Post-antibiotic growth suppression of linezolid against Gram-positive bacteria

The in vitro post-antibiotic effects (PAEs) of eight different concentrations of linezolid against Gram-positive cocci were investigated and the results analysed using the sigmoid E-max model for mathematically modelling the PAE. Mean maximal linezolid PAEs against strains of Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Enterococcus faecium and Streptococcus pneumoniae were 2.2, 1.8, 2.8, 2.0 and 3.0 h, respectively. Resistance to methicillin (for the staphylococci), vancomycin (for the enterococci) and penicillin (for the pneumococci) had no effect on the duration of the PAE. Results of PAE testing support twice-daily dosing of linezolid in humans.

Enhancing the immunogenicity and modulating the fine epitope recognition of antisera to a helical group A streptococcal peptide vaccine candidate from the M protein using lipid-core peptide technology

A conserved helical peptide vaccine candidate from the M protein of group A streptococci, p145, has been described. Minimal epitopes within p145 have been defined and an epitope recognized by protective antibodies, but not by autoreactive T cells, has been identified. When administered to mice, p145 has low immunogenicity. Many boosts of peptide are required to achieve a high antibody titre (> 12 800). To attempt to overcome this low immunogenicity, lipid-core peptide technology was employed. Lipid-core peptides (LCP) consist of an oligomeric polylysine core, with multiple copies of the peptide of choice, conjugated to a series of lipoamino acids, which acts as an anchor for the antigen. Seven different LCP constructs based on the p145 peptide sequence were synthesized (LCP1-->LCP7) and the immunogenicity of the compounds examined. The most immunogenic constructs contained the longest alkyl side-chains. The number of lipoamino acids in the constructs affected the immunogenicity and spacing between the alkyl side-chains increased immunogenicity. An increase in immunogenicity (enzyme-linked immunosorbent assay (ELISA) titres) of up to 100-fold was demonstrated using this technology and some constructs without adjuvant were more immunogenic than p145 administered with complete Freund's adjuvant (CFA). The fine specificity of the induced antibody response differed for the different constructs but one construct, LCP4, induced antibodies of identical fine specificity to those found in endemic human serum. Opsonic activity of LCP4 antisera was more than double that of p145 antisera. These data show the potential for LCP technology to both enhance immunogenicity of complex peptides and to focus the immune response towards or away from critical epitopes.

Immunoglobulins in saliva of preterm and full-term infants. A longitudinal study from 0-18 months of age

The aim of this longitudinal study was to determine salivary levels of total IgA, IgG and IgM in 84 preterm and 214 full-term infants, from birth to 18 months of age. Unstimulated whole saliva was collected from each infant at birth, and subsequently at 3-monthly intervals. Immunoglobulin levels were estimated using an ELISA technique. At birth, IgA was detected in 147/214 (69%) full-term infants but only 47/84 (56%) preterm infants (P

Evaluation of encapsulation techniques of probiotics for yoghurt

The health benefits provided by probiotic bacteria have led to their increasing use in fermented and other dairy products. However, their viability in these products is low. Encapsulation has been investigated to protect the bacteria in the product's environment and improve their survival. There are two common encapsulation techniques, namely extrusion and emulsion, to encapsulate the probiotics for their use in the fermented and other dairy products. This review evaluates the merits and limitations of these two techniques, and also discusses the supporting materials and special treatments used in encapsulation processes. (C) 2003 Elsevier Science Ltd. All rights reserved.

Identification and characterization of pptA: a gene involved in the phase-variable expression of phosphorylcholine on pili of Neisseria meningitidis

Pili of pathogenic Neisseria are major virulence factors associated with adhesion, cytotoxicity, twitching motility, autoaggregation, and DNA transformation. Pili are modified posttranslationally by the addition of phosphorylcholine. However, no genes involved in either the biosynthesis or the transfer of phosphorylcholine in Neisseria meningitidis have been identified. In this study, we identified five candidate open reading frames (ORFs) potentially involved in the biosynthesis or transfer of phosphorylcholine to pilin in N. meningitidis. Insertional mutants were constructed for each ORF in N. meningitidis strain C311#3 to determine their effect on phosphorylcholine expression. The effect of the mutant ORFs on the modification by phosphorylcholine was analyzed by Western analysis with phosphorylcholine-specific monoclonal antibody TEPC-15. Analysis of the mutants showed that ORF NMB0415, now defined as pptA (pilin phosphorylcholine transferase A), is involved in the addition of phosphorylcholine to pilin in N. meningitidis. Additionally, the phase variation (high frequency on-off switching of expression) of phosphorylcholine on pilin is due to changes in a homopolymeric guanosine tract in pptA.