Beneficial impact of genome projects on tuberculosis control

The M. tuberculosis genome project is a landmark achievement in the history of TB research. The DNA sequence has provided valuable insights, along with a few surprises, into the complete genetic complement of M. tuberculosis. This information has been used to gain a better understanding of isoniazid-induced alteration in gene expression. It also has been used to construct a genealogy tree of different BCG strains, besides identifying genes that may be responsible for the human-specificity of M. tuberculosis. The impact of this project is far-reaching and in the next few years should yield innovative vaccines and therapeutic agents, besides aiding in the rapid and accurate diagnosis of TB.     

Comparison of C(18)-carboxypropylbetaine and standard N-acetyl-L-cysteine-NaOH processing of respiratory specimens for increasing tuberculosis smear sensitivity in Brazil

Techniques to improve the sensitivity of smear microscopy would facilitate early tuberculosis (TB) diagnosis and disease control, especially in low-income countries where the positive predictive value is high. C(18)-carboxypropylbetaine (CB-18) is a zwitterionic detergent that helps to compensate for the innate buoyancy of mycobacteria, potentially enhancing recovery by centrifugation. Previous data suggest that CB-18 may increase the sensitivity of smear, culture, and molecular amplification diagnostic testing. The goal of the present study was to evaluate if the sensitivity of the smear technique using light microscopy could be improved by treating respiratory samples with CB-18. In the first phase, respiratory specimens were collected consecutively from patients with suspected pulmonary tuberculosis in a tertiary-care hospital in Rio de Janeiro, Brazil (236 specimens were analyzed). After protocol modifications, another 120 respiratory specimens were evaluated. The standard technique was N-acetyl-L-cysteine with sodium hydroxide (NALC-NaOH) treatment, smear concentration with centrifugation, and Ziehl-Neelsen staining. Culture on L?wenstein-Jensen slants was performed on all specimens for use as the "gold standard." No specimens from patients undergoing active TB treatment were included. The initial protocol for CB-18 processing resulted in a sensitivity of 59.6% and specificity of 96.8% compared to standard processing with a sensitivity of 66.0% and specificity of 96.8%. Using the modified protocol, the sensitivity of CB-18 increased to 71.4% with a specificity of 97.0% versus standard processing with a sensitivity of 61.9% and a specificity of 99.0%. The diagnostic yield of acid-fast bacillus smear with CB-18 in the absence of fluorescence microscopy and PCR compared to standard processing with NALC-NaOH was not significantly different, although the power to detect a difference by the modified assay was low.     

Characterization and virulence analysis of catalase mutants of Haemophilus influenzae.

In addition to detoxifying peroxides generated by aerobic metabolism, the catalases of pathogenic bacteria have also been hypothesized to serve as virulence factors by enabling microorganisms to resist the oxidative bursts of host inflammatory cells. Using transposon mutagenesis of the hktE gene, encoding the Haemophilus influenzae structural gene for catalase, we constructed defined catalase mutants of H. influenzae strains Rd- and Eagan b+. These mutants show no detectable catalase production during exponential or stationary phases or following induction with hydrogen peroxide or ascorbic acid, indicating that hktE is the only functional hydroperoxidase gene present in these two strains of H. influenzae. Exponential-phase cultures of hktE mutants are 8- to 25-fold more sensitive to hydrogen peroxide than the wild type. Using the infant rat model, hktE mutants of strain Eagan b+ were 2.3-fold less virulent than the wild type following intraperitoneal inoculation (P = 0.07). When administered intranasally, the Eagan b+ hktE mutant produced wild-type levels of bacteremia and nasal colonization. The results of this study show that while the H. influenzae hktE gene is important for survival in the presence of peroxides, deletion of the gene produces only a modest reduction in ability to cause lethal sepsis following parenteral challenge and no change in ability to colonize following intranasal inoculation in the infant rat model of infection.     

A practice-based intervention to enhance quality of care in the first 3 years of life: the Healthy Steps for Young Children Program

Context  There is growing concern regarding the quality of health care available in the United States for young children, and specific limitations have been noted in developmental and behavioral services provided for children in the first 3 years of life. Objective  To determine the impact of the Healthy Steps for Young Children Program on quality of early childhood health care and parenting practices. Design, Setting, and Participants  Prospective controlled clinical trial enrolling participants between September 1996 and November 1998 at 6 randomization and 9 quasi-experimental sites across the United States. Participants were 5565 children enrolled at birth and followed up through age 3 years. Intervention  Incorporation of developmental specialists and enhanced developmental services into pediatric care in participants' first 3 years of life. Main Outcome Measures  Quality of care was operationalized across 4 domains: effectiveness (eg, families received =" BORDER="0">4 Healthy Steps–related services or discussed >6 anticipatory guidance topics), patient-centeredness (eg, families were satisfied with care provided), timeliness (eg, children received timely well-child visits and vaccinations), and efficiency (eg, families remained at the practice for =" BORDER="0">20 months). Parenting outcomes included response to child misbehavior (eg, use of severe discipline) and practices to promote child development and safety (eg, mothers at risk for depression discussed their sadness with someone at the practice). Results  Of the 5565 enrolled families, 3737 (67.2%) responded to an interview at 30 to 33 months (usual care, 1716 families; Healthy Steps, 2021 families). Families who participated in the Healthy Steps Program had greater odds of receiving 4 or more Healthy Steps–related services (for randomization and quasi-experimental sites, respectively: odds ratio [OR], 16.90 [95% confidence interval {CI}, 12.78 to 22.34] and OR, 23.05 [95% CI, 17.38 to 30.58]), of discussing more than 6 anticipatory guidance topics (OR, 8.56 [95% CI, 6.47 to 11.32] and OR, 12.31 [95% CI, 9.35 to 16.19]), of being highly satisfied with care provided (eg, someone in the practice went out of the way for them) (OR, 2.06 [95% CI, 1.64 to 2.58] and OR, 2.11 [95% CI, 1.72 to 2.59]), of receiving timely well-child visits and vaccinations (eg, age-appropriate 1-month visit) (OR, 1.98 [95% CI, 1.08 to 3.62] and OR, 2.11 [95% CI, 1.16 to 3.85]), and of remaining at the practice for 20 months or longer (OR, 2.02 [95% CI, 1.61 to 2.55] and OR, 1.75 [95% CI, 1.43 to 2.15]). They also had reduced odds of using severe discipline (eg, slapping in face or spanking with object) (OR, 0.82 [95% CI, 0.54 to 1.26] and OR, 0.67 [95% CI, 0.46 to 0.97]). Among mothers considered at risk for depression, those who participated in the Healthy Steps Program had greater odds of discussing their sadness with someone at the practice (OR, 0.95 [95% CI, 0.56 to 1.63] and OR, 2.82 [95% CI, 1.57 to 5.08]). Conclusion  Universal, practice-based interventions can enhance quality of care for families of young children and can improve selected parenting practices.