The production characteristics of volatile organic compounds and their relation to growth status of Staphylococcus aureus in milk environment.

In our previous research, 3-methyl-butanal and 3-methyl-butanoic acid were identified as representative and specific volatile organic compounds released by Staphylococcus aureus in broth. In this study, we explored the production of the 2 volatiles and their correlation to Staph. aureus growth in milk under different conditions. We found significant correlations between the production of 3-methyl-butanoic acid and cell counts of 5 Staph. aureus strains in sterile milk, and there were no obvious differences for its production among 5 tested strains. The intensities of the 2 volatiles were similar and positively correlated with bacterial counts in cultures at 25°C and 37°C despite delayed production of volatiles at 25°C; however, neither compound could be detected at 4°C. The production of 3-methyl-butanoic acid was strongly correlated with growth of Staph. aureus mixed with Streptococcus agalactiae, Escherichia coli O157:H7, and Shigella flexneri, whereas correlations for 3-methyl-butanal were not statistically significant. Compared with the monoculture of Staph. aureus, in mixed cultures, production of 3-methyl-butanal was decreased and that of 3-methyl-butanoic acid was comparatively higher. In pasteurized and raw milks, production of 3-methyl-butanoic acid was correlated with growth of Staph. aureus, and 3-methyl-butanoic acid could be detected when Staph. aureus populations reached 106 to 107 cfu/mL in pasteurized milk and 105 to 106 cfu/mL in raw milk; the correlations for 3-methyl-butanal were not statistically significant. Our results suggest that 3-methyl-butanoic acid is a more suitable marker for high counts of Staph. aureus in milk, whereas 3-methyl-butanal is a transient metabolite and easily depressed by environmental factors.

Catheter-related right internal jugular vein thrombosis after chest surgery.

BACKGROUND: Central venous catheters (CVCs) are frequently used for monitoring haemodynamic status and rapidly delivering fluid therapy during the peri- and postoperative periods. Indwelling CVCs are typically used 7-14 days postoperatively for additional monitoring and treatment, but patients may develop asymptomatic catheter-related thrombosis, leading to life-threatening pulmonary embolism and death. Early detection helps to avoid such complications. METHODS: This prospective observational study investigated the risk factors associated with catheter-related right internal jugular vein thrombosis in patients undergoing chest surgery. The study enrolled 24 patients who were scheduled to receive chest surgeries during which catheters were needed. To detect thrombus formation, Doppler ultrasound examinations from the thyroid cartilage level to the supraclavicular region were used after CVC placement and on each of the following days until the catheter was removed. RESULTS: No thrombosis was found in patients before surgery, but it appeared in 75% (18/24) after surgery. The risks of thrombosis increased with a longer duration of anaesthesia, greater amounts of bleeding, and use of postoperative ventilator support. CONCLUSIONS: Earlier catheter removal may reduce the risk of catheter-related thrombosis and avoid possibly fatal complications after catheter-related thrombosis.

Production of characteristic volatile markers and their relation to Staphylococcus aureus growth status in pork.

The 3-methyl-butanal and 3-methyl-butanoic acid are known as fingerprint compounds from Staphylococcus aureus. In this study, we investigated production of these two volatile biomarkers and their correlation to S. aureus growth in pork. Both 3-methyl-butanal and 3-methyl-butanoic acid presented high specificity for S. aureus in either media or pork. In sterile minced pork and pork broth, production of volatile biomarkers and the growth of S. aureus were significantly correlated for most single cultures. However, for mixed cultures, only 3-methyl-butanoic acid indicated correlations with growth of S. aureus. Similar trending was also discovered in raw pork, where production of 3-methyl-butanoic acid was significantly correlated with the growth of S. aureus, but not for 3-methyl-butanal. In summary, 3-methyl-butanoic acid was a more stable metabolic marker than 3-methyl-butanal which could be used as an indicator for the presence of S. aureus in pork. This rapid, convenient and cost-effective detection approach could be applied in meat industry to achieve specific detection of S. aureus.

Functional gamma-secretase inhibitors reduce beta-amyloid peptide levels in brain.

Converging lines of evidence implicate the beta-amyloid peptide (Ass) as causative in Alzheimer's disease. We describe a novel class of compounds that reduce A beta production by functionally inhibiting gamma-secretase, the activity responsible for the carboxy-terminal cleavage required for A beta production. These molecules are active in both 293 HEK cells and neuronal cultures, and exert their effect upon A beta production without affecting protein secretion, most notably in the secreted forms of the amyloid precursor protein (APP). Oral administration of one of these compounds, N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester, to mice transgenic for human APP(V717F) reduces brain levels of Ass in a dose-dependent manner within 3 h. These studies represent the first demonstration of a reduction of brain A beta in vivo. Development of such novel functional gamma-secretase inhibitors will enable a clinical examination of the A beta hypothesis that Ass peptide drives the neuropathology observed in Alzheimer's disease.