Control of the growth of Alicyclobacillus acidoterrestris in industrialized orange juice using rosemary essential oil and nisin.

The use of rosemary essential oil (RO) and its combination with nisin (RO+N) in preventing the multiplication of Alicyclobacillus acidoterrestris in orange juice was evaluated. The minimum inhibitory and bactericidal concentrations (MIC and MBC) for RO were both 125 µg ml-1 while RO+N displayed a synergistic effect. The use of RO and RO+N at concentrations of 1, 4 and 8× MIC in orange juice for 96 h was evaluated in terms of their sporicidal effectiveness. With regard to the action against A. acidoterrestris spores, RO at 8× MIC was sporostatic, whereas RO+N at 1× MIC was sporicidal. Morphological changes in the structure of the micro-organism after treatment were also observed by microscopy. Furthermore, flow cytometric analysis showed that most cells were damaged or killed after treatment. In general, the antioxidant activity after addition of RO+N decreased with time. The results demonstrate that using the combination of RO and nisin can prevent the A. acidoterrestris growth in orange juice.

Photodynamic inactivation of foodborne bacteria by eosin Y.

AIMS: The aim of this study was evaluate the effect of photodynamic inactivation mediated by eosin Y in Salmonella enterica serotype Typhimurium ATCC 14028, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923 and Bacillus cereus ATCC 11778. METHODS AND RESULTS: Bacteria (107 CFU per ml) were incubated with eosin Y at concentrations ranging from 0·1 to 10 µmol l-1 , irradiated by green LED (λmax 490-570 nm) for 5, 10 and 15 min and the cellular viability was determined. Pseudomonas aeruginosa was completely inactivated when treated with 10 µmol l-1 eosin Y for 10 min. Treatments reduced B. cereus and Salm. Typhimurium counts to 2·7 log CFU per ml and 1·7 log CFU per ml, respectively. Escherichia coli counts were slightly reduced. Staphylococcus aureus presented the highest sensitivity, being completely inactivated by eosin Y at 5 µmol l-1 and 5 min of illumination. The reduction of cellular viability of photoinactivated Staph. aureus was also demonstrated by flow cytometry and morphological changes were observed by scanning electron microscopy. CONCLUSIONS: Eosin Y in combination with LED produced bacterial inactivation, being a potential candidate for photodynamic inactivation. SIGNIFICANCE AND IMPACT OF THE STUDY: This study evidenced the efficacy of photodynamic inactivation as a novel and promising alternative to bacterial control.

Protein-energy malnutrition alters histological and ultrastructural characteristics of the bone marrow and decreases haematopoiesis in adult mice.

Protein-energy malnutrition (PEM) decreases resistance to infection by impairing a number of physiological processes, including haematopoiesis. The aim of this study was to evaluate the microanatomical aspects of bone marrow (BM) in mice that were subjected to PEM, in particular, with respect to the components of the local extracellular matrix and the proliferative activity of haematopoietic cells. For this, histological, histochemical, immunohistochemical and ultrastructural techniques were used. Two-month old male Swiss mice were fed with a low-protein diet containing 4% protein and control mice fed a 20% protein diet. When the experimental group had attained a 25% loss of their original body weight, we collected the different biological samples. Malnourished mice had presented severe BM atrophy as well as a reduction in proliferating cell nuclear antigen and gelatinous degeneration. The malnourished mice had more fibronectin accretion in paratrabecular and endosteal regions and more laminin deposition in perisinusal sites than controls. Endosteal cell activation and hyperplasia were found, suggesting their participation in the process. Additionally, we have observed a decrease in the capacity of malnourished haematopoietic stroma to support the growth of haematopoietic stem cells (CD34+) in vitro. These findings point to a structural impairment of the haematopoietic microenvironments in mice with PEM, possibly hampering the interactions between cells and cellular signalling.