Prophylactic vitamin D in healthy infants: assessing the need.

The objective was to evaluate the need for vitamin D prophylaxis in healthy infants. This was a prospective and randomized study performed at primary care clinics. Eighty-eight full-term 1-month-old healthy infants were randomly assigned to receive (n = 41) or not (n = 47) 402 IU/d of vitamin D for 1 year. Primary outcome measures were serum 25-hydroxyvitamin D (25OHD) and parathyroid hormone (PTH) concentrations at 3, 6, and 12 months of age; secondary measures included data on feeding, habitat, season of birth, sun exposure, and physical examination. At 3 and 6 months of age, serum 25OHD levels (±SD) were significantly higher (P < .001) in the prophylaxis group. In the group without prophylaxis, serum 25OHD increased with age; and breast-fed infants aged 3 months had the lowest value (20.2 ± 9.4 ng/mL), which was significantly (P = .001) lower than that of formula-fed infants (35.0 ± 9.7 ng/mL). The PTH levels were not influenced by the prophylaxis or feeding. No influence of either the habitat or season of birth on serum 25OHD concentrations was demonstrated. No infant had clinical signs of vitamin D deficiency. Serum 25OHD and PTH concentrations were weakly but significantly correlated (r = -0.29, P = .009) at 3 months of age. Healthy infants without vitamin D prophylaxis had lower circulating concentrations of 25OHD at 3 and 6 months of age, the lowest value being found in 3-month breast-fed infants. The clinical relevance of these findings is probably negligible because serum 25OHD levels spontaneously increased with age and were not associated with high serum PTH. Clinical manifestations of rickets were not observed.

Simplified amplified-fragment length polymorphism method for genotyping Mycobacterium tuberculosis isolates.

A simplified amplified-fragment length polymorphism (AFLP) method was developed and applied to genotype 52 Mycobacterium tuberculosis isolates. This method can be carried out using only one restriction enzyme (XhoI), one double strand adapter, and one PCR primer. The amounts of DNA and DNA polymerase, and the concentrations of primer and Mg(2+) in the PCR step were optimized using the Basic Sequential Simplex method. AFLP analysis of the isolates generated a total of 24 differently sized bands ranging from 1537 to 121 bp, and 52 different band patterns, with a minimum of 2 and a maximum of 13 bands. The results were compared with the well-established IS6110 restriction fragment length polymorphism (IS6110-RFLP) typing method, which rendered a total of 32 differently sized bands from 1 to 12 kbp, and 52 different band patterns, with a minimum of 3 and a maximum of 15 bands. Therefore, both genotyping methods showed a discriminatory power of samples of 100%. Nevertheless, pairwise comparisons of the 1326 similarity indexes calculated for both typing methods showed a total absence of correlation between the similarity indexes of the two methods. The simplified AFLP method is expected to be more useful for genotyping M. tuberculosis isolates compared to the IS6110-RFLP method, since the former evaluates genetic variations throughout the M. tuberculosis genome. Furthermore, the relatively rapid and low-cost simplified AFLP method compares favorably to the IS6110-RFLP or conventional AFLP methods, and shows great promise for genotyping M. tuberculosis isolates, especially in developing countries or for preliminary screening.