The clonal composition of Mycobacterium tuberculosis in clinical specimens could be modified by culture

Martín, A.; Herránz, Marta; Serrano, Manuel Nistal Martín; Bouza, Emilio; Viedma, Darío García de

doi:10.1016/j.tube.2010.03.012

Cited by 57 publications

(47 citation statements)

References 27 publications

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“…Our data demonstrate that clonal complexity in the infection by M. tuberculosis is not anecdotal, especially in cases with simultaneous infection at independent sites. The real figures for clonal complexity in this study could be even higher if we had included more than a single sputum specimen in our screening design (13,18,19,28).…”

Section: Discussionmentioning

confidence: 91%

Systematic Survey of Clonal Complexity in Tuberculosis at a Populational Level and Detailed Characterization of the Isolates Involved

et al. 2011

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Clonally complex infections by Mycobacterium tuberculosis are progressively more accepted. Studies of their dimension in epidemiological scenarios where the infective pressure is not high are scarce. Our study systematically searched for clonally complex infections (mixed infections by more than one strain and simultaneous presence of clonal variants) by applying mycobacterial interspersed repetitive-unit (MIRU)-variable-number tandem-repeat (VNTR) analysis to M. tuberculosis isolates from two population-based samples of respiratory (703 cases) and respiratory-extrapulmonary (R؉E) tuberculosis (TB) cases (71 cases) in a context of moderate TB incidence. Clonally complex infections were found in 11 (1.6%) of the respiratory TB cases and in 10 (14.1%) of those with R؉E TB. Among the 21 cases with clonally complex TB, 9 were infected by 2 independent strains and the remaining 12 showed the simultaneous presence of 2 to 3 clonal variants. For the 10 R؉E TB cases with clonally complex infections, compartmentalization (different compositions of strains/clonal variants in independent infected sites) was found in 9 of them. All the strains/clonal variants were also genotyped by IS6110-based restriction fragment length polymorphism analysis, which split two MIRU-defined clonal variants, although in general, it showed a lower discriminatory power to identify the clonal heterogeneity revealed by MIRU-VNTR analysis. The comparative analysis of IS6110 insertion sites between coinfecting clonal variants showed differences in the genes coding for a cutinase, a PPE family protein, and two conserved hypothetical proteins. Diagnostic delay, existence of previous TB, risk for overexposure, and clustered/orphan status of the involved strains were analyzed to propose possible explanations for the cases with clonally complex infections. Our study characterizes in detail all the clonally complex infections by M. tuberculosis found in a systematic survey and contributes to the characterization that these phenomena can be found to an extent higher than expected, even in an unselected population-based sample lacking high infective pressure.In recent years, the application of molecular tools such as IS6110-based restriction fragment length polymorphism (RFLP), spoligotyping, and mycobacterial interspersed repetitive-unit (MIRU)-variable-number tandem-repeat (VNTR) analysis has revealed that infection by Mycobacterium tuberculosis could be more complex than initially assumed. Several clonally complex phenomena have been observed, including mixed infections with more than one strain (29,30,35), simultaneous presence of clonal variants (microevolution phenomena) (1, 2), or even different distributions of strains/clonal variants infecting independent anatomical sites in the same patient (6,15).Most reports of clonal complexity phenomena are descriptions of anecdotal cases and/or studies of clonal complexity are often restricted to contexts where overexposure to tuberculosis (TB) can be expected. This makes it difficult to evaluate the frequen...

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Section: Discussionmentioning

confidence: 91%

Systematic Survey of Clonal Complexity in Tuberculosis at a Populational Level and Detailed Characterization of the Isolates Involved

et al. 2011

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“…In addition, our assessments of phenotypic and genotypic resistance were performed on separate (individual) samples as opposed to split single samples, making it possible that the strain diversity and composition of the cultured samples (which eventually had phenotypic DST) were different than those tested by the Xpert assay. Further, our ability to detect mixed MTBC infections may have been compromised by not having tested unprocessed sputum samples for the presence of resistant strains (directly in the sputum sample), given that cultures can alter the strain composition present in the initial sample (8,38,39).…”

Section: Discussionmentioning

confidence: 99%

Mixed Mycobacterium tuberculosis Complex Infections and False-Negative Results for Rifampin Resistance by GeneXpert MTB/RIF Are Associated with Poor Clinical Outcomes

et al. 2014

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hThe Xpert MTB/RIF (Xpert) assay is becoming a principal screening tool for diagnosing rifampin-resistant Mycobacterium tuberculosis complex (MTBC) infection. However, little is known about the performance of the Xpert assay in infections with both drug-sensitive and drug-resistant strains (mixed MTBC infections). We assessed the performance of the Xpert assay for detecting rifampin resistance using phenotypic drug sensitivity testing (

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“…As all the clinical M. tuberculosis isolates used in this study had been subcultured, it is unlikely that they were representative of the clonal composition present in the sputum specimen from which they were isolated. Any culture technique introduces an element of strain selection, and it has recently been shown that culture affects the clonal complexity of M. tuberculosis (18), as in vitro culture conditions preferentially select some strains over others. Therefore, it is not surprising that the PCR assays of culture detected only one DNA type in the M. tuberculosis isolates from the two mixed infection patients.…”

Section: Discussionmentioning

confidence: 99%

Molecular Detection of Mixed Infections of Mycobacterium tuberculosis Strains in Sputum Samples from Patients in Karonga District, Malawi

Mallard¹,

McNerney²,

Crampin

et al. 2010

J Clin Microbiol

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The occurrence of mixed infections of Mycobacterium tuberculosis is no longer disputed. However, their frequency, and the impact they may have on our understanding of tuberculosis (TB) pathogenesis and epidemiology, remains undetermined. Most previous studies of frequency applied genotyping techniques to cultured M. tuberculosis isolates and found mixed infections to be rare. PCR-based techniques may be more sensitive for detecting multiple M. tuberculosis strains and can be applied to sputum. To date, one study in South Africa has used a PCR approach and suggested that mixed infection could be common. We investigated mixed infections in northern Malawi using two lineage-specific PCR assays targeting the Latin AmericanMediterranean (LAM) and Beijing lineages. Compared with spoligotyping, the specificity and sensitivity of both assays was 100%. From 160 culture-positive sputa, mixed LAM and non-LAM strains were detected in 4 sputa belonging to 2 (2.8%) patients. Both patients were HIV positive, with no history of TB. Cultured isolates from both patients showed only LAM by PCR and spoligotyping. In a set of 377 cultured isolates, 4 were mixed LAM and non-LAM. Only one showed evidence of more than one M. tuberculosis strain using IS6110-based restriction fragment length polymorphism (IS6110-RFLP) and spoligotyping analyses. Corresponding sputa for the 4 isolates were unavailable. Mixed Beijing and non-Beijing strains were not detected in this study. Mixed infections appear to be rare in our setting and are unlikely to affect findings based on DNA fingerprinting data. Molecular methods, which avoid the selective nature of culture and target distinct strains, are well suited to detection of mixed infections.It used to be thought that tuberculosis in the human host was caused by infection with a single Mycobacterium tuberculosis strain (25). This belief was first challenged when phage typing identified the presence of more than one M. tuberculosis strain in isolates obtained from a single patient (2,17). With the development of DNA fingerprinting (28) and other PCR-based genotyping methods (15, 27) to differentiate M. tuberculosis strains, the presence of multiple strains within a single patient has been demonstrated during routine genotyping studies (5,19,20,24,33). The results from these and further studies designed to specifically examine mixed infections (1,10,20,22,23,29,32) have shown that they occur in different geographical settings among both HIV-negative and HIV-positive tuberculosis (TB) patients.While the occurrence of mixed infections of M. tuberculosis is no longer questioned, the rate at which they occur is unknown. Yet this is of fundamental importance, as much of our understanding of tuberculosis pathogenesis and epidemiology has assumed that mixed infection is rare. The frequency is likely to differ according to the level of M. tuberculosis transmission in different settings. If mixed infections are common, it would necessitate reinterpretation of studies on recent infection, the importance of reinfe...

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The clonal composition of Mycobacterium tuberculosis in clinical specimens could be modified by culture

Cited by 57 publications

References 27 publications

Systematic Survey of Clonal Complexity in Tuberculosis at a Populational Level and Detailed Characterization of the Isolates Involved

Systematic Survey of Clonal Complexity in Tuberculosis at a Populational Level and Detailed Characterization of the Isolates Involved

Mixed Mycobacterium tuberculosis Complex Infections and False-Negative Results for Rifampin Resistance by GeneXpert MTB/RIF Are Associated with Poor Clinical Outcomes

Molecular Detection of Mixed Infections of Mycobacterium tuberculosis Strains in Sputum Samples from Patients in Karonga District, Malawi

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