Evaluation of VIDAS Salmonella (SLM) immunoassay method with Rappaport-Vassiliadis (RV) medium for detection of Salmonella in foods: collaborative study

A collaborative study was conducted to compare the VIDAS Salmonella (SLM) with Rappaport-Vassiliadis (RV) method for detection of Salmonella in foods to the current standard method presented in the U.S. Food and Drug Administration's Bacteriological Analytical Manual (BAM) and the culture method presented in AOAC's Official Methods of Analysis. The VIDAS SLM with RV method uses tetrathionate broth in combination with RV medium in place of selenite cystine broth for selective enrichment, thereby eliminating the hazardous waste issue for laboratories. Twenty five laboratories participated in the evaluation, each testing one or more of 8 test products: nonfat dry milk, dried egg, soy flour, lactic casein, milk chocolate, raw ground pork, raw ground turkey, and raw peeled shrimp. Results of the study showed no significant differences in the numbers of confirmed positive samples with the VIDAS SLM with RV procedure and the BAM/AOAC culture procedure. The VIDAS SLM with RV method was effective for rapid detection of Salmonella in foods. It is recommended that AOAC INTERNATIONAL modify the VIDAS Salmonella SLM procedure to include the RV method.     

A potent and highly selective sulfotransferase inhibitor

In the present work, we have used a newly developed, fluorescence-based assay to screen a library of >30 000 compounds as potential beta-arylsulfotransferase-IV inhibitors. A total of 11 inhibitors were discovered. Most of the compounds discovered showed low micromolar inhibition, but one of the compounds showed potent inhibition (Ki = 96 nM). The most potent of these inhibitors was tested against a variety of other purine binding enzymes and showed remarkable specificity.     

Dynamics of photoinduced processes in adenine and thymine base pairs

The excited-state dynamics of adenine and thymine dimers and the adenine-thymine base pair were investigated by femtosecond pump-probe ionization spectroscopy with excitation wavelengths of 250-272 nm. The base pairs showed a characteristic ultrafast decay of the initially excited pi pi* state to an n pi* state (lifetime tau(pi pi*) approximately 100 fs) followed by a slower decay of the latter with tau(n pi*) approximately 0.9 ps for (adenine)2, tau(n pi*) = 6-9 ps for (thymine)2, and tau(n pi*) approximately 2.4 ps for the adenine-thymine base pair. In the adenine dimer, a competing decay of the pi pi* state via the pi sigma* state greatly suppressed the n pi* state signals. Similarities of the excited-state decay parameters in the isolated bases and the base pairs suggest an intramonomer relaxation mechanism in the base pairs.     

Evaluation of the VIDAS Listeria (LIS) immunoassay for the detection of Listeria in foods using demi-Fraser and Fraser enrichment broths, as modification of AOAC Official Method 999.06 (AOAC Official Method 2004.06)

A multilaboratory study was conducted to compare the VIDAS LIS immunoassay with the standard cultural methods for the detection of Listeria in foods using an enrichment modification of AOAC Official Method 999.06. The modified enrichment protocol was implemented to harmonize the VIDAS LIS assay with the VIDAS LMO2 assay. Five food types--brie cheese, vanilla ice cream, frozen green beans, frozen raw tilapia fish, and cooked roast beef--at 3 inoculation levels, were analyzed by each method. A total of 15 laboratories representing government and industry participated. In this study, 1206 test portions were tested, of which 1170 were used in the statistical analysis. There were 433 positive by the VIDAS LIS assay and 396 positive by the standard culture methods. A Chi-square analysis of each of the 5 food types, at the 3 inoculation levels tested, was performed. The resulting average Chi square analysis, 0.42, indicated that, overall, there are no statistical differences between the VIDAS LIS assay and the standard methods at the 5% level of significance.