Citations

Abstract Mycobacterium avium complex (MAC) causes chronic lung disease in immunocompetent people and disseminated infection in patients with AIDS. MAC is intrinsically resistant to many conventional antimycobacterial agents, it develops drug resistance rapidly to macrolide antibiotics, and patients with MAC infection experience frequent relapses or the inability to completely eradicate the infection with current treatment. Treatment regimens are prolonged and complicated by drug toxicity or intolerances. We sought to identify biochemical pathways in MAC that can serve as targets for novel antimycobacterial treatment. The cytochrome P450 enzyme, CYP51, catalyzes an essential early step in sterol metabolism, removing a methyl group from lanosterol in animals and fungi, or from obtusifoliol in plants. Azoles inhibit CYP51 function, leading to an accumulation of methylated sterol precursors. This perturbation of normal sterol metabolism compromises cell membrane integrity, resulting in growth inhibition or cell death. We have cloned and characterized a CYP51 from MAC that functions as a lanosterol 14α-demethylase. We show the direct interactions of azoles with purified MAC-CYP51 by absorbance and electron paramagnetic resonance spectroscopy, and determine the minimum inhibitory concentrations (MICs) of econazole, ketoconazole, itraconazole, fluconazole, and voriconazole against MAC. Furthermore, we demonstrate that econazole has a MIC of 4 μg/ml and a minimum bacteriocidal concentration of 4 μg/ml, whereas ketoconazole has a MIC of 8 μg/ml and a minimum bacteriocidal concentration of 16 μg/ml. Itraconazole, voriconazole, and fluconazole did not inhibit MAC growth to any significant extent.

Background— A paradoxical increase in the uncorrected QT interval during infusion of low-dose epinephrine appears pathognomonic for type 1 long-QT syndrome (LQT1). We sought to determine the diagnostic accuracy of this response among patients referred for clinical evaluation of congenital long-QT syndrome (LQTS). Methods and Results— From 1999 to 2002, 147 genotyped patients (125 untreated and 22 undergoing β-blocker therapy) had an epinephrine QT stress test that involved a 25-minute infusion protocol (0.025 to 0.3 μg · kg −1 · min −1 ). A 12-lead ECG was monitored continuously, and repolarization parameters were measured. The sensitivity, specificity, and positive and negative predictive values for the paradoxical QT response (defined as a ≥30-ms increase in QT during infusion of ≤0.1 μg · kg −1 · min −1 epinephrine) was determined. The 125 untreated patients (44 genotype negative, 40 LQT1, 30 LQT2, and 11 LQT3) constituted the primary analysis. The median baseline corrected QT intervals (QTc) were 444 ms (gene negative), 456 ms (LQT1), 486 ms (LQT2), and 473 ms (LQT3). The median change in QT interval during low-dose epinephrine infusion was −23 ms in the gene-negative group, 78 ms in LQT1, −4 ms in LQT2, and −58 ms in LQT3. The paradoxical QT response was observed in 37 (92%) of 40 patients with LQT1 compared with 18% (gene-negative), 13% (LQT2), and 0% (LQT3; P <0.0001) of the remaining patients. Overall, the paradoxical QT response had a sensitivity of 92.5%, specificity of 86%, positive predictive value of 76%, and negative predictive value of 96% for LQT1 status. Secondary analysis of the subset undergoing β-blocker therapy indicated inferior diagnostic utility in this setting. Conclusions— The epinephrine QT stress test can unmask concealed type 1 LQTS with a high level of accuracy.

Abstract Rationale Although the serial dilution technique for quantitative culture of bronchoalveolar fluid is considered to be the gold standard for the diagnosis of ventilator-associated pneumonia, it is more labor intensive than the calibrated loop technique. Objective We sought to determine the agreement between the calibrated loop and serial dilution techniques in the diagnosis of ventilator-associated pneumonia. Methods We prospectively measured bacterial colony counts by the serial dilution and calibrated loop techniques in 121 bronchoalveolar lavage samples of 104 patients with suspected ventilator-associated pneumonia. Measurements and Main Results At the time of bronchoscopy, patients had received mechanical ventilation for a median of 8 d. Patients were receiving antibiotics when 90 of the 121 (74.4%) bronchoalveolar samples were obtained. The colony counts of 13 bacterial isolates were too numerous to count by the calibrated loop technique; by serial dilution technique, their counts ranged from 4.70 to 6.74 log10 cfu/ml. Fifty other bacteria had paired colony counts measured by each of the two techniques: the bias (95% confidence interval) between the two techniques was −0.380 (−0.665 to −0.095) log10 cfu/ml, with precision of 1.002 log10 cfu/ml and 95% limits of agreement of −2.344 to 1.584 log10 cfu/ml. Using the threshold of 4 log10 cfu/ml as a criterion for the diagnosis of ventilator-associated pneumonia, there was discordance only for one bacterial organism between the two techniques. Conclusions The calibrated loop technique can be used for the diagnosis of ventilator-associated pneumonia using bronchoalveolar lavage fluid.

Oligodendroglioma frequently (≥ 70%) responds to radiation and chemotherapy, and is the first CNS neoplasm in which a genetic signature (1p and 19q deletion) has been associated with outcome within the context of large clinical trials. Current translational investigations focus on deletions or mutations of potential tumor suppressor genes, epigenetic alterations, amplification or mutation of growth factor and regulatory genes, and characterization of signaling events and regulatory protein expression. The most compelling data has involved 1p and 19q loss, which is observed in over 50% of anaplastic oligodendrogliomas. In two randomized phase III trials (Radiation Therapy Oncology Group 9402 and European Organisation for Research and Treatment of Cancer 26951), the addition of neoadjuvant or adjuvant procarbazine, lomustine, and vincristine (PCV; respectively) to radiotherapy did not produce superior survival as compared with radiotherapy alone. A modest increase in progression-free survival was observed with the addition of PCV, but at the cost of increased toxicity. Combined 1p and 19q loss identified a favorable prognostic group in both studies, which appeared to be independent of treatment arms. However, it is unclear whether these deletions represent surrogate markers of a favorable biologic tumor behavior, or are predictive of outcome after specific treatment. Currently, there is insufficient data to allow therapeutic decisions to be made solely on the basis of 1p and 19q gene deletion status. Future phase III trials are evaluating other chemotherapeutic and targeted agents, including temozolomide, and include correlative investigations of aberrant molecular events in these neoplasms, which may lead to future therapeutic strategies that are based on specific molecular signatures.

Brain metastases are an important cause of morbidity and mortality, afflicting nearly 170,000 Americans annually. The prognosis for these patients is poor, with median survival times measured in months. In this review article, we present the standard treatment approach of whole-brain radiotherapy and discuss new directions, including the role of chemical modifiers and the management and prevention of neurocognitive deficits.