IS6110-based differentiation of Mycobacterium tuberculosis strains.

In this study, 62 Mycobacterium tuberculosis strains were characterized by fast ligation-mediated PCR (FLiP) and, previously performed, IS6110 restriction fragment length polymorphism (RFLP). FLiP proved a reproducible and specific method for differentiation between M. tuberculosis strains. The discriminatory power of FLiP was close to that of the reference IS6110 RFLP suggesting its usefulness in studying the genetic diversity of M. tuberculosis strains.

Application of FLiP method for differentiation of Mycobacterium tuberculosis strains in comparison to commonly used methods, spoligotyping and MIRU-VNTR typing.

The current "gold standard" in molecular epidemiological studies of Mycobacterium tuberculosis is IS6110 RFLP based on IS6110 polymorphism. However PCR-based methods are becoming increasingly important. Recently, fast ligation-mediated PCR (FLiP), based on IS6110 polymorphism was proposed. In this study, the discriminatory power of FLIP, spoligotyping and MIRU-VNTR typing, in differentiation of M. tuberculosis isolates was compared. The discriminatory index (HGI) of spoligotyping, MIRU-VNTR analysis, and FLiP was 0.653, 0.837, and 0.917, respectively. This indicates that FLiP allows a high level of differentiation among M. tuberculosis strains and it might be a valuable alternative to the other typing methods.

Mycobacterium tuberculosis complex genetic diversity: mining the fourth international spoligotyping database (SpolDB4) for classification, population genetics and epidemiology.

BACKGROUND: The Direct Repeat locus of the Mycobacterium tuberculosis complex (MTC) is a member of the CRISPR (Clustered regularly interspaced short palindromic repeats) sequences family. Spoligotyping is the widely used PCR-based reverse-hybridization blotting technique that assays the genetic diversity of this locus and is useful both for clinical laboratory, molecular epidemiology, evolutionary and population genetics. It is easy, robust, cheap, and produces highly diverse portable numerical results, as the result of the combination of (1) Unique Events Polymorphism (UEP) (2) Insertion-Sequence-mediated genetic recombination. Genetic convergence, although rare, was also previously demonstrated. Three previous international spoligotype databases had partly revealed the global and local geographical structures of MTC bacilli populations, however, there was a need for the release of a new, more representative and extended, international spoligotyping database. RESULTS: The fourth international spoligotyping database, SpolDB4, describes 1939 shared-types (STs) representative of a total of 39,295 strains from 122 countries, which are tentatively classified into 62 clades/lineages using a mixed expert-based and bioinformatical approach. The SpolDB4 update adds 26 new potentially phylogeographically-specific MTC genotype families. It provides a clearer picture of the current MTC genomes diversity as well as on the relationships between the genetic attributes investigated (spoligotypes) and the infra-species classification and evolutionary history of the species. Indeed, an independent Naïve-Bayes mixture-model analysis has validated main of the previous supervised SpolDB3 classification results, confirming the usefulness of both supervised and unsupervised models as an approach to understand MTC population structure. Updated results on the epidemiological status of spoligotypes, as well as genetic prevalence maps on six main lineages are also shown. Our results suggests the existence of fine geographical genetic clines within MTC populations, that could mirror the passed and present Homo sapiens sapiens demographical and mycobacterial co-evolutionary history whose structure could be further reconstructed and modelled, thereby providing a large-scale conceptual framework of the global TB Epidemiologic Network. CONCLUSION: Our results broaden the knowledge of the global phylogeography of the MTC complex. SpolDB4 should be a very useful tool to better define the identity of a given MTC clinical isolate, and to better analyze the links between its current spreading and previous evolutionary history. The building and mining of extended MTC polymorphic genetic databases is in progress.

Evaluation of multiple genetic markers for typing drug-resistant Mycobacterium tuberculosis strains from Poland.

In the present study, 77 drug-resistant Mycobacterium tuberculosis strains isolated in Poland in 2000 were characterized by the mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) typing and our novel method based on PCR amplification of DNA regions between IS6110 and 16-bp GC-rich frequent repeats (designated IS6110-Mtb1/Mtb2 PCR). The results were compared with previous data of the more commonly used methods, IS6110 restriction fragment length polymorphism (RFLP) and spoligotyping. The discriminatory power of IS6110-Mtb1/Mtb2 method was only slightly lower than that of IS6110 RFLP, whereas MIRU-VNTR typing was the least discriminative among the 4 methods used. Clustering of strains by using results of IS6110-Mtb1/Mtb2 PCR correlated well with RFLP-defined clusters, further confirming epidemiologic relationships among patients. These results indicate that the novel genotyping method could be an attractive alternative for other PCR-based typing procedures, such as spoligotyping and MIRU-VNTR typing. Also, it seems to be a valuable adjunct to the reference IS6110 RFLP method for studying the genetic diversity of drug-resistant M. tuberculosis strains in Poland.

Comparison of ligation-mediated PCR methods in differentiation of Mycobacterium tuberculosis strains.

Fast and inexpensive identification of epidemiological links between limited number of Mycobacterium tuberculosis strains is required to initially evaluate hospital outbreaks, laboratory crosscontaminations, and family or small community transmissions. The ligation-mediated PCR methods (LM-PCR) appear sufficiently discriminative and reproducible to be considered as a good candidate for such initial, epidemiological analysis. Here, we compared the discriminative power of the recently developed in our laboratory fast ligation amplification polymorphism (FLAP) method with fast ligation-mediated PCR (FLiP). Verification of the results was based on analyzing a set of reference strains and RFLP-IS6110 typing. The HGDI value was very similar for both LM-PCR methods and RFLP-IS6110 typing. However, only 52% of strains were correspondingly grouped by both FLiP and FLAP methods. Differentiation by FLAP method demonstrated a limited similarity to IS6110-RFLP (37,7%). As much as 78,7% of strains were grouped identically when differentiated by FLiP and IS6110-RFLP methods. The analysis differentiated 31, 35, and 36 groups when using FLAP, FLiP, and RFLP-IS6110 methods, respectively.

Genotyping of clinical Mycobacterium tuberculosis isolates based on IS6110 and MIRU-VNTR polymorphisms.

In this study, 155 clinical Mycobacterium tuberculosis isolates were subject to genotyping with fast ligation-mediated PCR (FLiP). This typing method is a modified mixed-linker PCR, a rapid approach based on the PCR amplification of HhaI restriction fragments of genomic DNA containing the 3' end of IS6110 and resolving the amplicons by polyacrylamide gel electrophoresis. The results were compared with previous data of the more commonly used methods, 15-locus mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) typing and, to verify combined FLiP/MIRU-VNTR clusters, the reference IS6110 restriction fragment length polymorphism (RFLP). FLiP banding patterns were highly reproducible and polymorphic. This method differentiated 119 types among the study set compared to 108 distinct MIRU-VNTR profiles. The discriminatory power of FLiP was slightly higher than that of MIRU-VNTR analysis (Hunter-Gaston Discriminatory Index = 0.991 and 0.990, resp.). Detailed comparison of the clusters defined by each of the methods revealed, however, a more apparent difference in the discriminatory abilities that favored FLiP. Clustering of strains by using combined results of these two PCR-based methods correlated well with IS6110 RFLP-defined clusters, further confirming high discriminatory potential of FLiP typing. These results indicate that FLiP could be an attractive and valuable secondary typing technique for verification of MIRU-VNTR clusters of M. tuberculosis strains.

hsp65 PCR-restriction analysis (PRA) with capillary electrophoresis for species identification and differentiation of Mycobacterium kansasii and Mycobacterium chelonae-Mycobacterium abscessus group.

OBJECTIVES: The aim of the present study was to identify and differentiate Mycobacterium kansasii and Mycobacterium chelonae-Mycobacterium abscessus group strains isolated from clinical and environmental sources in different countries. METHODS: PCR-restriction analysis of the hsp65 gene (PRA) with automated capillary electrophoresis was applied to the isolates previously identified by conventional biochemical testing and the molecular INNO-LiPA MYCOBACTERIA assay. RESULTS: PRA performed very well in comparison with the two other methods (96.4% concordance). Among 27 M. kansasii isolates, this method detected five genetic types, of which type 1 represented the most common clinical isolate, as it is worldwide. PRA differentiated 29 M. chelonae-M. abscessus group isolates into Mycobacterium immunogenum type 2 (n=13), M. chelonae (n=12), and M. abscessus types 1 (n=1) and 2 (n=1). M. immunogenum was the most frequent (69%) isolate from humans, but only one of 11 cases was clinically significant. M. chelonae was the most commonly (83%) recovered from water. PRA also identified two isolates with hsp65 alleles representing previously unreported patterns. CONCLUSIONS: PRA based on automated capillary electrophoresis is a rapid, simple, and reliable method for the identification and differentiation of both clinically relevant and environmental isolates of M. kansasii and M. chelonae-M. abscessus group.

Profiling Mycobacterium xenopi with restriction fragment length polymorphism of insertion element IS1395.

OBJECTIVES: The aim of the present study was to assess the usefulness of insertion element IS1395 for differentiation of Mycobacterium xenopi, an increasingly common opportunistic human pathogen. METHODS: Fifty-two isolates obtained from 51 patients in Poland in 1996, 1997, and 1999, were analyzed by IS1395 restriction fragment length polymorphism (RFLP), and their susceptibilities to 11 anti-tuberculosis drugs were also determined. RESULTS: IS1395-associated banding patterns of the isolates were not highly polymorphic; the RFLP patterns displayed several bands in common. Nevertheless, 44 of the 52 isolates were clearly distinguishable from each other. Only eight strains (15.4%) occurred in four clusters of two identical clones, one of which comprised two isolates obtained from one patient with a 12-month interval. The remaining six patients with clustered strains showed no apparent epidemiologic links with the other patients from the same cluster, and they were most likely infected by the same environmental source. No noticeable difference in RFLP pattern or IS1395 copy number between drug-sensitive and drug-resistant strains was shown. A high proportion (84.6%) of strains resistant to at least one drug was found, and 7.7% were resistant to more than three drugs. CONCLUSIONS: The stability and utility of IS1395 for further detailed epidemiological investigations of M. xenopi was confirmed and extended.

hsp65 PCR-restriction analysis (PRA) with capillary electrophoresis in comparison to three other methods for identification of Mycobacterium species.

We developed a scheme for rapid identification of Mycobacterium species using an automated fluorescence capillary electrophoresis instrument. A 441-bp region of the hsp65 gene was examined using PCR-restriction analysis (PRA). The assay was initially evaluated on 38 reference strains. The observed sizes of restriction fragments were consistently smaller than the real sizes for each of the species as deduced from the sequence analysis (mean variance=7bp). Nevertheless, the obtained PRA patterns were highly reproducible and resulted in correct species identifications. A blind test was then successfully performed on 64 test isolates previously characterized by conventional biochemical methods, a commercial INNO-LiPA Mycobacteria assay and/or sequence determination of the 5' end of 16S rRNA gene. A total of 14 of 64 isolates were erroneously identified by conventional methods (78% accuracy). In contrast, PRA performed very well in comparison with the LiPA (89% concordance) and especially with DNA sequencing (93.3% of concordant results). Also, PRA identified seven isolates representing five previously unreported hsp65 alleles. We conclude that hsp65 PRA based on automated capillary electrophoresis is a rapid, simple and reliable method for identification of mycobacteria.

Molecular characterization of Mycobacterium tuberculosis isolates from Lódz, Poland: analysis by IS6110 restriction fragment length polymorphism and double-repetitive-element PCR.

OBJECTIVES: The aim of the present study was to characterize Mycobacterium tuberculosis strains isolated in the area of Lódz, Poland, from 1996 to 2000. METHODS: Two hundred sixty three isolates from 250 patients with tuberculosis were analysed by IS6110 restriction fragment length polymorphism (RFLP) and the double-repetitive-element PCR (DRE-PCR) method when indicated. RESULTS: The isolates were found to show a great heterogeneity and only 52 strains (20.8%) occurred in 20 clusters of 2-5 identical clones. Despite this diversity of IS6110 RFLP patterns, a computer analysis of similarities revealed a high level of relatedness (at least 90%) among 38.4% of different patterns. Most of the patients with clustered strains showed no apparent epidemiologic links with other patients whose strains had the same pattern. Utilisation of the DRE-PCR analysis as an additional typing test allowed to differentiate M. tuberculosis strains with a discriminating capacity similar to that of the IS6110 RFLP. Also, DRE-PCR differentiated nine strains that were indistinguishable by the RFLP analysis. CONCLUSIONS: Both methods used for the molecular characterization of M. tuberculosis clinical isolates showed similar discriminating ability. DRE-PCR analysis proved a simple, rapid and cost-effective adjunct to the IS6110 RFLP reference method. It could be applied as a screening test, thus, reducing the number of isolates that need further subtyping with the IS6110 RFLP to those initially clustered.

PCR-based genotyping of Mycobacterium tuberculosis with new GC-rich repeated sequences and IS6110 inverted repeats used as primers.

In the present study we attempted to develop a PCR-based epidemiological tool for the differentiation of Mycobacterium tuberculosis isolates. Use of the designed primers Mtb1 (5'-CCG-GCG-GGG-CCG-GCG-G) and Mtb2 (5'-CGG-CGG-CAA-CGG-CGG-C) targeting frequently repeated 16-bp sequences in combination with primers sited at the inverted repeats flanking IS6110 allowed differentiation of M. tuberculosis isolates.

Molecular characterization of rifampin- and isoniazid-resistant Mycobacterium tuberculosis strains isolated in Poland.

A total of 105 rifampin (RMP)- and/or isoniazid (INH)-resistant strains of Mycobacterium tuberculosis isolated from different parts of Poland in 2000 were screened for mutations associated with resistance to these drugs by two molecular methods, namely sequence analysis and real-time PCR technology. Three loci associated with drug resistance were selected for characterization: they were rpoB (RMP), katG, and the regulatory region of inhA (INH). Nineteen different mutations were identified in 64 RMP-resistant strains, and five new alleles were described. The most common point mutations were in codons 531 (41%), 516 (16%), and 526 (9%) of the rpoB gene. Mutations were not found in two (3%) of the isolates. In the case of resistance to INH, six different mutations in the katG gene of 83 resistant strains were detected. Fifty-seven (69%) isolates exhibited nucleotide substitutions at codon 315. One strain harbored a mutation affecting codon 279 (Gly279Thr). Twelve of 26 INH-resistant strains with the wild-type codon 315 (14.5% of all strains tested) had the mutation -15C-->T in the regulatory region of inhA. A full correlation between the DNA sequence analysis and real-time PCR data was obtained. We conclude that the real-time PCR method is fast and reliable for the detection of RMP and INH resistance-associated mutations in M. tuberculosis clinical isolates.