Impact of rapid urbanization on the rates of infection by Vibrio cholerae O1 and enterotoxigenic Escherichia coli in Dhaka, Bangladesh

Background

In Bangladesh, increases in cholera epidemics are being documented with a greater incidence and severity. The aim of this prospective study was to identify the prevalence and importance of V. cholerae O1 and enterotoxigenic Escherichia coli (ETEC) as causal agents of severe diarrhea in a high diarrhea prone urban area in Dhaka city.

Methodology

Systematic surveillance was carried out on all diarrheal patients admitted from Mirpur between March 2008 to February 2010 at the ICDDR, B hospital. Stool or rectal swabs were collected from every third diarrheal patient for microbiological evaluation.

Principal Findings

Of diarrheal patients attending the hospital from Mirpur, 41% suffered from severe dehydration with 39% requiring intravenous rehydration therapy. More diarrheal patients were above five years of age (64%) than those below five years of age (36%). About 60% of the patients above five years of age had severe dehydration compared with only 9% of patients under five years of age. The most prevalent pathogen isolated was Vibrio cholerae O1 (23%) followed by ETEC (11%). About 8% of cholera infection was seen in infants with the youngest children being one month of age while in the case of ETEC the rate was 11%. Of the isolated ETEC strains, the enterotoxin type were almost equally distributed; ST accounted for 31% of strains; LT/ST for 38% and LT for 31%.

Conclusion

V. cholerae O1 is the major bacterial pathogen and a cause of severe cholera disease in 23% of patients from Mirpur. This represents a socioeconomic group that best reflects the major areas of high cholera burden in the country. Vaccines that can target such high risk groups in the country and the region will hopefully be able to reduce the disease morbidity and the transmission of pathogens that impact the life and health of people.     

Structure-function analysis of the C-terminus of IcmT of Legionella pneumophila in pore formation-mediated egress from macrophages

We have recently shown an essential role of the 32 amino acids C-terminus domain of IcmT of Legionella pneumophila in bacterial egress from macrophages. Mutants expressing an IcmT protein with a truncation in the C-terminus, replicate intracellularly but are defective in pore formation-mediated egress. The C-terminus domain of IcmT is the only hydrophilic domain of IcmT that is predicted to be in the cytoplasm while the rest of the protein is in the cytoplasmic membrane. In order to characterize the structure-function of the C-terminus of IcmT in the pore-forming activity and bacterial egress, we constructed 10 icmT missense mutant alleles differing by a single amino acid in the C-terminus of icmT and introduced them into the null icmT mutant. The H58Q, W69L, R71I, R79I and R86I icmT mutant alleles showed significantly lower pore-forming activity as measured by hemolysis of sRBC. The Y59S, R68L and S77L mutant alleles showed significantly lower cytopathogenicity to U937 macrophages. All 10 mutant alleles enabled the icmT null mutant to replicate intracellularly as efficiently as icmT null mutant harboring the wild-type icmT. Seven of the icmT alleles enabled the icmT null mutant to egress from infected macrophages as efficiently as icmT null mutant harboring the wild-type icmT. The other 3 substitutions conferred a partial defect in hemolysis and two of them also conferred a defect in egress from macrophages. Thus, two amino acid residues in the C-terminus of IcmT are required for both pore formation and bacterial egress. However, certain single amino acid substitutions in the C-terminus reduce the pore-forming activity when tested in vitro, but may or may not have a detectable effect on egress of L. pneumophila from U937 macrophages.     

Photon transmission study on conformational ordering of iota-carrageenan in CaCl2 solution

Coil-to-double helix (c-h) and double helix-to-dimer (h-d) phase transitions of iota-carrageenan in CaCl(2) solution upon cooling were studied using photon transmission technique. Photon transmission intensity, I(tr) was monitored against temperature to determine the (c-h) and (h-d) transition temperatures (T(ch) and T(hd)) and activation energies (DeltaE(ch) and DeltaE(hd)). An extra dimer-to-dimer (d-d) transition was also observed during cooling at low temperature region. However, upon heating dimers disappear to double helices by making dimer-to-double helix (d-h) transition. Further heating resulted double helix-to-coil (h-c) transition at high temperature region. T(dh) and T(ch) temperatures and DeltaE(dh) and DeltaE(hc) activation energies were also determined. It was observed that T(hc) and T(ch) temperatures and DeltaE(dh) and DeltaE(hd) activation energies do not effected by carrageenan content. However, T(hd), T(dh) and T(dd) temperatures and DeltaE(ch) and DeltaE(hc) activation energies were found to be strongly correlated to the carrageenan content in the system.     

Morphometry of pseudoepitheliomatous hyperplasia: objective comparison to normal and dysplastic oral mucosae

OBJECTIVE: To compare the architectural and morphometric features of pseudoepitheliomatous hyperplasia (PEH) associated with oral granular cell tumors (GCT), normal oral mucosa and oral epithelial dysplasia. STUDY DESIGN: Quantitative comparisons between the diagnostic entities were carried out at the tissue level by estimating the fractal complexity of the epithelial connective tissue interface and at the cellular level by analyzing the morphometric features of algorithmically segmented epithelial cell areas. RESULTS: Casewise multivariate analysis showed that the fractal properties produced a correct discrimination rate of 96.4% between PEH and normal mucosa. Cellular parameters gave a 100% correct discrimination rate between PEH and mild dysplasia. Combining the fractal and cellular properties also showed 100% discrimination between PEH and normal mucosa and between PEH and mild dysplasia. CONCLUSION: The results show that PEH associated with GCT displays quantifiable morphometric features that make it differentiable from normal oral mucosa and oral epithelial dysplasia.     

The Francisella tularensis pathogenicity island protein IglC and its regulator MglA are essential for modulating phagosome biogenesis and subsequent bacterial escape into the cytoplasm

The Francisella tularensis subsp. novicida-containing phagosome (FCP) matures into a late endosome-like stage that acquires the late endosomal marker LAMP-2 but does not fuse to lysosomes, for the first few hours after bacterial entry. This modulation in phagosome biogenesis is followed by disruption of the phagosome and bacterial escape into the cytoplasm where they replicate. Here we examined the role of the Francisella pathogenicity island (FPI) protein IglC and its regulator MglA in the intracellular fate of F. tularensis subsp. novicida within human macrophages. We show that F. tularensis mglA and iglC mutant strains are defective for survival and replication within U937 macrophages and human monocyte-derived macrophages (hMDMs). The defect in intracellular replication of both mutants is associated with a defect in disruption of the phagosome and failure to escape into the cytoplasm. Approximately, 80-90% of the mglA and iglC mutants containing phagosomes acquire the late endosomal/lysosomal marker LAMP-2 similar to the wild-type (WT) strain. Phagosomes harbouring the mglA or iglC mutants acquire the lysosomal enzyme Cathepsin D, which is excluded from the phagosomes harbouring the WT strain. In hMDMs in which the lysosomes are preloaded with BSA-gold or Texas Red Ovalbumin, phagosomes harbouring the mglA or the iglC mutants acquire both lysosomal tracers. We conclude that the FPI protein IglC and its regulator MglA are essential for modulating phagosome biogenesis and subsequent bacterial escape into the cytoplasm. Therefore, acquisition of the FPI, within which iglC is contained, is essential for the pathogenic evolution of F. tularensis to evade lysosomal fusion within human macrophages and cause tularemia. This is the first example of specific virulence factors of F. tularensis that are essential for evasion of fusion of the FCP to lysosomes.     

Binding of madindoline A to the extracellular domain of gp130

Elevated levels of IL-6 and IL-11 are associated with multiple myeloma, rheumatoid arthritis, hypercalcemia, cancer cachexia, and Castleman's disease. Madindoline A (MadA), isolated from Streptomyces nitrosporeus K93-0711, specifically inhibits the growth of IL-6- and IL-11-dependent cell lines, most likely by interfering with the homodimerization of gp130. This raises the possibility that MadA can be used as a model compound for the development of novel chemotherapeutic agents. In this report, we demonstrate that the binding of MadA to gp130 is specific and noncovalent, and displays a relatively low affinity. Furthermore, we show that the tricyclic 3a-hydroxytetrahydrofuro[2,3-b]indole (HFI) moiety of MadA alone is not sufficient for binding. Matrix-bound MadA precipitates a protein composed of the extracellular domain of gp130 fused to the Fc region of the immunoglobulin heavy chain. Binding is inhibited in a dose-dependent manner by preincubation with free MadA. The K(D) for binding of MadA to gp130 is 288 microM, as determined by surface plasmon resonance (SPR)-based biosensor analysis. The HFI portion of MadA does not bind to gp130 in either affinity precipitation or SPR analyses. Finally, MadA, but not the HFI portion, inhibits IL-6-dependent Stat3 tyrosine phosphorylation in HepG2 cells.     

Tumor cell alpha3beta1 integrin and vascular laminin-5 mediate pulmonary arrest and metastasis

Arrest of circulating tumor cells in distant organs is required for hematogenous metastasis, but the tumor cell surface molecules responsible have not been identified. Here, we show that the tumor cell alpha3beta1 integrin makes an important contribution to arrest in the lung and to early colony formation. These analyses indicated that pulmonary arrest does not occur merely due to size restriction, and raised the question of how the tumor cell alpha3beta1 integrin contacts its best-defined ligand, laminin (LN)-5, a basement membrane (BM) component. Further analyses revealed that LN-5 is available to the tumor cell in preexisting patches of exposed BM in the pulmonary vasculature. The early arrest of tumor cells in the pulmonary vasculature through interaction of alpha3beta1 integrin with LN-5 in exposed BM provides both a molecular and a structural basis for cell arrest during pulmonary metastasis.     

Nutritional factors affecting organic solvent-tolerant alkaline protease production by a newBacillus cereus strain 146

An organic solvent-tolerant bacterium designated as 146 capable of producing an organic solvent-stable alkaline protease was isolated from contaminated soil of a wood factory. The strain was a Gram-positive, spore-forming, nitrate-positive, rod-shaped organism capable of hydrolysing gelatine, starch, skim milk and identified asBacillus cereus. Activity of the protease was drastically increased in the presence of 1–decanol, isooctane, n-dodecane and n-tetradecane, but reduced in the presence of ethyl acetate, benzene, toluene, 1-heptanol, ethylbenzene and hexane. The bacterium was shown to require lactose as a carbon source and peptone as a nitrogen source. The optimum fermentation condition for the production of alkaline protease was in the presence of beef and yeast extract. Optimum pH was determined to be at 10.0 at incubation temperature of 37 °C for 48 h. Results from the studies suggest that 146 is a new strain of Bacillus cereus capable of producing organic solvent-tolerant alkaline protease with potential use in industries.