We performed a multicenter prevalence study of nontuberculous mycobacteria (NTM) involving 1,582 patients (mean age, 18.9 years; male/female ratio, 1.06) with cystic fibrosis in France. The overall NTM prevalence (percentage of patients with at least one positive culture) was 6.6% (104/1,582 patients), with prevalences ranging from 3.7% (in the east of France) to 9.6% (in the greater Paris area). Mycobacterium abscessus complex (MABSC; 50 patients) and Mycobacterium avium complex (MAC; 23 patients) species were the most common NTM, and the only ones associated with fulfillment of the American Thoracic Society bacteriological criteria for NTM lung disease. The “new” species, Mycobacterium bolletii and Mycobacterium massiliense, accounted for 40% of MABSC isolates. MABSC species were isolated at all ages, with a prevalence peak between 11 and 15 years of age (5.8%), while MAC species reached their highest prevalence value among patients over 25 years of age (2.2%).
The highly homologous PE_PGRS (Proline-glutamic acid_polymorphic GC-rich repetitive sequence) genes are members of the PE multigene family which is found only in mycobacteria. PE genes are particularly abundant within the genomes of pathogenic mycobacteria where they seem to have expanded as a result of gene duplication events. PE_PGRS genes are characterized by their high GC content and extensive repetitive sequences, making them prone to recombination events and genetic variability.
Comparative sequence analysis of Mycobacterium tuberculosis genes PE_PGRS17 (Rv0978c) and PE_PGRS18 (Rv0980c) revealed a striking genetic variation associated with this typical tandem duplicate. In comparison to the M. tuberculosis reference strain H37Rv, the variation (named the 12/40 polymorphism) consists of an in-frame 12-bp insertion invariably accompanied by a set of 40 single nucleotide polymorphisms (SNPs) that occurs either in PE_PGRS17 or in both genes. Sequence analysis of the paralogous genes in a representative set of worldwide distributed tubercle bacilli isolates revealed data which supported previously proposed evolutionary scenarios for the M. tuberculosis complex (MTBC) and confirmed the very ancient origin of "M. canettii" and other smooth tubercle bacilli. Strikingly, the identified polymorphism appears to be coincident with the emergence of the post-bottleneck successful clone from which the MTBC expanded. Furthermore, the findings provide direct and clear evidence for the natural occurrence of gene conversion in mycobacteria, which appears to be restricted to modern M. tuberculosis strains.
This study provides a new perspective to explore the molecular events that accompanied the evolution, clonal expansion, and recent diversification of tubercle bacilli.
Molecular epidemiologic findings suggest an ancient focus of TB.
Although India has the highest prevalence of tuberculosis (TB) worldwide, the genetic diversity of Mycobacterium tuberculosis in India is largely unknown. A collection of 91 isolates originating from 12 different regions spread across the country were analyzed by genotyping using 21 loci with variable-number tandem repeats (VNTRs), by spoligotyping, by principal genetic grouping (PGG), and by deletion analysis of M. tuberculosis–specific deletion region 1. The isolates showed highly diverse VNTR genotypes. Nevertheless, highly congruent groupings identified by using the 4 independent sets of markers permitted a clear definition of 3 prevalent PGG1 lineages, which corresponded to the "ancestral" East African–Indian, the Delhi, and the Beijing/W genogroups. A few isolates from PGG2 lineages and a single representative of the presumably most recent PGG3 were identified. These observations suggest a predominance of ancestral M. tuberculosis genotypes in the Indian subcontinent, which supports the hypothesis that India is an ancient endemic focus of TB.
tuberculosis; Mycobacterium tuberculosis; VNTR; spoligotyping; single nucleotide polymorphism; molecular epidemiology
We studied the prevalence and species distribution of nontuberculous mycobacteria (NTM) in relation to age in 385 patients with cystic fibrosis (CF) (mean age ± standard deviation [range], 12.0 ± 6.1 [1 to 24] years; sex ratio, 0.53) attending three Parisian centers. The overall prevalence of NTM in sputum was 8.1% (31 out of 385). The following NTM were isolated (n = 33): Mycobacterium abscessus (n = 13, 39.4%), Mycobacterium avium complex (MAC) (n = 7, 21.2%), Mycobacterium gordonae (n = 6, 18.2%), and other (n = 7, 21.2%). Sixteen patients met the American Thoracic Society microbiological criteria for NTM infection, including 11 patients positive for M. abscessus, 4 for MAC, and 1 for MAC and Mycobacterium kansasii. The overall prevalence of NTM was significantly lower in patients under 15 years old than for patients equal to or more than 15 years old (4.8 versus 14.9%, respectively; P = 0.001). M. abscessus was isolated at all ages, while MAC was not recovered before 15 years (prevalence of 0.0 and 5.2% in patients aged 1 to 14 and 15 to 24, respectively; P = 0.001).
Using INNO-LiPA-MYCOBACTERIA (Lipav1; Innogenetics) and the AccuProbe (Gen-Probe Inc./bioMérieux) techniques, 35 Mycobacterium avium-Mycobacterium intracellulare-Mycobacterium scrofulaceum (MAC/MAIS) complex strains were identified between January 2000 and December 2002. Thirty-four of 35 isolates were positive only for the MAIS complex probe by Lipav1 and were further analyzed by INNO-LiPA-MYCOBACTERIA version 2 (Lipav2), hsp65 PCR restriction pattern analysis (PRA), and ribosomal internal transcribed spacer (ITS), hsp65, and 16S rRNA sequences. Lipav2 identified 14 of 34 strains at the species level, including 11 isolates positive for the newly specific MAC sequevar Mac-A probe (MIN-2 probe). Ten of these 11 isolates corresponded to sequevar Mac-A, which was recently defined as Mycobacterium chimerae sp. nov. Among the last 20 of the 34 MAIS isolates, 17 (by hsp65 PRA) and 18 (by hsp65 sequence) were characterized as M. avium. Ten of the 20 were identified as Mac-U sequevar. All these 20 isolates were identified as M. intracellulare by 16S rRNA sequence except one isolate identified as Mycobacterium paraffinicum by 16S rRNA and ITS sequencing. One isolate out of 35 isolates that was positive for M. avium by AccuProbe and that was Mycobacterium genus probe positive and MAIS probe negative by Lipav1 and Lipav2 might be considered a new species. In conclusion, the new INNO-LiPA-MYCOBACTERIA allowed the identification of 40% of the previously unidentified MAIS isolates at the species level. The results of the Lipav2 assay on the MAIS isolates confirm the great heterogeneity of this group and suggest the use of hsp65 or ITS sequencing for precise identification of such isolates.
This study involves a first evaluation of 25 novel spacer oligonucleotides in addition to the 43 routine spacers for molecular characterization of a panel of 65 isolates of tubercle bacilli from different geographic origins that were initially classified as Mycobacterium africanum based on phenotypic characters. The 68-spacer format defined four additional patterns, and three groups were identified. The relatively homogeneous groups A1 and A2 included strains from West Africa, and A3-1 included strains from East Africa. The presence of deletion region RD9 confirmed the reclassification of the M. africanum subtype II spoligopattern within group A3-1 as Mycobacterium tuberculosis. These isolates may represent a diverging branch of M. tuberculosis in Africa. The use of new spacers also suggested an undergoing evolution of M. africanum subtype I in West Africa. Our results showed that the strain differentiation within the M. tuberculosis complex is improved by using novel spacers, and extensive studies using new-generation spoligotyping may be helpful to better understand the evolution of M. africanum.
The reliability of the MB/BACT system for susceptibility testing of Mycobacterium tuberculosis to pyrazinamide, rifampin, isoniazid, streptomycin, and ethambutol was compared to the BACTEC 460TB system. The proportion method was used to resolve discrepant results by an independent arbiter. Two interpretative methods were used, with an undiluted control (direct control) and a diluted control (10−1 control). As no significant difference was observed between the two controls, the method with the direct control was adopted as the most accurate one. One hundred sixty-six strains were tested, with an overall agreement of 98.3%. After resolution of the 18 discrepant results by the proportion method, the sensitivity and specificity of the MB/BACT system were 100% for rifampin, isoniazid, and pyrazinamide. For ethambutol, sensitivity was 92.3% at the critical concentration and 33% at the high concentration, and specificity was 100% at both concentrations. For streptomycin, sensitivity was 100% at the critical concentration and 80% at the high concentration, and specificity was 98.6% at the critical concentration and 100% at the high concentration. The rifampin, isoniazid, streptomycin, and ethambutol susceptibility test results were obtained in 6.6 days with the MB/BACT versus 5 days with the BACTEC 460TB. The pyrazinamide susceptibility test results were obtained in 7.8 days with the MB/BACT, versus 6.7 days with the BACTEC 460TB. These data demonstrate that the fully automated MB/BACT system is a very reliable method for rapid susceptibility testing of M. tuberculosis against rifampin, isoniazid, and pyrazinamide. Sensitivity results have to be improved for ethambutol and streptomycin, especially at the high concentration.
We studied the population genetics of Mycobacterium kansasii isolates from the United States by PCR restriction enzyme analysis (PRA) of the 441-bp Telenti fragment of the hsp-65 gene and pulsed-field gel electrophoresis (PFGE) of genomic DNA with the restriction endonucleases AseI, DraI, and XbaI, and we compared the patterns to those previously reported from France and Japan. By PRA, 78 of 81 clinical isolates (96%) from the United States belonged to subspecies I. With PFGE, 28 AseI patterns, 32 DraI patterns, and 35 XbaI patterns were produced. PFGE showed marked clonality of the U.S. isolates, with differences between genotypes involving only one or two bands. Isolates within Texas showed lower pattern diversity than those from different states. With DraI, 31 of 71 isolates (44%) had the same common PFGE pattern, which matched the predominant pattern in France (pattern Ia), determined by Picardeau et al. (M. Picardeau, G. Prod'hom, L. Raskine, M. P. LePennec, and V. Vincent, J. Clin. Microbiol. 35:25-32, 1997), and in Japan (type M), determined by Iinuma et al. (Y. Iinuma, S. Ichiyama, Y. Hasegawa, K. Shimokata, S. Kawahara, and T. Matsushima, J. Clin. Microbiol. 35:596-599, 1997). With AseI, 42% of isolates produced a common pattern indistinguishable from the common pattern seen in French isolates (Ia) and with only one band difference from the common pattern (type M) in Japan. This study demonstrates that subspecies I is the predominant subspecies of M. kansasii among clinical isolates in the United States, as it is in Europe and Japan, and that genotype I is highly clonal worldwide, with the same major genotype responsible for human infection. The fact that a single clone of M. kansasii is responsible for most cases of human disease suggests that specific virulence factors may be associated with this specific genotype.
We prospectively studied 298 patients with cystic fibrosis (mean age 11.3 years; range 2 months to 32 years; sex ratio, 0.47) for nontuberculous mycobacteria in respiratory samples from January 1, 1996, to December 31, 1999. Mycobacterium abscessus was by far the most prevalent nontuberculous mycobacterium: 15 patients (6 male, 9 female; mean age 11.9 years; range 2.5–22 years) had at least one positive sample for this microorganism (versus 6 patients positive for M. avium complex), including 10 with >3 positive samples (versus 3 patients for M. avium complex). The M. abscessus isolates from 14 patients were typed by pulsed-field gel electrophoresis: each of the 14 patients harbored a unique strain, ruling out a common environmental reservoir or person-to-person transmission. Water samples collected in the cystic fibrosis center were negative for M. abscessus. This major mycobacterial pathogen in children and teenagers with cystic fibrosis does not appear to be acquired nosocomially.
Cystic fibrosis; Mycobacterium abscessus; nontuberculous mycobacteria; hsp65 sequencing; pulsed-field gel electrophoresis; epidemiology
The frequency of recovery of atypical mycobacteria was estimated in two treatment plants providing drinking water to Paris, France, at some intermediate stages of treatment. The two plants use two different filtration processes, rapid and slow sand filtration. Our results suggest that slow sand filtration is more efficient for removing mycobacteria than rapid sand filtration. In addition, our results show that mycobacteria can colonize and grow on granular activated carbon and are able to enter distribution systems. We also investigated the frequency of recovery of mycobacteria in the water distribution system of Paris (outside buildings). The mycobacterial species isolated from the Paris drinking water distribution system are different from those isolated from the water leaving the treatment plants. Saprophytic mycobacteria (present in 41.3% of positive samples), potentially pathogenic mycobacteria (16.3%), and unidentifiable mycobacteria (54.8%) were isolated from 12 sites within the Paris water distribution system. Mycobacterium gordonae was preferentially recovered from treated surface water, whereas Mycobacterium nonchromogenicum was preferentially recovered from groundwater. No significant correlations were found among the presence of mycobacteria, the origin of water, and water temperature.
We identified an unusual strain of mycobacteria from two patients with pulmonary tuberculosis by its smooth, glossy morphotype and, primarily, its genotypic characteristics. Spoligotyping and restriction fragment length polymorphism typing were carried out with the insertion sequence IS6110 patterns. All known cases of tuberculosis caused by Mycobacterium canetti have been contracted in the Horn of Africa.
We studied the resistance of various mycobacteria isolated from a water distribution system to chlorine. Chlorine disinfection efficiency is expressed as the coefficient of lethality (liters per minute per milligram) as follows: Mycobacterium fortuitum (0.02) > M. chelonae (0.03) > M. gordonae (0.09) > M. aurum (0.19). For a C · t value (product of the disinfectant concentration and contact time) of 60 mg · min · liter−1, frequently used in water treatment lines, chlorine disinfection inactivates over 4 log units of M. gordonae and 1.5 log units of M. fortuitum or M. chelonae. C · t values determined under similar conditions show that even the most susceptible species, M. aurum and M. gordonae, are 100 and 330 times more resistant to chlorine than Escherichia coli. We also investigated the effects of different parameters (medium, pH, and temperature) on chlorine disinfection in a chlorine-resistant M. gordonae model. Our experimental results follow the Arrhenius equation, allowing the inactivation rate to be predicted at different temperatures. Our results show that M. gordonae is more resistant to chlorine in low-nutrient media, such as those encountered in water, and that an increase in temperature (from 4°C to 25°C) and a decrease in pH result in better inactivation.
Linear plasmids were unknown in mycobacteria until recently. Here, we report the complete nucleotide sequence of 23-kb linear plasmid pCLP from Mycobacterium celatum, an opportunistic pathogen. The sequence of pCLP revealed at least 19 putative open reading frames (ORFs). Expression of pCLP genes in exponential-phase cultures was determined by reverse transcriptase PCR (RT-PCR). Twelve ORFs were expressed, whereas no transcription of the 7 other ORFs of pCLP was detected. Five of the 12 transcribed ORFs detected by RT-PCR are of unknown function. Sequence analysis revealed similar loci in both M. celatum pCLP and the Mycobacterium tuberculosis chromosome, including transposase-related sequences. This result suggests horizontal transfer between these two organisms. pCLP also contains ORFs that are similar to genes of bacterial circular plasmids involved in partition (par operon) and postsegregational (pem operon) mechanisms. Functional analysis of these ORFs suggests that they probably carry out similar maintenance roles in pCLP.
Chemotaxonomic and genetic properties were determined for 14 mycobacterial isolates identified as members of a newly described species Mycobacterium bohemicum. The isolates recovered from clinical, veterinary, and environmental sources were compared for lipid composition, biochemical test results, and sequencing of the 16S ribosomal DNA (rDNA) and the 16S-23S rDNA internal transcribed spacer (ITS) regions. The isolates had a lipid composition that was different from those of other known species. Though the isolates formed a distinct entity, some variations were detected in the features analyzed. Combined results of the phenotypic and genotypic analyses were used to group the isolates into three clusters. The major cluster (cluster A), very homogenous in all respects, comprised the M. bohemicum type strain, nine clinical and veterinary isolates, and two of the five environmental isolates. Three other environmental isolates displayed an insertion of 14 nucleotides in the ITS region; they also differed from cluster A in fatty alcohol composition and produced a positive result in the Tween 80 hydrolysis test. Among these three, two isolates were identical (cluster B), but one isolate (cluster C) had a unique high-performance liquid chromatography profile, and its gas liquid chromatography profile lacked 2-octadecanol, which was present in all other isolates analyzed. Thus, sequence variation in the 16S-23S ITS region was associated with interesting variations in lipid composition. Two of the isolates analyzed were regarded as potential inducers of human or veterinary infections. Each of the environmental isolates, all of which were unrelated to the cases presented, was cultured from the water of a different stream. Hence, natural waters are potential reservoirs of M. bohemicum.
A collection of 105 clinical isolates originally identified as Mycobacterium africanum were characterized using both phenotypic and genotyping methods. The phenotypic methods included routine determination of cultural properties and biochemical tests used to discriminate among the members of the M. tuberculosis complex, whereas genotypic characterization was based on IS6110-restriction fragment length polymorphism (IS6110-RFLP) analysis, IS1081-RFLP analysis, direct repeat-based spacer oligonucleotide typing (spoligotyping), variable number of tandem DNA repeats (VNTR), and the polymorphism of the oxyR, pncA, and mtp40 loci. The results obtained showed that a majority of M. africanum isolates were characterized by a specific spoligotyping pattern that was intermediate between those of M. tuberculosis and M. bovis, which do not hybridize with spacers 33 to 36 and spacers 39 to 43, respectively. A tentative M. africanum-specific spoligotyping signature appeared to be absence of spacers 8, 9, and 39. Based on spoligotyping, as well as the polymorphism of oxyR and pncA, a total of 24 isolates were excluded from the final study (19 were identified as M. tuberculosis, 2 were identified as M. canetti, and 3 were identified as M. bovis). The remaining 81 M. africanum isolates were efficiently subtyped in three distinct subtypes (A1 to A3) by IS6110-RFLP analysis and spoligotyping. The A1 and A2 subgroups were relatively more homogeneous upon spoligotyping than A3. Further analysis of the three subtypes by VNTR corroborated the highly homogeneous nature of the A2 subtype but showed significant variations for subtypes A1 and A3. A phylogenetic tree based on a selection of isolates representing the three subtypes using VNTR and spoligotyping alone or in combination confirmed the subtypes described as well as the heterogeneity of subtype A3.
A nonchromogenic Mycobacterium species was isolated from an AIDS patient with acute lymphadenitis. On the basis of the results of conventional tests, the strain appeared to be an atypical nonphotochromogenic Mycobacterium kansasii strain. Sequencing of the 16S rRNA gene revealed a unique nucleic acid sequence, suggesting that the isolate represents an undescribed pathogenic species.