scholarly journals Housekeeping Gene Sequencing and Multilocus Variable-Number Tandem-Repeat Analysis To Identify Subpopulations within Pseudomonas syringae pv. maculicola and Pseudomonas syringae pv. tomato That Correlate with Host Specificity

2012 ◽  
Vol 78 (9) ◽  
pp. 3266-3279 ◽  
Author(s):  
S. Gironde ◽  
C. Manceau
Keyword(s):  
Pseudomonas Syringae ◽  
Tandem Repeat ◽  
Variable Number Tandem Repeat ◽  
Housekeeping Gene ◽  
Epidemiological Studies ◽  
Variable Number ◽  
Tomato Plants ◽  
Content Type ◽  
Genetic Lineages ◽  
Genetic Events

ABSTRACTPseudomonas syringaepv. maculicola causes bacterial spot onBrassicaceaeworldwide, and for the last 10 years severe outbreaks have been reported in the Loire Valley, France.P. syringaepv. maculicola resemblesP. syringaepv. tomato in that it is also pathogenic for tomato and causes the same types of symptoms. We used a collection of 106 strains ofP. syringaeto characterize the relationships betweenP. syringaepv. maculicola and related pathovars, paying special attention toP. syringaepv. tomato. Phylogenetic analysis ofgyrBandrpoDgene sequences showed thatP. syringaepv. maculicola, which causes diseases inBrassicaceae, forms six genetic lineages within genomospecies 3 ofP. syringaestrains as defined by L. Gardan et al. (Int. J. Syst. Bacteriol. 49[Pt 2]:469–478, 1999), whereasP. syringaepv. tomato forms two distinct genetic lineages. A multilocus variable-number tandem-repeat (VNTR) analysis (MLVA) conducted with eight minisatellite loci confirmed the genetic structure obtained withrpoDandgyrBsequence analyses. These results provide promising tools for fine-scale epidemiological studies on diseases caused byP. syringaepv. maculicola andP. syringaepv. tomato. The two pathovars had distinct host ranges; onlyP. syringaepv. maculicola strains were pathogenic forBrassicaceae. A subpopulation ofP. syringaepv. maculicola strains that are pathogenic for Pto-expressing tomato plants were shown to lackavrPto1andavrPtoBor to contain a disruptedavrPtoBhomolog. Taking phylogenetic and pathological features into account, our data suggest that the DC3000 strain belongs toP. syringaepv. maculicola. This study shows thatP. syringaepv. maculicola andP. syringaepv. tomato appear multiclonal, as they did not diverge from a single common ancestral group within the ancestralP. syringaegenomospecies 3, and suggests that pathovar specificity withinP. syringaemay be due to independent genetic events.

scholarly journals New Multilocus Variable-Number Tandem-Repeat Analysis Tool for Surveillance and Local Epidemiology of Bacterial Leaf Blight and Bacterial Leaf Streak of Rice Caused by Xanthomonas oryzae

2014 ◽  
Vol 81 (2) ◽  
pp. 688-698 ◽  
Author(s):  
L. Poulin ◽  
P. Grygiel ◽  
M. Magne ◽  
L. Gagnevin ◽  
L. M. Rodriguez-R ◽  
...  
Keyword(s):  
Tandem Repeat ◽  
Variable Number Tandem Repeat ◽  
Variable Number ◽  
Leaf Blight ◽  
Xanthomonas Oryzae ◽  
Bacterial Leaf Blight ◽  
Bacterial Leaf Streak ◽  
Content Type ◽  
Genetic Lineages ◽  
Repeat Analysis

ABSTRACTMultilocus variable-number tandem-repeat analysis (MLVA) is efficient for routine typing and for investigating the genetic structures of natural microbial populations. Two distinct pathovars ofXanthomonas oryzaecan cause significant crop losses in tropical and temperate rice-growing countries. Bacterial leaf streak is caused byX. oryzaepv. oryzicola, and bacterial leaf blight is caused byX. oryzaepv. oryzae. For the latter, two genetic lineages have been described in the literature. We developed a universal MLVA typing tool both for the identification of the threeX. oryzaegenetic lineages and for epidemiological analyses. Sixteen candidate variable-number tandem-repeat (VNTR) loci were selected according to their presence and polymorphism in 10 draft or complete genome sequences of the threeX. oryzaelineages and by VNTR sequencing of a subset of loci of interest in 20 strains per lineage. The MLVA-16 scheme was then applied to 338 strains ofX. oryzaerepresenting different pathovars and geographical locations. Linkage disequilibrium between MLVA loci was calculated by index association on different scales, and the 16 loci showed linear Mantel correlation with MLSA data on 56X. oryzaestrains, suggesting that they provide a good phylogenetic signal. Furthermore, analyses of sets of strains for different lineages indicated the possibility of using the scheme for deeper epidemiological investigation on small spatial scales.

scholarly journals Origin of the Outbreak in France of Pseudomonas syringae pv. actinidiae Biovar 3, the Causal Agent of Bacterial Canker of Kiwifruit, Revealed by a Multilocus Variable-Number Tandem-Repeat Analysis

2015 ◽  
Vol 81 (19) ◽  
pp. 6773-6789 ◽  
Author(s):  
A. Cunty ◽  
S. Cesbron ◽  
F. Poliakoff ◽  
M.-A. Jacques ◽  
C. Manceau
Keyword(s):  
New Zealand ◽  
Pseudomonas Syringae ◽  
Tandem Repeat ◽  
Variable Number Tandem Repeat ◽  
Variable Number ◽  
Bacterial Canker ◽  
Content Type ◽  
Leaf Spots ◽  
Genetic Level ◽  
Dispersal Routes

ABSTRACTThe first outbreaks of bacterial canker of kiwifruit caused byPseudomonas syringaepv. actinidiae biovar 3 were detected in France in 2010.P. syringaepv. actinidiae causes leaf spots, dieback, and canker that sometimes lead to the death of the vine.P. syringaepv. actinidifoliorum, which is pathogenic on kiwi as well, causes only leaf spots. In order to conduct an epidemiological study to track the spread of the epidemics of these two pathogens in France, we developed a multilocus variable-number tandem-repeat (VNTR) analysis (MLVA). MLVA was conducted on 340 strains ofP. syringaepv. actinidiae biovar 3 isolated in Chile, China, France, Italy, and New Zealand and on 39 strains ofP. syringaepv. actinidifoliorum isolated in Australia, France, and New Zealand. Eleven polymorphic VNTR loci were identified in the genomes ofP. syringaepv. actinidiae biovar 3 ICMP 18744 and ofP. syringaepv. actinidifoliorum ICMP 18807. MLVA enabled the structuring ofP. syringaepv. actinidiae biovar 3 andP. syringaepv. actinidifoliorum strains in 55 and 16 haplotypes, respectively. MLVA and discriminant analysis of principal components revealed that strains isolated in Chile, China, and New Zealand are genetically distinct fromP. syringaepv. actinidiae strains isolated in France and in Italy, which appear to be closely related at the genetic level. In contrast, no structuring was observed forP. syringaepv. actinidifoliorum. We developed an MLVA scheme to explore the diversity withinP. syringaepv. actinidiae biovar 3 and to trace the dispersal routes of epidemicP. syringaepv. actinidiae biovar 3 in Europe. We suggest using this MLVA scheme to trace the dispersal routes ofP. syringaepv. actinidiae at a global level.

scholarly journals Prediction of Local Transmission of Mycobacterium tuberculosis Isolates of a Predominantly Beijing Lineage by Use of a Variable-Number Tandem-Repeat Typing Method Incorporating a Consensus Set of Hypervariable Loci

2017 ◽  
Vol 56 (1) ◽  
Author(s):  
Yoshiro Murase ◽  
Kiyohiko Izumi ◽  
Akihiro Ohkado ◽  
Akio Aono ◽  
Kinuyo Chikamatsu ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Tandem Repeat ◽  
Variable Number Tandem Repeat ◽  
Variable Number ◽  
Trend Test ◽  
Typing Method ◽  
Content Type ◽  
Tuberculosis Transmission ◽  
High Prevalence ◽  
Hypervariable Loci

ABSTRACT Strain genotyping based on the variable-number tandem repeat (VNTR) is widely applied for identifying the transmission of Mycobacterium tuberculosis. A consensus set of four hypervariable loci (1982, 3232, 3820, and 4120) has been proposed to improve the discrimination of Beijing lineage strains. Herein, we evaluated the utility of these four hypervariable loci for tracing local tuberculosis transmission in 981 cases over a 14-month period in Japan (2010 to 2011). We used six different VNTR systems, with or without the four hypervariable loci. Patient ages and weighted standard distances (a measure of the dispersion of genotype-clustered cases) were used as proxies for estimating local tuberculosis transmission. The highest levels of isolate discrimination were achieved with VNTR systems that incorporated the four hypervariable loci (i.e., the Japan Anti-Tuberculosis Association [JATA]18-VNTR, mycobacterial interspersed repetitive unit [MIRU]28-VNTR, and 24Beijing-VNTR). The clustering rates by JATA12-VNTR, MIRU15-VNTR, JATA15-VNTR, JATA18-VNTR, MIRU28-VNTR, and 24Beijing-VNTR systems were 52.2%, 51.0%, 39.0%, 24.1%, 23.1%, and 22.0%, respectively. As the discriminative power increased, the median weighted standard distances of the clusters tended to decrease (from 311 to 80 km, P < 0.001, Jonckheere-Terpstra trend test). Concurrently, the median ages of patients in the clusters tended to decrease (from 68 to 60 years, P < 0.001, Jonckheere-Terpstra trend test). These findings suggest that strain typing using the four hypervariable loci improves the prediction of active local tuberculosis transmission. The four-locus set can therefore contribute to the targeted control of tuberculosis in settings with high prevalence of Beijing lineage strains.

scholarly journals Phylogenetic and Variable-Number Tandem-Repeat Analyses Identify Nonpathogenic Xanthomonas arboricola Lineages Lacking the Canonical Type III Secretion System

2015 ◽  
Vol 81 (16) ◽  
pp. 5395-5410 ◽  
Author(s):  
Salwa Essakhi ◽  
Sophie Cesbron ◽  
Marion Fischer-Le Saux ◽  
Sophie Bonneau ◽  
Marie-Agnès Jacques ◽  
...  
Keyword(s):  
Tandem Repeat ◽  
Type Iii Secretion ◽  
Variable Number Tandem Repeat ◽  
Type Iii Secretion System ◽  
Variable Number ◽  
Secretion System ◽  
Content Type ◽  
Type Iii ◽  
Xanthomonas Arboricola ◽  
Canonical Type

ABSTRACTXanthomonas arboricolais conventionally known as a taxon of plant-pathogenic bacteria that includes seven pathovars. This study showed thatX. arboricolaalso encompasses nonpathogenic bacteria that cause no apparent disease symptoms on their hosts. The aim of this study was to assess theX. arboricolapopulation structure associated with walnut, including nonpathogenic strains, in order to gain a better understanding of the role of nonpathogenic xanthomonads in walnut microbiota. A multilocus sequence analysis (MLSA) was performed on a collection of 100X. arboricolastrains, including 27 nonpathogenic strains isolated from walnut. Nonpathogenic strains grouped outside clusters defined by pathovars and formed separate genetic lineages. A multilocus variable-number tandem-repeat analysis (MLVA) conducted on a collection ofX. arboricolastrains isolated from walnut showed that nonpathogenic strains clustered separately from clonal complexes containingXanthomonas arboricolapv. juglandis strains. Some nonpathogenic strains ofX. arboricoladid not contain the canonical type III secretion system (T3SS) and harbored only one to three type III effector (T3E) genes. In the nonpathogenic strains CFBP 7640 and CFBP 7653, neither T3SS genes nor any of the analyzed T3E genes were detected. This finding raises a question about the origin of nonpathogenic strains and the evolution of plant pathogenicity inX. arboricola. T3E genes that were not detected in any nonpathogenic isolates studied represent excellent candidates to be those responsible for pathogenicity inX. arboricola.

scholarly journals Development of a Multiple-Locus Variable-Number Tandem-Repeat Typing Scheme for Genetic Fingerprinting of Burkholderia cenocepacia and Application to Nationwide Epidemiological Analysis

2014 ◽  
Vol 53 (2) ◽  
pp. 398-409 ◽  
Author(s):  
Christine Segonds ◽  
Michelle Thouverez ◽  
Antoine Barthe ◽  
Nadège Bossuet-Greif ◽  
Lenka Tisseyre ◽  
...  
Keyword(s):  
Tandem Repeat ◽  
Burkholderia Cepacia ◽  
Genetic Relatedness ◽  
Variable Number Tandem Repeat ◽  
Cost Effective ◽  
Variable Number ◽  
Discriminatory Power ◽  
Burkholderia Cenocepacia ◽  
Content Type ◽  
Burkholderia Multivorans

Organisms of theBurkholderia cepaciacomplex are especially important pathogens in cystic fibrosis (CF), with a propensity for patient-to-patient spread and long-term respiratory colonization.B. cenocepaciaandBurkholderia multivoransaccount for the majority of infections in CF, and major epidemic clones have been recognized throughout the world. The aim of the present study was to develop and evaluate a multilocus variable-number tandem-repeat (VNTR) analysis (MLVA) scheme forB. cenocepacia. Potential VNTR loci were identified upon analysis of the annotated genome sequences ofB. cenocepaciastrains AU1054, J2315, and MCO-3, and 10 of them were selected on the basis of polymorphisms and size. A collection of 100B. cenocepaciastrains, including epidemiologically related and unrelated strains, as well as representatives of the major epidemic lineages, was used to evaluate typeability, epidemiological concordance, and the discriminatory power of MLVA-10 compared with those of pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Longitudinal stability was assessed by testing 39 successive isolates from 14 patients. Typeability ranged from 0.91 to 1, except for that of one marker, which was not amplified in 53% of theB. cenocepaciaIIIA strains. The MLVA types were shown to be stable in chronically colonized patients and within outbreak-related strains, with excellent epidemiological concordance. Epidemic and/or globally distributed lineages (epidemic Edinburgh-Toronto electrophoretic type 12 [ET-12], sequence type 32 [ST-32], ST-122, ST-234, and ST-241) were successfully identified. Conversely, the discriminatory power of MLVA was lower than that of PFGE or MLST, although PFGE variations within the epidemic lineages sometimes masked their genetic relatedness. In conclusion, MLVA represents a promising cost-effective first-line tool inB. cenocepaciasurveillance.

scholarly journals Prevalence and Characterization of Heterogeneous Variable-Number Tandem-Repeat Clusters Comprising Drug-Susceptible and/or Variable ResistantMycobacterium tuberculosisComplex Isolates in the Netherlands from 2004 to 2016

2018 ◽  
Vol 56 (11) ◽  
Author(s):  
Inge Roof ◽  
Rana Jajou ◽  
Miranda Kamst ◽  
Arnout Mulder ◽  
Albert de Neeling ◽  
...  
Keyword(s):  
The Netherlands ◽  
Tandem Repeat ◽  
Variable Number Tandem Repeat ◽  
Multivariate Logistic Regression Analysis ◽  
Variable Number ◽  
Linkage Data ◽  
Nucleotide Polymorphisms ◽  
Typing Method ◽  
Content Type ◽  
Heterogeneous Clustering

ABSTRACTThe variable-number tandem-repeat (VNTR) typing method is used to study tuberculosis (TB) transmission. Clustering ofMycobacterium tuberculosisisolates with identical VNTR patterns is assumed to reflect recent transmission. Hence, clusters are thought to be homogeneous regarding antibiotic resistance. In practice, however, heterogeneous clusters are also identified. This study investigates the prevalence and characteristics of heterogeneous VNTR clusters and assesses whether isolates in these clusters remain clustered when subjected to whole-genome sequencing (WGS). In the period from 2004 to 2016, 9,072 isolates were included. Demographic and epidemiological linkage data were obtained from the Netherlands Tuberculosis Register. VNTR clusters were defined as homogeneous when isolates shared identical resistance profiles or as heterogeneous if both susceptible and (variable) resistant isolates were found. Multivariate logistic regression analysis was performed to identify factors associated with heterogeneous clustering. Isolates from 2016 were subjected to WGS, and a genetic distance of 12 single nucleotide polymorphisms (SNPs) was used as the cutoff for WGS clustering. In total, 4,661/9,072 (51%) isolates were clustered into 985 different VNTR clusters, of which 217 (22%) were heterogeneous. Patient characteristics associated with heterogeneous clustering were non-Dutch ethnicity (odds ratio [OR], 1.46 [95% confidence interval {CI}, 1.22 to 1.75]), asylum seeker (OR, 1.51 [95% CI, 1.24 to 1.85]), extrapulmonary TB (OR, 1.26 [95% CI, 1.09 to 1.46]), previous TB diagnosis (OR, 1.38 [95% CI, 1.04 to 1.82]), and not being a contact of a TB patient (OR, 1.35 [95% CI, 1.08 to 1.69]). With WGS, 34% of heterogeneous and 78% of homogeneous isolates from 2016 remained clustered. Heterogeneous VNTR clusters are common but seem to be explained by a substantial degree of false clustering by VNTR typing compared to WGS.

scholarly journals Application of Variable-Number Tandem-Repeat Typing To Discriminate Ralstonia solanacearum Strains Associated with English Watercourses and Disease Outbreaks

2013 ◽  
Vol 79 (19) ◽  
pp. 6016-6022 ◽  
Author(s):  
Neil Parkinson ◽  
Ruth Bryant ◽  
Janice Bew ◽  
Christine Conyers ◽  
Robert Stones ◽  
...  
Keyword(s):  
River Water ◽  
Tandem Repeat ◽  
Ralstonia Solanacearum ◽  
Tandem Repeats ◽  
Variable Number Tandem Repeat ◽  
Disease Outbreaks ◽  
Variable Number ◽  
Content Type ◽  
Clonal Type ◽  
The United Kingdom

ABSTRACTVariable-number tandem-repeat (VNTR) analysis was used for high-resolution discrimination amongRalstonia solanacearumphylotype IIB sequevar 1 (PIIB-1) isolates and further evaluated for use in source tracing. Five tandem-repeat-containing loci (comprising six tandem repeats) discriminated 17 different VNTR profiles among 75 isolates from potato, geranium, bittersweet (Solanum dulcamara), tomato, and the environment.R. solanacearumisolates from crops at three unrelated outbreak sites where river water had been used for irrigation had distinct VNTR profiles that were shared with PIIB-1 isolates from infected bittersweet growing upriver of each site. The VNTR profiling results supported the implication that the source ofR. solanacearumat each outbreak was contaminated river water. Analysis of 51 isolates from bittersweet growing in river water at different locations provided a means to evaluate the technique for studying the epidemiology of the pathogen in the environment. Ten different VNTR profiles were identified among bittersweet PIIB-1 isolates from the River Thames. Repeated findings of contiguous river stretches that produced isolates that shared single VNTR profiles supported the hypothesis that the pathogen had disseminated from infected bittersweet plants located upriver. VNTR profiles shared between bittersweet isolates from two widely separated Thames tributaries (River Ray and River Colne) suggested they were independently contaminated with the same clonal type. Some bittersweet isolates had VNTR profiles that were shared with potato isolates collected outside the United Kingdom. It was concluded that VNTR profiling could contribute to further understanding ofR. solanacearumepidemiology and assist in control of future disease outbreaks.

scholarly journals Intergenic Variable-Number Tandem-Repeat Polymorphism Upstream ofrocAAlters Toxin Production and Enhances Virulence in Streptococcus pyogenes

2016 ◽  
Vol 84 (7) ◽  
pp. 2086-2093 ◽  
Author(s):  
Luchang Zhu ◽  
Randall J. Olsen ◽  
Nicola Horstmann ◽  
Samuel A. Shelburne ◽  
Jia Fan ◽  
...  
Keyword(s):  
Streptococcus Pyogenes ◽  
Tandem Repeat ◽  
Variable Number Tandem Repeat ◽  
Toxin Production ◽  
Variable Number ◽  
Altered Level ◽  
Content Type ◽  
Vntr Polymorphism ◽  
New Findings ◽  
Vntr Polymorphisms

Variable-number tandem-repeat (VNTR) polymorphisms are ubiquitous in bacteria. However, only a small fraction of them has been functionally studied. Here, we report an intergenic VNTR polymorphism that confers an altered level of toxin production and increased virulence inStreptococcus pyogenes. The nature of the polymorphism is a one-unit deletion in a three-tandem-repeat locus upstream of therocAgene encoding a sensor kinase.S. pyogenesstrains with this type of polymorphism cause human infection and produce significantly larger amounts of the secreted cytotoxinsS. pyogenesNADase (SPN) and streptolysin O (SLO). Using isogenic mutant strains, we demonstrate that deleting one or more units of the tandem repeats abolished RocA production, reduced CovR phosphorylation, derepressed multiple CovR-regulated virulence factors (such as SPN and SLO), and increased virulence in a mouse model of necrotizing fasciitis. The phenotypic effect of the VNTR polymorphism was nearly the same as that of inactivating therocAgene. In summary, we identified and characterized an intergenic VNTR polymorphism inS. pyogenesthat affects toxin production and virulence. These new findings enhance understanding ofrocAbiology and the function of VNTR polymorphisms inS. pyogenes.

Molecular characterization of Shiga-toxigenicEscherichia coliisolated from diverse sources from India by multi-locus variable number tandem repeat analysis (MLVA)

2014 ◽  
Vol 142 (12) ◽  
pp. 2572-2582 ◽  
Author(s):  
A. KUMAR ◽  
N. TANEJA ◽  
R. K. SHARMA ◽  
H. SHARMA ◽  
T. RAMAMURTHY ◽  
...  
Keyword(s):  
Tandem Repeat ◽  
Geographical Area ◽  
Variable Number Tandem Repeat ◽  
Epidemiological Studies ◽  
Variable Number ◽  
North India ◽  
E Coli ◽  
Repeat Analysis ◽  
Large Geographical Area ◽  
Human Infections

SUMMARYIn a first study from India, a diverse collection of 140 environmental and clinical non-O157 Shiga-toxigenicEscherichia colistrains from a large geographical area in north India was typed by multi-locus variable number tandem repeat analysis (MLVA). The distribution of major virulence genesstx1,stx2andeaewas found to be 78%, 70% and 10%, respectively; 15 isolates were enterohaemorrhagicE. coli(stx1+/stx2+andeae+). By MLVA analysis, 44 different alleles were obtained. Dendrogram analysis revealed 104 different genotypes and 19 MLVA-type complexes divided into two main lineages, i.e. mutton and animal stool. Human isolates presented a statistically significant greater odds ratio for clustering with mutton samples compared to animal stool isolates. Five human isolates clustered with animal stool strains suggesting that some of the human infections may be from cattle, perhaps through milk, contact or the environment. Further epidemiological studies are required to explore these sources in context with occurrence of human cases.

scholarly journals A Predominant Variable-Number Tandem-Repeat Cluster of Mycobacterium tuberculosis Isolates among Asylum Seekers in the Netherlands and Denmark, Deciphered by Whole-Genome Sequencing

2017 ◽  
Vol 56 (2) ◽  
Author(s):  
Rana Jajou ◽  
Albert de Neeling ◽  
Erik Michael Rasmussen ◽  
Anders Norman ◽  
Arnout Mulder ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
The Netherlands ◽  
Genetic Distance ◽  
Genome Sequencing ◽  
Tandem Repeat ◽  
Variable Number Tandem Repeat ◽  
Variable Number ◽  
Whole Genome ◽  
Average Genetic Distance ◽  
Content Type

ABSTRACT In many countries, Mycobacterium tuberculosis isolates are routinely subjected to variable-number tandem-repeat (VNTR) typing to investigate M. tuberculosis transmission. Unexpectedly, cross-border clusters were identified among African refugees in the Netherlands and Denmark, although transmission in those countries was unlikely. Whole-genome sequencing (WGS) was applied to analyze transmission in depth and to assess the precision of VNTR typing. WGS was applied to 40 M. tuberculosis isolates from refugees in the Netherlands and Denmark (most of whom were from the Horn of Africa) that shared the exact same VNTR profile. Cluster investigations were undertaken to identify in-country epidemiological links. Combining WGS results for the isolates (all members of the central Asian strain [CAS]/Delhi genotype), from both European countries, an average genetic distance of 80 single-nucleotide polymorphisms (SNPs) (maximum, 153 SNPs) was observed. The few pairs of isolates with confirmed epidemiological links, except for one pair, had a maximum distance of 12 SNPs. WGS divided this refugee cluster into several subclusters of patients from the same country of origin. Although the M. tuberculosis cases, mainly originating from African countries, shared the exact same VNTR profile, most were clearly distinguished by WGS. The average genetic distance in this specific VNTR cluster was 2 times greater than that in other VNTR clusters. Thus, identical VNTR profiles did not represent recent direct M. tuberculosis transmission for this group of patients. It appears that either these strains from Africa are extremely conserved genetically or there is ongoing transmission of this genotype among refugees on their long migration routes from Africa to Europe.

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