Tuberculosis associated with Mycobacterium tuberculosis Beijing and non-Beijing genotypes: a clinical and immunological comparison

BACKGROUND: The Mycobacterium tuberculosis Beijing genotype is biologically different from other genotypes. We aimed to clinically and immunologically compare human tuberculosis caused by Beijing and non-Beijing strains. METHODS: Pulmonary tuberculosis patients were prospectively enrolled and grouped by their M. tuberculosis genotypes. The clinical features, plasma cytokine levels, and cytokine gene expression levels in peripheral blood mononuclear cells (PBMC) were compared between the patients in Beijing and non-Beijing groups. RESULTS: Patients in the Beijing group were characterized by significantly lower frequency of fever (odds ratio, 0.12, p = 0.008) and pulmonary cavitation (odds ratio, 0.2, p = 0.049). Night sweats were also significantly less frequent by univariate analysis, and the duration of cough prior to diagnosis was longer in Beijing compared to non-Beijing groups (medians, 60 versus 30 days, p = 0.048). The plasma and gene expression levels of interferon (IFN) γ and interleukin (IL)-18 were similar in the two groups. However, patients in the non-Beijing group had significantly increased IL-4 gene expression (p = 0.018) and lower IFN-γ : IL-4 cDNA copy number ratios (p = 0.01). CONCLUSION: Patients with tuberculosis caused by Beijing strains appear to be less symptomatic than those who have disease caused by other strains. Th1 immune responses are similar in patients infected with Beijing and non-Beijing strains, but non-Beijing strains activate more Th2 immune responses compared with Beijing strains, as evidenced by increased IL-4 expression

Effect of exfoliation and dispersion on the yield behavior of melt-compounded polyethylene-montmorillonite nanocomposites

The yield behavior of melt-mixed nanocomposites containing 5 wt % organically modified montmorillonite in matrices of a linear low-density polyethylene (LLDPE) or a modified polyethylene was studied as a function of the temperature. and strain rate. In the melt-mixed LLDPE nanocomposite, the montmorillonite showed a slight increase in the clay spacing, which suggested that the clay was at best intercalated. Transmission electron microscopy (TEM) images showed that the dispersion in this nanocomposite was poor. The use of the modified polyethylene promoted exfoliation of the clay tactoids in the nanocomposite, as assessed by X-ray diffraction and TEM. In both nanocomposites, the yield mechanisms were insensitive to the addition of the organoclay, even though modest increases in the modulus were produced. (c) 2006 Wiley Periodicals, Inc

The effects of polymer topology and chain length on the antimicrobial activity and hemocompatibility of amphiphilic ternary copolymers

Investigation into the macromolecular structure-Activity relationship of synthetic antimicrobial polymers has been gaining scientific interest due to the possibility of discovering new alternatives for combating the increase of multidrug resistance in bacteria. Recently, we reported the development of new antimicrobial polymers in the form of amphiphilic ternary copolymers that consist of low-fouling (oligoethylene glycol), cationic and hydrophobic side chains. The combination of these three main functional groups is crucial in endowing the polymers with high antimicrobial potency against Gram-negative pathogens and low cytotoxicity. Following on from our previous study, we herein present a systematic assessment on the effects of the polymer chain length and architecture (i.e., random vs. block copolymers and linear vs. hyperbranched) on the antimicrobial activity and hemocompatibility of antimicrobial ternary copolymers. The polymer chain length in random copolymers slightly affects the antimicrobial activity where longer chains are marginally more bacteriostatic against Pseudomonas aeruginosa and Escherichia coli. In terms of hemocompatibility, polymers with shorter chains are more prone to hemagglutination. Interestingly, when the hydrophilic and hydrophobic segments are separated into diblock copolymers, the antimicrobial activity is lost, possibly due to the stable core-shell architecture. The hyperbranched structure which consists of 2-ethylhexyl groups as hydrophobic side-chains yields the best overall biological properties, having similar antimicrobial activity (MIC = 64 μg mL-1) and >4-fold increase in HC50 compared to the linear random copolymers (HC50 > 10000 μg mL-1) with no hemagglutination. The hyperbranched polymers are also bactericidal and kill ≥99% and 90% of planktonic and biofilm Pseudomonas aeruginosa, respectively. This study thus highlights the importance of determining macromolecular structural aspects that govern the biological activity of antimicrobial polymers