Enteroaggregative Escherichia coli: An Emerging Enteric Food Borne Pathogen

Enteroaggregative Escherichia coli (EAEC) are quite heterogeneous category of an emerging enteric pathogen associated with cases of acute or persistent diarrhea worldwide in children and adults, and over the past decade has received increasing attention as a cause of watery diarrhea, which is often persistent. EAEC infection is an important cause of diarrhea in outbreak and non-outbreak settings in developing and developed countries. Recently, EAEC has been implicated in the development of irritable bowel syndrome, but this remains to be confirmed. EAEC is defined as a diarrheal pathogen based on its characteristic aggregative adherence (AA) to HEp-2 cells in culture and its biofilm formation on the intestinal mucosa with a “stacked-brick” adherence phenotype, which is related to the presence of a 60 MDa plasmid (pAA). At the molecular level, strains demonstrating the aggregative phenotype are quite heterogeneous; several virulence factors are detected by polymerase chain reaction; however, none exhibited 100% specificity. Although several studies have identified specific virulence factor(s) unique to EAEC, the mechanism by which EAEC exerts its pathogenesis is, thus, far unknown. The present review updates the current knowledge on the epidemiology, chronic complications, detection, virulence factors, and treatment of EAEC, an emerging enteric food borne pathogen

Performance and inheritance of yield and maize streak virus disease resistance in white maize and yellow conversions

In sub Saharan Africa, past effort has registered success in developing high yielding and foliar disease resistant maize ( Zea mays L.) varieties, which are deficient in pro-vitamin A. A new initiative is to develop maize varieties, tolerant to foliar diseases and rich in pro-vitamin A carotenoids. To achieve this, yellow conversions of white testers and other elite maize varieties have been developed by the International Center for Maize and Wheat Development (CIMMYT). Unlike the white lines, limited information on agronomic performance and disease resistance is available for yellow maize conversions. This study was conducted to evaluate the performance of white maize and their corresponding yellow maize conversions for yield and tolerance to Maize streak virus (MSV) disease; and determine the inheritance patterns of these traits. Fourty seven three-way hybrids generated in a Line by tester mating design (North Carolina 2), 12 inbred lines (used as male parents), 4 single crosses (used as female parents) and 3 commercials checks were screened for resistance to Maize streak virus (MSV) disease at the National Crop Resources Research Institute (NaCRRI) in Uganda. The same genotypes were evaluated in a 9x5 alpha lattice design in three locations of Uganda (National Crop Resources Research Institute (NACRRI), National Semi Arid Resources Research Institute (NaSARRI) and Bulambuli) for agronomic performance. Results confirmed tolerance to MSV in testers CML202, CML395, CML444, CML445 and CML312-SR (white). Genotypes performed significantly differently for yield, anthesis days, plant height, ear height, husk cover, grain texture, reaction to Gray leaf spot (GLS) (P<0.001) and ear aspect (P<0.01). However, pairwise comparison of white and yellow conversions indicated no significant difference (P>0.05) in agronomic performance and tolerance to diseases. General combining ability (GCA) was more important than specific combining ability (SCA) for most traits, except for anthesis days, Turcicum leaf blight (TLB), GLS and yield. GCA effects for yield were not significant in both lines (male parents) and single cross testers (female parents) of white and yellow conversions. However, two unique cases were observed for diseases; yellow conversion of line CML444 significantly combined for susceptibility to TLB; while tester CML312/CML442 combined for resistance to GLS. Additionally, there was low heritably estimates for tolerance to MSV and yield. Generally, there was no significant difference between white and corresponding yellow maize conversion, implying that there is no significant loss in MSV resistance and yield performance while converting white into yellow maize.En Afrique sub-Saharienne, les efforts ant\ue9rieurs ont connu de grands succ\ue8s dans le d\ue9veloppement des vari\ue9t\ue9s tr\ue8s productives et tol\ue9rantes aux maladies foliaires du ma\uefs ( Zea mays L.), mais qui sont pauvres en provitamine A. La nouvelle vision est de d\ue9velopper des vari\ue9t\ue9s de ma\uefs r\ue9sistantes aux principales maladies foliaires, et riche en carot\ue9no\uefdes provitamine A. Pour y arriver, les conversions jaunes issues des testeurs blancs de ma\uefs ainsi que les vari\ue9t\ue9s \ue9lite ont \ue9t\ue9 d\ue9velopp\ue9es par le Centre International pour l\u2019Am\ue9lioration du Ma\uefs et du Bl\ue9 (CIMMYT). Contrairement aux lign\ue9es blanches de ma\uefs, la performance agronomique et le niveau de r\ue9sistance aux maladies des lign\ue9es jaunes reste m\ue9connue. Cette \ue9tude a \ue9t\ue9 men\ue9e dans le but d\u2019\ue9valuer la performance au niveau du rendement et la r\ue9sistance \ue0 la maladie des bandes (MSV) des vari\ue9t\ue9s de ma\uefs \ue0 grain de couleur blanche et leurs conversions de couleur jaune et d\ue9terminer le mode d\u2019h\ue9ritabilit\ue9 de ces deux param\ue8tres \ue9tudi\ue9s. Quarante-sept hybrides trois voies produits dans un mode de croisement Lign\ue9e par testeur (North Carolina II), 12 lign\ue9es \ue9pur\ue9es (utilis\ue9es comme parents m\ue2les), 4 hybrides simples (utilis\ue9s comme parents femelles) et 3 t\ue9moins ont \ue9t\ue9 inocul\ue9s par l\u2019agent causal de la maladie des bandes \ue0 NaCRRI (National Crop Ressources Research Institute) en Ouganda. La performance agronomique des m\ueames g\ue9notypes a \ue9t\ue9 \ue9valu\ue9e dans un dispositif exp\ue9rimental d\u2019alpha lattice (5parcelles \ue9l\ue9mentaires x 9 blocks) dans 3 sites de l\u2019Ouganda \ue0 savoir NaCRRI (National Crop Ressources Research Institute), NaSARRI (National Semi Arid Resources Research Institute) et Bulambuli. Les r\ue9sultats ont confirm\ue9 la tol\ue9rance \ue0 la MSV des testeurs \ue0 grains blancs CML202, CML395, CML444, CML445 et CML 312-SR. La performance des g\ue9notypes \ue9tait hautement significativement diff\ue9rente pour le rendement, le nombre de jours de floraison m\ue2le, la hauteur des plants, le niveau d\u2019insertion des \ue9pis sur les plants, la couverture des \ue9pis par les spathes, la texture des grains, la r\ue9action \ue0 la GLS (Glay leaf spot) (P<0.001) ainsi que pour l\u2019aspect des \ue9pis (P<0.01). Cependant, la comparaison entre le ma\uefs blanc et sa conversion jaune a montr\ue9 une diff\ue9rence non significative (P>0.05) au niveau de leur performance agronomique et la tol\ue9rance aux maladies. L\u2019aptitude g\ue9n\ue9rale \ue0 la combinaison (GCA) \ue9tait plus importante que l\u2019aptitude sp\ue9cifique \ue0 la combinaison (SCA) pour la plupart des param\ue8tres \ue0 l\u2019exception du nombre de jours \ue0 floraison m\ue2le, la tol\ue9rance \ue0 l\u2019helminthosporiose (TLB), GLS et le rendement. Les effets dus \ue0 la GCA pour le rendement n\u2019\ue9taient pas significatifs pour les parents m\ue2les (lign\ue9es) et femelles (hybrides simples) des g\ue9notypes \ue0 grain de couleur blanche et leurs conversions \ue0 grain de couleur jaune. N\ue9anmoins, deux cas exceptionnels ont \ue9t\ue9 observ\ue9s pour la tol\ue9rance aux maladies: la conversion jaune de la lign\ue9e CML444 \ue9tait un mauvais combinateur pour la TLB, alors que le testeur CML312/CML442 combinait bien pour la tol\ue9rance \ue0 la GLS. En plus, l\u2019h\ue9ritabilit\ue9 \ue9tait faible pour la tol\ue9rance \ue0 la MSV et le rendement. En g\ue9n\ue9ral, il n\u2019y avait pas de diff\ue9rence significative entre les g\ue9notypes \ue0 grain blanc et leurs conversions jaunes respectives, ce qui signifie que, lors de la conversion des vari\ue9t\ue9s \ue0 grain blanc en vari\ue9t\ue9s \ue0 grain jaune, il n\u2019y a aucune perte significative en ce qui est de la tol\ue9rance \ue0 la MSV et la performance en rendement des grains

Determination of the heterotic groups of maize inbred lines and the inheritance of their resistance to the maize weevil

Maize weevil ( Sitophilus zeamais Motschulsky) is a major maize ( Zea mays L) storage insect pest in the tropics. Fifty-two inbred lines developed for weevil resistance were crossed to two testers, A and B, to determine their heterotic groups and inheritance of resistance to maize weevil. For 10 testcrosses selected for performance by tester, the correspondent testcrosses onto the opposite tester and all the parents involved in those crosses, were included in the combining study. Of 52 inbred lines, 7 had significantly positive general combining ability (GCA) for yield, with a maximum GCA effect of 1.24t.ha-1. Based on the specific combining ability (SCA) effect, 23 inbred lines were assigned to heterotic Group A, 24 to Group B, and 5 to both A and B. The combining ability test for weevil resistance revealed that only one inbred, WL118-9, was classified as moderately resistant with a susceptibility index (SI=5.4), two lines were moderately susceptible; and the remaining inbreds were susceptible to highly susceptible to the maize weevil. Additive and non-additive gene action were important for yield, but for weevil resistance, additive gene action was more important. Weevil resistance exists and is moderately heritable.Le charan\ue7on du ma\uefs ( Sitophilus zeamais Motschulsky) est un plus grand ravageur du ma\uefs ( Zea mays L) dans les tropiques. Cinquante-deux lign\ue9es d\ue9velopp\ue9es pour la r\ue9sistance au charan\ue7on du ma\uefs \ue9taient crois\ue9es aux testeurs A et B afin de d\ue9terminer leurs groupes h\ue9t\ue9rotiques ainsi que la transmission de la r\ue9sistance au charan\ue7on du ma\uefs. Pour dix lign\ue9es s\ue9lectionn\ue9es pour test de performance par le testeur, les croisements correspondants au testeur oppos\ue9 ainsi que tous les parents impliqu\ue9s dans le croisement \ue9taient inclus dans l\u2019 \ue9tude d\u2019aptitude. Parmi les 52 lign\ue9es, 7 avaient significativement montr\ue9 une positive Aptitude G\ue9n\ue9rale \ue0 la combinaison (GCA) pour le rendement, avec un effet maximum GCA de 1.24 t ha-1. Bas\ue9 sur l\u2019 Aptitude Sp\ue9cifique \ue0 la Combinaison (SCA), 23 lign\ue9es ont \ue9t\ue9 attribu\ue9es au groupe h\ue9t\ue9rotique A, 24 au groupe B et 5 aux deux groupes h\ue9t\ue9rotiques A et B. Le test d\u2019aptitude \ue0 la r\ue9sistance au charan\ue7on a r\ue9v\ue9l\ue9e q\u2019une seule lign\ue9e, WL118-9 \ue9tait classifi\ue9e comme mod\ue9r\ue9ment r\ue9sistante avec un index de susceptibilit\ue9 de 5.4, deux lign\ue9es \ue9taient mod\ue9r\ue9ment susceptibles tandis que les lign\ue9es restantes \ue9taient soit susceptibles ou hautement susceptibles au charan\ue7on du ma\uefs. L\u2019action additive et non additive des g\ue8nes \ue9taient tr\ue8s importante. Les g\ue8nes de r\ue9sistance au charan\ue7on du ma\uefs existent et sont mod\ue9r\ue9ment transmissibles \ue0 la descendance

Reaction of rice cultivars to a virulent rice yellow mottle virus strain in Uganda

Rice ( Oryza spp.) has long been an important food staple for many traditional rice growing communities. Key developments in efforts to improve rice production such as the development of NERICA varieties have been widely recognised. Nonetheless, emerging diseases such as the Rice Yellow Mottle Virus sobemovirus (RYMV) undermine dissemination of new technologies and sustained productivity of the crop. The RYMV is highly variable and several resistance-breaking strains have been identified. Appropriate sources of resistance to RYMV should be identified and characterised in order to pyramid genes for both complete and partial resistance. In this study, reaction of nine (9) rice cultivars to RYMV virulent strain in Uganda was determined. Four upland and three lowland NERICA varieties, an O. Sativa lowland variety, Gigante and IR64 were observed. Isolates of RYMV were collected from three "hot-spots" in Uganda (Lira, Luweero and Iganga). The isolate from Iganga was most virulent on RYMV susceptible cultivar (IR64), and thus used to constitute study treatment evaluated in the study. Cultivars were potted and raised in a screenhouse experiment arranged in a randomised complete block design (RCBD) with three replicates. Significant differences for relative area under disease progress curve (RAUDPC) (P 640.01) were detected among the cultivars. Similarly, significant positive correlations (P 640.05) were observed between mean disease score and percentage reduction in grain weight and between percentage grain weight and reduction in plant height. Susceptible cultivars were characterised based on premature death, and significantly reduced grain weight and plant height (P 640.01 and P 640.05), respectively. These results demonstrated the aggressive nature of the specific RYMV strain, and provided evidence with regard to the importance of grain weight and plant height in evaluating RYMV disease resistance.Le riz ( Oryza spp.) a \ue9t\ue9 depuis longtemps un aliment de base pour plusieurs communaut\ue9s cultivatrices de riz. Les d\ue9veloppements-cl\ue9s dans l\u2019effort d\u2019am\ue9liorer la production rizicole, tel que le d\ue9veloppement des vari\ue9t\ue9s NERICA, ont \ue9t\ue9 largement reconnus. N\ue9anmoins, l\u2019apparition des maladies telle que le virus de la panachure jaune de type sobemovirus contraint la diss\ue9mination des nouvelles technologies et la productivit\ue9 soutenue de la culture. Le virus de la panachure jaune du riz est tr\ue8s variable et plusieurs souches virulentes ont \ue9t\ue9 identifi\ue9es. De sources appropri\ue9es de r\ue9sistance \ue0 la maladie de la panichure jaune du riz devront \ueatre identifi\ue9es et caract\ue9ris\ue9es afin de pyramider les g\ue8nes pour une r\ue9sistance complete et/ou partielle. Dans cette \ue9tude, la r\ue9action de 9 cultivars de riz au virus virulent de la panachure jaune en Ouganda \ue9tait d\ue9termin\ue9e. Quatre vari\ue9t\ue9s NERICA de montagne et trois vari\ue9t\ue9s NERICA des bas-fonds, ainsi qu\u2019une vari\ue9t\ue9 des bas-fonds de type O. sativa, Gigante et IR64, \ue9taient observ\ue9es. Les isolats du virus de la panachure jaune du riz \ue9taient collect\ue9s des \u201czones dangereuses\u201d de l\u2019Ouganda, notamment Lira, Luwero et Iganga. L\u2019isolat de l\u2019Iganga \ue9tait le plus virulent au cultivar IR64 susceptible au virus de la panachure jaune et donc \ue9tait utilis\ue9 pour constituer le traitement \ue9valu\ue9 dans cette \ue9tude. Les cultivars \ue9taient cultiv\ue9s en pots dans une serre et arranges en blocs al\ue9atoires complets avec trois r\ue9p\ue9titions. Des diff\ue9rences significatives pour la surface relative sous la courbe progressive de la maladie (P 640.01) \ue9taient d\ue9tect\ue9es parmi les cultivars. De fa\ue7on similaire, des corr\ue9lations positives significatives (P 640.05) \ue9taient observ\ue9es entre les moyennes des cotations de la maladie et le pourcentage de r\ue9duction du poids des grains, et entre le pourcentage du poids des grains et la r\ue9duction de la hauteur de plant. Les cultivars susceptibles \ue9taient caract\ue9ris\ue9s sur base de la mort pr\ue9matur\ue9e, et la r\ue9duction significative du poids des grains et la hauteur de plant (P 640.01 et P 640.05), respectivement. Ces r\ue9sultats ont d\ue9montr\ue9 la nature aggressive du virus de la panachure jaune et fournissent l\u2019 \ue9vidence de l\u2019omportance du poids en grains et la hauteur de plants dans l\u2019\ue9valuation de la r\ue9sistance \ue0 la maladie de la panachure jaune du riz

Extracellular Hsp72 concentration relates to a minimum endogenous criteria during acute exercise-heat exposure

Extracellular heat-shock protein 72 (eHsp72) concentration increases during exercise-heat stress when conditions elicit physiological strain. Differences in severity of environmental and exercise stimuli have elicited varied response to stress. The present study aimed to quantify the extent of increased eHsp72 with increased exogenous heat stress, and determine related endogenous markers of strain in an exercise-heat model. Ten males cycled for 90 min at 50% O2peak in three conditions (TEMP, 20°C/63% RH; HOT, 30.2°C/51%RH; VHOT, 40.0°C/37%RH). Plasma was analysed for eHsp72 pre, immediately post and 24-h post each trial utilising a commercially available ELISA. Increased eHsp72 concentration was observed post VHOT trial (+172.4%) (P<0.05), but not TEMP (-1.9%) or HOT (+25.7%) conditions. eHsp72 returned to baseline values within 24hrs in all conditions. Changes were observed in rectal temperature (Trec), rate of Trec increase, area under the curve for Trec of 38.5°C and 39.0°C, duration Trec ≥ 38.5°C and ≥ 39.0°C, and change in muscle temperature, between VHOT, and TEMP and HOT, but not between TEMP and HOT. Each condition also elicited significantly increasing physiological strain, described by sweat rate, heart rate, physiological strain index, rating of perceived exertion and thermal sensation. Stepwise multiple regression reported rate of Trec increase and change in Trec to be predictors of increased eHsp72 concentration. Data suggests eHsp72 concentration increases once systemic temperature and sympathetic activity exceeds a minimum endogenous criteria elicited during VHOT conditions and is likely to be modulated by large, rapid changes in core temperature

Genetic analysis of resistance to rice bacterial blight in Uganda

Rice bacterial blight ( Xanthomonas oryzae pv. oryzae ) is a major constraint to rice ( Oryza sativa L.) production in Uganda and as part of strategies to develop resistant cultivars, it is important to evaluate resistance of commonly used cultivars. A full-diallel mating design involving three resistant and three susceptible rice cultivars was used to produce F1 and F2 progenies in a screen-house at the National Crop Resources Research Institute (NaCRRI), Namulonge in Uganda. The parents and F2 populations were challenged with the 64 Xanthomonas oryzae pv. oryzae isolate (UX00) and lesion lengths were scored 21 days after inoculation (DAI). Griffing\u2019s combining ability analysis showed significant specific combining ability (SCA) and non-significant general combining ability (GCA) effects, indicating the preponderance of non-additive gene effects in controlling the resistance to bacterial leaf blight (BLB) in rice. Rice genotypes, NERICA14, NERICA10 and NERICA4 had desirable GCA estimates, and were, therefore, the best general combiners. Crosses CO39 x NERICA10 and NERICA14 x IRAT104 had favorable SCA values. These hybrids are thus, promising in developing the BLB resistant progenies. Significant reciprocal effects indicate the importance of maternal contribution in controlling the BLB virulence. For this, resistant lines can be used as female parents for fear of affecting transfer of resistance to the progenies, and the hybrids and their reciprocals would be handled separately. Low estimates of narrow sense coefficient of genetic determination (NSCGD) (0.9%) and medium broad sense coefficient of genetic determination (BSCGD) estimates (16.4%) highlight the influence of non-additive gene action in controlling the resistance to BLB, confirming an effective selection of superior genotypes at advanced generations when the maximum homozygosity is fixed.Le fl\ue9trissement bact\ue9rien des feuilles du riz ( Xanthomonas oryzae ) constitue une contrainte majeur \ue0 la production du riz ( Oryza sativa L.) en Uganda. L\u2019\ue9valuation de la r\ue9sistance des cultivars commun\ue9ment utilis\ue9s s\u2019av\ue8re n\ue9cessaire comme une des strategies de d\ue9veloppement des cultivars r\ue9sistants. Des cultivars de riz (Oryza sativa L.) dont trois r\ue9sistants et trois susceptibles \ue9taient crois\ue9s en dispositif diall\ue8le complet pour produire des g\ue9n\ue9rations F1 et F2 dans une serre de l\u2019 Institut National de Recherche sur les Resources V\ue9g\ue9tales (NaCRRI) \ue0 Namulonge en Ouganda. Les parents et les populations F2 \ue9taient soumis \ue0 l\u2019isolat UX00 du Xanthomonas oryzae pv.oryzae et les longueurs de la l\ue9sion \ue9taient \ue9valu\ue9es 21 jours apr\ue8s l\u2019inoculation. L\u2019analyse de l\u2019aptitude \ue0 la combinaison par la m\ue9thode de Griffing ont r\ue9v\ue9l\ue9 des effets significatifs de l\u2019Aptitude Sp\ue9cifique \ue0 la Combinaison (ASC) et non significatifs de l\u2019Aptitude G\ue9n\ue9rale \ue0 la Combinaison (AGC), indiquant la pr\ue9pond\ue9rance des effets g\ue9n\ue9tiques non additifs dans le contr\uf4le de la r\ue9sistance au fl\ue9trissement bact\ue9rien des feuilles (FBF). Des g\ue9notypes NERICA14, NERICA10 et NERICA4 avaient des valeurs souhaitables d\u2019AGC, et \ue9taient ainsi des meilleurs combinants pour la r\ue9sistance au FBF. Des hybrides CO39 x NERICA10 et NERICA14 x IRAT104 avaient des valeurs favorables d\u2019ASC. Ils sont donc promettant dans le d\ue9veloppement des descendants r\ue9sistants au FBF. Des effets r\ue9ciproques significatifs indiquent l\u2019importance de la contribution maternelle dans le contr\uf4le de la virulence du FBF. Pour ce faire, des lign\ue9es r\ue9sistantes peuvent \ueatre utilis\ue9es comme parents femelles de peur d\u2019affecter le transfert de la r\ue9sistance aux descendants, et les hybrids ainsi que leur r\ue9ciproques pourraient \ueatre manipul\ue9s s\ue9par\ue9ment. De faibles valeurs (0.9%) du coefficient g\ue9n\ue9tique de d\ue9termination au sens restreint et valeurs moyennes (16.4%) du coefficient g\ue9n\ue9tique de d\ue9termination au sens large accentuent l\u2019influence de l\u2019action g\ue9n\ue9tique non additive dans le contr\uf4le de la r\ue9sistance au FBF, ce qui confirme une s\ue9lection effective des meilleurs g\ue9notypes aux g\ue9n\ue9rations avanc\ue9es quand le maximum d\u2019homozygotie est fix\ue9

Molecular characterization of tropical maize inbred lines using microsatellite DNA markers

An insight on diversity and relationships among germplasm is important in any breeding program for crop improve¬ment. The main objectives of our study were to: (i) determine the level of genetic diversity within mid altitude maize inbred lines resistant to weevils, aflatoxin accumulation and drought, (ii) to suggest potential heterotic groups using their genetic structures and distance based on cluster analysis with the aim to generate broad based source germ¬plasm for mid altitude maize breeding program with combined traits of importance against Aflatoxin accumulation. In this study, 25 SSR markers were used to finger print forty two maize inbred lines to assess the genetic diversity, genetic relationships, and their population structure. A total of 184 alleles were identified at all the loci with an aver¬age of 7.36 and a range between two and 19 alleles per locus. The major allele frequency varied from 0.17 to 0.90 with an average of 0.49 while the minor allele frequency varied from 0.10 to 0.83 with an average of 0.51. The gene diversity values varied from 0.18 to 0.92 with an average of 0.65. Average heterozygosity percentage of the inbred lines was 4%, ranging from 0% to 2%, indicating the low level of heterozygosity within the inbred lines. The aver¬age polymorphism information content (PIC) was 0.61. A dendrogram constructed using unweighted Neighbour Joining algorithm suggested three heterotic groups among the inbred lines. The three heterotic patterns based on the SSR markers need to be verified by field testing to confirm what appears to be promising alternative heterotic patterns. The fixed pattern detected using SSR markers could potentially contribute towards effective utilization of the inbred lines for the exploitation of heterosis and formation of genetically diverse sources population