Comparative polyphasic characterization of Streptococcus phocae strains with different host origin and description of the subspecies Streptococcus phocae subsp. salmonis subsp. nov.

A polyphasic study was undertaken to clarify the taxonomic position of Streptococcus phocae strains isolated from Atlantic salmon (Salmo salar) cage-farmed in Chile. Four salmon and three seal isolates showed minor differences in the SDS-PAGE protein analysis. Thus, a major protein band present in the salmon isolates, of approximately 22.4 kDa, was absent in the pinniped strains, regardless of the growth media employed. In addition, the pinniped strains showed protein bands with molecular masses of 71.5 and 14.2 kDa, when grown on trypticase soy agar supplemented with 1% NaCl, or 25.6 kDa, when grown on Columbia blood agar, not present in the Atlantic salmon strains. A high similarity in the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS spectra of the strains was observed, although some minor peaks were absent in the fish isolates. Fatty acid methyl esters from isolates with different host origin significantly (P<0.05) differed in the content of C16:0, C17:0, C18:1ω9c, C20:4ω6,9,12,15c and summed features 3, 5 and 8. The salmon isolates formed a separate cluster in the phylogenetic analysis of housekeeping genes, separately or as concatenated sequences. Sequence divergences among salmon and seal strains were in the range of inter-subspecies differentiation for groEL (2.5%), gyrB (1.8%), recN (2.1%), rpoB (1.7%) and sodA (2.0%) genes. DNA-DNA hybridization results confirmed those of sequencing, showing reassociation values between seal and salmon strains close to the borderline of species definition. Differences in growth at low temperatures and in the haemolytic capacities were also observed between both groups of isolates. On the basis of all these results, the salmon isolates represent a novel subspecies of S. phocae, for which the name Streptococcus phocae subsp. salmonis subsp. nov. is proposed. The type strain is C-4T (=CECT 7921T=DSM 24768T). The subspecies Streptococcus phocae subsp. phocae subsp. nov. is automatically created. An emended description of S. phocae is also provided.

Soybean and green tea polyphenols improve immune function and redox status in very old ovariectomized mice.

In previous work we have observed that ovariectomy in rodents, a good model of mimicking human ovarian hormone loss, causes premature aging of the immune system. The prooxidative and inflammatory state that underlies the aging process is the base of that premature immunosenescence. It has been found that nutritional interventions with polyphenolic antioxidants constitute a good alternative to rejuvenate age-affected immune functions. In this study, we administered a diet supplemented with polyphenols (coming from soybean isoflavones and green tea) to sham-operated and ovariectomized mature mice for 15 weeks, until they reached a very old age. We have studied the effect of this supplementation on a broad range of parameters of immune function (in macrophages and lymphocytes) and oxidative stress (enzymatic and nonenzymatic antioxidant defences, oxidant compounds, and lipid peroxidation damage) in peritoneal leukocytes. The results showed that ovariectomy accelerates the age-related impairment of immune functions in very old mice as well as the oxidative and proinflammatory imbalance, and that the administration of soybean isoflavones and green tea improve the immune and redox state in these animals. Because the immune system is a good marker of health and a predictor of longevity, we suggest that an adequate nutritional treatment with polyphenols could be a highly recommended tool to fight against the detrimental effects of the lack of female sex hormones, through an improvement of the immune cell functions and redox state.

Improvement of immune cell functions in aged mice treated for five weeks with soybean isoflavones.

Aging is associated with an impaired immune system as well as with a decline of several hormones, such as estrogens. Dietary phytoestrogens have been proposed as an alternative to hormone replacement therapy. The beneficial action of soybean compounds is probably due to isoflavones, whose role as immunomodulators has been investigated with increasing interest. The aim of the present work was to study whether a 5-week administration of a diet enriched in soybean isoflavones and green tea could influence the immune function of mice that were sham-operated or ovariectomized. Natural killer activity (NK) and lymphoproliferation in response to the mitogens concanavaline A (Con A) and lipopolysaccharide (LPS), were studied in peritoneal leukocytes. Both treatments with soybean or green tea plus soybean were highly effective in improving these immune parameters with respect to control groups. Since the immune system is a marker of health and a predictor of longevity, an adequate treatment with isoflavones could be useful in slowing down the effects of the aging process through an improvement in the two relevant immune functions studied.