Characteristics of the home bacterial contamination and endotoxin related release.

In several occupational settings, endotoxin, a characteristic external fraction from the outer membrane of Gram negative bacteria (GNB), is an important component of the environmental endotoxin exposure may have a dual influence on atopy and asthma. The aim of this study was to characterise the bacterial and endotoxin composition of settled and airborne dusts from domestic environments. In the nine studied homes, 52 species of GNB were identified on settled dusts and only 13 in the airborne dust. Bacterial levels ranged from 2.76 10(5) to 1.14 10(8) CFU/g in mattresses and from 7.82 10(5) to 6.38 10(7) CFU/g in carpets. In the air 0.39 10(3) to 4.66 10(3) cfu/m3were recorded. Endotoxin varied from 1.85 to 549.0 EU/mg dust and was higher in the carpets compared with the mattresses. The medians of airborne endotoxin levels were 0.239 EU/m3 and 0.062 EU/m3 in inhalable and respirable particles, respectively. Our investigation demonstrates clearly the presence of numerous GNB in domestic environments and shows that domestic environnements contain in some cases relative high amounts of endotoxin.

Glycine betaine, an osmotic effector in Klebsiella pneumoniae and other members of the Enterobacteriaceae.

Osmoregulation was examined in members of the Enterobacteriaceae. Exogenous glycine betaine at a concentration as low as 1 mM was found to stimulate the growth rate of Escherichia coli, Salmonella typhimurium, and Klebsiella pneumoniae in media of inhibitory osmotic strength. The stimulation was shown to be independent of any specific solutes, electrolytes, or nonelectrolytes. Therefore, the stimulatory effect of glycine betaine was a consequence of high osmotic potential. This effect was found to be far greater than the proline effect previously observed in S. typhimurium. Whereas nitrogen fixation by K. pneumoniae is completely inhibited under conditions of osmotic stress, nitrogenase activity could be partially restored by the addition of exogenous glycine betaine to the culture medium. Furthermore, glycine betaine in combination with proline, especially proline produced internally at a high level because of regulatory mutations affecting proline biosynthesis, strongly stimulated nitrogen fixation activity during osmotic stress. Glycine betaine was accumulated by the cells, and the amount taken up was correlated with the osmolarity of the medium. These findings are discussed in relation to the possible mechanisms by which glycine betaine might cause enhanced osmotolerance.

Evaluation of the preservative properties of Thymus vulgaris essential oil in topically applied formulations under a challenge test.

The preservative properties of thyme essential oil (3%) with a known composition were evaluated in two types of final formulations, suitable for use as pharmaceutical or cosmetic vehicles, by means of a standard challenge test proposed by the latest European Pharmacopoeia. The required preservation efficacy criteria were satisfied against the bacterial strains, against the yeast in one of the formulations, but not against the mould strain involved in this study. Interactions between the essential oil compounds and other factors present in the final formulation might have influenced the activity of this essential oil, leading to an incomplete satisfaction of the criteria.