Biotype 2 Research Articles

A Diagnosis and Biotype Comparison Across the Psychosis Spectrum: Investigating Volume and Shape Amygdala-Hippocampal Differences from the B-SNIP Study.

Brain-based Biotypes for psychotic disorders have been developed as part of the B-SNIP consortium to create neurobiologically distinct subgroups within idiopathic psychosis, independent from traditional phenomenological diagnostic methods. In the current study, we aimed to validate the Biotype model by assessing differences in volume and shape of the amygdala and hippocampus contrasting traditional clinical diagnoses with Biotype classification. A total of 811 participants from 6 sites were included: probands with schizophrenia (n = 199), schizoaffective disorder (n = 122), psychotic bipolar disorder with psychosis (n = 160), and healthy controls (n = 330). Biotype classification, previously developed using cognitive and electrophysiological data and K-means clustering, was used to categorize psychosis probands into 3 Biotypes, with Biotype-1 (B-1) showing reduced neural salience and severe cognitive impairment. MAGeT-Brain segmentation was used to determine amygdala and hippocampal volumetric data and shape deformations. When using Biotype classification, B-1 showed the strongest reductions in amygdala-hippocampal volume and the most widespread shape abnormalities. Using clinical diagnosis, probands with schizophrenia and schizoaffective disorder showed the most significant reductions of amygdala and hippocampal volumes and the most abnormal hippocampal shape compared with healthy controls. Biotype classification provided the strongest neuroanatomical differences compared with conventional DSM diagnoses, with the best discrimination seen using bilateral amygdala and right hippocampal volumes in B-1. These findings characterize amygdala and hippocampal volumetric and shape abnormalities across the psychosis spectrum. Grouping individuals by Biotype showed greater between-group discrimination, suggesting a promising approach and a favorable target for characterizing biological heterogeneity across the psychosis spectrum.

O10.6. ANTERIOR VERSUS POSTERIOR HIPPOCAMPUS WITHIN PSYCHOSIS: A BSNIP STUDY

BackgroundSymptoms of mental diseases can be cross-diagnostic. For example psychosis is not limited to schizophrenia (SZ), but can be also present in bipolar (BPP) and schizoaffective (SA) disorders. Morphometric findings are often also cross-diagnostic, For example, volume decreases of the hippocampus (HP), essential to memory functions, is affected in both schizophrenia and bipolar disorder. Biotyping, grouping of patients according to biomarker-based categories is one attempt to approach cross-diagnostic features in the hope of better classification and ultimately tailored interventions. Here we combine biotyping, in addition to traditional diagnosing, with analysis of the HP volume. Furthermore, we explore the HP according to its anterior (aHP) versus posterior (pHP) anatomical division, following the functional division of this medial temporal lobe structure. Our hypothesis is that aHP and pHP are differentially affected in biotypes and diagnostic groups and reflective of differences in cognitive functions affected in each biotype and/or diagnostic group.MethodsThe sample included 450 probands (age 35±12.0 yo) and 325 healthy controls (HC; 37±12.0 yo). Of the probands 187 were diagnosed with SZ, 150 with BPP (psychosis type), 113 with SA disorders; after biotyping the same probands were categorized into three biotypes: 118 biotype 1 (BP1), 142 biotype 2 (BP2), 187 biotype 3 (BP3). 3T MRI data were quality checked and processed with FreeSurfer 6.0. The HP measures extracted were: the whole HP, and further HP subfields according to aHP and pHP. aHP and pHP subfields were reconstituted into left and right aHP and pHP. BACS cognitive data and PANSS, SAPS, MADRS and mania clinical ratings were collected.ResultsAnalysis According to Diagnoses: There were no aHP or pHP volume differences among diagnostic groups, but all diagnostic groups demonstrated volume decreases of the left and right aHP compared to HC with effect sizes (Cohen’s d) between 0.3 and 0.6. Further, SA had decreases of the left and right pHP as well and SZ of the left pHP (effect sizes 0.3–0.4) compared to HC. BPP pHP volume were not different than pHP volumes measured in HC.Analysis According to Biotyping: Decreases of left and right aHP and pHP volumes were present in BP1 compared to HC while decreases of left pHP and left and right aHP were present in BT2 compared to HC. Only aHP was affected in BT3 compared to HC. Left and right aHP and pHP distinguished BT1 and BT3. BT1 had further decreased left pHP volume compared to BP2. Several anterior portions of the subfields volumes were driving the aHP vs pHP differences among biotypes while differences of the posterior portions of the subfields were fewer. aHP differences between BP1 and BP2 were driven by the anterior portion of the right subiculum.DiscussionBiotypes are more effective than diagnoses in discriminating abnormalities of the HP across psychosis categories. Further, analysis of the aHP versus the pHP demonstrates that the HP should be analyzed not as a whole, or as its subfields, but according to anterior versus posterior divisions of its subfields and to the sum of anterior versus posterior subfields in aHP and pHP. Further studies need to elucidate the cognitive functional correlates of aHP- pHP differences across psychoses and healthy populations.

Genome scan detection of selective sweeps among biotypes of the soybean aphid, Aphis glycines, with differing virulence to resistance to A. glycines (Rag) traits in soybean, Glycine max

Multiple biotypes of soybean aphid, Aphis glycines, occur in North America adapted for survival (virulence) on soybean, Glycine max, with one or more different resistance to A. glycines (Rag) traits. The degree of genome-wide variance between biotypes and the basis of virulence remains unknown, but the latter is hypothesized to involve secreted effector proteins. Between 167,249 and 217,750 single nucleotide polymorphisms (SNPs) were predicted from whole genome re-sequencing of A. glycines avirulent biotype 1 (B1) and virulent B2, B3 and B4 colony-derived iso-female lines when compared to the draft B1 genome assembly, Ag_bt1_v6.0. Differences in nucleotide diversity indices (π) estimated within 1000 bp sliding windows demonstrated that 226 of 353 (64.0%) regions most differentiated between B1 and ≥ 2 virulent biotypes, representing < 0.1% of the 308 Mb assembled genome size, are located on 15 unordered scaffolds. Furthermore, these 226 intervals were coincident and show a significant association with 326 of 508 SNPs with significant locus-by-locus FST estimates between biotype populations (r = 0.6271; F1,70 = 45.36, P < 0.001) and genes showing evidence of directions selection (πN/πS > 2.0; r = 0.6233; F1,70 = 50.20, P < 0.001). A putative secreted effector glycoprotein is encoded in proximity to genome intervals of low estimated π (putative selective sweep) within avirulent B1 compared to all three virulent biotypes. Additionally, SNPs are clustered in or in proximity to genes putatively involved in intracellular protein cargo transport and the regulation of secretion. Results of this study indicate that factors on a small number of scaffolds of the A. glycines genome may contribute to variance in virulence towards Rag traits in G. max.

Mutations involved in the emergence of Yersinia ruckeri biotype 2 in France.

Yersina ruckeri is an enterobacteria responsible for Enteric redmouth disease (ERM), which causes significant economic losses in the aquaculture industry worldwide. Two biotypes have been described within Y. ruckeri: biotype 1 (BT1) and biotype 2 (BT2). Unlike BT1, BT2 is negative for motility and lipase secretion. The emergence of BT2 Y. ruckeri has been associated with disease outbreaks in vaccinated fish in several countries, notably France in the early 2000s. In this study, 15 BT2 strains (14 BT2 strains isolated in France and the BT2 reference strain EX5) were studied to compare the phenotypic characters of the BT1 and BT2 strains and to determine the genetic origin of the emergence of BT2 in France. BT1 bacteria are significantly longer in size than BT2 bacteria (a difference of 0.222µm). The loss of motility of some French BT2 strains could be due to the loss of their ability to produce flagella caused by three mutations within the fliG, flhC and flgA genes. In the light of these results, the emergence of BT2 Yersinia ruckeri in France is discussed.

The flagellar master operon flhDC is a pleiotropic regulator involved in motility and virulence of the fish pathogen Yersinia ruckeri.

To investigate the function of the master flagellar operon flhDC in the fish pathogen Yersinia ruckeri and compare the effect of a constructed flhD mutation to a naturally occurring fliR mutation causing loss-of-motility in emergent biotype 2 (BT2) strains. Yersinia ruckeri flhD and fliR mutants were constructed in a motile strain. Both mutations caused loss-of-motility, ablation of flagellin synthesis and phospholipase secretion, similar to naturally occurring BT2 strains. Transcriptome analysis confirmed flhDC regulation of flagellar, chemotaxis and phospholipase loci as well as other genes of diverse function. The flhD mutation confers a competitive advantage within the fish host when compared with its parent strain, while this advantage was not seen with the naturally occurring fliR mutation. An intact flhD is necessary for expression of the flagellar secretion system as well as other diverse loci, consistent with a role for flhD as a pleiotropic regulator. The maintenance of the flhD locus in Y. ruckeri strains suggests its importance for aspects of Y. ruckeri biology other than virulence, since the flhD mutation conferred a competitive advantage during experimental challenge of rainbow trout. Yersinia ruckeri is the causative agent of enteric red mouth disease, an invasive septicaemia that affects farmed salmonid fish species. Disease outbreaks can cause severe economic losses in aquaculture. BT2 variants, which have independently emerged worldwide, are an increasing threat to farmed fish production. Knowledge of mechanisms involved in virulence, conserved functions and gene regulation among strains may be exploited for the development of novel disease control strategies to prevent pathogen growth or virulence phenotypes within aquaculture.

Vibrio vulnificus: From Oyster Colonist to Human Pathogen.

Vibrio vulnificus is a Gram-negative halophilic bacterium commonly found in warm coastal waters. The bacterium can cause severe gastroenteritis from consumption of raw seafood as well as wound infections and necrotizing fasciitis, with mortality rates for sepsis and wound infection at 50% and 17%, respectively [1]. Although infections are rare, V. vulnificus is responsible for the most deaths caused by Vibrios [1] and has the highest per case economic impact of all food-related diseases in the United States [2]. Additionally, the geographical area impacted by V. vulnificus is expanding due to global warming and rising sea temperatures, such that the incidence of infection has risen worldwide [3]. Even more troublesome, recent studies have identified V. vulnificus in previously unaffected regions, suggesting there may be future increase of infections [3]. Risk factors for infection include advanced age, male gender, and underlying disease, particularly liver cirrhosis, immunodeficiency, diabetes, and hemochromatosis [1]. However, illness occurs from less than 1 in 10,000 raw oyster meals served to persons with cirrhotic liver, suggesting factors beyond host susceptibility contribute to productive infection [1]. One factor to be considered is whether human-pathogenic V. vulnificus are relatively rare in food and the environment. As V. vulnificus is a diverse bacterial species [4], the specific factor(s) that might define why some isolates cause disease in humans, while the majority of strains are seemingly non-pathogenic, is poorly understood. The identity of these “human-tropic” factors remains the single largest question regarding V. vulnificus pathogenesis. Discovery and characterization of these factors may then facilitate identifying potentially deadly strains. However, this requires researchers to address critical questions regarding V. vulnificus human pathogenesis in the context of its natural environment. Can Pathogenic Potential be Predicted by Genomes? For years, researchers have attempted to identify genotypic or phenotypic markers to classify this species into “pathogenic” or “non-pathogenic” strains. However, this has proven difficult due to the nature of the bacterium: V. vulnificus is naturally competent and frequently exchanges DNA via horizontal gene transfer (HGT), complicating classification systems [4]. One method has been to classify V. vulnificus into biotypes, with Biotype 1 (BT1) originally composed of human clinical and related environmental strains, Biotype 2 (BT2) containing mostly eel pathogens, and Biotype 3 (BT3) representing a recent outbreak of systemic hybrid strains geographically limited to Israel [5, 6]. BT1 strains were further classified by allelic variation in the gene vcg into Clinical (C) and Environmental (E) types [7]. This split of BT1 into two lineages was apparent also by multilocus sequence typing (MLST) [8], with most clinical isolates clustered. However, this linkage of clinical isolates to a single phylogenetic branch has recently been challenged. First, PCR and MLST-based studies showed that V. vulnificus is in linkage disequilibrium, meaning there is a nonrandom association of alleles at multiple loci [9]. Additionally, BOX-PCR genomic fingerprinting identified 52 unique genotypes, demonstrating that the association between genotype and strain source (environmental or clinical) was not significant. This reveals that genotypic profiles alone are not sufficient predictors of virulence. These authors suggest instead the existence of two different ecotypes, lineages A and B, which represent two major monophyletic groups. A separate whole-genome SNP analysis of hundreds of clinical and environmental V. vulnificus strains suggested two ecotypes, A and B [10]. Unexpectedly, BT2 strains previously categorized separately, overlapped with BT1 in the B ecotype, and BT3 strains emerged as an independent branch within the B ecotype. In both the BOX-PCR [9] and whole-genome SNP analyses [10], most of the previously characterized clinical isolates sort to the A lineage or ecotype, but now many sort to the B groupings. Thus, phylogeny does not seem to hold the predictive value for pathogenicity as the number of strains included in these studies expands. Indeed, the genome-wide SNP analysis suggests that it is HGT of chromosomal segments between strains that leads to the continuous evolution of this pathogen [10] and that pathogenesis approaches could be more informative than phylogenetic approaches to understanding V. vulnificus pathogenicity.

Sensibilidade de biótipos de azevém a glyphosate, iodossulfurom-metílico e clethodim

O azevém (Lolium multiflorum) é uma gramínea anual, tradicionalmente utilizada como forrageira que se tornou planta daninha em lavouras no sul do Brasil. Tem-se observado biótipos de azevém, resistentes ao glyphosate, sobrevivendo à aplicação de herbicidas inibidores de ALS e ACCase. Assim, objetivou-se avaliar a sensibilidade de diferentes biótipos de azevém aos herbicidas glyphosate, iodosulfurom-metílico e clethodim. O experimento foi conduzido em casa de vegetação, em blocos casualizados, arranjo fatorial triplo com três repetições. Foram utilizados quatro biótipos de azevém, sendo: B1, suscetível ao glyphosate; B2, resistente ao glyphosate; B3 e B4, biótipos suspeitos de resistência ao iodosulfurom-metílico. As doses foram padronizadas em 0; 0,25; 0,5; 1; 2; 4 e 8 vezes as doses comerciais dos herbicidas glyphosate (1080 g ha-1e.a.), iodosulfurom-metílico (5 g ha-1 i.a.) e clethodim (96 g ha-1 i.a.). As variáveis avaliadas foram controle, em escala percentual, e massa seca da parte aérea (MSPA) das plantas aos 28 dias após a aplicação dos tratamentos (DAT). Com esses dados, foram calculados os parâmetros da equação, a partir dos quais, determinou-se a dose necessária para reduzir a MSPA em 50% em relação às plantas não tratadas (GR50) e o fator de resistência (F). Os biótipos B2, B3 e B4 obtiveram fatores de Resistência (F) acima de 10 em relação aos herbicidas glyphosate e iodosulfurom-metilico, destacando-se o biótipo B3, que além de possuir resistência a esses dois herbicidas, também demonstrou valor de F próximo do limiar para o clethodim, o que pode caracterizar um baixo nível de resistência a esse herbicida. Todos os biótipos, exceto o controle, foram resistentes aos herbicidas iodosulfurom-metílico e glyphosate, o que caracteriza a resistência múltipla a esses herbicidas. O herbicida clethodim pode ser uma alternativa para o controle de biótipos resistentes ao glyphosate e iodosulfurom-metílico, porém, deve-se ter atenção no manejo químico dessas populações, pois se identificou biótipos com baixo nível de resistência a esse herbicida.

Genotypic diversity and pathogenic potential of Yersinia enterocolitica biotype 2 strains isolated in Brazil.

To investigate the pathogenic potential and genotypic diversity of Yersinia enterocolitica biotype 2 strains isolated in Brazil and to compare these strains with other Y. enterocolitica biotypes using ERIC-PCR and PFGE. Forty strains of Y. enterocolitica biotype 2 (B2) isolated from humans (5), the environment (34) and animal (1), in Brazil over 19 years were studied. In addition to these isolates, we also analysed 26 Y. enterocolitica strains belonging to the biotypes 1A, 1B, and 3-5. All of the B2 strains contained the genes inv, ail, ystA, hreP, tccC and myfA. The genes fepD and fes were detected in 39 (97·5%) strains, virF was found in three (7·5%) strains, and ystB and fepA were not detected in any strains. The B2 strains showed genotypic similarities of more than 84·8% by ERIC-PCR and of more than 69·0% by PFGE. The pathogenic potential of the B2 strains examined in this study was highlighted by the occurrence of the majority of the virulence markers searched. The results of the ERIC-PCR and PFGE showed that the B2 strains evaluated in this study had a high genotypic similarity, suggesting that these strains differed little over the 19 year study period and that the environment was a possible source of contamination of humans and animals in Brazil. Furthermore, the ERIC-PCR technique grouped the strains belonging to Y. enterocolitica biotypes 1A, 1B, 2, 3, 4 and 5 according to their pathogenicity. This study provided new information about the pathogenic potential and genotypic similarity of Y. enterocolitica B2 isolated from diverse sources in Brazil. Furthermore, ERIC-PCR showed to be a valuable tool for grouping Y. enterocolitica of different biotypes according their pathogenicity.

Yersinia ruckeri Biotypes 1 and 2 in France: presence and antibiotic susceptibility.

Yersinia ruckeri is the causative agent of yersiniosis, a disease reported in a number of fish species, especially rainbow trout. This study was undertaken to describe the phenotypes of Y. ruckeri on French rainbow trout farms. More than 100 isolates, collected during recent outbreaks on trout farms, were characterized by phenotypic tests, namely using biochemical tests of the API 20E system, serotyping, biotyping (tests for motility and lipase activity) and by describing the pattern of susceptibility to several antibiotics. The isolates showed a low phenotypic diversity with a prevalent serotype (O1) and API 20E profile 5 1(3)07 100. As in other European countries, Biotype 2 (BT2), which lacks both motility and secreted lipase activity, was found to be present in France. The emergence of 'French' BT2 was different than that observed for other European countries (Finland, Spain, Denmark and the UK). The antibiotic pattern was uniform for all isolates, regardless of the geographical area studied. The results indicate that no resistance has yet emerged, and the efficacy of the antibiotic generally used against yersiniosis in France, trimethoprim/sulfamethoxasol, is not compromised (minimum inhibitory concentrations [MIC] of between 0.016 and 0.128 µg ml-1). Enrofloxacin and doxycycline, not used as a first-line treatment in fish diseases, have reasonably good efficacies (with MICs ≤0.128 and 0.256, respectively).

Development of genic‐SSRs markers from soybean aphid sequences generated by high‐throughput sequencing of cDNA library

AbstractThe soybean aphid (Aphis glycines Matsumura) is one of the most important insect pests of soybean [Glycine max (L.) Merr.] in North America, and three biotypes of the aphid have been confirmed. Genetic studies of the soybean aphid are needed to determine genetic diversity, movement pattern, biotype distribution and mapping of virulence genes for efficient control of the pest. Simple sequence repeats (SSR) markers are useful for population and classical genetic studies, but few are currently available for the soybean aphid. In this study, we designed primers for 342 genic‐SSR markers from a dataset of more than 102 024 transcript reads generated by 454 GS FLX sequencing of a cDNA library of the soybean aphid. Two hundred forty‐six markers generated PCR products of expected size and 26 were polymorphic among four pooled aphid DNA samples. An additional five markers that were fixed for two alleles among the pooled samples were found to be polymorphic when tested on 96 individual aphids. Sequencing of the PCR products generated by two polymorphic SSR markers revealed that the polymorphisms were strictly because of variations in the SSR repeats among the aphids tested. The genetic diversity among 96 soybean aphids, 24 each from two field collections (South Dakota and Michigan, biotype unknown) and two laboratory colonies [biotype 1 (B1) and biotype 2 (B2)], was assessed with 29 polymorphic SSR markers. These markers discriminated laboratory colonies from field collections and field collections from different states. The genic‐SSR markers developed and validated in this study will be a significant addition to the limited number of SSR markers, mostly genomic‐SSR, currently available for the soybean aphid. These markers will be useful for genetic studies, including population genetics, genetic and QTL mapping, migration and biotype differentiation of the soybean aphid.

Rapid genotyping assays for the identification and differentiation of Yersinia ruckeri biotype 2 strains

To establish PCR-based assays for the rapid identification and differentiation of each of four known biotype 2 (BT2) phenotype-causing alleles in Yersinia ruckeri strains currently circulating in Europe and the United States. Novel assays were developed relying on detection of mutant allele-specific changes in restriction enzyme cleavage sites within targeted PCR products. The developed assays were validated against isolates previously genotyped by DNA sequencing. The described methods were specific, rapid and simple to perform and interpret. The developed genotyping assays provide a valuable tool for identification and differentiation of specific BT2 strains of Y. ruckeri. These assays will be critical for the design and validation of new vaccines or other measures meant to control BT2 strains.

Temporal and pathogen-load dependent changes in rainbow trout ( Oncorhynchus mykiss) immune response traits following challenge with biotype 2 Yersinia ruckeri

Rainbow trout infected with Yersinia ruckeri, the causative agent of enteric redmouth disease (ERM), produce a pro-inflammatory and acute-phase response attributed in part to the innate recognition of bacterial-produced flagellin. Recently, variants of Y. ruckeri have been identified that lack flagella and associated motility. These strains are classified as biotype 2 (BT2) Y. ruckeri and these are considered an emerging problem in salmonid aquaculture. Little is known about the salmonid immune response to these variants. Herein, we report temporal and quantitative changes in rainbow trout immune response parameters following a primary challenge with BT2 Y. ruckeri strain YRNC10. Fish were injection-challenged with ten-fold dilutions of viable bacteria and sampled on days 1, 3, 5 and 7 post-challenge. TNFα1 and IL1-β1 transcripts were increased by day 1 post-challenge, and on days 3, 5 and 7 maximal gene transcript up-regulation occurred at a threshold of ∼64–256 CFU per mg spleen tissue. Infection induced robust SAA gene up-regulation that was significantly correlated with increased gene expression of IL-1β1 ( r = 0.81, P < 0.0001) and TNFα1 ( r = 0.55, P < 0.0001). Y. ruckeri infection induced modest changes in INFγ and Mx-1 gene transcript abundance at intermediate or high challenge doses and the expression patterns of both genes were positively correlated with pro-inflammatory gene and acute-phase gene transcription patterns. TNF superfamily 13b (BAFF) gene expression was significantly down-regulated in response to infection on days 3, 5 and 7 at the highest challenge doses. The spleen somatic index was significantly increased on days 3, 5 and 7 post-infection and positively correlated with spleen colony forming units and abundance of gene transcripts SAA, TNFα1, and IL1-β1. In summary, rainbow trout had a strong innate response following challenge with BT2 Y. ruckeri strain YRNC10 indicating that flagellin expression is not required for production of a robust pro-inflammatory and acute-phase gene transcription response. This study further supports the use of SAA transcript abundance and spleen somatic index as general measures of immunological status and fish health.

Role of the metalloprotease Vvp and the virulence plasmid pR99 of Vibrio vulnificus serovar E in surface colonization and fish virulence

The virulence for eels of Vibrio vulnificus biotype 2 serovar E (VSE) is conferred by a plasmid that codifies ability to survive in eel serum and cause septicaemia. To find out whether the plasmid and the selected chromosomal gene vvp plays a role in the initial steps of infection, the VSE strain CECT4999, the cured strain CT218 and the Vvp-deficient mutant CT201 (obtained in this work by allelic exchange) were used in colonization and virulence experiments. The eel avirulent biotype 1 (BT1) strain YJ016, whose genome has been sequenced, was used for comparative purposes. The global results demonstrate that the plasmid does not play a significant role in surface colonization because (i) CECT4999 and CT218 were equally chemoattracted towards and adherent to eel mucus and gills, and (ii) CT218 persisted in gills from bath-infected eels 2 weeks post infection. In contrast, mutation in vvp gene reduced significantly chemoattraction and attachment to eel mucus and gills, as well as virulence degree by immersion challenge. Co-infection experiments by bath with CECT4999 and CT201 confirmed that Vvp was involved in eel colonization and persistence in gills, because CECT4999 was recovered at higher numbers compared with CT201 from both internal organs of moribund fish (ratio 4:1) and gills from survivors (ratio 50:1). Interestingly, YJ016 also showed chemoattraction and attachment to mucus, and complementation of CT201 with BT1-vvp gene restored both activities together with virulence degree by immersion challenge. Additional experiments with algae mucus and purified mucin gave similar results. In conclusion, the protease Vvp of V. vulnificus seems to play an essential role in colonization of mucosal surfaces present in aquatic environments. Among the V. vulnificus strains colonizing fish mucus, only those harbouring the plasmid could survive in blood and cause septicaemia.

Phenotypic and genotypic characterization of a new fish-virulent Vibrio vulnificus serovar that lacks potential to infect humans

Vibrio vulnificus is a bacterial species that is virulent for humans and fish. Human isolates are classified into biotypes 1 and 3 (BT1 and BT3) and fish isolates into biotype 2 (BT2). However, a few human infections caused by BT2 isolates have been reported worldwide (zoonosis). These BT2 human isolates belong to serovar E (SerE), which is also present in diseased fish. The aim of the present work was to characterize a new BT2 serovar [serovar A (SerA)], which emerged in the European fish-farming industry in 2000, by means of phenotypic, serological and genetic [plasmid profiling, ribotyping and random amplified polymorphic DNA (RAPD)] methodologies. The results confirmed that SerA constitutes a homogeneous O-serogroup within the species that shares plasmidic information with SerE. Like SerE, this new serogroup was resistant to fresh fish serum, as well as being highly virulent for fish. In contrast, it was sensitive to human serum and avirulent for mice, even after pretreatment with iron. The two serovars presented different biochemical profiles as well as specific patterns by ribotyping and RAPD analysis. In conclusion, SerA seems to constitute a different clonal group that has recently emerged within the species V. vulnificus, with pathogenic potential for fish but not for humans.

Comparative Biology of a Novel Strain of Russian Wheat Aphid (Homoptera: Aphididae) on Three Wheat Cultivars

In spring 2003, several outbreaks of the Russian wheat aphid, Diuraphis noxia (Mordvilko), were reported in fields of supposedly resistant wheat cultivars ('Stanton', 'Halt', and 'Prairie Red') in eastern Colorado. We conducted two laboratory experiments to compare the biological performance of this new biotype 2 (B2) to that of two D. noxia collections of biotype 1 (B1) from western Kansas by using three wheat cultivars as host plants: 'Trego', a susceptible cultivar, and Stanton and Halt, two cultivars with different genetic sources of resistance. Survival of solitary nymphs from first instar to adult for the two clones of B1 on Trego was 96 and 90%, respectively, compared with 67 and 43% on Stanton, and 65 and 57% on Halt. In contrast, B2 had 60% survival on Trego, 43% survival on Halt, and 85% survival on Stanton. One clone of B1 required longer to mature on Halt compared with Trego or Stanton, but no other differences in developmental time among cultivars were significant. The standardized fecundity of solitary foundresses of the B1 clones was 19.6 and 20.1 nymphs on Trego, compared with 4.6 and 0.9 on Stanton, and 2.8 and 1.1 on Halt, respectively, over the same period. In contrast, fecundity of B2 was 21.1, 20.8, and 19.7 on Trego, Stanton, and Halt, respectively. When larger colonies developed on individual plants over longer periods, Trego supported the largest number of B1 aphids by experiment's end, whereas Stanton and Halt yielded the largest numbers of B2. The order of overall plant damage was Trego > Stanton > Halt when infested with B1, with no significant differences for B2. Trego had more pronounced leaf rolling than other cultivars, independent of biotype. Collectively, the results suggest that D. noxia B2 from Colorado has evolved cross-virulence to both Dn4- and Dny-based resistance sources.