Molecular fingerprinting of Mycobacterium tuberculosis on a Caribbean island with IS6110 and DRr probes

Mutations in lysX as the new and reliable markers for tuberculosis Beijing and modern Beijing strains

Genotyping results and DNA sequencing analysis of 235 Mycobacterium tuberculosis (M. tuberculosis) isolates from China indicated that mutations at codon 995 (Pro CCG to Pro CCA) and 701 (Ile ATT to Thr ACT) in lysX gene (Rv1640c), are specific markers for Beijing and modern Beijing strains, respectively. This observation was also confirmed by 24 genomes of M. tuberculosis strains from other countries. Moreover, a simple and fast multiplex allele-specific PCR (MAS-PCR) method for detecting mutations at codon 995 and 701 in lysX has been established and used to screen 235 DNA samples obtained from M. tuberculosis isolates. In all cases, Beijing and modern Beijing strains were identified correctly.

Clustured regularly interspersed short palindromic repeats (CRISPR) genetic diversity studies as a mean to reconstruct the evolution of the Mycobacterium tuberculosis complex

The natural history of tuberculosis may be tackled by various means, among which the record of molecular scars that have been registered by the Mycobacterium tuberculosis complex (MTBC) genomes transmitted from patient to patient for tens of thousands years and possibly more. Recently discovered polymorphic loci, the CRISPR sequences, are indirect witnesses of the historical phage-bacteria struggle, and may be related to the time when the ancestor of today's tubercle bacilli were environmental bacteria, i.e. before becoming intracellular parasites. In this article, we present what are CRISPRs and try to summarize almost 20 years of research results obtained using the genetic diversity of the CRISPR loci in MTBC as a perspective for studying new models. We show that the study of the diversity of CRISPR sequences, thanks to «spoligotyping», has played a great role in our global understanding of the population structure of MTBC.

Comparison of the genetic convergence between mycobacterium strains by three RFLP-based methods in central province of Iran

OBJECTIVES

The utilization of molecular techniques in the epidemiology of tuberculosis have provided an opportunity for using effective markers to trace the transmission of the disease. The purpose of this study was to compare the genetic patterns of Mycobacterium tuberculosis by three methods of RFLP technique.

MATERIALS AND METHODS

In a cross-sectional and prospective study, 95 strains of M. tuberculosis isolates were selected for DNA fingerprinting. Extraction of DNA from Mycobacterium strains and DNA fingerprinting with IS-6110, PGRS and DR probe were performed by standard protocols.

RESULTS

Overall, the diversity of RFLP among 95 tuberculosis patients were 48, 50 and 45 on the basis of IS6110, PGRS and DR patterns, respectively. Twenty of these patterns (21.1%) with IS6110-RFLP, twenty-two (23.2%) with PGRS-RFLP and seventeen (17.9%) with DR-RFLP occurred with unique RFLP patterns, whereas the remaining 28 patterns were communal. The risk factors of clustering among tuberculosis patients were age < 45 years, new cases, degree of sputum smear ≥ 2+, and close contact.

CONCLUSION

Our study demonstrated that IS6110-RFLP, PGRS-RFLP and DR-RFLP genotyping could roughly identify similar proportions of clustered (secondary) cases as well as the same risk factors for clustering.

Use of genotyping based clustering to quantify recent tuberculosis transmission in Guadeloupe during a seven years period: analysis of risk factors and access to health care

BACKGROUND

The present study aimed to characterize Mycobacterium tuberculosis population structure and to identify transmission chains and risk factors by prospective molecular typing in conjunction with conventional epidemiological investigations in the French overseas department of Guadeloupe.

METHODS

The study included all the culture-positive TB cases (1 clinical isolate per patient; n = 129) diagnosed between a seven year period (April 4th, 1999 to December 31st, 2005). Prospective molecular typing was performed using spoligotyping and VNTRs, and a subset of 44 M. tuberculosis isolates found to be clustered was retrospectively typed using 12-loci MIRUs. Data were compared using the SITVIT2 database, followed by analysis of risk factors in function of clustering of the isolates and available demographic and socioeconomic data.

RESULTS

The study sample was characterized by a majority of new cases (87.4%); a moderate proportion of drug-resistance (7.8%); a high level of immigration (51.2% foreign-born) originating from high TB/HIV incidence neighboring islands such as Haiti or Dominican Republic; lower socioeconomic conditions (70.7% of jobless, average income 824 EUR/month); and a significantly higher proportion of TB/HIV co-infected cases (38.2% vs. 8.5%; p < 0.001), and extrapulmonary disease (18.2% vs. 4.8%; p < 0.02) among migrants as compared to French patients. The study revealed an important delay in access to healthcare with a median delay of 74.5 days between the 1st symptoms and clinical suspicion of TB. Prospective molecular typing based on spoligotyping and 5-loci VNTRs showed that evolutionary recent Euro-American lineages predominated in Guadeloupe (91.5% of isolates). In conjunction with epidemiological data, it allowed to estimate a recent transmission rate of 18.6%, which was close to the rate of 16.7% estimated using retrospective 12-loci MIRU typing. Although a higher proportion of cases in older age-group were apparently linked to reactivation; univariate analysis of risk factors did not allow pinpointing specific risk factors for a patient to belong to a TB transmission group.

CONCLUSIONS

Ongoing TB transmission in the insular, low TB-incidence setting of Guadeloupe can be defined as follows: (i) a significant proportion of imported cases of the disease from neighboring islands; (ii) significantly higher TB/HIV coinfection among foreign-born cases; and, (iii) a higher proportion of cases affecting older age-group among French patients due to reactivation. This study emphasizes the need for universal typing using spoligotyping and 15-loci MIRUs in prospective studies.

Genetic diversity, population structure and drug resistance of Mycobacterium tuberculosis in Peru

This paper presents the first evaluation of the molecular epidemiology of Mycobacterium tuberculosis in Peru. We characterised 323 isolates using spoligotyping and mycobacterial interspersed repetitive units variable number tandem repeats (MIRU-VNTR) typing. We aimed to determine the levels of genetic diversity and genetic differentiation among and within Peruvian isolates and the epidemiological factors which may be driving patterns of population structure and evolution of M. tuberculosis in Peru. Our results compared to the fourth international spoligotyping database (SpolDB4) and MIRU-VNTRplus, show that the main M. tuberculosis families present are Latin American-Mediterranean, Haarlem, T, and Beijing. Bayesian clustering recovered 15 groups in the Peruvian M. tuberculosis isolates, among which two were composed mainly of orphans, implying the presence of native "Peruvian" strains not previously reported. Variable levels of association with drug resistance were observed, with Beijing genotypes not showing any association with multidrug resistance, while in other groups MIRU-VNTR loci 2, 23, 31, and 40 were found to be associated with the multidrug-resistant tuberculosis (MDR-TB) phenotype, suggesting that a linkage disequibrium between these MIRU and drug resistance loci may be present. Genetic differentiation was present among drug resistant and sensitive strains. Ethambutol appeared to be the main driver of differentiation, suggesting that strong selection pressure could have been exerted by drug treatment in Peru over recent years.

Épidémiologie moléculaire de la tuberculose en Guadeloupe de 1994 à 2000

In Guadeloupe, the incidence of tuberculosis decreased between 1994 and 2000. The rate of resistance to at least one antibiotic remained constant at 11%, whereas the rate of multiple-drug resistance increased from 0.9 to 2.4% in 2000. The proportion of patients of foreign origin (mainly from Haiti and the Dominican Republic) increased whereas the number of French patients decreased. These results show that the epidemiology of tuberculosis in Guadeloupe is similar to industrialized countries as older people, foreigners from countries where TB is endemic, and HIV+ patients are at a higher risk to declare tuberculosis disease. Molecular typing realized by spoligotyping showed the importance of previous successive colonizations and migrations as characterized by the presence of major phylogenetic families originating essentially from Northern Europe (Haarlem), Latin America and Mediterranean (LAM) and from Anglo-Saxon countries (X). The sub-typing of clustered strains by IS6110-RFLP and by a PCR method based on the variable number of tandem DNA repeats (VNTR), highlighted 29 clusters, corresponding to 44.8% of clustered strains, and allowed to estimate the rate of recent transmission at 32.2%. The epidemiologic data associated with fingerprinting results underlined the importance of reactivation cases among older people, a significant number of imported TB cases without evident links, and casual contacts.

High rates of clustering of strains causing tuberculosis in Harare, Zimbabwe: a molecular epidemiological study

We examined the pattern of tuberculosis (TB) transmission (i.e., reactivation versus recent transmission) and the impact of human immunodeficiency virus (HIV) infection in Harare, Zimbabwe. Consecutive adult smear-positive pulmonary TB patients presenting to an urban hospital in Harare were enrolled. A detailed epidemiological questionnaire was completed, and tests for HIV type 1 and CD4 cell counts were performed for each patient. Molecular fingerprinting of the genomic DNA recovered from cultures of sputum was performed by two molecular typing methods: spacer oligonucleotide typing (spoligotyping) and analysis of variable number of tandem DNA repeats (VNTRs). A cluster was defined as isolates from two or more patients that shared the same spoligotype pattern or the same VNTR pattern, or both. DNA suitable for typing was recovered from 224 patients. The prevalence of HIV infection was 79%. Of 187 patient isolates (78.6%) typed by both spoligotyping and analysis of VNTRs, 147 were identified as part of a cluster by both methods. By spoligotyping alone, 84.1% of patient isolates were grouped into 20 clusters. The cluster size was generally <8 patient isolates, although three large clusters comprised 68, 25, and 23 patient isolates. A total of 89.4% of the patient isolates grouped into 12 clusters defined by analysis of VNTRs, with 2 large clusters consisting of 127 and 13 patient isolates, respectively. Thirty-six percent of patient isolates with a shared spoligotype and 17% with a shared VNTR pattern were geographically linked within Harare, but they were not linked on the basis of the patient's home district. In a multivariate analysis, there were no independent predictors of clustering, including HIV infection status. Comparison with the International Spoligotype database (Pasteur Institute, Pointe a Pitre, Guadeloupe) demonstrated that our three largest spoligotype clusters are well recognized and ubiquitous in Africa. In this epidemiologically well characterized urban population with a high prevalence of HIV infection, we identified a very high level of strain clustering, indicating substantial ongoing recent TB transmission. Geographic linkage could be detected in a proportion of these clusters. A small group of actively circulating strains accounted for most of the cases of TB transmission.

Evaluation and utilization as a public health tool of a national molecular epidemiological tuberculosis outbreak database within the United Kingdom from 1997 to 2001

The aim of this study was to develop a national model and analyze the value of a molecular epidemiological Mycobacterium tuberculosis DNA fingerprint-outbreak database. Incidents were investigated by the United Kingdom PHLS Mycobacterium Reference Unit (MRU) from June 1997 to December 2001, inclusive. A total of 124 incidents involving 972 tuberculosis cases, including 520 patient cultures from referred incidents and 452 patient cultures related to two population studies, were examined by using restriction fragment length polymorphism IS6110 fingerprinting and rapid epidemiological typing. Investigations were divided into the following three categories, reflecting different operational strategies: retrospective passive analysis, retrospective active analysis, and retrospective prospective analysis. The majority of incidents were in the retrospective passive analysis category, i.e., the individual submitting isolates has a suspicion they may be linked. Outbreaks were examined in schools, hospitals, farms, prisons, and public houses, and laboratory cross-contamination events and unusual clinical presentations were investigated. Retrospective active analysis involved a major outbreak centered on a high school. Contact tracing of a teenager with smear-positive pulmonary tuberculosis matched 14 individuals, including members of his class, and another 60 cases were identified in schools clinically and radiologically and by skin testing. Retrospective prospective analysis involved an outbreak of 94 isoniazid-resistant tuberculosis cases in London, United Kingdom, that began after cases were identified at one hospital in January 2000. Contact tracing and comparison with MRU databases indicated that the earliest matched case had occurred in 1995. Subsequently, the MRU changed to an active prospective analysis targeting linked isoniazid-monoresistant isolates for follow up. The patients were multiethnic, born mainly in the United Kingdom, and included professionals, individuals from the music industry, intravenous drug abusers, and prisoners.

Evolutionary relationships among strains of Mycobacterium tuberculosis with few copies of IS6110

Molecular typing of Mycobacterium tuberculosis by using IS6110 shows low discrimination when there are fewer than five copies of the insertion sequence. Using a collection of such isolates from a study of the epidemiology of tuberculosis in London, we have shown a substantial degree of congruence between IS6110 patterns and both spoligotype and PGRS type. This indicates that the IS6110 types mainly represent distinct families of strains rather than arising through the convergent insertion of IS6110 into favored positions. This is supported by identification of the genomic sites of the insertion of IS6110 in these strains. The combined data enable identification of the putative evolutionary relationships of these strains, comprising three lineages broadly associated with patients born in South Asia (India and Pakistan), Africa, and Europe, respectively. These lineages appear to be quite distinct from M. tuberculosis isolates with multiple copies of IS6110.

Molecular differentiation of Mycobacterium tuberculosis strains without IS6110 insertions

By using standard restriction fragment length polymorphism, 6 zero-copy IS6110 Mycobacterium tuberculosis isolates were identified from 1180 Maryland isolates as part of the National Tuberculosis Genotyping and Surveillance Network Project. By using various genotyping methods, we demonstrated that this zero band cluster can be differentiated into six genotypes.

IS6110 fingerprinting of sensitive and resistant strains (1991-1992) of Mycobacterium tuberculosis in Colombia

The standardized method to study the polymorphism of IS 6110 was used to characterize 53 isolates of Mycobacterium tuberculosis obtained during 1991-1992 from 14 regions in Colombia. In Valle region cluster rate was 25% (4/16). The mean number of IS6110 band was 10 +/- 3. Similarity between strains was of 60% in 81% of strains and this tended to be correlated with geographic origin. For the first time M. tuberculosis without IS6110 bands in restriction fragment length polymorphism analysis was found in Colombia. Additional studies are necessaries in order to best characterize the situation in relation to human immunodeficiency virus epidemic and recent changes in tuberculosis control program.

Use of spoligotyping for accurate classification of recurrent tuberculosis

The spoligotyping method has become an important tool for the tracking of Mycobacterium tuberculosis strains in different epidemiological settings. In this study, we demonstrate the ability of the spoligotyping technique to accurately determine the pathogenetic mechanism of recurrent disease. This methodology has advantages over conventional restriction fragment length polymorphism methods which may be useful in large-scale intervention studies.

Molecular epidemiology of Mycobacterium tuberculosis in Norway

The incidence of tuberculosis in Norway is one of the lowest in the world, and approximately half of the cases occur in first- and second-generation immigrants. In the present study, the genetic diversity of 92% of all strains of Mycobacterium tuberculosis isolated in Norway in 1994 to 1998 was assessed using restriction fragment length polymorphism (RFLP) analysis, with the insertion sequence IS6110 and the repetitive element DR as probes, to determine the degree of active transmission between patients. The DR probe was used as a secondary molecular marker to support or rule out clustering of strains with fewer than five copies of IS6110. After exclusion of 20 cultures representing laboratory contamination, 573 different IS6110 patterns were found among the 698 strains analyzed. Of these 573 patterns, 542 were observed only once and 31 were shared by 2 to 14 isolates. Among 81 strains (11.5%) carrying fewer than five copies of IS6110, 56 RFLP patterns were found when the results of both the IS6110 and DR methods were combined. Among the 698 strains, 570 were considered to be independent cases. A total of 14.5% of the native Norwegians and 19.7% of the foreign patients were part of a cluster. Thus, the degree of recent transmission of tuberculosis in Norway is low and the great majority of the cases are due to reactivation of previous disease. Transmission between immigrants and native Norwegians is uncommon. Two outbreaks, one among native Norwegians and one mainly among immigrants, have been ongoing for several years, indicating that, even in a low-incidence country such as Norway, with a good national program for tuberculosis surveillance, certain transmission chains are difficult to break.

Usefulness of IS6110-restriction fragment length polymorphism typing of Brazilian strains of Mycobacterium tuberculosis and comparison with an international fingerprint database

Strains of Mycobacterium tuberculosis isolated from 219 different tuberculosis patients, 115 from patients residing in Rio de Janeiro, 79 from Rio Grande do Sul and the remaining from other regions of the country, were analyzed by IS6110-restriction fragment length polymorphism fingerprinting. The IS6110-DNA patterns from these strains were highly polymorphic: 174 different patterns were observed and 25 patterns were shared by 70 isolates (32%). Most strains (93.4%) had multicopy patterns and only 17% of clustered strains had less than six IS6110 copies. Strain clustering was significantly higher for isolates from Rio Grande do Sul (36.7%) in comparison with strains from Rio de Janeiro (22.6%), but only when using high stringency during cluster analysis. Upon screening of an international database containing 3,970 fingerprints of M. tuberculosis strains, 15% of the patterns of Brazilian strains (21% of the strains) were identical to a fingerprint of an isolate from another country and one particular eight-band pattern forming the largest Brazilian cluster was detected in seven additional countries, suggesting that international transmission of tuberculosis from and to Brazil could be occurring frequently. Alternatively,preferential use of certain IS6110 integration sites could also be important in high-copy number strains, having important consequences for the use of databases for epidemiological studies on a large scale.

Simultaneous infection with two drug-susceptible Mycobacterium tuberculosis strains in an immunocompetent host

An important assumption for DNA fingerprinting of Mycobacterium tuberculosis is that patients are infected with only one strain at a time. Nonetheless, we demonstrate a case of simultaneous infection with two drug-susceptible strains of M. tuberculosis in an immunocompetent patient by IS6110 restriction fragment length polymorphism and spoligotyping. Epidemiological data prove the patient's involvement in two independent clusters. Thus, double infections should be suspected with fingerprints showing divergent band intensities.

Tuberculosis in the Caribbean: using spacer oligonucleotide typing to understand strain origin and transmission

We used direct repeat (DR)-based spacer oligonucleotide typing (spoligotyping) (in association with double-repetitive element polymerase chain reaction, IS6110-restriction fragment length polymorphism [RFLP], and sometimes DR-RFLP and polymorphic GC-rich sequence-RFLP) to detect epidemiologic links and transmission patterns of Mycobacterium tuberculosis on Martinique, Guadeloupe, and French Guiana. In more than a third of the 218 strains we typed from this region, clusters and isolates shared genetic identity, which suggests epidemiologic links. However, because of limited epidemiologic information, only 14.2% of the strains could be directly linked. When spoligotyping patterns shared by two or more isolates were pooled with 392 spoligotypes from other parts of the world, new matches were detected, which suggests imported transmission. Persisting foci of endemic disease and increased active transmission due to high population flux and HIV-coinfection may be linked to the recent reemergence of tuberculosis in the Caribbean. We also found that several distinct families of spoligotypes are overrepresented in this region.

IS990, a new species-specific insertion-sequence-related element of the Mycobacterium tuberculosis complex

The structure and distribution of 1S990, a new Mycobacterium tuberculosis DNA sequence with homology to characterized insertion sequences (ISs), were investigated. IS990 was related to IS elements of the IS3 family and was present as a single copy in all 21 investigated M. tuberculosis strains, two Mycobacterium bovis strains and two M. bovis BCG strains. The sequence appears to be specific for the M. tuberculosis complex. The element carries two frameshift mutations and appears to be defective.

Molecular fingerprinting of mycobacterium tuberculosis isolates obtained in havana, cuba, by IS6110 restriction fragment length polymorphism analysis and by the double-repetitive-element PCR method

Mycobacterium tuberculosis sputum isolates from 38 patients, obtained in the first 6 months of 1997 in Havana, Cuba, were characterized by IS6110 restriction fragment length polymorphism (RFLP) analysis and the double-repetitive-element PCR (DRE-PCR) method. Among 41 strains from 38 patients, 24 and 25 unique patterns, and 5 and 4 cluster patterns, were found by the RFLP and DRE-PCR methods, respectively. Patients within two of these clusters were found to be epidemiologically related, while no relation was observed in patients in the other clusters. The DRE-PCR method is rapid, and it was as discriminating as IS6110 RFLP analysis in identifying an epidemiological association. Its simplicity makes the technique accessible for subtyping of M. tuberculosis strains in laboratories not equipped to perform RFLP analysis.

Follow up of Mycobacterium tuberculosis transmission in the French West Indies by IS6110-DNA fingerprinting and DR-based spoligotyping

A total of 115 Mycobacterium tuberculosis isolates from 80 patients were typed using IS6110-DNA fingerprinting and DR-based spoligotyping to describe the active transmission of tuberculosis in a Caribbean setting over a 2-year period. A total of 61 different pattern types were observed by IS6110-RFLP and 10 clusters containing between two and 15 patients could be defined. By spoligotyping, 45 different pattern types were observed with 12 clusters containing two to 11 patients. Thirty-two patients could be included in eight spoligotype-defined clusters and in nine RFLP-defined clusters when strictly concordant matching results were put together. In conclusion, about 40% of the patient isolates were clustered by DNA fingerprinting suggesting recent transmission of tuberculosis in our region. This study confirmed the increased accuracy and discriminatory power of the association of IS6110-RFLP and spoligotyping for studies on the molecular epidemiology of M. tuberculosis, and suggests that despite good implementation of tuberculosis control programs in Guadeloupe, active transmission of tuberculosis may be far more important than suspected.

Combined numerical analysis based on the molecular description of Mycobacterium tuberculosis by four repetitive sequence-based DNA typing systems

Mycobacterium tuberculosis clinical isolates (113 isolates from 78 patients) were typed using IS6110-RFLP, DR-RFLP, DR-based spoligotyping and direct repetitive element PCR (DRE-PCR). The similarities among isolates were compared for each individual method. The individual matrix distance files for each method were summed and averaged, and the resulting unique distance file was analysed by the UPGMA (unweighted pair group method with arithmetic averages). Combined numerical analysis with 3 genetic markers (IS6110-RFLP, DR-RFLP and spoligotyping) was performed for all 78 clinical isolates, whereas analysis with 4 genetic markers (with the addition of DRE-PCR) was performed on the 10 main clusters described. When compared to molecular analysis based on individual markers, the molecular description based on multiple genetic markers enabled comparison of the results obtained by individual methods and the obtaining of a more accurate view of strain identity and clusters comparison. The resulting cumulative dendrogram was more accurate for studying the population structure of M. tuberculosis and may be a good tool for elucidating intraspecies genetic microevolution.

Spoligotyping followed by double-repetitive-element PCR as rapid alternative to IS6110 fingerprinting for epidemiological studies of tuberculosis

A total of 129 clinical isolates of Mycobacterium tuberculosis representing 91 patients were typed by a combination of direct-repeat (DR)-based spoligotyping and an inter-IS6110-PGRS (polymorphic GC-rich region)-PCR, also designated double-repetitive-element PCR (DRE-PCR). During the first phase of this investigation, 72 clinical strains representing 52 patients were initially typed by IS6110-restriction fragment length polymorphism (RFLP) and DR-RFLP, followed by spoligotyping and DRE-PCR. In the second phase of this investigation, the discriminating ability of spoligotyping plus DRE-PCR was studied for 57 isolates from 39 patients who were suspected to be epidemiologically linked, and the typing results were later confirmed by IS6110-RFLP and DR-RFLP analyses. The molecular clustering of the isolates remained identical irrespective of the methods used. These results show that the association of two PCR-based fingerprinting techniques for molecular epidemiology of tuberculosis has a discriminating ability similar to the IS6110-RFLP reference method.

IS6110 fingerprinting of drug-resistant Mycobacterium tuberculosis strains isolated in Germany during 1995

The epidemiological relatedness of drug-resistant Mycobacterium tuberculosis strains isolated in Germany in 1995 was evaluated by the standardized IS6110 fingerprinting method. Altogether, 196 M. tuberculosis isolates from 167 patients were analyzed. A large degree of IS6110 polymorphism was found, ranging from 1 to 20 copies. Multiple isolates from one patient generally remained stable over a period of up to 1 year. However, one strain showed an additional fragment 7 months after the first isolate was obtained. Isolates from 55 patients (33%) showed identical fingerprint patterns or fingerprint patterns that differed only in one band, and thus they were clustered in 22 fingerprint groups. Specific transmission links could be established between members of four groups, e.g., transmission by family contacts. In one case, transmission of a multidrug-resistant strain to a patient initially infected with a drug-susceptible strain could be shown. Besides these fingerprint groups, 30 of the 167 isolates (approximately 18%) could be grouped in two fingerprint clusters with a similarity of at least 78%. Approximately 60% of the patients of these two clusters were known to be immigrants from the former Soviet Union, and one patient is still living in Belarus. In conclusion, our results indicate that (i) transmission of drug-resistant strains contributes substantially to the emergence of drug-resistant tuberculosis in Germany and (ii) drug-resistant M. tuberculosis strains were presumably carried over from the former Soviet Union to Germany by immigrants.

DNA fingerprinting of Mycobacterium tuberculosis strains from patients with pulmonary tuberculosis in Honduras

Mycobacterium tuberculosis isolates from 84 patients with pulmonary tuberculosis in Honduras were characterized by restriction fragment length polymorphism analysis. Seventy-three different IS6110 patterns were found; 63 of these were unique and 10 were shared by two to three strains each. Thus, no ongoing spread of any specific clone of bacteria could be demonstrated.