This study has validated the use of the culture-independent technique T-RFLP in sinonasal samples. Preliminary characterization of the microbial diversity in CRS suggests a complex range of common and novel bacterial species within the upper airway in CRS, providing further evidence for the polymicrobial etiology of CRS.

A colorimetric DNA hybridization assay has been developed for the rapid detection of Escherichia coli in foods. The method employs two oligonucleotide probes which are specific for the 16S ribosomal RNA of E. coli. Probes are added to lysates of test cultures and allowed to hybridize to target rRNA if present. The probe-target complex is captured via hybridization to a polystyrene dipstick. The immobilized target is detected using an antibody-horseradish peroxidase conjugate which binds to the immobilized probe-target complex. The probe-target-antibody complex generates a colorimetric signal when exposed to a substrate/chromogen mixture. A total of 233 E. coli isolates representing typical, toxigenic, invasive, hemorrhagic serotype 0157:H7, and other pathogenic strains all resulted in a positive assay signal. Dose-response experiments indicate the sensitivity of the assay is approximately 1 × 106 CFU/ml. Specificity of the assay was determined by testing 207 strains of non-E. coli species at 109 CFU/ml. All of the non-E. coli organisms tested were negative with the exception of Escherichia fergusonii and Shigella species. A total of 345 enriched samples including inoculated, uninoculated, and naturally-contaminated foods was tested for the presence of E. coli by the hybridization assay and a conventional cultural method. The false-negative rate for the hybridization assay was 1.2%. By comparison, the false-negative rate for the culture method in these studies was 23.4%. Based on these data, the DNA hybridization method is significantly more accurate than conventional methods for the detection of E. coli in foods.

A second generation nucleic acid hybridization assay has been developed and evaluated against the conventional culture method for detection of salmonellae In foods. The assay Involves a liquid hybridization with Sa/mone/fo-speclflc oligonucleotide probes, capture of probe:target hybrids onto a solid support (plastic dipstick), and a colorimetric end point detection. The assay can be completed In 2.5 h, following approximately 44 h of culture enrichment. One thousand samples representing 20 food types were analyzed in parallel by both methods. Samples Included unlnoculated test product, and product Inoculated with Salmonella at 2 levels. Eighteen Salmonella serotypes were used as Inocula. The data demonstrate that the colorlmetric hybridization method and the conventional culture method are equivalent In their ability to detect Salmonella contamination of foods.