Novel genetic polymorphisms that further delineate the phylogeny of the Mycobacterium tuberculosis complex

Rapid identification of veterinary-relevant Mycobacterium tuberculosis complex species using 16S rDNA, IS6110 and Regions of Difference-targeted dual-labelled hydrolysis probes

Members of the Mycobacterium tuberculosis complex (MTC) are causative agents of tuberculosis (TB) in both humans and animals. MTC species are genetically very similar but may differ in their epidemiology, namely geographic distribution and host preferences, virulence traits and antimicrobial susceptibility patterns. However, the conventional laboratory diagnosis does not routinely differentiate between the species of the MTC. In this work we describe a rapid and robust two-step five-target probe-based real-time PCR identification algorithm, based on genomic deletion analysis, to identify the MTC species most commonly associated with TB in livestock and other animals. The first step allows the confirmation of the cultures as MTC members, by targeting their IS6110 element, or as a mycobacterial species, if only a 16S rDNA product is detected in the duplex amplification reaction. If a MTC member is identified, the second amplification step allows the assessment of the presence or absence of the RD1, RD4 and RD9 genomic regions. The correspondent pattern allows us to infer the species of the isolate as M. tuberculosis (if all RDs are present), Mycobacterium caprae (if only RD1 and RD4 are present) and Mycobacterium bovis (if only RD1 is present). The identification algorithm developed presented an almost perfect agreement with the results of the routine bacteriological analysis, with a kappa coefficient of 0.970 (CI(P95%) 0.929-1.000). The assay is able to be adaptable to automation and implementation in the routine diagnostic framework of veterinary diagnostic laboratories, with a particular focus for reference laboratories.

Novel cause of tuberculosis in meerkats, South Africa

The organism that causes tuberculosis in meerkats (Suricata suricatta) has been poorly characterized. Our genetic analysis showed it to be a novel member of the Mycobacterium tuberculosis complex and closely related to the dassie bacillus. We have named this epidemiologically and genetically unique strain M. suricattae.

Dominant modern sublineages and a new modern sublineage of Mycobacterium tuberculosis Beijing family clinical isolates in Heilongjiang Province, China

Mycobacterium tuberculosis Beijing family includes a variety of sublineages. Knowledge of the distribution of a certain sublineage of the Beijing family may help to understand the mechanisms of its rapid spread and to establish an association between a certain genotype and the disease outcome. We have previously found that M. tuberculosis Beijing family clinical isolates represent approximately 90% of the clinical isolates from Heilongjiang Province, China. To clarify the distribution of M. tuberculosis Beijing family sublineages in Heilongjiang Province, China and to investigate the regularity rule for their evolution, we examined single nucleotide polymorphisms (SNPs) of 250 M. tuberculosis Beijing family clinical isolates using 10 SNP loci that have been identified as appropriate for defining Beijing sublineages. After determining the sequence type (ST) of each isolate, the sublineages of all M. tuberculosis Beijing family isolates were determined, and phylogenetic analysis was performed. We found that 9 out of the 10 SNP loci displayed polymorphisms, but locus 1548149 did not. In total, 92.8% of the isolates in Heilongjiang Province are modern sublineages. ST10 is the most prevalent sublineage (ST10 and ST22 accounted for 63.2% and 23.6% of all the Beijing family isolates, respectively). A new ST, accounting for 4% of the Beijing family isolates in this area, was found for the first time. Each new ST isolate showed a unique VNTR pattern, and none were clustered. The present findings suggest that controlling the spread of these modern sublineages is important in Heilongjiang Province and in China.

The T2 Mycobacterium tuberculosis genotype, predominant in Kampala, Uganda, shows negative correlation with antituberculosis drug resistance

Surveillance of the circulating Mycobacterium tuberculosis complex (MTC) strains in a given locality is important for understanding tuberculosis (TB) epidemiology. We performed molecular epidemiological studies on sputum smear-positive isolates that were collected for anti-TB drug resistance surveillance to establish the variability of MTC lineages with anti-TB drug resistance and HIV infection. Spoligotyping was performed to determine MTC phylogenetic lineages. We compared patients' MTC lineages with drug susceptibility testing (DST) patterns and HIV serostatus. Out of the 533 isolates, 497 (93.2%) had complete DST, PCR, and spoligotyping results while 484 (90.1%) participants had results for HIV testing. Overall, the frequency of any resistance was 75/497 (15.1%), highest among the LAM (34.4%; 95% confidence interval [CI], 18.5 to 53.2) and lowest among the T2 (11.5%; 95% CI, 7.6 to 16.3) family members. By multivariate analysis, LAM (adjusted odds ratio [OR(adj)], 5.0; 95% CI, 2.0 to 11.9; P < 0.001) and CAS (OR(adj), 2.9; 95% CI, 1.4.0 to 6.3; P = 0.006) families were more likely to show any resistance than was T2. All other MTC lineages combined were more likely to be resistant to any of the anti-TB drugs than were the T2 strains (OR(adj), 1.7; 95% CI, 1.0 to 2.9; P = 0.040). There were no significant associations between multidrug resistance and MTC lineages, but numbers of multidrug-resistant TB strains were small. No association was established between MTC lineages and HIV status. In conclusion, the T2 MTC lineage negatively correlates with anti-TB drug resistance, which might partly explain the reported low levels of anti-TB drug resistance in Kampala, Uganda. Patients' HIV status plays no role with respect to the MTC lineage distribution.

Evaluation of molecular markers for the diagnosis of Mycobacterium bovis

Mycobacterium tuberculosis complex (MTC) comprises a group of bacteria that have a high degree of genetic similarity. Two species in this group, Mycobacterium tuberculosis and Mycobacterium bovis, are the main cause of human and bovine tuberculosis, respectively. M. bovis has a broader host range that includes humans; thus, the differentiation of mycobacterium is of great importance for epidemiological and public health considerations and to optimize treatment. The current study aimed to evaluate primers and molecular markers described in the literature to differentiate M. bovis and M. tuberculosis by PCR. Primers JB21/22, frequently cited in scientific literature, presented in our study the highest number of errors to identify M. bovis or M. tuberculosis (73%) and primers Mb.400, designed to flank region of difference 4 (RD4), were considered the most efficient (detected all M. bovis tested and did not detect any M. tuberculosis tested). Although also designed to flank RD4, primers Mb.115 misidentified eight samples due to primer design problems. The results showed that RD4 is the ideal region to differentiate M. bovis from other bacteria classified in MTC, but primer design should be considered carefully.

Novel DNA chip based on a modified DigiTag2 assay for high-throughput species identification and genotyping of Mycobacterium tuberculosis complex isolates

A multipurpose high-throughput genotyping tool for the assessment of recent epidemiological data and evolutional pattern in Mycobacterium tuberculosis complex (MTBC) clinical isolates was developed in this study. To facilitate processing, 51 highly informative single nucleotide polymorphisms (SNPs) were selected for discriminating the clinically most relevant MTBC species and genotyping M. tuberculosis into its principle genetic groups (PGGs) and SNP cluster groups (SCGs). Because of the high flexibility of the DigiTag2 assay, the identical protocol and DNA array containing the identical set of probes were applied to the highly GC-rich mycobacterial genome. The specific primers with multiplex amplification and hybridization conditions based on the DigiTag2 principle were optimized and evaluated with 14 MTBC reference strains, 4 nontuberculous mycobacteria (NTM) isolates, and 322 characterized M. tuberculosis clinical isolates. The DNA chip that was developed revealed a 99.85% call rate, a 100% conversion rate, and 99.75% reproducibility. For the accuracy rate, 98.94% of positive calls were consistent with previous molecular characterizations. Our cost-effective technology was capable of simultaneously identifying the MTBC species and the genotypes of 96 M. tuberculosis clinical isolates within 6 h using only simple instruments, such as a thermal cycler, a hybridization oven, and a DNA chip scanner, and less technician skill was required than for other techniques. We demonstrate this approach's potential as a simple, flexible, and rapid tool for providing clearer information regarding circulating MTBC isolates.

Overview and phylogeny of Mycobacterium tuberculosis complex organisms: implications for diagnostics and legislation of bovine tuberculosis

Members of the Mycobacterium tuberculosis complex (MTBC) cause a serious disease with similar pathology, tuberculosis; in this review, bovine tuberculosis will be considered as disease caused by any member of the MTBC in bovids. Bovine tuberculosis is responsible for significant economic loss due to costly eradication programs and trade limitations and poses a threat to both endangered and protected species as well as to public health. We here give an overview on all members of the MTBC, focusing on their isolation from different animal hosts. We also review the recent advances made in elucidating the evolutionary and phylogenetic relationships of members of the MTBC. Because the nomenclature of the MTBC is controversial, its members have been considered species, subspecies or ecotypes, this review discusses the possible implications for diagnostics and the legal consequences of naming of new species.

Comparative evaluation of three immunochromatographic identification tests for culture confirmation of Mycobacterium tuberculosis complex

BACKGROUND

The rapid identification of acid-fast bacilli recovered from patient specimens as Mycobacterium tuberculosis complex (MTC) is critically important for accurate diagnosis and treatment. A thin-layer immunochromatographic (TLC) assay using anti-MPB64 or anti-MPT64 monoclonal antibodies was developed to discriminate between MTC and non-tuberculosis mycobacteria (NTM). Capilia TB-Neo, which is the improved version of Capilia TB, is recently developed and needs to be evaluated.

METHODS

Capilia TB-Neo was evaluated by using reference strains including 96 Mycobacterium species (4 MTC and 92 NTM) and 3 other bacterial genera, and clinical isolates (500 MTC and 90 NTM isolates). M. tuberculosis isolates tested negative by Capilia TB-Neo were sequenced for mpt64 gene.

RESULTS

Capilia TB-Neo showed 100% agreement to a subset of reference strains. Non-specific reaction to M. marinum was not observed. The sensitivity and specificity of Capilia TB-Neo to the clinical isolates were 99.4% (99.6% for M. tuberculosis, excluding M. bovis BCG) for clinical MTC isolates and 100% for NTM isolates tested, respectively. Two M. tuberculosis isolates tested negative by Capilia TB-Neo: one harbored a 63-bp deletion in the mpt64 gene and the other possessed a 3,659-bp deletion from Rv1977 to Rv1981c, a region including the entire mpt64 gene.

CONCLUSIONS

Capilia TB-Neo is a simple, rapid and highly sensitive test for identifying MTC, and showed better specificity than Capilia TB. However, Capilia TB-Neo still showed false-negative results with mpt64 mutations. The limitation should be recognized for clinical use.

Mycobacterium pinnipedii in a stranded South American sea lion (Otaria byronia) in Brazil

We report tuberculosis in a stranded South American sea lion (Otaria byronia) in Brazil caused by Mycobacterium pinnipedii, a member of Mycobacterium tuberculosis complex.

Novel Mycobacterium tuberculosis complex isolate from a wild chimpanzee

Tuberculosis (TB) is caused by gram-positive bacteria known as the Mycobacterium tuberculosis complex (MTBC). MTBC include several human-associated lineages and several variants adapted to domestic and, more rarely, wild animal species. We report an M. tuberculosis strain isolated from a wild chimpanzee in Côte d’Ivoire that was shown by comparative genomic and phylogenomic analyses to belong to a new lineage of MTBC, closer to the human-associated lineage 6 (also known as M. africanum West Africa 2) than to the other classical animal-associated MTBC strains. These results show that the general view of the genetic diversity of MTBC is limited and support the possibility that other MTBC variants exist, particularly in wild mammals in Africa. Exploring this diversity is crucial to the understanding of the biology and evolutionary history of this widespread infectious disease.

Sub-speciation of Mycobacterium tuberculosis complex from tuberculosis patients in Japan

Mycobacterium tuberculosis is the major causative agent of tuberculosis in humans. It is well known that Mycobacterium bovis and other species in the M. tuberculosis complex (MTC) can cause respiratory diseases as zoonosis. We analyzed the MTC isolates collected from tuberculosis patients from Japan in 2002 using a multiplex PCR system that detected cfp32, RD9 and RD12. A total of 970 MTC isolates that were representative of the tuberculosis cases throughout Japan, were examined using this method. As a result, 966 (99.6%) M. tuberculosis, two Mycobacterium africanum and two Mycobacterium canettii were identified using a multiplex PCR system, while no M. bovis was detected. Two isolates that lacked RD9 were initially considered to be M. canettii, but further analysis of the hsp65 sequence revealed them to be M. tuberculosis. Also two M. africanum were identified as M. tuberculosis using the -215 narG nucleotide polymorphism. Though PCR-linked methods have been used for a rapid differentiation of MTC and NTM, from our cases we suggest careful interpretation of RD based identification.

Simple multiplex PCR assay for identification of Beijing family Mycobacterium tuberculosis isolates with a lineage-specific mutation in Rv0679c

The Beijing genotype of Mycobacterium tuberculosis is known to be a worldwide epidemic clade. It is suggested to be a possibly resistant clone against BCG vaccination and is also suggested to be highly pathogenic and prone to becoming drug resistant. Thus, monitoring the prevalence of this lineage seems to be important for the proper control of tuberculosis. The Rv0679c protein of M. tuberculosis has been predicted to be one of the outer membrane proteins and is suggested to contribute to host cell invasion. Here, we conducted a sequence analysis of the Rv0679c gene using clinical isolates and found that a single nucleotide polymorphism, C to G at position 426, can be observed only in the isolates that are identified as members of the Beijing genotype family. Here, we developed a simple multiplex PCR assay to detect this point mutation and applied it to 619 clinical isolates. The method successfully distinguished Beijing lineage clones from non-Beijing strains with 100% accuracy. This simple, quick, and cost-effective multiplex PCR assay can be used for a survey or for monitoring the prevalence of Beijing genotype M. tuberculosis strains.

Species and genotypic diversity of non-tuberculous mycobacteria isolated from children investigated for pulmonary tuberculosis in rural Uganda

BACKGROUND

Smear microscopy, a mainstay of tuberculosis (TB) diagnosis in developing countries, cannot differentiate M. tuberculosis complex from NTM infection, while pulmonary TB shares clinical signs with NTM disease, causing clinical and diagnostic dilemmas. This study used molecular assays to identify species and assess genotypic diversity of non-tuberculous mycobacteria (NTM) isolates from children investigated for pulmonary tuberculosis at a demographic surveillance site in rural eastern Uganda.

METHODS

Children were investigated for pulmonary tuberculosis as part of a TB vaccine surveillance program (2009-2011). Two cohorts of 2500 BCG vaccinated infants and 7000 adolescents (12-18 years) were recruited and followed up for one to two years to determine incidence of tuberculosis. Induced sputum and gastric aspirates were processed by the standard N-acetyl L-cysteine (NALC)-NaOH method. Sediments were cultured in the automated MGIT (Becton Dickson) liquid culture system and incubated at 37°C for at least six weeks. Capilia TB assay was used to classify mycobacteria into MTC and NTM. The GenoType CM/AS assays were performed to identify species while Enterobacterial Repetitive Intergenic Consensus (ERIC) PCR genotyping was used to assess genetic diversity of the strains within each species.

RESULTS

Among 2859 infants and 2988 adolescents screened, the numbers of TB suspects were 710 and 1490 infants and adolescents respectively. The prevalence of NTM in infant suspects was 3.7% (26/710) (95% CI 2.5-5.2) while that in adolescent suspects was 4.6% (69/1490) (95% CI 3.6-5.8). On culture, 127 isolates were obtained, 103 of which were confirmed as mycobacteria comprising of 95 NTM and eight M. tuberculosis complex. The Genotype CM/AS assay identified 63 of the 95 NTM isolates while 32 remained un-identified. The identified NTM species were M. fortuitum (40 isolates, 63.5%), M. szulgai (9 isolates, 14.3%), M. gordonae (6 isolates, 9.5%), M. intracellulare (3 isolates, 4.7%), M. scrofulaceum (2 isolates, 3.2%), M. lentiflavum (2 isolates, 3.2%), and M. peregrinum (1 isolate, 1.6%). Genotyping did not reveal any clustering in M. intracellulare, M. gordonae and M. szulgai species. M. fortuitum, on the other hand, had two clusters, one with three isolates of M. fortuitum 1 and the other with two isolates of M. fortuitum 2 subspecies. The remaining 35 of the 40 isolates of M. fortuitum had unique fingerprint patterns.

CONCLUSION

M. fortuitum is the most common cause of infection by NTM among Infants and adolescents in rural Uganda. There is a varied number of species and genotypes, with minimal clustering within species, suggesting ubiquitous sources of infection to individuals in this community.

Single nucleotide polymorphisms in Mycobacterium tuberculosis and the need for a curated database

Recent advances in DNA sequencing have led to the discovery of thousands of single nucleotide polymorphisms (SNPs) in clinical isolates of Mycobacterium tuberculosis complex (MTBC). This genetic variation has changed our understanding of the differences and phylogenetic relationships between strains. Many of these mutations can serve as phylogenetic markers for strain classification, while others cause drug resistance. Moreover, SNPs can affect the bacterial phenotype in various ways, which may have an impact on the outcome of tuberculosis (TB) infection and disease. Despite the importance of SNPs for our understanding of the diversity of MTBC populations, the research community currently lacks a comprehensive, well-curated and user-friendly database dedicated to SNP data. First attempts to catalogue and annotate SNPs in MTBC have been made, but more work is needed. In this review, we discuss the biological and epidemiological relevance of SNPs in MTBC. We then review some of the analytical challenges involved in processing SNP data, and end with a list of features, which should be included in a new SNP database for MTBC.

Mycobacterium bovis infection at the interface between domestic and wild animals in Zambia

BACKGROUND

In Zambia, the presence of bovine tuberculosis in both wild and domestic animals has long been acknowledged and mutual transmission between them has been predicted without any direct evidence. Elucidation of the circulating Mycobacterium bovis strains at wild and domestic animals interphase area in Zambia, where bovine tuberculosis was diagnosed in wildlife seemed to be important.

RESULTS

A PCR identified 15 and 37 M. bovis isolates from lechwe and cattle, respectively. Spoligotype analysis revealed that M. bovis strains from lechwe and cattle in Kafue basin clustered into a major node SB0120, where isolates outside the Kafue basin clustered into different nodes of SB0131 and SB0948. The comparatively higher variety of strains in cattle compared to lechwe elucidated by Mycobacterial Interspersed Repetitive Units-Variable Number Tandem Repeats analyses are consistent with cattle being the probable source of M. bovis in wild and domestic animals interphase area in Zambia.

CONCLUSIONS

These results provide strong evidence of M. bovis strains transfer between cattle and lechwe, with the latter having developed into a sylvatic reservoir host.

A first insight into the genotypic diversity of Mycobacterium tuberculosis from Rwanda

Background

Mycobacterium tuberculosis complex (MTC) is the causative agent of tuberculosis (TB). Globally, increasing evidence shows that in M. tuberculosis, transmission varies from strain to strain and that different strains exhibit a range of geographical and host specificities, pathogenicity, and drug susceptibility. Therefore rapid and accurate differentiation of the members of MTC is critical in guiding treatment and public health decisions. We carried out a study at different health units and the National Reference Laboratory in Rwanda identify Mycobacterium tuberculosis complex species prevalent in TB patients in Rwanda. We further characterized the isolates using spoligotyping in order to gain an insight into the strain diversity of drug resistant and susceptible isolates of M. tuberculosis in this setting.

Methods

A total of 151 isolates from culture positive sputum samples were harvested, heat killed at 80°C for two hours, and then shipped to Makerere University College of Health Sciences, Uganda, for speciation and typing. Species identification was achieved by regions of difference (RD) analysis, while Spoligotyping was done to identify strain types.

Results

Region of difference analysis identified all the 151 isolates as M. tuberculosis. Spoligotyping revealed predominance of the T2 family (58.3%, 88/151), with SIT 52 being the most prevalent strain (31.8%, 48/151). Among the 151 isolates, 64 (42.4%) were multidrug resistant (MDR) with 3 cases on mono-resistance. Of 94 retreatment cases, 48 (51.1%) were MDR and of 46 newly presenting cases 14 (30.4%) were MDR. There was a significant difference (p=0.01) in anti-TB drug resistance between new and retreatment cases in the sample. However, there was no significant relationship between HIV serostatus and the two major strain types SIT 52 (p =0.15and SIT 152 (p = 0.41).

Conclusion

Mycobacterium tuberculosis is the most prevalent species of Mycobacterium tuberculosis complex in Rwanda, and SIT 52 (T2) the predominant strain. There is significantly more MDR in the retreatment cases but no significant difference was observed by HIV status in relation to any spoligotypes.

Genotype of a historic strain of Mycobacterium tuberculosis

The use of ancient DNA in paleopathological studies of tuberculosis has largely been restricted to confirmation of disease identifications made by skeletal analysis; few attempts at obtaining genotype data from archaeological samples have been made because of the need to perform different PCRs for each genetic locus being studied in an ancient DNA extract. We used a next generation sequencing approach involving hybridization capture directed at specific polymorphic regions of the Mycobacterium tuberculosis genome to identify a detailed genotype for a historic strain of M. tuberculosis from an individual buried in the 19th century St. George's Crypt, Leeds, West Yorkshire, England. We obtained 664,500 sequencing by oligonucleotide ligation and detection (SOLiD) reads that mapped to the targeted regions of the M. tuberculosis genome; the coverage included 218 of 247 SNPs, 10 of 11 insertion/deletion regions, and the repeat elements IS1081 and IS6110. The accuracy of the SOLiD data was checked by conventional PCRs directed at 11 SNPs and two insertion/deletions. The data placed the historic strain of M. tuberculosis in a group that is uncommon today, but it is known to have been present in North America in the early 20th century. Our results show the use of hybridization capture followed by next generation sequencing as a means of obtaining detailed genotypes of ancient varieties of M. tuberculosis, potentially enabling meaningful comparisons between strains from different geographic locations and different periods in the past.

Importance of the genetic diversity within the Mycobacterium tuberculosis complex for the development of novel antibiotics and diagnostic tests of drug resistance

Despite being genetically monomorphic, the limited genetic diversity within the Mycobacterium tuberculosis complex (MTBC) has practical consequences for molecular methods for drug susceptibility testing and for the use of current antibiotics and those in clinical trials. It renders some representatives of MTBC intrinsically resistant against one or multiple antibiotics and affects the spectrum and consequences of resistance mutations selected for during treatment. Moreover, neutral or silent changes within genes responsible for drug resistance can cause false-positive results with hybridization-based assays, which have been recently introduced to replace slower phenotypic methods. We discuss the consequences of these findings and propose concrete steps to rigorously assess the genetic diversity of MTBC to support ongoing clinical trials.

Highlights on molecular identification of closely related species

The term "complex" emerged in the literature at the beginning of the genomic era associated to taxonomy and grouping organisms that belong to different species but exhibited similar patterns according to their morphological, physiological and/or other phenotypic features. DNA-DNA hybridization values ~70% and high identity on 16S rRNA gene sequences were recommended for species delineation. Electrophoretic methods showed in some cases to be useful for species identification and population structure but the reproducibility was questionable. Later, the implementation of polyphasic approaches involving phenotypic and molecular methods brought new insights into the analysis of population structure and phylogeny of several "species complexes", allowing the identification of new closely related species. Likewise, the introduction of multilocus sequence typing and sequencing analysis of several genes offered an evolutionary perspective to the term "species complex". Several centres worldwide have recently released increasing genetic information on distinct microbial species. A brief review will be presented to highlight the definition of "species complex" for selected microorganisms, mainly the prokaryotic Acinetobacter calcoaceticus -Acinetobacter baumannii, Borrelia burgdorferi sensu lato, Burkholderia cepacia, Mycobacterium tuberculosis and Nocardia asteroides complexes, and the eukaryotic Aspergillus fumigatus, Leishmania donovani and Saccharomyces sensu stricto complexes. The members of these complexes may show distinct epidemiology, pathogenicity and susceptibility, turning critical their correct identification. Dynamics of prokaryotic and eukaryotic genomes can be very distinct and the term "species complex" should be carefully extended.

Combined species identification, genotyping, and drug resistance detection of Mycobacterium tuberculosis cultures by MLPA on a bead-based array

The population structure of Mycobacterium tuberculosis is typically clonal therefore genotypic lineages can be unequivocally identified by characteristic markers such as mutations or genomic deletions. In addition, drug resistance is mainly mediated by mutations. These issues make multiplexed detection of selected mutations potentially a very powerful tool to characterise Mycobacterium tuberculosis. We used Multiplex Ligation-dependent Probe Amplification (MLPA) to screen for dispersed mutations, which can be successfully applied to Mycobacterium tuberculosis as was previously shown. Here we selected 47 discriminative and informative markers and designed MLPA probes accordingly to allow analysis with a liquid bead array and robust reader (Luminex MAGPIX technology). To validate the bead-based MLPA, we screened a panel of 88 selected strains, previously characterised by other methods with the developed multiplex assay using automated positive and negative calling. In total 3059 characteristics were screened and 3034 (99.2%) were consistent with previous molecular characterizations, of which 2056 (67.2%) were directly supported by other molecular methods, and 978 (32.0%) were consistent with but not directly supported by previous molecular characterizations. Results directly conflicting or inconsistent with previous methods, were obtained for 25 (0.8%) of the characteristics tested. Here we report the validation of the bead-based MLPA and demonstrate its potential to simultaneously identify a range of drug resistance markers, discriminate the species within the Mycobacterium tuberculosis complex, determine the genetic lineage and detect and identify the clinically most relevant non-tuberculous mycobacterial species. The detection of multiple genetic markers in clinically derived Mycobacterium tuberculosis strains with a multiplex assay could reduce the number of TB-dedicated screening methods needed for full characterization. Additionally, as a proportion of the markers screened are specific to certain Mycobacterium tuberculosis lineages each profile can be checked for internal consistency. Strain characterization can allow selection of appropriate treatment and thereby improve treatment outcome and patient management.

An outbreak of tuberculosis by Mycobacterium bovis in coatis (Nasua nasua)

Mycobacterium tuberculosis complex, which includes Mycobacterium bovis, infrequently causes severe or lethal disease in captive wildlife populations. A dead coati from a wildlife triage center showing pulmonary lesions compatible with tuberculosis had raised suspicion of a potential disease caused by mycobacteria species and was further investigated. Four native coatis (Nasua nasua) with suspected mycobacterial infection were sedated, and bronchoalveolar lavages and tuberculin skin tests (TSTs) were performed. All animals tested positive upon TST. Mycobacterial culturing, Ziehl-Neelsen staining, and genetic testing were performed on postmortem samples and the etiologic agent was identified as M. bovis. Molecular genetic identification using a polymerase chain reaction panel was crucial to achieving a definitive diagnosis.

Characterization of Mycobacterium orygis as M. tuberculosis complex subspecies

The oryx bacilli are Mycobacterium tuberculosis complex organisms for which phylogenetic position and host range are unsettled. We characterized 22 isolates by molecular methods and propose elevation to subspecies status as M. orygis. M. orygis is a causative agent of tuberculosis in animals and humans from Africa and South Asia.

Transmission of Mycobacterium orygis (M. tuberculosis complex species) from a tuberculosis patient to a dairy cow in New Zealand

Mycobacterium orygis, previously called the oryx bacillus, is a member of the Mycobacterium tuberculosis complex and has been reported only recently as a cause of human tuberculosis in patients of South Asian origin. We present the first case documenting the transmission of this organism from a human to a cow.

SeekTB, a two-stage multiplex real-time-PCR-based method for differentiation of the Mycobacterium tuberculosis complex

Tuberculosis (TB) in humans is caused by members of the Mycobacterium tuberculosis complex (MTC). The accurate identification of the MTC member causing human infection is important because the treatment of TB caused by some MTC members requires an alteration of the standard drug regimen, it can inform whether transmission is human to human or zoonotic, and it enables accurate epidemiology studies that help improve TB control. In this study, an internally controlled two-stage multiplex real-time PCR-based method, SeekTB, was developed for the accurate identification of all members of the MTC. The method was tested against a panel of well-characterized bacterial strains (n = 180) and determined to be 100% specific for members of the MTC. Additionally, 125 Mycobacteria Growth Indicator Tube (MGIT)-positive cultures were blindly tested by using SeekTB, and the results were compared to those of the GenoType MTBC and TBc ID tests. The SeekTB and GenoType MTBC results were 100% concordant, identifying 84 of these isolates as M. tuberculosis isolates and 41 as non-MTC isolates. Nine discordant results between the molecular methods and the TBc ID culture confirmation test were observed; however, nucleotide sequencing confirmed the results obtained with GenoType MTBC and SeekTB. SeekTB is the first-described internally controlled multiplex real-time PCR diagnostic method for the accurate identification of all eight members of the MTC. This method, designed for use on cultured patient samples, is specific, sensitive, and rapid, with a turnaround time to results of approximately 1.5 to 3.5 h, depending on which, if any, member of the MTC is present.

The genome of Mycobacterium africanum West African 2 reveals a lineage-specific locus and genome erosion common to the M. tuberculosis complex

Background

M. africanum West African 2 constitutes an ancient lineage of the M. tuberculosis complex that commonly causes human tuberculosis in West Africa and has an attenuated phenotype relative to M. tuberculosis.

Methodology/Principal Findings

In search of candidate genes underlying these differences, the genome of M. africanum West African 2 was sequenced using classical capillary sequencing techniques. Our findings reveal a unique sequence, RD900, that was independently lost during the evolution of two important lineages within the complex: the “modern” M. tuberculosis group and the lineage leading to M. bovis. Closely related to M. bovis and other animal strains within the M. tuberculosis complex, M. africanum West African 2 shares an abundance of pseudogenes with M. bovis but also with M. africanum West African clade 1. Comparison with other strains of the M. tuberculosis complex revealed pseudogenes events in all the known lineages pointing toward ongoing genome erosion likely due to increased genetic drift and relaxed selection linked to serial transmission-bottlenecks and an intracellular lifestyle.

Conclusions/Significance

The genomic differences identified between M. africanum West African 2 and the other strains of the Mycobacterium tuberculosis complex may explain its attenuated phenotype, and pave the way for targeted experiments to elucidate the phenotypic characteristic of M. africanum. Moreover, availability of the whole genome data allows for verification of conservation of targets used for the next generation of diagnostics and vaccines, in order to ensure similar efficacy in West Africa.

Mycobacterium africanum, a close relative of M. tuberculosis, is studied for the following reasons: M. africanum is commonly isolated from West African patients with tuberculosis yet has not spread beyond this region, it is more common in HIV infected patients, and it is less likely to lead to tuberculosis after one is exposed to an infectious case. Understanding this organism's unique biology gets a boost from the decoding of its genome, reported in this issue. For example, genome analysis reveals that M. africanum contains a region shared with “ancient” lineages in the M. tuberculosis complex and other mycobacterial species, which was lost independently from both M. tuberculosis and M. bovis. This region encodes a protein involved in transmembrane transport. Furthermore, M. africanum has lost genes, including a known virulence gene and genes for vitamin synthesis, in addition to an intact copy of a gene that may increase its susceptibility to antibiotics that are insufficiently active against M. tuberculosis. Finally, the genome sequence and analysis reported here will aid in the development of new diagnostics and vaccines against tuberculosis, which need to take into account the differences between M. africanum and other species in order to be effective worldwide.

Molecular epidemiology of mycobacteriosis in wildlife and pet animals

The ecology of mycobacteria is shifting in accordance with environmental change and new patterns of interaction between wildlife, humans, and nondomestic animals. Infection of vertebrate hosts throughout the world is greater now than ever and includes a growing prevalence in free ranging and captive wild animals. Molecular epidemiologic studies using standardized methods with high discriminatory power are useful for tracking individual cases and outbreaks, identifying reservoirs, and describing patterns of transmission and are used with increasing frequency to characterize disease wildlife. This review describes current features of mycobacteriosis in wildlife species based on traditional descriptive studies and recent molecular applications.

A novel multiplex real-time PCR for the identification of mycobacteria associated with zoonotic tuberculosis

BACKGROUND

Tuberculosis (TB) is the leading cause of death worldwide from a single infectious agent. An ability to detect the Mycobacterium tuberculosis complex (MTC) in clinical material while simultaneously differentiating its members is considered important. This allows for the gathering of epidemiological information pertaining to the prevalence, transmission and geographical distribution of the MTC, including those MTC members associated with zoonotic TB infection in humans. Also differentiating between members of the MTC provides the clinician with inherent MTC specific drug susceptibility profiles to guide appropriate chemotherapy.

METHODOLOGY/PRINCIPAL FINDINGS

The aim of this study was to develop a multiplex real-time PCR assay using novel molecular targets to identify and differentiate between the phylogenetically closely related M. bovis, M. bovis BCG and M. caprae. The lpqT gene was explored for the collective identification of M. bovis, M. bovis BCG and M. caprae, the lepA gene was targeted for the specific identification of M. caprae and a Region of Difference 1 (RD1) assay was incorporated in the test to differentiate M. bovis BCG. The multiplex real-time PCR assay was evaluated on 133 bacterial strains and was determined to be 100% specific for the members of the MTC targeted.

CONCLUSIONS/SIGNIFICANCE

The multiplex real-time PCR assay developed in this study is the first assay described for the identification and simultaneous differentiation of M. bovis, M. bovis BCG and M. caprae in one internally controlled reaction. Future validation of this multiplex assay should demonstrate its potential in the rapid and accurate diagnosis of TB caused by these three mycobacteria. Furthermore, the developed assay may be used in conjunction with a recently described multiplex real-time PCR assay for identification of the MTC and simultaneous differentiation of M. tuberculosis, M. canettii resulting in an ability to differentiate five of the eight members of the MTC.

Laboratory diagnosis of tuberculosis in resource-poor countries: challenges and opportunities

With an estimated 9.4 million new cases globally, tuberculosis (TB) continues to be a major public health concern. Eighty percent of all cases worldwide occur in 22 high-burden, mainly resource-poor settings. This devastating impact of tuberculosis on vulnerable populations is also driven by its deadly synergy with HIV. Therefore, building capacity and enhancing universal access to rapid and accurate laboratory diagnostics are necessary to control TB and HIV-TB coinfections in resource-limited countries. The present review describes several new and established methods as well as the issues and challenges associated with implementing quality tuberculosis laboratory services in such countries. Recently, the WHO has endorsed some of these novel methods, and they have been made available at discounted prices for procurement by the public health sector of high-burden countries. In addition, international and national laboratory partners and donors are currently evaluating other new diagnostics that will allow further and more rapid testing in point-of-care settings. While some techniques are simple, others have complex requirements, and therefore, it is important to carefully determine how to link these new tests and incorporate them within a country's national diagnostic algorithm. Finally, the successful implementation of these methods is dependent on key partnerships in the international laboratory community and ensuring that adequate quality assurance programs are inherent in each country's laboratory network.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry-based single nucleotide polymorphism genotyping assay using iPLEX gold technology for identification of Mycobacterium tuberculosis complex species and lineages

The major goal of the present study was to investigate the potential use of a novel single nucleotide polymorphism (SNP) genotyping technology, called iPLEX Gold (Sequenom), for the simultaneous analysis of 16 SNPs that have been previously validated as useful for identification of Mycobacterium tuberculosis complex (MTBC) species and classification of MTBC isolates into distinct genetic lineages, known as principal genetic groups (PGGs) and SNP cluster groups (SCGs). In this context, we developed a 16-plex iPLEX assay based on an allele-specific-primer single-base-extension reaction using the iPLEX Gold kit (Sequenom), followed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis on the commercially available Sequenom MassARRAY platform. This assay was tested on a panel of 55 well-characterized MTBC strains that were also genotyped for the same loci using the previously reported SNaPshot assay, as well as 10 non-MTBC mycobacteria and 4 bacteria not belonging to the genus Mycobacterium. All MTBC samples were successfully analyzed with the iPLEX assay, which yielded clear allelic data for 99.9% of the SNPs (879 out of 880). No false-positive results were obtained with the negative controls. Compared to the SNaPshot assay, the newly developed 16-plex iPLEX assay produced fully concordant results that allowed reliable differentiation of MTBC species and recognition of lineages, thus demonstrating its potential value in diagnostic, epidemiological, and evolutionary applications. Compared to the SNaPshot approach, the implementation of the iPLEX technology could offer a higher throughput and could be a more flexible and cost-effective option for microbiology laboratories.

Overview of errors in the reference sequence and annotation of Mycobacterium tuberculosis H37Rv, and variation amongst its isolates

Since its publication in 1998, the genome sequence of the Mycobacterium tuberculosis H37Rv laboratory strain has acted as the cornerstone for the study of tuberculosis. In this review we address some of the practical aspects that have come to light relating to the use of H37Rv throughout the past decade which are of relevance for the ongoing genomic and laboratory studies of this pathogen. These include errors in the genome reference sequence and its annotation, as well as the recently detected variation amongst isolates of H37Rv from different laboratories.

Tuberculosis: new aspects of an old disease

Tuberculosis is an ancient infectious disease that remains a threat for public health around the world. Although the etiological agent as well as tuberculosis pathogenesis is well known, the molecular mechanisms underlying the host defense to the bacilli remain elusive. In this paper we focus on the innate immunity of this disease reviewing well-established and consensual mechanisms like Mycobacterium tuberculosis interference with phagosome maturation, less consensual mechanism like nitric oxide production, and new mechanisms, such as mycobacteria translocation to the cytosol, autophagy, and apoptosis/necrosis proposed mainly during the last decade.

The Guinea-Bissau family of Mycobacterium tuberculosis complex revisited

The Guinea-Bissau family of strains is a unique group of the Mycobacterium tuberculosis complex that, although genotypically closely related, phenotypically demonstrates considerable heterogeneity. We have investigated 414 M. tuberculosis complex strains collected in Guinea-Bissau between 1989 and 2008 in order to further characterize the Guinea-Bissau family of strains. To determine the strain lineages present in the study sample, binary outcomes of spoligotyping were compared with spoligotypes existing in the international database SITVIT2. The major circulating M. tuberculosis clades ranked in the following order: AFRI (n = 195, 47.10%), Latin-American-Mediterranean (LAM) (n = 75, 18.12%), ill-defined T clade (n = 53, 12.8%), Haarlem (n = 37, 8.85%), East-African-Indian (EAI) (n = 25, 6.04%), Unknown (n = 12, 2.87%), Beijing (n = 7, 1.68%), X clade (n = 4, 0.96%), Manu (n = 4, 0.97%), CAS (n = 2, 0.48%). Two strains of the LAM clade isolated in 2007 belonged to the Cameroon family (SIT61). All AFRI isolates except one belonged to the Guinea-Bissau family, i.e. they have an AFRI_1 spoligotype pattern, they have a distinct RFLP pattern with low numbers of IS6110 insertions, and they lack the regions of difference RD7, RD8, RD9 and RD10, RD701 and RD702. This profile classifies the Guinea-Bissau family, irrespective of phenotypic biovar, as part of the M. africanum West African 2 lineage, or the AFRI_1 sublineage according to the spoligtyping nomenclature. Guinea-Bissau family strains display a variation of biochemical traits classically used to differentiate M. tuberculosis from M. bovis. Yet, the differential expression of these biochemical traits was not related to any genes so far investigated (narGHJI and pncA). Guinea-Bissau has the highest prevalence of M. africanum recorded in the African continent, and the Guinea-Bissau family shows a high phylogeographical specificity for Western Africa, with Guinea-Bissau being the epicenter. Trends over time however indicate that this family of strains is waning in most parts of Western Africa, including Guinea-Bissau (p = 0.048).

Web-accessible database of hsp65 sequences from Mycobacterium reference strains

Mycobacteria include a large number of pathogens. Identification to species level is important for diagnoses and treatments. Here, we report the development of a Web-accessible database of the hsp65 locus sequences (http://msis.mycobacteria.info) from 149 out of 150 Mycobacterium species/subspecies. This database can serve as a reference for identifying Mycobacterium species.

A review of bovine tuberculosis in the kafue basin ecosystem

The Kafue basin ecosystem is the only remaining natural habitat for the endangered Kafue lechwe antelope (Kobus leche Kafuensis). However, hydroelectricity power production, large-scale sugar plantations, commercial fishing and increasing livestock production are threatening its natural existence and sustainability. Further, increasing human settlements within and around the Kafue basin have resulted in decreased grazing grounds for the Kafue lechwe antelopes despite a corresponding increase in cattle population sharing the same pasture. Baseline epidemiological data have persistently reported findings of bovine tuberculosis (BTB) in both wild and domestic animals, although these have been deficient in terms of describing direct evidence in the role of either lechwe antelopes or cattle in the reported observations. Despite the current literature being deficient in establishing the casual role and transmission patterns of BTB, a bimodal route of infection at the livestock/wildlife interface has been postulated. Likewise, it is not known how much of (BTB) has the potential of causing disease in humans. This paper, seeks to underline those aspects that need further research and update available data on BTB in the Kafue basin with regards to the prevalence, distribution, risk factors, threats on wildlife conservation, livestock production, public health implications, and possible mitigatory measures.

Advances in molecular diagnostics for Mycobacterium bovis

The two most important molecular diagnostic techniques for bovine tuberculosis are the polymerase chain reaction (PCR) because of its rapid determination of infection, and DNA strain typing because of its ability to answer important epidemiological questions. PCR tests for Mycobacterium bovis have been improved through recent advances in PCR technology, but still lack the sensitivity of good culture methods, and in some situations are susceptible to giving both false negative and false positive results. Therefore, PCR does not usually replace the need for culture, but is used to provide fast preliminary results. DNA typing of M. bovis isolates by restriction endonuclease analysis (REA) was developed 25 years ago in New Zealand, and remains an important tool in the New Zealand control scheme, where the typing results are combined with other information to determine large and expensive possum poisoning operations. A range of other DNA typing systems developed for M. bovis in the 1990 s have assisted epidemiological investigations in some countries but are now less commonly used. Variable number tandem repeat (VNTR) typing and spoligotyping, either alone or together, have now become the preferred approaches as they are robust and amenable to electronic analysis and comparison. Spoligotyping gives only moderate discrimination but can be easily applied to large numbers of isolates, and VNTR typing provides better discrimination than all other methods except for REA. While the current typing techniques are sufficient for most epidemiological purposes, more discriminating methods are likely to become available in the near future.

Novel multiplex real-time PCR diagnostic assay for identification and differentiation of Mycobacterium tuberculosis, Mycobacterium canettii, and Mycobacterium tuberculosis complex strains

Tuberculosis (TB) in humans is caused by members of the Mycobacterium tuberculosis complex (MTC). Rapid detection of the MTC is necessary for the timely initiation of antibiotic treatment, while differentiation between members of the complex may be important to guide the appropriate antibiotic treatment and provide epidemiological information. In this study, a multiplex real-time PCR diagnostics assay using novel molecular targets was designed to identify the MTC while simultaneously differentiating between M. tuberculosis and M. canettii. The lepA gene was targeted for the detection of members of the MTC, the wbbl1 gene was used for the differentiation of M. tuberculosis and M. canettii from the remainder of the complex, and a unique region of the M. canettii genome, a possible novel region of difference (RD), was targeted for the specific identification of M. canettii. The multiplex real-time PCR assay was tested using 125 bacterial strains (64 MTC isolates, 44 nontuberculosis mycobacteria [NTM], and 17 other bacteria). The assay was determined to be 100% specific for the mycobacteria tested. Limits of detection of 2.2, 2.17, and 0.73 cell equivalents were determined for M. tuberculosis/M. canettii, the MTC, and M. canettii, respectively, using probit regression analysis. Further validation of this diagnostics assay, using clinical samples, should demonstrate its potential for the rapid, accurate, and sensitive diagnosis of TB caused by M. tuberculosis, M. canettii, and the other members of the MTC.

Novel Mycobacterium tuberculosis complex pathogen, M. mungi

Seven outbreaks involving increasing numbers of banded mongoose troops and high death rates have been documented. We identified a Mycobacterium tuberculosis complex pathogen, M. mungi sp. nov., as the causative agent among banded mongooses that live near humans in Chobe District, Botswana. Host spectrum and transmission dynamics remain unknown.

Mycobacterium africanum--review of an important cause of human tuberculosis in West Africa

Mycobacterium africanum consists of two phylogenetically distinct lineages within the Mycobacterium tuberculosis complex, known as M. africanum West African 1 and M. africanum West African 2. These lineages are restricted to West Africa, where they cause up to half of human pulmonary tuberculosis. In this review we discuss the definition of M. africanum, describe the prevalence and restricted geographical distribution of M. africanum West African 1 and 2, review the occurrence of M. africanum in animals, and summarize the phenotypic differences described thus far between M. africanum and M. tuberculosis sensu stricto.

Molecular characteristics of "Mycobacterium canettii" the smooth Mycobacterium tuberculosis bacilli

Since the first discovery of the smooth tubercle (SmTB) bacilli "Mycobacterium canettii" less than 60 isolates have been reported, all but one originating from a limited geographical location, the Horn of Africa. In spite of its rarity, the SmTB lineage deserves special attention. Previous investigations suggested that SmTB isolates represent an ancestral lineage of the Mycobacterium tuberculosis complex (MTBC) and that consequently they might provide essential clues on the origin and evolution of the MTBC. There is evidence that unlike the rest of the MTBC, SmTB strains recombine chromosomal sequences with a yet unknown Mycobacterium species. This behavior contributes to the much larger genetic heterogeneity observed in the SmTB isolates compared to the other members of the MTBC. We have collected 59 SmTB isolates of which 14 were newly recovered since previous reports, and performed extensive phenotypical and genotypical characterization. We take advantage of these investigations to review the current knowledge of "M. canettii". Their characteristics and the apparent lack of human to human transmission are consistent with the previously proposed existence of non-human sources of infection. SmTB strains show remarkably common features together with secondary and taxonomically minor genetic differences such as the presence or absence of the CRISPR (Clustered Regularly Interspersed Palindromic Repeat) locus (usually called Direct Repeat or DR region) or number of IS sequences. Multiple Locus Variable number of tandem repeat Analysis (MLVA) and DR region analyses reveal one predominant clone, one minor clone and a number of more distantly related strains. This suggests that the two most frequent clones may represent successfully emerging lineages.

Identification of Mycobacterium tuberculosis clinical isolates in Bangladesh by a species distinguishable multiplex PCR

Background

Species identification of isolates belonging to the Mycobacterium tuberculosis complex (MTC) seems to be important for the appropriate treatment of patients, since M. bovis is naturally resistant to a first line anti-tuberculosis (TB) drug, pyrazinamide, while most of the other MTC members are susceptible to this antimicrobial agent. A simple and low-cost differentiation method was needed in higher TB burden countries, such as Bangladesh, where the prevalence of M. bovis among people or cattle has not been investigated.

Methods

Genetic regions cfp32, RD9 and RD12 were chosen as targets for a species distinguishable multiplex PCR and the system was evaluated with twenty reference strains of mycobacterial species including non-tubercular mycobacteria (NTM). A total of 350 clinical MTC isolates obtained in Bangladesh were then analyzed with this multiplex PCR.

Results

All of the MTC reference strains gave expected banding patterns and no non-specific amplifications were observed in the NTM strains. Out of 350 clinical isolates examined by this method, 347 (99.1%) were positive for all of the cfp32, RD9 and RD12 and determined as M. tuberculosis. Two isolates lacked cfp32 PCR product and one lacked RD12, however, those three samples were further examined and identified as M. tuberculosis by the sequence analyses of hsp65 and gyrB.

Conclusions

The MTC-discrimination multiplex PCR (MTCD-MPCR) developed in this study showed high specificity and was thought to be very useful as a routine test because of its simplicity. In the current survey, all the 350 MTC isolates obtained from Bangladesh TB patients were determined as M. tuberculosis and no other MTC were detected. This result suggested the general TB treatment regimen including pyrazinamide to be the first choice in Bangladesh.