Wednesday, December 12, 2012
Antibody orientation at bacterial surfaces is related to invasive infection.
Antibody orientation at bacterial surfaces is related to invasive infection.
Dec 2012
Source
Department of Clinical Sciences, Faculty of Medicine; and 2 Department of Immunotechnology, Faculty of Engineering, Lund University, Lund, Sweden.
Abstract
Several of the most significant bacterial pathogens in humans, including Streptococcus pyogenes, express surface proteins that bind IgG antibodies via their fragment crystallizable (Fc) region, and the dogma is that this protects the bacteria against phagocytic killing in blood. However, analysis of samples from a patient with invasive S. pyogenes infection revealed dramatic differences in the presence and orientation of IgG antibodies at the surface of bacteria from different sites. In the throat, IgG was mostly bound to the bacterial surface via Fc, whereas in the blood IgG was mostly bound via fragment antigen-binding (Fab). In infected and necrotic tissue, the Fc-binding proteins were removed from the bacterial surface. Further investigation showed that efficient bacterial IgGFc-binding occurs only in IgG-poor environments, such as saliva. As a consequence, the bacteria are protected against phagocytic killing, whereas in blood plasma where the concentration of IgG is high, the antibodies preferentially bind via Fab, facilitating opsonization and bacterial killing. IgG-poor environments represent the natural habitat for IgGFc-binding bacteria, and IgGFc-binding proteins may have evolved to execute their function in such environments. The lack of protection in plasma also helps to explain why cases of severe invasive infections with IgGFc-binding bacteria are so rare compared with superficial and uncomplicated infections.
Labels: Antibody orientation, Bacterial Pathogens, bacterial surfaces, invasive infection, Streptococcus pyogene
# posted by Pat O'Connor @ 10:43 AM
Sunday, November 04, 2012
Antibiofilm Activity of Dendrophthoe falcata against Different Bacterial Pathogens.
Antibiofilm Activity of Dendrophthoe falcata against Different Bacterial Pathogens.
Oct 2012
Source
Department of Biotechnology, Alagappa University, Karaikudi, Tamil Nadu, India.
Abstract
Dendrophthoe falcata is a hemiparasitic plant commonly used for ailments such as ulcers, asthma, impotence, paralysis, skin diseases, menstrual troubles, pulmonary tuberculosis, and wounds. In this context, the validations of the traditional claim that the leaf extract of D. falcata possesses antibiofilm and anti-quorum sensing activity against different bacterialpathogens were assessed. The bacterial biofilms were quantified by crystal violet staining. Among the 17 bacterial pathogens screened, the methanolic fraction of the leaf extract clearly demonstrated antibiofilm activity for Proteus mirabilis, Vibrio vulnificus, Aeromonas hydrophila, Shigella sonnei, Chromobacterium violaceum ATCC 12472, Vibrio parahaemolyticus, Vibrio harveyi, Vibrio alginolyticus, Vibrio cholerae, and Proteus vulgaris. At biofilm inhibitory concentrations, biofilm formation was reduced by up to 70-90 %. Furthermore, the potential quorum-sensing activity of the leaf extract was tested by agar well diffusion using Chromobacterium violaceum (ATCC 12472 & CV O26) reporter strains. The inhibition of violacein production may be due to direct or indirect interference on QS by active constituents or the interactive effect of different phytocompounds present in the extracts. This is the first report on antibiofilm and QS activity of D. falcata leaf extracts, signifying the scope for development of complementary medicine for biofilm-associated infections.
Labels: Antibiofilm, asthma, Bacterial Pathogens, Dendrophthoe falcata, hemiparasitic plant, impotence, menstrual troubles, paralysis, phytocompounds, pulmonary tuberculosis, skin diseases, ulcers, wounds
# posted by Pat O'Connor @ 7:19 AM
