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1.
Proc Natl Acad Sci U S A ; 117(15): 8494-8502, 2020 04 14.
Article in English | MEDLINE | ID: mdl-32229570

ABSTRACT

Human tuberculosis is caused by members of the Mycobacterium tuberculosis complex (MTBC) that vary in virulence and transmissibility. While genome-wide association studies have uncovered several mutations conferring drug resistance, much less is known about the factors underlying other bacterial phenotypes. Variation in the outcome of tuberculosis infection and diseases has been attributed primarily to patient and environmental factors, but recent evidence indicates an additional role for the genetic diversity among MTBC clinical strains. Here, we used metabolomics to unravel the effect of genetic variation on the strain-specific metabolic adaptive capacity and vulnerability. To define the functionality of single-nucleotide polymorphisms (SNPs) systematically, we developed a constraint-based approach that integrates metabolomic and genomic data. Our model-based predictions correctly classify SNP effects in pyruvate kinase and suggest a genetic basis for strain-specific inherent baseline susceptibility to the antibiotic para-aminosalicylic acid. Our method is broadly applicable across microbial life, opening possibilities for the development of more selective treatment strategies.


Subject(s)
Antitubercular Agents/pharmacology , Genomics/methods , Host-Pathogen Interactions , Metabolome , Mycobacterium tuberculosis/genetics , Polymorphism, Single Nucleotide , Tuberculosis/genetics , Aminosalicylic Acid/pharmacology , Genome, Bacterial , Genome-Wide Association Study , Humans , Models, Molecular , Mycobacterium tuberculosis/classification , Mycobacterium tuberculosis/drug effects , Mycobacterium tuberculosis/metabolism , Phenotype , Phylogeny , Pyruvate Kinase/metabolism , Tuberculosis/drug therapy , Tuberculosis/microbiology , Virulence
2.
Mol Biol Evol ; 37(1): 195-207, 2020 Jan 01.
Article in English | MEDLINE | ID: mdl-31532481

ABSTRACT

Fluoroquinolones (FQ) form the backbone in experimental treatment regimens against drug-susceptible tuberculosis. However, little is known on whether the genetic variation present in natural populations of Mycobacterium tuberculosis (Mtb) affects the evolution of FQ-resistance (FQ-R). To investigate this question, we used nine genetically distinct drug-susceptible clinical isolates of Mtb and measured their frequency of resistance to the FQ ofloxacin (OFX) in vitro. We found that the Mtb genetic background led to differences in the frequency of OFX-resistance (OFX-R) that spanned two orders of magnitude and substantially modulated the observed mutational profiles for OFX-R. Further, in vitro assays showed that the genetic background also influenced the minimum inhibitory concentration and the fitness effect conferred by a given OFX-R mutation. To test the clinical relevance of our in vitro work, we surveyed the mutational profile for FQ-R in publicly available genomic sequences from clinical Mtb isolates, and found substantial Mtb lineage-dependent variability. Comparison of the clinical and the in vitro mutational profiles for FQ-R showed that 51% and 39% of the variability in the clinical frequency of FQ-R gyrA mutation events in Lineage 2 and Lineage 4 strains, respectively, can be attributed to how Mtb evolves FQ-R in vitro. As the Mtb genetic background strongly influenced the evolution of FQ-R in vitro, we conclude that the genetic background of Mtb also impacts the evolution of FQ-R in the clinic.


Subject(s)
Anti-Bacterial Agents , Biological Evolution , Drug Resistance, Bacterial/genetics , Genetic Background , Mycobacterium tuberculosis/genetics , Ofloxacin , Genome, Bacterial , Mutation Rate
3.
Antimicrob Agents Chemother ; 65(9): e0050421, 2021 08 17.
Article in English | MEDLINE | ID: mdl-34228548

ABSTRACT

Antimicrobial resistance (AMR) poses a threat to global health and the economy. Rifampicin-resistant Mycobacterium tuberculosis accounts for a third of the global AMR burden. Gaining the upper hand on AMR requires a deeper understanding of the physiology of resistance. AMR often results in a fitness cost in the absence of drug. Identifying the molecular mechanisms underpinning this cost could help strengthen future treatment regimens. Here, we used a collection of M. tuberculosis strains that provide an evolutionary and phylogenetic snapshot of rifampicin resistance and subjected them to genome-wide transcriptomic and proteomic profiling to identify key perturbations of normal physiology. We found that the clinically most common rifampicin resistance-conferring mutation, RpoB Ser450Leu, imparts considerable gene expression changes, many of which are mitigated by the compensatory mutation in RpoC Leu516Pro. However, our data also provide evidence for pervasive epistasis-the same resistance mutation imposed a different fitness cost and functionally distinct changes to gene expression in genetically unrelated clinical strains. Finally, we report a likely posttranscriptional modulation of gene expression that is shared in most of the tested strains carrying RpoB Ser450Leu, resulting in an increased abundance of proteins involved in central carbon metabolism. These changes contribute to a more general trend in which the disruption of the composition of the proteome correlates with the fitness cost of the RpoB Ser450Leu mutation in different strains.


Subject(s)
DNA-Directed RNA Polymerases , Mycobacterium tuberculosis , Bacterial Proteins/genetics , DNA-Directed RNA Polymerases/genetics , Drug Resistance, Bacterial/genetics , Microbial Sensitivity Tests , Mutation , Mycobacterium tuberculosis/genetics , Phylogeny , Proteomics , Rifampin/pharmacology
5.
Prax Kinderpsychol Kinderpsychiatr ; 67(8): 720-735, 2018 Dec.
Article in German | MEDLINE | ID: mdl-31801427

ABSTRACT

ReSi: Evaluation of a Program for Competency Training and Prevention of Sexual Abuse in Kindergarten This paper describes the "ReSi-Kompetenzförderprogramm" and its evaluation. Based on the resilience approach, this programme aims to foster the social-emotional, body-related and linguistic competencies of kindergarteners and teach them age-appropriate preventive knowledge concerning sexual abuse. A randomized-controlled trial was conducted (n = 412). At three different points in time the Kindergarten teachers and the parents filled in questionnaires about the children's competency development. To assess the knowledge and action strategies of the children, standardisized children interviews were conducted. Effects of the programme were found for self-assertion, stress management, communicative and interactional competencies, body-related competencies, conflict resolution competence and the communicative behaviour. Besides, children in the intervention group show greater knowledge about body parts, emotions and action strategies in security-relevant situations.


Subject(s)
Child Abuse/prevention & control , Health Education , Program Evaluation , Schools , Sex Education , Sex Offenses/prevention & control , Child Abuse/psychology , Child, Preschool , Humans , Parents , School Teachers , Sex Offenses/psychology , Surveys and Questionnaires
6.
BMC Vet Res ; 13(1): 272, 2017 Aug 25.
Article in English | MEDLINE | ID: mdl-28841870

ABSTRACT

BACKGROUND: Bovine tuberculosis (BTB) is caused by Mycobacterium bovis, which belongs to the Mycobacterium tuberculosis complex. Mycobacterium bovis have been described to be responsible of most cases of bovine tuberculosis. Although M. tuberculosis, M. africanum and non-complex mycobacteria were isolated from cattle. In Morocco, so far, no molecular studies were conducted to characterize the strains responsible of BTB. The present study aims to characterize M. bovis in Morocco. The present study was conducted in slaughterhouses in Rabat and El Jadida. Samples were collected from 327 slaughtered animals with visible lesions suggesting BTB. RESULTS: A total of 225 isolates yielded cultures, 95% (n = 215) of them were acid-fast (AF). Sixty eight per cent of the AF positive samples were confirmed as tuberculous mycobacteria (n = 147), 99% of these (n = 146) having RD9 and among the latter, 98% (n = 143) positive while 2% (n = 3) negative for RD4 A total of 134 samples were analyzed by spoligotyping of which 14 were in cluster and with 41 different spoligotypes, ten of them were new patterns (23%). The most prevalent spoligotypes were SB0121, SB0265, and SB0120, and were already identified in many other countries, such as Algeria, Spain, Tunisia, the United States and Argentina. CONCLUSION: The shared borders between Algeria and Morocco, in addition to the previous importation of cattle from Europe and the US could explain the similarities found in M. bovis spoligotypes. On the other hand, the desert of Morocco could be considered as an efficient barrier preventing the introduction of BTB to Morocco from West Central and East Africa. Our findings suggest a low level endemic transmission of BTB similar to other African countries. However, more research is needed for further knowledge about the transmission patterns of BTB in Morocco.


Subject(s)
Abattoirs , Mycobacterium bovis/genetics , Mycobacterium tuberculosis/genetics , Tuberculosis, Bovine/microbiology , Tuberculosis/veterinary , Animals , Cattle , Molecular Typing , Morocco , Mycobacterium bovis/classification , Mycobacterium bovis/isolation & purification , Mycobacterium tuberculosis/classification , Mycobacterium tuberculosis/isolation & purification , Tuberculosis/microbiology
7.
J Infect Dis ; 211(8): 1306-16, 2015 Apr 15.
Article in English | MEDLINE | ID: mdl-25362193

ABSTRACT

BACKGROUND: Whole-genome sequencing (WGS) is increasingly used in molecular-epidemiological investigations of bacterial pathogens, despite cost- and time-intensive analyses. We combined strain-specific single-nucleotide polymorphism (SNP) typing and targeted WGS to investigate a tuberculosis cluster spanning 21 years in Bern, Switzerland. METHODS: On the basis of genome sequences of 3 historical outbreak Mycobacterium tuberculosis isolates, we developed a strain-specific SNP-typing assay to identify further cases. We screened 1642 patient isolates and performed WGS on all identified cluster isolates. We extracted SNPs to construct genomic networks. Clinical and social data were retrospectively collected. RESULTS: We identified 68 patients associated with the outbreak strain. Most received a tuberculosis diagnosis in 1991-1995, but cases were observed until 2011. Two thirds were homeless and/or substance abusers. Targeted WGS revealed 133 variable SNP positions among outbreak isolates. Genomic network analyses suggested a single origin of the outbreak, with subsequent division into 3 subclusters. Isolates from patients with confirmed epidemiological links differed by 0-11 SNPs. CONCLUSIONS: Strain-specific SNP genotyping allowed rapid and inexpensive identification of M. tuberculosis outbreak isolates in a population-based strain collection. Subsequent targeted WGS provided detailed insights into transmission dynamics. This combined approach could be applied to track bacterial pathogens in real time and at high resolution.


Subject(s)
Genome, Bacterial/genetics , Mycobacterium tuberculosis/genetics , Polymorphism, Single Nucleotide/genetics , Tuberculosis/epidemiology , Tuberculosis/microbiology , Adult , Aged , Bacterial Typing Techniques/methods , DNA, Bacterial/genetics , Disease Outbreaks , Female , Genotype , Humans , Male , Middle Aged , Molecular Epidemiology/methods , Retrospective Studies , Sequence Analysis, DNA/methods , Switzerland/epidemiology
8.
BMC Microbiol ; 14: 307, 2014 Dec 05.
Article in English | MEDLINE | ID: mdl-25476850

ABSTRACT

BACKGROUND: Papua New Guinea (PNG) is a high tuberculosis (TB) burden country of the WHO Western Pacific Region, but so far research on drug resistance (DR) and genotypes of Mycobacterium tuberculosis (M. tuberculosis) was only conducted in few provinces in the country. The aim of the present study was to obtain baseline data on the level of drug resistance and the genotypic diversity of circulating M. tuberculosis in additional provinces and to investigate the differences between three selected sites across PNG. RESULTS: Genotyping of 147 M. tuberculosis clinical isolates collected in Goroka, Eastern Highlands Province, in Alotau, Milne Bay Province and in Madang, Madang Province revealed three main lineages of M. tuberculosis: Lineage 4 (European-American lineage), Lineage 2 (East-Asian lineage) and Lineage 1 (Indo-Oceanic lineage). All three lineages were detected in all three sites, but the individual lineage compositions varied significantly between sites. In Madang Lineage 4 was the most prevalent lineage (76.6%), whereas in Goroka and Alotau Lineage 2 was dominating (60.5% and 84.4%, respectively) (p < 0.001). Overall, phenotypic drug susceptibility testing showed 10.8% resistance to at least one of the first-line drugs tested. Of all resistant strains (23/212) 30.4% were Streptomycin mono-resistant, 17.4% were Isoniazid mono-resistant and 13% were Rifampicin mono-resistant. Multi-drug resistant (MDR) TB was found in 2.8% of all tested cases (6/212). The highest amount of MDR TB was found in Alotau in Milne Bay Province (4.6%). CONCLUSION: A large number of drug resistant TB infections are present in the country and MDR TB has already been detected in all three surveyed regions of PNG, highlighting the importance of monitoring drug resistance and making it a high priority for the National Control Program. Due to the high prevalence of Lineage 2 in Milne Bay Province and given the frequent association of this lineage with drug resistance, monitoring of the latter should especially be scaled up in that province.


Subject(s)
Drug Resistance, Bacterial , Genetic Variation , Mycobacterium tuberculosis/classification , Mycobacterium tuberculosis/drug effects , Tuberculosis/microbiology , Adolescent , Adult , Aged , Aged, 80 and over , Antitubercular Agents/pharmacology , Female , Genotype , Humans , Male , Microbial Sensitivity Tests , Middle Aged , Molecular Typing , Mycobacterium tuberculosis/genetics , Mycobacterium tuberculosis/isolation & purification , Papua New Guinea/epidemiology , Tuberculosis/epidemiology , Young Adult
9.
F1000Res ; 10: 60, 2021.
Article in English | MEDLINE | ID: mdl-33732436

ABSTRACT

Background: Lineage 1 (L1) and 3 (L3) are two lineages of the Mycobacterium tuberculosis complex (MTBC) causing tuberculosis (TB) in humans. L1 and L3 are prevalent around the rim of the Indian Ocean, the region that accounts for most of the world's new TB cases. Despite their relevance for this region, L1 and L3 remain understudied. Methods: We analyzed 2,938 L1 and 2,030 L3 whole genome sequences originating from 69 countries. We reconstructed the evolutionary history of these two lineages and identified genes under positive selection. Results: We found a strongly asymmetric pattern of migration from South Asia toward neighboring regions, highlighting the historical role of South Asia in the dispersion of L1 and L3. Moreover, we found that several genes were under positive selection, including genes involved in virulence and resistance to antibiotics. For L1 we identified signatures of local adaptation at the esxH locus, a gene coding for a secreted effector that targets the human endosomal sorting complex, and is included in several vaccine candidates. Conclusions: Our study highlights the importance of genetic diversity in the MTBC, and sheds new light on two of the most important MTBC lineages affecting humans.


Subject(s)
Mycobacterium tuberculosis , Genotype , Humans , Indian Ocean , Mycobacterium tuberculosis/genetics
10.
Avian Dis ; 54(2): 875-84, 2010 Jun.
Article in English | MEDLINE | ID: mdl-20608533

ABSTRACT

After the spread of H5N1 highly pathogenic avian influenza virus (AIV) from Asia into Russia, the Middle East, Europe, and Africa in 2005-06, the Swiss national AIV surveillance program was extended. One of the new focal points was Lake Constance, where sentinel duck stations and swim-in traps were established within the project Constanze in collaboration with Germany and Austria. More than 2000 samples from 41 species were collected in Switzerland between September 2006 and December 2008. Approximately 4% were AIV-positive by quantitative reverse transcriptase-PCR. Subsequent typing revealed 13 different AIV subtypes, of which H5N2 and H9N2 were the most prevalent. All H7 isolates and all but one H5 isolate were characterized as low pathogenic; however, a highly pathogenic H5N1 AIV was detected in a healthy pochard. This study demonstrates that a wide selection of different AIV subtypes can cocirculate among the waterfowl population in wild bird habitats.


Subject(s)
Birds , Influenza A virus/isolation & purification , Influenza in Birds/virology , Animals , Animals, Wild , Influenza A virus/classification , Influenza A virus/genetics , Influenza in Birds/epidemiology , Phylogeny , Sentinel Surveillance , Switzerland/epidemiology , Time Factors
11.
Front Cell Dev Biol ; 8: 583115, 2020.
Article in English | MEDLINE | ID: mdl-33117810

ABSTRACT

Van der Woude syndrome (VWS) is a genetic syndrome that leads to typical phenotypic traits, including lower lip pits and cleft lip/palate (CLP). The majority of VWS-affected patients harbor a pathogenic variant in the gene encoding for the transcription factor interferon regulatory factor 6 (IRF6), a crucial regulator of orofacial development, epidermal differentiation and tissue repair. However, most of the underlying mechanisms leading from pathogenic IRF6 gene variants to phenotypes observed in VWS remain poorly understood and elusive. The availability of one VWS individual within our cohort of CLP patients allowed us to identify a novel VWS-causing IRF6 variant and to functionally characterize it. Using VWS patient-derived keratinocytes, we reveal that most of the mutated IRF6_VWS transcripts are subject to a non-sense-mediated mRNA decay mechanism, resulting in IRF6 haploinsufficiency. While moderate levels of IRF6_VWS remain detectable in the VWS keratinocytes, our data illustrate that the IRF6_VWS protein, which lacks part of its protein-binding domain and its whole C-terminus, is noticeably less stable than its wild-type counterpart. Still, it maintains transcription factor function. As we report and characterize a so far undescribed VWS-causing IRF6 variant, our results shed light on the physiological as well as pathological role of IRF6 in keratinocytes. This acquired knowledge is essential for a better understanding of the molecular mechanisms leading to VWS and CLP.

12.
PLoS One ; 14(3): e0214088, 2019.
Article in English | MEDLINE | ID: mdl-30908506

ABSTRACT

The Mycobacterium tuberculosis complex (MTBC) causes tuberculosis (TB) in humans and various other mammals. The human-adapted members of the MTBC comprise seven phylogenetic lineages that differ in their geographical distribution. There is growing evidence that this phylogeographic diversity modulates the outcome of TB infection and disease. For decades, TB research and development has focused on the two canonical MTBC laboratory strains H37Rv and Erdman, both of which belong to Lineage 4. Relying on only a few laboratory-adapted strains can be misleading as study results might not be directly transferrable to clinical settings where patients are infected with a diverse array of strains, including drug-resistant variants. Here, we argue for the need to expand TB research and development by incorporating the phylogenetic diversity of the MTBC. To facilitate such work, we have assembled a group of 20 genetically well-characterized clinical strains representing the seven known human-adapted MTBC lineages. With the "MTBC clinical strains reference set" we aim to provide a standardized resource for the TB community. We hope it will enable more direct comparisons between studies that explore the physiology of MTBC beyond the laboratory strains used thus far. We anticipate that detailed phenotypic analyses of this reference strain set will increase our understanding of TB biology and assist in the development of new control tools that are broadly effective.


Subject(s)
Genetic Variation , Mycobacterium tuberculosis/genetics , Humans , Mycobacterium tuberculosis/isolation & purification , Phylogeny , Phylogeography
13.
PLoS One ; 14(4): e0206334, 2019.
Article in English | MEDLINE | ID: mdl-30978186

ABSTRACT

BACKGROUND: Human tuberculosis (TB) is caused by seven phylogenetic lineages of the Mycobacterium tuberculosis complex (MTBC), Lineage 1-7. Recent advances in rapid genotyping of MTBC based on single nucleotide polymorphisms (SNP), allow for phylogenetically robust strain classification, paving the way for defining genotype-phenotype relationships in clinical settings. Such studies have revealed that, in addition to host and environmental factors, strain variation in the MTBC influences the outcome of TB infection and disease. In Tanzania, such molecular epidemiological studies of TB however are scarce in spite of a high TB burden. METHODS AND FINDINGS: Here we used SNP-typing to characterize a nationwide collection of 2,039 MTBC clinical isolates representative of 1.6% of all new and retreatment TB cases notified in Tanzania during 2012 and 2013. Four lineages, namely Lineage 1-4 were identified within the study population. The distribution and frequency of these lineages varied across regions but overall, Lineage 4 was the most frequent (n = 866, 42.5%), followed by Lineage 3 (n = 681, 33.4%) and 1 (n = 336, 16.5%), with Lineage 2 being the least frequent (n = 92, 4.5%). We found Lineage 2 to be independently associated with female sex (adjusted odds ratio [aOR] 2.14; 95% confidence interval [95% CI] 1.31 - 3.50, p = 0.002) and retreatment cases (aOR 1.67; 95% CI 0.95 - 2.84, p = 0. 065) in the study population. We found no associations between MTBC lineage and patient age or HIV status. Our sublineage typing based on spacer oligotyping on a subset of Lineage 1, 3 and 4 strains revealed the presence of mainly EAI, CAS and LAM families. Finally, we detected low levels of multidrug resistant isolates among a subset of 144 retreatment cases. CONCLUSIONS: This study provides novel insights into the MTBC lineages and the possible influence of pathogen-related factors on the TB epidemic in Tanzania.


Subject(s)
Mycobacterium tuberculosis/genetics , Phylogeny , Polymorphism, Single Nucleotide , Tuberculosis, Pulmonary/genetics , Adolescent , Adult , Aged , Female , Humans , Male , Middle Aged , Tanzania/epidemiology , Tuberculosis, Pulmonary/epidemiology , Tuberculosis, Pulmonary/microbiology
14.
Sci Rep ; 7(1): 14647, 2017 11 07.
Article in English | MEDLINE | ID: mdl-29116204

ABSTRACT

Zoonotic tuberculosis is a risk for human health, especially when animals are in close contact with humans. Mycobacterium tuberculosis was cultured from several organs, including lung tissue and gastric mucosa, of three captive elephants euthanized in a Swiss zoo. The elephants presented weight loss, weakness and exercise intolerance. Molecular characterization of the M. tuberculosis isolates by spoligotyping revealed an identical profile, suggesting a single source of infection. Multilocus variable-number of tandem-repeat analysis (MLVA) elucidated two divergent populations of bacteria and mixed infection in one elephant, suggesting either different transmission chains or prolonged infection over time. A total of eight M. tuberculosis isolates were subjected to whole-genome sequence (WGS) analysis, confirming a single source of infection and indicating the route of transmission between the three animals. Our findings also show that the methods currently used for epidemiological investigations of M. tuberculosis infections should be carefully applied on isolates from elephants. Moreover the importance of multiple sampling and analysis of within-host mycobacterial clonal populations for investigations of transmission is demonstrated.


Subject(s)
Diagnostic Tests, Routine/veterinary , Disease Outbreaks/veterinary , Minisatellite Repeats , Multilocus Sequence Typing/veterinary , Mycobacterium tuberculosis/genetics , Tuberculosis/diagnosis , Whole Genome Sequencing/veterinary , Animals , Elephants , Mycobacterium tuberculosis/classification , Switzerland/epidemiology , Tuberculosis/epidemiology , Tuberculosis/genetics , Tuberculosis/microbiology
15.
Science ; 355(6330): 1206-1211, 2017 Mar 17.
Article in English | MEDLINE | ID: mdl-28302858

ABSTRACT

Antibiotic resistance is one of the biggest threats to human health globally. Alarmingly, multidrug-resistant and extensively drug-resistant Mycobacterium tuberculosis have now spread worldwide. Some key antituberculosis antibiotics are prodrugs, for which resistance mechanisms are mainly driven by mutations in the bacterial enzymatic pathway required for their bioactivation. We have developed drug-like molecules that activate a cryptic alternative bioactivation pathway of ethionamide in M. tuberculosis, circumventing the classic activation pathway in which resistance mutations have now been observed. The first-of-its-kind molecule, named SMARt-420 (Small Molecule Aborting Resistance), not only fully reverses ethionamide-acquired resistance and clears ethionamide-resistant infection in mice, it also increases the basal sensitivity of bacteria to ethionamide.


Subject(s)
Antitubercular Agents/pharmacology , Drug Resistance, Multiple, Bacterial/drug effects , Ethionamide/metabolism , Extensively Drug-Resistant Tuberculosis/microbiology , Isoxazoles/pharmacology , Mycobacterium tuberculosis/drug effects , Spiro Compounds/pharmacology , Animals , DNA/metabolism , Ethionamide/pharmacology , Humans , Mice , Mutation , Mycobacterium tuberculosis/genetics , Mycobacterium tuberculosis/metabolism , Oxadiazoles/pharmacology , Piperidines/pharmacology , Protein Binding/drug effects , Repressor Proteins/antagonists & inhibitors , Repressor Proteins/metabolism
16.
PLoS Negl Trop Dis ; 9(1): e3370, 2015 Jan.
Article in English | MEDLINE | ID: mdl-25569290

ABSTRACT

Mycobacterium africanum is a member of the Mycobacterium tuberculosis complex (MTBC) and an important cause of human tuberculosis in West Africa that is rarely observed elsewhere. Here we genotyped 613 MTBC clinical isolates from Ghana, and searched for associations between the different phylogenetic lineages of MTBC and patient variables. We found that 17.1% (105/613) of the MTBC isolates belonged to M. africanum, with the remaining belonging to M. tuberculosis sensu stricto. No M. bovis was identified in this sample. M. africanum was significantly more common in tuberculosis patients belonging to the Ewe ethnic group (adjusted odds ratio: 3.02; 95% confidence interval: 1.67-5.47, p<0.001). Stratifying our analysis by the two phylogenetic lineages of M. africanum (i.e. MTBC Lineages 5 and 6) revealed that this association was mainly driven by Lineage 5 (also known as M. africanum West Africa 1). Our findings suggest interactions between the genetic diversity of MTBC and human diversity, and offer a possible explanation for the geographical restriction of M. africanum to parts of West Africa.


Subject(s)
Mycobacterium tuberculosis/classification , Tuberculosis/ethnology , Adolescent , Adult , Aged , Child , Female , Genotype , Ghana , Humans , Male , Middle Aged , Mycobacterium tuberculosis/genetics , Phylogeny , Tuberculosis/microbiology
17.
J Virol Methods ; 188(1-2): 168-74, 2013 Mar.
Article in English | MEDLINE | ID: mdl-23000751

ABSTRACT

The neutralization test is used commonly for quantifying neutralizing antibodies and for distinguishing among different virus serotypes (serotyping). Due to the co-circulation of multiple serotypes of Bluetongue virus (BTV), the neutralization test has become an important surveillance method in Europe. However, the existence of different protocols makes test standardization and interpretation of results difficult. The current paper describes the development of a neutralization test using plasma and addresses the factors critical for detection of neutralizing antibodies against BTV serotype 8 (BTV-8), such as virus propagation, stability of virus infectivity and origin of the BTV-8 strain. The results indicated that animals exposed to the Northern European BTV-8 strain developed low neutralizing antibody titers, particularly after vaccination and experimental infection. Although clearly ELISA-positive, these samples often yielded false negative results when tested by the neutralization test using the OIE recommended virus concentration of 100 TCID50/50 µl. The sensitivity of the neutralization test could be improved significantly with retained specificity by using a reduced TCID50 and the homologous European BTV-8 strain instead of the South African reference strain.


Subject(s)
Antibodies, Neutralizing/blood , Antibodies, Viral/blood , Bluetongue virus/immunology , Bluetongue/diagnosis , Neutralization Tests/methods , Veterinary Medicine/methods , Animals , Bluetongue virus/classification , Cattle , Europe , Plasma , Sensitivity and Specificity , Serotyping/methods , Sheep
18.
Evol Med Public Health ; 2013(1): 65-74, 2013 Jan.
Article in English | MEDLINE | ID: mdl-24481187

ABSTRACT

BACKGROUND AND OBJECTIVES: Multidrug resistant (MDR) bacteria are a growing threat to global health. Studies focusing on single antibiotics have shown that drug resistance is often associated with a fitness cost in the absence of drug. However, little is known about the fitness cost associated with resistance to multiple antibiotics. METHODOLOGY: We used Mycobacterium smegmatis as a model for human tuberculosis (TB) and an in vitro competitive fitness assay to explore the combined fitness effects and interaction between mutations conferring resistance to rifampicin (RIF) and ofloxacin (OFX); two of the most important first- and second-line anti-TB drugs, respectively. RESULTS: We found that 4 out of 17 M. smegmatis mutants (24%) resistant to RIF and OFX showed a statistically significantly higher or lower competitive fitness than expected when assuming a multiplicative model of fitness effects of each individual mutation. Moreover, 6 out of the 17 double drug-resistant mutants (35%) had a significantly higher fitness than at least one of the corresponding single drug-resistant mutants. The particular combinations of resistance mutations associated with no fitness deficit in M. smegmatis were the most frequent among 151 clinical isolates of MDR and extensively drug-resistant (XDR) Mycobacterium tuberculosis from South Africa. CONCLUSIONS AND IMPLICATIONS: Our results suggest that epistasis between drug resistance mutations in mycobacteria can lead to MDR strains with no fitness deficit, and that these strains are positively selected in settings with a high burden of drug-resistant TB. Taken together, our findings support a role for epistasis in the evolution and epidemiology of MDR- and XDR-TB.

19.
PLoS One ; 7(12): e52297, 2012.
Article in English | MEDLINE | ID: mdl-23300635

ABSTRACT

BACKGROUND: Tuberculosis (TB) is a major public health problem in Nepal. Strain variation in Mycobacterium tuberculosis may influence the outcome of TB infection and disease. To date, the phylogenetic diversity of M. tuberculosis in Nepal is unknown. METHODS AND FINDINGS: We analyzed 261 M. tuberculosis isolates recovered from pulmonary TB patients recruited between August 2009 and August 2010 in Nepal. M. tuberculosis lineages were determined by single nucleotide polymorphisms (SNP) typing and spoligotyping. Drug resistance was determined by sequencing the hot spot regions of the relevant target genes. Overall, 164 (62.8%) TB patients were new, and 97 (37.2%) were previously treated. Any drug resistance was detected in 50 (19.2%) isolates, and 16 (6.1%) were multidrug-resistant. The most frequent M. tuberculosis lineage was Lineage 3 (CAS/Delhi) with 106 isolates (40.6%), followed by Lineage 2 (East-Asian lineage, includes Beijing genotype) with 84 isolates (32.2%), Lineage 4 (Euro-American lineage) with 41 (15.7%) isolates, and Lineage 1 (Indo-Oceanic lineage) with 30 isolates (11.5%). Based on spoligotyping, we found 45 different spoligotyping patterns that were previously described. The Beijing (83 isolates, 31.8%) and CAS spoligotype (52, 19.9%) were the dominant spoligotypes. A total of 36 (13.8%) isolates could not be assigned to any known spoligotyping pattern. Lineage 2 was associated with female sex (adjusted odds ratio [aOR] 2.58, 95% confidence interval [95% CI] 1.42-4.67, p = 0.002), and any drug resistance (aOR 2.79; 95% CI 1.43-5.45; p = 0.002). We found no evidence for an association of Lineage 2 with age or BCG vaccination status. CONCLUSIONS: We found a large genetic diversity of M. tuberculosis in Nepal with representation of all four major lineages. Lineages 3 and 2 were dominating. Lineage 2 was associated with clinical characteristics. This study fills an important gap on the map of the M. tuberculosis genetic diversity in the Asian region.


Subject(s)
Genetic Variation , Mycobacterium tuberculosis/genetics , Phylogeny , Adult , Drug Resistance, Bacterial/genetics , Female , Genotype , Humans , Male , Mycobacterium tuberculosis/drug effects , Mycobacterium tuberculosis/isolation & purification , Mycobacterium tuberculosis/physiology , Nepal , Polymorphism, Single Nucleotide , Tuberculosis, Pulmonary/microbiology
20.
PLoS One ; 7(7): e41253, 2012.
Article in English | MEDLINE | ID: mdl-22911768

ABSTRACT

There is increasing evidence that strain variation in Mycobacterium tuberculosis complex (MTBC) might influence the outcome of tuberculosis infection and disease. To assess genotype-phenotype associations, phylogenetically robust molecular markers and appropriate genotyping tools are required. Most current genotyping methods for MTBC are based on mobile or repetitive DNA elements. Because these elements are prone to convergent evolution, the corresponding genotyping techniques are suboptimal for phylogenetic studies and strain classification. By contrast, single nucleotide polymorphisms (SNP) are ideal markers for classifying MTBC into phylogenetic lineages, as they exhibit very low degrees of homoplasy. In this study, we developed two complementary SNP-based genotyping methods to classify strains into the six main human-associated lineages of MTBC, the "Beijing" sublineage, and the clade comprising Mycobacterium bovis and Mycobacterium caprae. Phylogenetically informative SNPs were obtained from 22 MTBC whole-genome sequences. The first assay, referred to as MOL-PCR, is a ligation-dependent PCR with signal detection by fluorescent microspheres and a Luminex flow cytometer, which simultaneously interrogates eight SNPs. The second assay is based on six individual TaqMan real-time PCR assays for singleplex SNP-typing. We compared MOL-PCR and TaqMan results in two panels of clinical MTBC isolates. Both methods agreed fully when assigning 36 well-characterized strains into the main phylogenetic lineages. The sensitivity in allele-calling was 98.6% and 98.8% for MOL-PCR and TaqMan, respectively. Typing of an additional panel of 78 unknown clinical isolates revealed 99.2% and 100% sensitivity in allele-calling, respectively, and 100% agreement in lineage assignment between both methods. While MOL-PCR and TaqMan are both highly sensitive and specific, MOL-PCR is ideal for classification of isolates with no previous information, whereas TaqMan is faster for confirmation. Furthermore, both methods are rapid, flexible and comparably inexpensive.


Subject(s)
Molecular Typing/methods , Mycobacterium tuberculosis/classification , Mycobacterium tuberculosis/genetics , Phylogeny , Polymorphism, Single Nucleotide , Alleles , Genome, Bacterial , Humans
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