Genomic comparison of virulent and non-virulent Streptococcus agalactiae in fish.

Streptococcus agalactiae infections in fish are predominantly caused by beta-haemolytic strains of clonal complex (CC) 7, notably its namesake sequence type (ST) 7, or by non-haemolytic strains of CC552, including the globally distributed ST260. In contrast, CC23, including its namesake ST23, has been associated with a wide homeothermic and poikilothermic host range, but never with fish. The aim of this study was to determine whether ST23 is virulent in fish and to identify genomic markers of fish adaptation of S. agalactiae. Intraperitoneal challenge of Nile tilapia, Oreochromis niloticus (Linnaeus), showed that ST260 is lethal at doses down to 10(2) cfu per fish, whereas ST23 does not cause disease at 10(7) cfu per fish. Comparison of the genome sequence of ST260 and ST23 with those of strains derived from fish, cattle and humans revealed the presence of genomic elements that are unique to subpopulations of S. agalactiae that have the ability to infect fish (CC7 and CC552). These loci occurred in clusters exhibiting typical signatures of mobile genetic elements. PCR-based screening of a collection of isolates from multiple host species confirmed the association of selected genes with fish-derived strains. Several fish-associated genes encode proteins that potentially provide fitness in the aquatic environment.

Effects of two marine dietary supplements with high calcium content on calcium metabolism and biochemical marker of bone resorption.

BACKGROUND/OBJECTIVE: Calcium is essential for the bone metabolism but daily calcium requirements are not met in a significant proportion of the population. Fortunately, oral calcium supplementation can help to meet these needs; however, the calcium bioavailability depends on the calcium sources. The calcium absorption and bioavailability of dietary supplements from marine sources are not known. The objectives of this study were to evaluate the effects of two marine dietary supplements with a high calcium content: a fishbone powder (Phoscalim) and a ray cartilage hydrolysate (Glycollagene), in comparison with milk, and a placebo (maltodextrin), on calcium metabolism and a biochemical marker of bone resorption, using the oral calcium tolerance test. SUBJECTS: Twenty male volunteers were randomized to eat 836 mg of calcium from different sources compared to maltodextrin during a Latin square study. Serum calcium concentrations and other parameters of the calcium metabolism, such as serum intact parathyroid hormone (iPTH) and serum C telopeptides (s-CTX), were measured after an acute oral calcium load based on the Pak protocol. RESULTS: An increase in serum-corrected calcium areas under the curve (AUC) occurred with Phoscalim and Glycollagene when compared to milk. Significantly lower iPTH concentrations were observed with Glycollagene than with milk at T0+1 h, T0+3 h, T0+6 h and with Phoscalim than with milk at T0+6 h. A significantly lower s-CTX concentration was observed with Glycollagene than with milk and Phoscalim at T0+6 h. Furthermore, the urinary calcium/creatinine ratio increased significantly more with Glycollagen than with milk in T0 h+3 h and T3 h+6 h. CONCLUSION: These two dietary supplements from marine sources constitute oral calcium sources when compared to milk on calcium absorption and bone resorption markers on short time.

Splanchnic uptake and release of energy substrates in the fasting baboon infant.

Estimates of splanchnic energy substrate exchange in the primate infant have been obtained using a baboon model. The splanchnic bed of the fasting baboon newborn released glucose at an estimated rate of 14.5 +/- 5.0 mumol/min X kg body weight. Splanchnic glucose release in the fasting 5-7 wk old baboon infant proceeded similarly at an estimated rate of 15.5 +/- 4.5 mumol/min X kg body weight. The principal precursors taken up by the splanchnic bed were lactate, glycerol, and alanine. Uptake of alanine correlated in a linear fashion with glucose release. Lactate was the most important precursor in both age groups. Glucose recycling through lactate is an active mechanism in the primate fetus as well as in the young of other species.

Arterial blood levels of energy substrates and evidence for renal glucose production in the baboon infant.

The age-related changes in fasting arterial levels of energy substrates and insulin were studied at birth and/or 6 wk in eleven baboon infants. In addition, the renal contribution to glucose release in the primate infant was estimated. Arterial blood glucose levels were similar in six fasted newborns and in nine fasted 6-wk-old infants. Arterial blood lactate, alanine, pyruvate, glutamate, and glutamine levels were significantly higher (P < 0.01) in the new born animals, and beta-hydroxybutyrate was significantly higher in the older animals (P < 0.001). Arterial plasma insulin levels were low in both groups. Levels of blood glucose in the inferior vena cava below the renal vein were significantly lower than levels in the aorta (P < 0.01). In contrast, levels of blood glucose in the inferior vena cava above the renal vein were significantly higher than in the aorta (P < 0.05). Computed renal vein glucose levels were higher than those in the aorta (P < 0.01). In the newborn infants, there was significant renal uptake of lactate, pyruvate, glycerol, and glutamine (P < 0.01), and release of beta-hydroxybutyrate (P < 0.05). In the older animals, there was renal uptake of alanine, lactate, pyruvate, and glycerol (P 0.01). Mean cardiac output per kg body weight did not differ significantly in the newborn and 6-wk-old infants. Lactate uptake was potentially responsible for 59% of mean renal glucose output in the newborn and 76% of mean renal glucose output in the older infant. Net renal glucose release in eight 6-wk-old infants was estimated to be 3.5 +/- 1.1 microM/min . kg (95% confidence limits, 0.7 < 3.5 < 6.2). Net renal glucose release in three newborn infants was 4.7, 5.4, and 19.8 microM/min . kg. There was a significant linear relationship between arterial lactate levels and renal glucose production in the older infants (P < 0.05). Extremely low arterial pH was associated with increased renal glucose release in the newborn, and high arterial pH with decreased or absent glucose release in the 6-wk-old animals.

Fasting plasma levels of glucose, acetoacetate, D-beta-hydroxybutyrate, glycerol, and lactate in the baboon infant: correlation with cerebral uptake of substrates and oxygen.

The energy-rich substrates available to the fasting stressed baboon neonate and infant are quantitatively similar to the metabolic fuels presented to the stressed low birth weight human newborn. Within a few hours after birth, fasting arterial plasma glucose levels in the baboon neonate approximate those of 4-6-week-old baboon infants after a 20-hr fast. Lactate levels are high and comparable for both age groups. In contrast, beta-hydroxybutyrate is quite low in the immediate neonatal period, but rises to significantly higher levels (P less than 0.001) after a fast at 4-6 weeks. In addition, glycerol levels are higher (P less than 0.02) in the fasted older infant compared with the fasting neonate. Computation of mean cerebral blood arteriovenous differences and oxygen equivalents for animals studied in the first 50 hr of life demonstrates that glucose uptake can account for 50% or less of cerebral oxygen consumption in the newborn period. In confirmation, the respiratory quotient in these animals is 0.52 +/- 0.06. Cerebral oxygen consumption in the immediate neonate is greater than can be explained by utilization of glucose and the small quantities of acetoacetate and beta-hydroxybutyrate available at this time. At birth, cerebral uptake of lactate is noted, but this phenomenon is not observed at 6 and 12 weeks of age.