HANDS-FREE, "POP-UP," ADHESIVE TAPE METHOD FOR MICROBIAL SAMPLING OF MEAT SURFACES

Microbial contamination of food is a concern to both food producers and consumers. For the food production industry surface sampling of foods is one of the simplest ways to monitor the microbial load. The objective of this experiment was to investigate the feasibility of using the less expensive and quicker "Pop-up" tape method instead of the conventional swab/rinse method for the microbial sampling of meat surfaces. An analyst can place the unit on the wrist and then use both hands to lay out all the necessary materials and take the sample with one hand. The "Pop-up" tape method was able to measure microbial loads up to 2.2 log CFU/cm² on meat surfaces. The conventional swab/rinse method was able to measure up to 8.3 log CFU/cm² on meat surfaces. The correlation coefficient (R) between the two methods was 0.91 (n=42). These data show that the "Pop-up" tape method is a viable alternative to other methods for estimating microbial surface contamination.     

中国部分丛生竹类染色体数目报道

本文报道了我国13属94种丛生竹类的染色体数目。其中21种已见报道,74种为首次报道。作者推测竹类染色体原始基数可能为x=8。多数丛生竹类染色体数目为2n=70±2。     

RAPID DETECTION OF LISTERIA MONOCYTOGENES USING A REFLECTANCE COLORBMETRIC METHOD WITH MEMBRANE FRACTIONS FROM OXIDATIVE BACTERIA

Membrane fractions obtained from Escherichia coli, Gluconobacter oxydans, and Acetobacter xylinum significantly stimulated rapid growth of Listeria monocytogenes (strains 101, 103, and Scott A) under atmospheric conditions of the OmniSpec Bioactivity System. L. monocytogenes demonstrated a shorter lag phase and faster growth compared to culture systems without the membrane fractions as determined by shorter color detection times, the durations of time for a significant color change to occur. The growth stimulating effect increased as the concentrations of membrane fractions increased. The use of membrane fractions to recover facultative Listeria spp. also lowered the detection limit of the method to < 10 cells/ml by increasing small cell numbers to the detectable level (10⁷ cells/m) faster under aerobic conditions. The application of membrane fractions with the OmniSpec Bioactivity System shortened the detection time for the bacteria by 0.5–10 h, depending on the specific membrane and initial cell concentrations, compared to the conventional OmniSpec method. This method is very useful as a tool for studying food microbiology. Membrane fractions produced in our laboratory effectively dissipated oxygen in Fraser broth and had growth-enhancing activities comparable to that of commercial Oxyrase^TM.     

The Admixture Linkage Disequilibrium and Genetic Linkage Inference on the Gradual Admixture Population

Through the theoretical analysis of the admixture linkage disequilibrium (ALD) in the gradual admixture (GA) model, in which admixture occurs in every generation, the ALD is found to be proportional to the difference in marker allele frequencies, p₁-p₂, between two subpopulations. Based on this property, we can employ a strict monotonic function (Δ_ker=Δ/(p₁-p₂), where Δ denotes the linkage disequilibrium (LD)) of the recombination fraction between the marker locus and the disease locus to infer the true genetic linkage. We construct a quasi likelihood ratio test (LRT) for the case-only data utilizing the information of unlinked markers in the human genome. The simulation results show that our tests can be used to fine map a disease locus. The effects of parameter values in the ALD mapping are also discussed.     

EFFECTIVE METHOD FOR DRY INOCULATION of BACTERIAL CULTURES

An effective way for inoculation of bacteria into dry foods/ingredients that gives a uniform mixture was developed. In the first part of this experiment, Salmonella typhimurium was successfully inoculated into chalk. Chalk tubes were weighed then soaked in a broth with S. typhimurium and allowed to dry back to their original weight. the dried chalk was made into a powder form. A viable cell count of this chalk, using a selective media for S. typhimurium , showed that the organism survived the drying while entrapped in the chalk. the "charged" chalk was used in an experiment as a dry inoculum where it was mixed with a low-moisture poultry feed. In comparison to a liquid inoculum, the "charged" chalk was a superior way of inoculating into dry particles because it created a more homogenous mixture with the feed without altering any properties of the feed itself. the second part of this experiment entailed a shelf-life study of the "charged" chalk. the same procedures for inoculating chalk were done using ten different cultures including Bacillus cereus, Clostridium perfringens, Escherichia coli, Enterobacter aerogenes, Lactobacillus plantarum, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella typhimurium, Staphylococcus aureus , and Streptococcus faecalis. Data showed that the cultures are stable in the chalk for at least six months.