PCR detection and identification of oral streptococci in saliva samples using GTF genes

A mixed self-assembled monolayer-based surface plasmon immunosensor for detection of E. coli O157:H7

The sensitivity and specificity of a polyethylene glycol terminated alkanethiol mixed self-assembled monolayers (SAM) on surface plasmon resonance (SPR) immunosensor to detect Escherichia coli O157:H7 is demonstrated. Purified monoclonal (Mabs) or polyclonal antibodies (PAbs) against E. coli O157:H7 were immobilized on an activated sensor chip and direct and sandwich assays were carried to detect E. coli O157:H7. Effect of Protein G based detection and effect of concentrations of primary and secondary antibodies in sandwich assay were investigated. The sensor surface was observed under an optical microscope at various stages of the detection process. The sensor could detect as low as 10(3)CFU/ml of E. coli O157:H7 in a sandwich assay, with high specificity against Salmonella Enteritidis. The detection limit using direct assay and Protein G were 10(6)CFU/ml and 10(4)CFU/ml, respectively. Results indicate that an alkanethiol SAM based SPR biosensor has the potential for rapid and specific detection of E. coli O157:H7, using a sandwich assay.

Use of housekeeping gene sequencing for species identification of viridans streptococci

Based on the genetic analysis of 20 reference strains, we describe an approach using the sequencing of 2 housekeeping genes, zwf and gki, to identify members of the mitis-sanguinis group of viridans streptococci to the species level, with a better discrimination compared with 16S rDNA sequencing. This approach also suggested that some reference strains may not be correctly classified.

Oral diagnostics for the geriatric populations: current status and future prospects

Because it is a noninvasive technique, there is growing interest in replacing blood with oral-based methods of diagnostics. Oral diagnostics may be used for diagnosis and therapeutic drug monitoring of both oral diseases (eg, caries, periodontal disease,oral lesions, oral cancer) and systemic diseases (eg, infectious diseases, including HIV and AIDS, autoimmune diseases, cancer,and endocrine disorders). The authors address both existing techniques and oral-based diagnostics that will be applicable to the aging population in the future. They also highlight those techniques that are uniquely suited to point-of-care applications.

Development of a PCR method for rapid identification of new Streptococcus mutans serotype k strains

In a previous study, we isolated and characterized a new serotype k of Streptococcus mutans from human blood and oral cavities. Analysis of the genes involved in biosynthesis of the serotype-specific polysaccharide of serotype k strains revealed that the serotype k-specific nucleotide alignment was commonly present in the 5' region of the rgpF gene (350 bp from the initial sequence) compared to the reference strains, and then a method for rapid identification of serotype k strains was developed by use of PCR with primers designed on the basis of the sequence of the variable region. PCR assays with primers specific for amplification of serotype k strains showed a negative reaction with serotype c, e, and f strains and a positive reaction with serotype k strains, with the sensitivity for identification of the serotype k strains shown to range from 5 to 50 cells. Next, the frequency of positive reactions for serotype k-specific primers was surveyed with DNA taken from saliva samples from 200 subjects (2 to 18 years of age), and 10 of those showed a positive reaction, which was higher than the frequency in our previous survey with a serological method. In addition, all saliva samples from subjects with serotype k strains in our previous study were shown to be positive with the serotype k-specific primers. These results indicate that this new PCR method is effective for identification of subjects with S. mutans serotype k.