Electrical protein array chips for the detection of staphylococcal virulence factors

Oral administration of recombinant Bacillus subtilis spores expressing mutant staphylococcal enterotoxin B provides potent protection against lethal enterotoxin challenge

Pathogenicity of Staphylococcus aureus is induced by staphylococcal enterotoxin B (SEB). A mutant form of SEB (mSEB) is immunogenic as well as less toxic. Recombinant mSEB and SEB were expressed in pET28a prokaryotic plasmids. Tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels in mSEB-stimulated macrophages were lower than those in SEB-stimulated macrophages (p < 0.001, p < 0.01 respectively). Using CotC as a fusion protein, we constructed recombinant Bacillus subtilis spores expressing mSEB on the spore surface and evaluated their safety and protective efficacy via mouse models. Oral administration of mSEB-expressing spores increased SEB-specific IgA in feces and SEB-specific IgG1 and IgG2a in the sera, compared with mice in naïve and CotC spore-treated groups (p < 0.001, p < 0.01, p < 0.001 respectively). Six weeks following oral dosing of recombinant spores, significant differences were not found in the serum biochemical indices between the mSEB group and the naïve and CotC groups. Furthermore, oral administration of mSEB spores increased the survival rate by 33.3% in mice intraperitoneally injected with 5 µg of wild-type SEB plus 25 µg lipopolysaccharide (LPS). In summation, recombinant spores stably expressing mSEB were developed, and oral administration of such recombinant spores induced a humoral immune response and provided protection against SEB challenge in mice.

Multiplex Immunoassay Techniques for On-Site Detection of Security Sensitive Toxins

Biological toxins are a heterogeneous group of high molecular as well as low molecular weight toxins produced by living organisms. Due to their physical and logistical properties, biological toxins are very attractive to terrorists for use in acts of bioterrorism. Therefore, among the group of biological toxins, several are categorized as security relevant, e.g., botulinum neurotoxins, staphylococcal enterotoxins, abrin, ricin or saxitoxin. Additionally, several security sensitive toxins also play a major role in natural food poisoning outbreaks. For a prompt response to a potential bioterrorist attack using biological toxins, first responders need reliable, easy-to-use and highly sensitive methodologies for on-site detection of the causative agent. Therefore, the aim of this review is to present on-site immunoassay platforms for multiplex detection of biological toxins. Furthermore, we introduce several commercially available detection technologies specialized for mobile or on-site identification of security sensitive toxins.

Phenotype and expression profile analysis of Staphylococcus aureus biofilms and planktonic cells in response to licochalcone A

Staphylococcus aureus is one of the most important pathogens in humans and animals. The formation of biofilm by S. aureus is considered an important mechanism of antimicrobial resistance. Therefore, finding effective drugs against the biofilm produced by S. aureus has been a high priority. Licochalcone A (LAA), a natural plant product, was reported to have antibacterial activities and showed good activity against all 21 tested strains of S. aureus biofilm and planktonic cells. To detect the possible molecular mechanism of LAA against S. aureus biofilm or planktonic cells, Affymetrix GeneChips were used to determine the global comparative transcription of S. aureus biofilm and planktonic cells triggered by treatment with sub-bactericidal and sub-inhibitory concentrations of LAA, respectively. LAA significantly altered (greater than a 2- or less than -2-fold change) the expression of 693 genes in planktonic cells and 817 genes in biofilm. The levels of genes encoding autolysis-associated proteins, cell wall proteins, pathogenic factors, protein synthesis genes, and enzymes involved in capsule synthesis were significantly altered in LAA-treated S. aureus. Furthermore, some differences observed in the microarray analysis were verified by real-time RT-PCR. To our knowledge, this is the first observation of phenotype and expression profiles of S. aureus biofilm and planktonic cells in response to LAA treatment.

Attomole sensitivity of staphylococcal enterotoxin B detection using an aptamer-modified surface-enhanced Raman scattering probe

In this report, we present a new homogeneous detection method for staphylococcal enterotoxin B (SEB) utilizing core-shell-structured iron-gold magnetic nanoparticles and a gold nanorod surface-enhanced Raman scattering (SERS) probe in solution. Peptide ligand (aptamer) functionalized magnetic gold nanorod particles were used as scavengers for target SEB. After the SEB molecules were separated from the matrix, the sandwich assay procedure was tested by gold nanorod particles that act as SERS probes. The binding constant between SEB and peptide-nanoparticle complex was determined as 8.0 × 10(7) M(-1). The correlation between the SEB concentration and SERS signal was found to be linear within the range of 2.5 fM to 3.2 nM. The limit of detection for the homogeneous assay was determined as 224 aM (ca. 2697 SEB molecules/20 μL sample volume). Also, gold-coated surfaces were used as capture substrates and performances of the two methods were compared. Furthermore, the developed method was evaluated for investigating the SEB specificity on bovine serum albumin (BSA) and avidin and detecting SEB in artificially contaminated milk, blood, and urine.

Discerning Trends in Multiplex Immunoassay Technology with Potential for Resource-Limited Settings

BACKGROUND

In the search for more powerful tools for diagnoses of endemic diseases in resource-limited settings, we have been analyzing technologies with potential applicability. Increasingly, the process focuses on readily accessible bodily fluids combined with increasingly powerful multiplex capabilities to unambiguously diagnose a condition without resorting to reliance on a sophisticated reference laboratory. Although these technological advances may well have important implications for the sensitive and specific detection of disease, to date their clinical utility has not been demonstrated, especially in resource-limited settings. Furthermore, many emerging technological developments are in fields of physics or engineering, which are not readily available to or intelligible to clinicians or clinical laboratory scientists.

CONTENT

This review provides a look at technology trends that could have applicability to high-sensitivity multiplexed immunoassays in resource-limited settings. Various technologies are explained and assessed according to potential for reaching relevant limits of cost, sensitivity, and multiplex capability. Frequently, such work is reported in technical journals not normally read by clinical scientists, and the authors make enthusiastic claims for the potential of their technology while ignoring potential pitfalls. Thus it is important to draw attention to technical hurdles that authors may not be publicizing.

SUMMARY

Immunochromatographic assays, optical methods including those involving waveguides, electrochemical methods, magnetorestrictive methods, and field-effect transistor methods based on nanotubes, nanowires, and nanoribbons reveal possibilities as next-generation technologies.

Adsorption characteristics of an enteric virus-binding protein to norovirus, rotavirus and poliovirus

BACKGROUND

Water contamination with human enteric viruses has posed human health risks all over the world. Reasonable and facile methodologies for recovering and quantifying infectious enteric viruses in environmental samples are needed to address the issues of waterborne viral infectious diseases. In this study, a bacterial protein that has a binding capability with several enteric viruses is discovered, and its binding characteristics were investigated for utilizing it as a viral adsorbent in virus recovery and detection technologies.

RESULTS

A gene of an enteric virus-binding protein (EVBP), derived from a monomer of a bacterial chaperon protein GroEL, was successfully acquired from a genomic DNA library of activated sludge microorganisms with nested PCR. Equilibrium dissociation constants between EVBP and norovirus-like particles (NoVLPs) of genotypes GI.7 and GII.4, estimated with quartz crystal microbalance method, were 240 and 210 nM, respectively. These values of equilibrium dissociation constant imply that the binding affinity between EVBP and NoVLPs is 1 to 3-log weaker than that in general antigen-antibody interactions, but about 2-log stronger than that in weak specific interactions of proteins with cations and organic polymers. The adsorptions of EVBP to norovirus, group A rotavirus and poliovirus type 1 were found to be significant in enzyme-linked immunosorbent assay. Meanwhile, the binding of native GroEL tetradecamer to viral particles was weaker than that of EVBP, presumably because of a steric hindrance. The small molecule of EVBP could have an advantage in the access to the surface of viral particles with rugged structure.

CONCLUSIONS

EVBP that has a broad binding spectrum to enteric viruses was newly discovered. The broad binding characteristic of EVBP would allow us to utilize it as a novel adsorbent for detecting diverse enteric viruses in clinical and environmental samples.

Multiplex bioanalytical methods for food and environmental monitoring

Recent advances in miniaturization of analytical systems and newly emerging technologies offer platforms with greater automation and multiplexing capabilities than traditional biological binding assays. Multiplexed bioanalytical techniques provide control agencies and food industries with new possibilities for improved, more efficient monitoring of food and environmental contaminants. This review deals with recent developments in planar-array and suspension-array technologies, and their applications in detecting pathogens, food allergens and adulterants, toxins, antibiotics and environmental contaminants.