Extent of thermal processing of infant formula affects copper status in infant rhesus monkeys

Enterobacter sakazakii: an emerging problem in paediatric nutrition

Recently there has been considerable concern related to the presence of bacteria, in particular Enterobacter sakazakii, in powdered infant formula milk. E. sakazakii, a member of the family Enterobacteriaceae, is an emerging opportunistic pathogen that has been associated with cases of meningitis, necrotizing enterocolitis and sepsis in premature and full-term infants. Feeding with powdered infant formula has been epidemiologically implicated in several clinical cases. Powdered infant formula is not a sterile product; good hygienic practice is, therefore, necessary in its reconstitution to reduce the risk of infection. The ingestion of raised numbers of E. sakazakii resulting from storage at room temperature after reconstitution is highlighted as well as the uncertain routes of E. sakazakii product contamination.

Pressure inactivation kinetics of Enterobacter sakazakii in infant formula milk

Survival curves of Enterobacter sakazakii inactivated by high hydrostatic pressure were obtained at four pressure levels (250, 300, 350, and 400 MPa), at temperatures below 30 degrees C, in buffered peptone water (BPW; 0.3%, wt/vol) and infant formula milk (IFM; 16%, wt/vol). A linear model and four nonlinear models (Weibull, log-logistic, modified Gompertz, and Baranyi) were fitted to the data, and the performances of the models were compared. The linear regression model for the survival curves in BPW and IFM at 250 MPa has fitted regression coefficient (R2) values of 0.940 to 0.700, respectively, and root mean square errors (RMSEs) of 0.770 to 0.370. For the other pressure levels, the linear regression function was not appropriate, as there was a strong curvature in the plotted data. The nonlinear regression models with the log-logistic and modified Gompertz equations had R2 values of 0.960 to 0.992 and RMSE values of 0.020 to 0.130 within pressure levels of 250 to 400 MPa, respectively. These results indicate that they are both better models for describing the pressure inactivation kinetics of E. sakazakii in IFM and BPW than the Weibull distribution function, which has an R2 minimum value of 0.832 and an RMSE maximum value of 0.650 at 400 MPa. On the other hand, the parameters for the Weibull distribution function, log-logistic model, and modified Gompertz equation did not have a clear dependence on pressure. The Baranyi model was also analyzed, and it was concluded that this model provided a reasonably good fit and could be used to develop predictions of survival data at pressures other than the experimental pressure levels in the range studied. The results provide accurate predictions of survival curves at different pressure levels and will be beneficial to the food industry in selecting optimum combinations of pressure and time to obtain desired target levels of E. sakazakii inactivation in IFM.

Heat Processing in Infant Formulas Induces Changes in Copper Tissue Levels in Suckling and Weanling Rats

AIM

To assess the effects of dehydration, conventional in-bottle sterilization, and ultrahigh-temperature (UHT) sterilization, involved in the production of infant formulas, on the copper bioavailability in rats at two stages.

METHODS

Two-week-old suckling rats were fed a reconstituted powder (P1) and an in-bottle-sterilized liquid infant formula (SC1) in a drinking bottle for 7 days. Weanling rats were fed P1, SC1, another powder (P2), and a liquid UHT formula (UHT2) complemented with a standard rat diet. Intake, body weight, and percentage copper absorption were calculated, and whole-body, serum, liver, skin, and erythrocyte copper concentrations were determined.

RESULTS

Food intake, body weight, and copper intake were reduced in suckling rats consuming SC1, but the percentage copper absorption increased, and whole-body and tissue copper concentrations were unaffected, except for the erythrocyte copper concentration which was significantly higher as compared with pups fed P1. In weanling rats, the only difference observed was the significantly higher liver copper concentration in animals fed the diet containing P1 as compared with the diets containing SC1 and UHT2.

CONCLUSIONS

Consuming the SC1 formula induced high erythrocyte copper levels in suckling rats, whereas the equivalent dehydrated formula (P1) induced elevated liver copper concentrations in weanling rats. This is associated with the different Maillard reaction products resulting from the processing of each infant formula and with the developmental stage of the animals.

Behavioral consequences of developmental iron deficiency in infant rhesus monkeys

Human studies have shown that iron deficiency and iron deficiency anemia in infants are associated with behavioral impairment, but the periods of brain development most susceptible to iron deficiency have not been established. In the present study, rhesus monkeys were deprived of iron by dietary iron restriction during prenatal (n=14, 10 microg Fe/g diet) or early postnatal (n=12, 1.5 mg Fe/L formula) brain development and compared to controls (n=12, 100 microg Fe/g diet, 12 mg Fe/L formula) in behavioral evaluations conducted during the first four months of life in the nonhuman primate nursery. Iron deficiency anemia was detected in the pregnant dams in the third trimester and compromised iron status was seen in the prenatally iron-deprived infants at birth, but no iron deficiency was seen in either the prenatally or postnatally iron-deprived infants during the period of behavioral evaluation. Neither prenatal nor postnatal iron deprivation led to significant delays in growth, or gross or fine motor development. Prenatally deprived infants demonstrated a 20% reduced spontaneous activity level, lower inhibitory response to novel environments, and more changes from one behavior to another in weekly observation sessions. Postnatally deprived infants demonstrated poorer performance of an object concept task, and greater emotionality relative to controls. This study indicates that different syndromes of behavioral effects are associated with prenatal and postnatal iron deprivation in rhesus monkey infants and that these effects can occur in the absence of concurrent iron deficiency as reflected in hematological measures.

Iron bioavailability from powdered and in-bottle-sterilized infant formulas in suckling and weanling rats

OBJECTIVE

The Maillard reaction and lactose isomerization may be induced during the manufacture of infant formulas. We studied the effects of dehydration and sterilization on iron bioavailability from an infant formula in suckling and weanling rats.

METHODS

In experiment 1, a previously reconstituted powdered infant formula and an in-bottle-sterilized liquid infant formula from the same manufacturer were fed from drinking bottles to 2-wk-old suckling rat pups for 7 d. In experiment 2, the same formulas were complemented with AIN-76 and fed to weanling rats for 7 d after a 4-d adaptation period. In both experiments, intake, body weight, and fecal and urinary excretions were monitored, and the following iron indexes were calculated: apparent absorption and retention and the coefficients percentage of absorption versus intake, percentage of retention versus absorption, and percentage of retention versus intake.

RESULTS

The liquid infant formula resulted in lower body weights on day 4, particularly among the younger rats that had significantly lower food intakes (P = 0.045). In weanling rats fed powdered and liquid infant formulas, food intake and body weight were not significantly different. The pups showed significantly higher absorption (percentage of absorption versus intake) and retention (percentages of retention versus absorption and retention versus intake) efficiencies than did the weanling rats (P < 0.001 for the three indexes). Hemoglobin values (P = 0.001) and liver iron concentrations (P = 0.009) were significantly higher in the weanling rats than in the pups. In contrast, erythrocyte iron concentrations and hematocrit were higher in the pups (P = 0.016 and 0.053, respectively).

CONCLUSIONS

In rat pups, iron bioavailability is negatively affected by the consumption of in-bottle-sterilized infant formula, possibly as the result of the content of Maillard reaction products, altered proteins, and lactulose. However, when this formula is included in a mixed diet and given to weanling rats, this detrimental effect no longer occurs.

Preparation and handling of powdered infant formula: a commentary by the ESPGHAN Committee on Nutrition

Powdered infant formulae are not sterile and may contain pathogenic bacteria. In addition, milk products are excellent media for bacterial proliferation. Multiplication of Enterobacter sakazakii in prepared formula feeds can cause devastating sepsis, particularly in the first 2 months of life. In approximately 50 published case reports of severe infection, there are high rates of meningitis, brain abscesses and necrotizing enterocolitis, with an overall mortality from 33% to 80%. Breast feeding provides effective protection against infection, one of the many reasons why it deserves continued promotion and support. To minimize the risk of infection in infants not fully breastfed, recommendations are made for preparation and handling of powdered formulae for children younger than 2 months of age. In the home setting, powdered infant formulae should be freshly prepared for each feed. Any milk remaining should be discarded rather than used in the following feed. Infant feeds should never be kept warm in bottle heaters or thermoses. In hospitals and other institutions written guidelines for preparation and handling of infant formulae should be established and their implementation monitored. If formula needs to be prepared in advance, it should be prepared on a daily basis and kept at 4 degrees C or below. Manufacturers of infant formulae should make every effort to minimize bacterial contamination of powdered products.

Enzymolysis approach to compare cu availability from human milk and infant formulas

The purpose of the present paper is to develop an easy and quick in vitro method to compare copper availability from breast milk and infant formulas. This study focuses on the differences caused by the use of pH 2.0 (adult gastric pH) or pH 5.0 (newborn gastric pH) in the first stage of the enzymolysis. pH affects Cu solubility, a possible estimator of the availability. Selection of a digestor, times of enzymolysis, centrifugation parameters, and Cu determination by ETAAS were discussed as well. Percentage of Cu solubility was larger from breast milk (gastric pH 2.0, 65.3 +/- 14.0 vs 40.0 +/- 13.9%; gastric pH 5.0, 61.2 +/- 16.5 vs 26.6 +/- 10.3%), but the soluble content was larger from infant formulas for both pHs (gastric pH 2.0, 245.3 +/- 82.1 vs 113.0 +/- 103.4 ng mL(-1); gastric pH 2.0, 169.3 +/- 76.9 vs 75.3 +/- 21.9 vs ng mL(-1)).

Copper deficiency and excess in infancy: developing a research agenda

Copper deficiency and excess have been recognized as potential health problems for infants and children worldwide. Clinical manifestations of copper deficiency and excess are well characterized but the precise sequence by which high copper intake interacts with genetic control systems, leading to liver damage in infants, is unknown. The possibility that genetic mutations or epigenetic factors related to the functional development of copper homeostasis, could make otherwise normal infants on normal copper intake more susceptible to copper toxicity has been an issue of concern. In January 2001 a group of pediatricians and researchers interested in this area met at Tegernsee, Bavaria, Germany, to reviewing the state of knowledge on the topic. They addressed six main issues: 1) The relevance of copper deficit and excess as health problems. 2) The appropriate biomarkers to identify and characterize copper status 3) The genetic variability in copper metabolism 4) The mechanisms of whole body copper homeostasis in early life and their changes with age 5) The development of experimental and animal models to address research questions on copper homeostasis in infants. 6) The safe upper and lower limits of copper intake/exposure from water and food. We present here the highlights of the discussions and the main conclusions of the meeting.

Lactoferrin in the preterm infants' diet attenuates iron-induced oxidation products

Free radical injury is thought to play a significant role in the pathogenesis of several disease processes in low birth weight premature infants including retinopathy of prematurity and necrotizing enterocolitis. Because iron is a known catalyst in free radical-mediated oxidation reactions, the objectives of the present in vitro studies were to determine whether after exposure to air 1) iron present in infant formula, or that added to human milk or formula as medicinal iron or as iron contained in human milk fortifier, increases free radical and lipid peroxidation products; and 2) recombinant human lactoferrin added to formula or human milk attenuates iron-mediated free radical formation and lipid peroxidation. Before adding medicinal iron to formula and human milk, significantly more ascorbate and alpha-hydroxyethyl radical production and more lipid peroxidation products (i.e. thiobarbituric acid reactive substances, malondialdehyde, and ethane) were observed in formula. After the addition of medicinal iron to either formula or human milk, further increases were observed in free radical and lipid peroxidation products. When iron-containing human milk fortifier was added to human milk, free radicals also increased. In contrast, the addition of apo-recombinant human lactoferrin to formula or human milk decreased the levels of oxidative products when medicinal iron or human milk fortifier was present. We speculate that the presence of greater concentration of iron and the absence of lactoferrin in formula compared with human milk results in greater in vitro generation of free radicals and lipid peroxidation products. Whether iron-containing formula with lactoferrin administered enterally to preterm infants will result in less free radical generation in vivo has yet to be established.

The timing of perinatal copper deficiency in mice influences offspring survival

Copper is an essential metal during development. Female Swiss Webster mice were fed a modified AIN-76A diet low in copper (0.3 mg Cu/kg and 43 mg Fe/kg; -Cu). One-half the mice received copper in their drinking water (20 mg Cu/L; +Cu). Female mice were mated to normal males and offered the -Cu or +Cu treatments starting at gestational d 13. Treatments did not affect litter size or pregnancy outcome. For three litters of +Cu mice, 26/26 offspring born were weaned on postnatal d 21 (P21). For three litters of -Cu dams, 0/26 pups survived beyond P13. The -Cu dams kept on treatment for this 3-wk period were killed and compared biochemically with +Cu dams and to nonpregnant females that were kept on the +Cu or -Cu treatment and fed the same diet for 3 wk. Compared with +Cu dams, -Cu dams had 48% lower hematocrits, 89% lower plasma ceruloplasmin activities, 45% lower liver copper level, and > 2-fold higher liver iron concentration. The -Cu, nonpregnant female mice did not differ in any of these copper status indicators from the +Cu dams or nonpregnant, +Cu females. When -Cu treatment was delayed until embryonic d 19, all -Cu pups survived weaning. Additional studies should be conducted to establish the human copper requirement for perinatal development and determine whether the 11 and 44% extra copper intakes recommended for pregnancy and lactation in the new United States recommended dietary allowance are sufficient.