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were determined and compared. The sequence data were used to infer a phylogenetic tree, which provided the basis for a systematic phylogenetic analysis of the genus Mycobacterium. The groups of slow-and fast-growing mycobacteria could be differentiated as distinct entities. We found that M. simiae occupies phylogenetically an intermediate position between these two groups. The phylogenetic relatedness within the slow-growing species did not reflect the Runyon classification of photochromogenic, scotochromogenic, and nonchromogenic mycobacteria. In general, the phylogenetic units identified by using rRNA sequences confirmed the validity of phenotypically defined species; an exception was M. gastri, which was indistinguishable from M. kunsasii when this kind of analysis was used.Mycobacteria are aerobic, nonmobile bacteria that are characteristically acid fast. The property of acid fastness, which is due to waxy materials in cell walls, is particularly important for recognizing mycobacteria. Members of the genus Mycobacterium are widespread in nature and range from soil-dwelling saprophytes to pathogens of humans and animals (22, 34). A major descriptive division of mycobacteria is related to growth rate and pigmentation. On the basis of these criteria, the genus Mycobacterium has been divided into four groups. Group I consists of the photochromogenic (pigmented) species of slow growers; members of group I1 are scotochromogenic slow growers; group I11 contains the nonchromogenic slow growers; and group IV consists of rapid growers (defined as maturing in less than 1 week) (22,34).Taxonomic analysis of the genus Mycobacterium is complicated by the fact that a variety of specialized and complex tests must be used. Numerical taxonomic analysis, which requires that some dozens of characters be tested (e.g., enzymatic activity, growth, morphology, and drug susceptibility), is now being applied to circumscription of clusters and description of strains. Early on, the problems and difficulties of traditional taxonomy with respect to mycobacteria were recognized, prompting a number of investigators in the field to organize themselves into the International Working Group on Mycobacterial Taxonomy and to undertake a number of cooperative taxonomic studies (18, 29, Attempts to subdivide mycobacterial species by using immunological approaches, DNA composition, and similar characteristics (1-3,9,10) proved to be taxonomically useful but gave little phylogenetic information. The use of macromolecular comparisons to infer phylogenetic relationships is generally accepted and well established. Of the macromolecules used for phylogenetic analysis, the rRNAs, in particular 16s rRNA, have proven to be the most useful for establishing phylogenetic relationships because of their high information content, conservative nature, and universal dis-31-33).* Corresponding author. tribution (7,35). We recently developed a general procedure for the isolation and direct complete nucleotide determination of entire genes coding for 16s rRNA in w...

Adult patients with acute lymphoblastic leukemia (ALL) who are stratified into the standard-risk (SR) group due to the absence of adverse prognostic factors relapse in 40% to 55% of the cases. To identify complementary markers suitable for further treatment stratification in SR ALL, we evaluated the predictive value of minimal residual disease (MRD) and prospectively monitored MRD in 196 strictly defined SR ALL patients at up to 9 time points in the first year of treatment by quantitative polymerase chain reaction (PCR). Frequency of MRD positivity decreased from 88% during early induction to 13% at week 52. MRD was predictive for relapse at various follow-up time points. Combined MRD information from different time points allowed definition of 3 risk groups (P < .001): 10% of patients with a rapid MRD decline to lower than 10 ؊4 or below detection limit at day 11 and day 24 were classified as low risk and had a 3-year relapse rate (RR) of 0%. A subset of 23% with an MRD of 10 ؊4 or higher until week 16 formed the high-risk group, with a 3-year RR of 94% (95% confidence interval [CI] 83%-100%). The remaining patients whose RR was 47% (31%- 63% IntroductionInvestigation of minimal residual disease (MRD) has been proven to be a valuable tool for predicting outcome in childhood acute lymphoblastic leukemia (ALL). [1][2][3][4][5] In contrast, only a few studies have focused on adult ALL, and they were based mostly on patients with heterogeneous risk profiles and different kinds and intensities of treatment. [6][7][8] However, monitoring homogeneous patient cohorts at different time points during therapy might provide additional insight into the nature and clinical relevance of MRD kinetics in adult ALL, which is particularly relevant for the large population of standard-risk (SR) patients without conventional risk factors. Relapses in this patient group occur in about 40% to 55% of cases and cannot be predicted by any known conventional risk factor. [9][10][11] In a number of clinical studies this led to a policy of stem cell transplantation (SCT) in first remission, 12-14 causing overtreatment and additional expenses for those patients who are cured by conventional chemotherapy alone. Therefore, definition of prognostic factors allowing discrimination of SR patients with poor outcome after standard chemotherapy from those with a favorable prognosis is highly warranted. Currently, the most widely used techniques to detect and quantify residual disease in patients with ALL are multiparameter immunophenotypic evaluation of aberrant protein expression 2,3,8 and clone-specific polymerase chain reaction (PCR) amplification of immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements. 1,4,5 Such molecular targets can be identified in more than 90% of patients with ALL by the use of various PCR primer sets. Besides its large applicability and high sensitivity, a main advantage of PCR-based assays is the use of DNA as a stable and easy conveyable specimen, which is particularly relevant in large multicenter studies....

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