In vitro assessment of properties associated with the survival through the gastro-intestinal tract of staphylococci isolated from traditional sausage fermentation

Thirteen Staphylococcus sp. strains, previously isolated from spontaneous sausage fermentation, were in vitro examined for properties associated with their ability to survive through the gastro-intestinal tract. None of the strains were able to survive exposure to pH 1 or pH 2, while for most of them, a population reduction, ranging from 77.3% to 99.0% and a surviving population from 1.7 x 10(8) to 9.0 x 10(6) was observed after exposure to pH 3. None of the strains exhibited bile salt hydrolase activity or production of antimicrobial compounds, while all of them were resistant to pancreatin. Only S. cohnii cohnii LQC 5112 was found to be alpha-haemolytic, seven other strains were beta-haemolytic and the rest gamma-haemolytic. All strains were sensitive to erythromycin, ampicillin (but S. intermedius LQC 5023) and chloramphenicol while most of them were sensitive to tetracycline. On the other hand, most of the strains were resistant to novobiocin. Furthermore, their aptitude, not only to withstand, but to proliferate in the presence of bile salts, as well, even at an acidic environment and their ability to adhere to stainless-steel plates, indicate the need for an in vivo study.     

Effect of granulometry on cementitious properties of ladle furnace slag

Ladle furnace slag (LFS), a by-product of the steel making process, was tested for its potential use as a supplementary cementing material. The material used for the tests was screened or ground, producing three samples of different fineness, and the granulometry of these LFS samples was also tested by particle size analysis. Their chemical and mineralogical composition was assessed by chemical analysis, X-ray diffraction and thermogravimetric analysis. Finally, in order to determine the cementitious and pozzolanic character of LFS in relation to its granulometry, slag-lime and slag-cement mortars were produced and tested in compression. The results show that although LFS is a weak supplementary cementing material, it shows some self-cementing and pozzolanic properties that can be enhanced by screening or grinding the raw material. Even though different levels of fineness and granulometry can be reached with each method, generally, grinding seems to improve LFS binding properties more than sieving.