Evaluation of the BAX system for detection of Listeria monocytogenes in foods: collaborative study.

A multilaboratory study was conducted to compare the automated BAX system and the standard cultural methods for detection of Listeria monocytogenes in foods. Six food types (frankfurters, soft cheese, smoked salmon, raw, ground beef, fresh radishes, and frozen peas) were analyzed by each method. For each food type, 3 inoculation levels were tested: high (average of 2 CFU/g), low (average of 0.2 CFU/g) and uninoculated controls. A total of 25 laboratories representing government and industry participated. Of the 2335 samples analyzed, 1109 were positive by the BAX system and 1115 were positive by the standard method. A Chi square analysis of each of the 6 food types, at the 3 inoculation levels tested, was performed. For all foods, except radishes, the BAX system performed as well as or better than the standard reference methods based on the Chi square results.

The novel BLM3 gene encodes a protein that protects against lethal effects of oxidative damage.

Mutational alteration of the BLM3 gene in Saccharomyces cerevisiae confers hypersensitivities to lethal effects of ionizing radiation, anticancer bleomycins and structurally-related phleomycins. Bleomycin is used clinically in the treatment of many types of cancers, including Kaposi's sarcoma. The BLM3 gene was cloned from a genomic library by complementing the drug hypersensitivities conferred by the codominant blm3-1 mutation. The nucleotide sequence of BLM3 encodes a predicted integral protein of 1804 amino acids with seven to ten potential transmembrane domains and additional motifs. The blm3 null mutation was created by gene replacement, and found not to be essential for growth in the absence of the bleomycin-phleomycin antibiotics. Sequence analyses suggest the Blm3p could be a potential member of the major facilitator superfamily (MFS) of permeases. Northern dot blot analyses using a human RNA master tissue blot containing RNA from fifty different fetal and adult tissues revealed sequence homology in adult tissues to BLM3, but no sequence homology in fetal tissues. The function of the Blm3p is presently unknown. We propose several functions for the Blm3p in protecting cells against oxidative agents, including roles in detoxification, transport and defending against DNA damage.

Cloning, characterization and identification of the gene encoding phosphatidylinositol 4-kinase.

The vast majority of AIDS-related deaths are associated with opportunistic infections. For fungal infections, there are few effective antifungals, particularly for systemic use. The discovery that very low doses of the bleomycin family of anticancer chemical congeners compromise the integrity of fungal cell walls led to our approach to identify genes that complement-cell wall defects, and develop methods to facilitate the identification of new antifungals targeted to fungal cell walls. This report describes one of the genes cloned by complementation of the blm1-1 mutation of S. cerevisiae using a YCp50-based yeast genomic library. Characterization and identification of the gene were carried out using drug screening tests, Southern hybridization analyses, DNA sequencing and DNA sequence similarity searches in databases. The gene STT4, is essential for viability and encodes a phosphatidylinositol 4-kinase that plays an important role in the phosphatidylinositol-mediated signal transduction pathway required for cell wall integrity. Like blm1-1 mutant strains, stt4 cells arrest mostly in the G2/M phase of the cell cycle. Further studies using this approach should help us understand the role of PI4-K in maintaining fungal cell-wall integrity, identify additional genes affecting potential target structures in cell walls of opportunistic fungal pathogens in AIDS patients, and assist in drug discovery and antifungal drug design.