlations between weep and rinse were 0.814 with 0.5 mL of rinse and 0.6294 when applying 0.1 mL of rinse The quantitative regression analyses for these 2 corresponding tests were log10 rinse (for 0.5 mL of inoculum) = 1.1965 log10 weep + 0.4979, and log10 rinse (for 0.1 mL of inoculum) = 1.322 log10 weep − 0.1521. FlaA SVR sequencing of isolates indicated that the same genotypes were found in weep and rinse samples. Weep and rinse sampling led to different proportions of Campylobacter-positive carcasses detection, but we demonstrated that this difference was reduced by increasing the amount of rinse fluid used for plating.
N. J. Stern; F. Georgsson; R. Lowman; J.-R. Bisaillon; J. Reiersen; Kenneth Callicott; M. Geirsdóttir; R. Hrolfsdóttir; K. L. Hiett. Frequency and Enumeration of Campylobacter Species from Processed Broiler Carcasses by Weep and Rinse Samples. Poultry Science 2007, 86, 394 -399.
AMA StyleN. J. Stern, F. Georgsson, R. Lowman, J.-R. Bisaillon, J. Reiersen, Kenneth Callicott, M. Geirsdóttir, R. Hrolfsdóttir, K. L. Hiett. Frequency and Enumeration of Campylobacter Species from Processed Broiler Carcasses by Weep and Rinse Samples. Poultry Science. 2007; 86 (2):394-399.
Chicago/Turabian StyleN. J. Stern; F. Georgsson; R. Lowman; J.-R. Bisaillon; J. Reiersen; Kenneth Callicott; M. Geirsdóttir; R. Hrolfsdóttir; K. L. Hiett. 2007. "Frequency and Enumeration of Campylobacter Species from Processed Broiler Carcasses by Weep and Rinse Samples." Poultry Science 86, no. 2: 394-399.
Campylobacter jejuni is a major cause of bacterial food-borne infection in the industrial world. There is evidence that C. jejuni is present in eggs and hatchery fluff, opening the possibility for vertical transmission from hens to progeny. Poultry operations in Iceland provide an excellent opportunity to study this possibility, since breeding flocks are established solely from eggs imported from grandparent flocks in Sweden. This leaves limited opportunity for grandparents and their progeny to share isolates through horizontal transmission. While Campylobacter was not detected in all grandparent flocks, 13 of the 16 egg import lots consisted of eggs gathered from one or more Campylobacter -positive grandparent flocks. No evidence of Campylobacter was found by PCR in any of the 10 relevant quarantine hatchery fluff samples examined, and no Campylobacter was isolated from the parent birds through 8 weeks, while they were still in quarantine rearing facilities. After the birds were moved to less biosecure rearing facilities, Campylobacter was isolated, and 29 alleles were observed among the 224 isolates studied. While three alleles were found in both Sweden and Iceland, in no case was the same allele found both in a particular grandparent flock and in its progeny. We could find no evidence for vertical transmission of Campylobacter to the approximately 60,000 progeny parent breeders that were hatched from eggs coming from Campylobacter -positive grandparent flocks. If vertical transmission is occurring, it is not a significant source for the contamination of chicken flocks with Campylobacter spp.
Kenneth Callicott; Vala Friðriksdóttir; Jarle Reiersen; Ruff Lowman; Jean-Robert Bisaillon; Eggert Gunnarsson; Eva Berndtson; Kelli L. Hiett; David S. Needleman; Norman J. Stern. Lack of Evidence for Vertical Transmission of Campylobacter spp. in Chickens. Applied and Environmental Microbiology 2006, 72, 5794 -5798.
AMA StyleKenneth Callicott, Vala Friðriksdóttir, Jarle Reiersen, Ruff Lowman, Jean-Robert Bisaillon, Eggert Gunnarsson, Eva Berndtson, Kelli L. Hiett, David S. Needleman, Norman J. Stern. Lack of Evidence for Vertical Transmission of Campylobacter spp. in Chickens. Applied and Environmental Microbiology. 2006; 72 (9):5794-5798.
Chicago/Turabian StyleKenneth Callicott; Vala Friðriksdóttir; Jarle Reiersen; Ruff Lowman; Jean-Robert Bisaillon; Eggert Gunnarsson; Eva Berndtson; Kelli L. Hiett; David S. Needleman; Norman J. Stern. 2006. "Lack of Evidence for Vertical Transmission of Campylobacter spp. in Chickens." Applied and Environmental Microbiology 72, no. 9: 5794-5798.
Isolates of Campylobacter jejuni shipped internationally often arrive in a noncultivable state. We describe a PCR-based methodology whereby phylogenetic information can be recovered from noncultivable C. jejuni stored in Wang's transport medium. The robustness of this methodology was initially tested using 5 previously characterized strains of C. jejuni isolated from various sources associated with poultry production. These isolates were stored in Wang's transport medium before being subjected to 1 of 5 treatments designed to render the stored cells noncultivable: prolonged storage at room temperature, prolonged incubation at 42 degrees C, multiple rounds of freezing and thawing, boiling, or contamination with Pseudomonas aeruginosa (ATCC 27853). This method resulted in DNA appropriate for PCR. An approximately 400-nucleotide amplicon from the flaA gene and an approximately 800-nucleotide amplicon from 16S rDNA were readily obtained, and a 1.5-kb section of the flaA locus was amplified from about half of the samples. These results indicate that this method may be useful for isolate typing schemes based on PCR amplification of Campylobacter DNA, including flaA short variable region (flaA SVR) sequencing, multilocus sequence typing (MLST), and flaA PCR-RFLP. By using this method, isolates unrecoverable from transport medium can still be used to provide phylogenetic information for epidemiological studies.
K.A. Callicott; N.J. Stern; K.L. Hiett; Campy-on-Ice Consortium. Isolation of DNA for PCR assays from noncultivable Campylobacter jejuni isolates. Poultry Science 2005, 84, 1530 -1532.
AMA StyleK.A. Callicott, N.J. Stern, K.L. Hiett, Campy-on-Ice Consortium. Isolation of DNA for PCR assays from noncultivable Campylobacter jejuni isolates. Poultry Science. 2005; 84 (10):1530-1532.
Chicago/Turabian StyleK.A. Callicott; N.J. Stern; K.L. Hiett; Campy-on-Ice Consortium. 2005. "Isolation of DNA for PCR assays from noncultivable Campylobacter jejuni isolates." Poultry Science 84, no. 10: 1530-1532.
William B. Ludington; Kenneth A. Callicott; Anthony W. Detomaso. Genetic variation in Mastocarpus papillatus (Rhodophyta) in central California using amplified fragment length polymorphisms. Plant Species Biology 2004, 19, 107 -113.
AMA StyleWilliam B. Ludington, Kenneth A. Callicott, Anthony W. Detomaso. Genetic variation in Mastocarpus papillatus (Rhodophyta) in central California using amplified fragment length polymorphisms. Plant Species Biology. 2004; 19 (2):107-113.
Chicago/Turabian StyleWilliam B. Ludington; Kenneth A. Callicott; Anthony W. Detomaso. 2004. "Genetic variation in Mastocarpus papillatus (Rhodophyta) in central California using amplified fragment length polymorphisms." Plant Species Biology 19, no. 2: 107-113.
The monomeric subunit composition of the hemocyanin of the sand fiddler crab Uca pugilator was examined in six samples totalling 342 individuals and representing latitudinal and salinity gradients. A total of 12 different polypeptide chains were separated electrophoretically, of which as few as four and as many as nine were present in an individual. The small quantities of several chains suggest a mixed population of the predominantly 2×6 aggregates in the blood. There was no effect of sex and no clear effect of salinity. Samples of populations found near the northern and southern limits of the species, however, were very different from each other and also from samples of populations in the middle of the geographic range. Specifically, samples from the geographic limits exhibit far less variation than those from the middle of the species range. Only one group of three minor chains clearly varies as if they might be encoded at the same locus. Moreover, the condition of most of the monomers, including those three as well as several of the major chains, is not genetically fixed in the adult stage.
Kenneth A. Callicott; Charlotte P. Mangum. Phenotypic variation and lability of the subunit composition of the hemocyanin of Uca pugilator. Journal of Experimental Marine Biology and Ecology 1993, 165, 143 -159.
AMA StyleKenneth A. Callicott, Charlotte P. Mangum. Phenotypic variation and lability of the subunit composition of the hemocyanin of Uca pugilator. Journal of Experimental Marine Biology and Ecology. 1993; 165 (2):143-159.
Chicago/Turabian StyleKenneth A. Callicott; Charlotte P. Mangum. 1993. "Phenotypic variation and lability of the subunit composition of the hemocyanin of Uca pugilator." Journal of Experimental Marine Biology and Ecology 165, no. 2: 143-159.