Identification of diarrheagenic Escherichia coli isolated from infants and children in Dar es Salaam, Tanzania

<p>Abstract</p> <p>Background</p> <p>Relatively few studies have been done in Tanzania to detect and classify diarrheagenic <it>Escherichia coli </it>(DEC) strains among children with diarrhea. This study aimed at investigating DEC among children in Dar es Salaam aged less than five years hospitalized due to acute/persistent diarrhea.</p> <p>Methods</p> <p>DEC were isolated from stool samples collected from two hundred and eighty children with acute/persistent diarrhea at Muhimbili National Hospital and Ilala and Mwananyamala Municipal Hospitals in Dar es Salaam. A multiplex PCR system method was used to detect a species specific gene for <it>E.coli </it>and ten different virulence genes for detection of five pathogroups of DEC namely enteroaggregative- (EAEC), enteropathogenic- (EPEC), enterotoxigenic- (ETEC), enteroinvasive- (EIEC) and enterohemorghagic- <it>Escherichia coli </it>(EHEC).</p> <p>Results</p> <p>Sixty-four patients (22.9%) harbored DEC. Forty-one of them (14.6%) were categorized as EAEC. Most of the EAEC (82.9%) were classified as typical EAEC possessing the <it>aggR </it>gene, and 92.6% carried the <it>aat </it>gene. Isolates from thirteen patients were EPEC (4.6%) and most of these (92.3%) were typical EPEC with both <it>eae </it>and <it>bfpA </it>genes. Ten isolates were identified as ETEC (3.6%) with only the heat stable toxin; either <it>st1a </it>or <it>st1b </it>but not both. Age wise, EAEC and EPEC were significantly more prevalent among the age group 0–6 months (p < 0.05). Genes for EHEC (<it>stx</it>₁and <it>stx</it>₂) and EIEC <it>(ial</it>) were not detected in this study group.</p> <p>Conclusion</p> <p>The results show a high proportion of DEC among Tanzanian children with diarrhea, with typical EAEC and typical EPEC predominating. The use of primers for both variants of ST1 (st1a and st1b) increased the sensitivity for detection of ETEC strains.</p

Reversible and Noisy Progression towards a Commitment Point Enables Adaptable and Reliable Cellular Decision-Making

Cells must make reliable decisions under fluctuating extracellular conditions, but also be flexible enough to adapt to such changes. How cells reconcile these seemingly contradictory requirements through the dynamics of cellular decision-making is poorly understood. To study this issue we quantitatively measured gene expression and protein localization in single cells of the model organism Bacillus subtilis during the progression to spore formation. We found that sporulation proceeded through noisy and reversible steps towards an irreversible, all-or-none commitment point. Specifically, we observed cell-autonomous and spontaneous bursts of gene expression and transient protein localization events during sporulation. Based on these measurements we developed mathematical population models to investigate how the degree of reversibility affects cellular decision-making. In particular, we evaluated the effect of reversibility on the 1) reliability in the progression to sporulation, and 2) adaptability under changing extracellular stress conditions. Results show that reversible progression allows cells to remain responsive to long-term environmental fluctuations. In contrast, the irreversible commitment point supports reliable execution of cell fate choice that is robust against short-term reductions in stress. This combination of opposite dynamic behaviors (reversible and irreversible) thus maximizes both adaptable and reliable decision-making over a broad range of changes in environmental conditions. These results suggest that decision-making systems might employ a general hybrid strategy to cope with unpredictably fluctuating environmental conditions

”En skola för vissa”

Sammanfattning Syftet med examensarbetet är att bidra till diskussionen angående hur väl den svenska skolan är en ”skola för alla”. Frågeställningen som skall uppnå syftet är frågan om hur väl ”en skola för alla” fungerar i praktiken. Är skolan verkligen en skola för alla? I skolans styrdokument står det att den skall vara det, men går det i själva verket att uppfylla detta i verkligheten? ”En skola för alla” är ett brett begrepp med många olika aspekter och infallsvinklar. Det skulle vara omöjligt att undersöka allt under den tidsram jag har haft till mitt förfogande. Jag har därför valt att inrikta mig på hjälpaspekten, alltså i vilken mån eleverna får den hjälp de behöver i skolan och hur mycket de själva efterfrågar hjälp. Som forskningsmetod valde jag att använda mig av observationer. Tre kategorier av elever kunde under observationerna identifieras genom i vilken mån de behövde hjälp och på vilket sätt de uttryckte det på. Kategorierna som kunde urskiljas var: ”Stökiga”, störande elever, ”Osynliga”, tystlåtna elever och ”Duktiga”, ambitiösa elever. De elever som verkade klara sig bäst var de ”duktiga” eleverna för de behövde sällan hjälp, de som fick mest hjälp var de ”stökiga” eleverna för de hördes mest och fick därför mest uppmärksamhet av lärarna. De ”osynliga” glömdes oftast bort eftersom de var tystlåtna och inte märktes av när de behövde hjälp. Att eleverna inte efterfrågar hjälp betyder inte att de inte behöver hjälp. Här är lärarens roll av stor vikt. Attityden och engagemanget läraren har gentemot eleverna är av oerhörd betydelse för hur det går för eleverna i skolan

The methylotrophic yeast Hansenula polymorpha contains an inducible import pathway for peroxisomal matrix proteins with an N-terminal targeting signal (PTS2 proteins).

Two main types of peroxisomal targeting signals have been identified that reside either at the extreme C terminus (PTS1) or the N terminus (PTS2) of the protein. In the methylotrophic yeast Hansenula polymorpha the majority of peroxisomal matrix proteins are of the PTS1 type. Thus far, for H. polymorpha only amine oxidase (AMO) has been shown to contain a PTS2 type signal. In the present study we expressed H. polymorpha AMO under control of the strong endogenous alcohol oxidase promoter. Partial import of AMO into peroxisomes was observed in cells grown in methanol/(NH4)2SO4-containing medium. However, complete import of AMO occurred if the cells were grown under conditions that induce expression of the endogenous AMO gene. Similar results were obtained when the heterologous PTS2 proteins, glyoxysomal malate dehydrogenase from watermelon and thiolase from Saccharomyces cerevisiae, were synthesized in H. polymorpha. The import of PTS1 proteins, however, was not affected by the growth conditions. These results indicate that the reduced rate of AMO import in (NH4)2SO4-grown cells is not due to competition with PTS1 proteins for the same import pathway. Apparently, AMO is imported via a separate pathway that is induced by amines and functions for PTS2 proteins in general