The transcontinental transmission of tuberculosis: A molecular epidemiological assessment

Whole-Genome Sequencing Reveals Recent Transmission of Multidrug-Resistant Mycobacterium tuberculosis CAS1-Kili Strains in Lusaka, Zambia

Globally, tuberculosis (TB) is a major cause of death due to antimicrobial resistance. Mycobacterium tuberculosis CAS1-Kili strains that belong to lineage 3 (Central Asian Strain, CAS) were previously implicated in the spread of multidrug-resistant (MDR)-TB in Lusaka, Zambia. Thus, we investigated recent transmission of those strains by whole-genome sequencing (WGS) with Illumina MiSeq platform. Twelve MDR CAS1-Kili isolates clustered by traditional methods (MIRU-VNTR and spoligotyping) were used. A total of 92% (11/12) of isolates belonged to a cluster (≤12 SNPs) while 50% (6/12) were involved in recent transmission events, as they differed by ≤5 SNPs. All the isolates had KatG Ser315Thr (isoniazid resistance), EmbB Met306 substitutions (ethambutol resistance) and several kinds of rpoB mutations (rifampicin resistance). WGS also revealed compensatory mutations including a novel deletion in embA regulatory region (−35A > del). Several strains shared the same combinations of drug-resistance-associated mutations indicating transmission of MDR strains. Zambian strains belonged to the same clade as Tanzanian, Malawian and European strains, although most of those were pan-drug-susceptible. Hence, complimentary use of WGS to traditional epidemiological methods provides an in-depth insight on transmission and drug resistance patterns which can guide targeted control measures to stop the spread of MDR-TB.

Genomic analysis of the emergence of drug-resistant strains of Mycobacterium tuberculosis in the Middle East

Tuberculosis (TB) represents a significant challenge to public health authorities, especially with the emergence of drug-resistant (DR) and multidrug-resistant (MDR) isolates of Mycobacterium tuberculosis. We sought to examine the genomic variations among recently isolated strains of M. tuberculosis in two closely related countries with different population demography in the Middle East. Clinical isolates of M. tuberculosis from both Egypt and Saudi Arabia were subjected to phenotypic and genotypic analysis on gene and genome-wide levels. Isolates with MDR phenotypes were highly prevalent in Egypt (up to 35%) despite its relatively stable population structure (sympatric pattern). MDR-TB isolates were not identified in the isolates from Saudi Arabia despite its active guest worker program (allopatric pattern). However, tuberculosis isolates from Saudi Arabia, where lineage 4 was more prevalent (>65%), showed more diversity than isolates from Egypt, where lineage 3 was the most prevalent (>75%). Phylogenetic and molecular dating analyses indicated that lineages from Egypt were recently diverged (~78 years), whereas those from Saudi Arabia were diverged by over 200 years. Interestingly, DR isolates did not appear to cluster together or spread more widely than drug-sensitive isolates, suggesting poor treatment as the main cause for emergence of drug resistance rather than more virulence or more capacity to persist.

Analysis of Clinical Profile and Outcome of Tuberculosis in Patients with Acute Leukemia

Patients with acute leukemia (AL) are predisposed to develop infections including tuberculosis (TB). The risk is specifically higher in patients from TB endemic areas. Patients (≥12 years) with AL treated between January-2014 to January-2017 who developed TB were reviewed. Patients were classified into three groups: acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML) and acute promyelocytic leukemia (APML) and a systematic analysis of clinical features and outcomes was conducted. Over the study period, 26 patients of AL developed TB. The median time to diagnosis of TB was 8 weeks (0-432 weeks) following the diagnosis of AL and it was comparable between the three leukemia groups. The diagnosis of TB required alteration of anti-leukemia therapy in 26.9% patients and rescheduling in another 42.3% patients. Therapy alteration/rescheduling were more frequent in patients with AML as compared to ALL and APML (p < 0.03, <0.04). Disseminated TB was more common in AML patients (p < 0.016). ATT could be successfully administered in 86.9% patients with improvement of TB. The incidence of ATT induced hepatitis was 34.9%. Mortality was directly attributable to TB in 10% patients. Managing tuberculosis remains a challenge during treatment of acute leukemia. With this analysis, we advocate for a need of early suspicion and evaluation for TB in patients receiving treatment for acute leukemia. Rescheduling and or alteration of anticancer therapy due to TB is associated with significantly higher mortality. Therefore, in carefully selected cases, antileukemia therapy should continue after starting ATT as early as possible.

Sino-European Transcontinental Basic and Clinical High-Tech Acupuncture Studies-Part 4: "Fire of Life" Analysis of Heart Rate Variability during Acupuncture in Clinical Studies

This fourth part of a series of Sino-European high-tech acupuncture studies describes the first clinical transcontinental teleacupuncture measurements in two patients (cervical spine syndrome and tachycardia; both 27 years old) from the Beijing Hospital of Traditional Chinese Medicine affiliated to Capital Medical University, China. The electrocardiographic data were transferred to the Stronach Research Unit for Complementary and Integrative Laser Medicine and the TCM Research Center in Graz via conventional internet connections. Data analysis was performed in Graz using a new “Fire of Life” heart rate variability analysis. Analysis was performed without any technical problems in both subjects. Heart rate decreased significantly during acupuncture in the two patients from Beijing. At the same time, total HRV increased during acupuncture. The different influences of HRV (respiratory sinus arrhythmia, blood pressure waves, etc.) could be clearly documented using the new “Fire of Life” analysis.

Incidence of Tuberculosis in Mountain Areas and Surrounding Townships: Dose–Response Relationship by Geographic Analysis

PURPOSE

The incidence of tuberculosis (TB) in Taiwan is known to be high in aboriginal mountain areas and low in the surrounding non-mountain areas. The aim of this study was to assess whether TB incident cases in the surroundings of mountain areas decreased with distance from foci of mountain areas.

METHODS

The mountain areas in Taiwan are adjacent to each other and divided into four geographic groups. Townships with high TB incidence in each group were treated as the foci of TB infection. The surrounding townships were then classified, by distance away from foci, into three levels: < 20 km, 20 to 40 km, and 40 to 60 km. Data were obtained on a total of 84,366 TB cases from 1991 to 1997 from the Taiwan Tuberculous Disease Registry Center.

RESULTS

The incidence of TB in each of the four groups was significantly higher in the mountain areas compared with non-mountain areas, with relative risks ranging from 8.4 (95% confidence interval [CI], 7.8-9.1) for the southern group to 15.0 (95% CI, 13.4-16.9) for the northern group. Relative risks for surrounding townships decreased with distance in all four groups. Such a gradient relationship was statistically significant.

CONCLUSIONS

A significant dose-response relationship between distance from townships with a high incidence of TB and the incidence of TB in the surrounding areas has been demonstrated.

Molecular epidemiology of tuberculosis and recent developments in understanding the epidemiology of tuberculosis

The development of molecular typing techniques during the last decade has led to remarkable improvements in epidemiological studies of tuberculosis (TB) and other infectious disease. In this paper, the burden of TB disease, current issues about disease control in developed countries including Australia and the contribution of molecular typing to improved understanding of TB epidemiology are reviewed.

Prehistoric tuberculosis in america: adding comments to a literature review

Tuberculosis is a prehistoric American human disease. This paper reviews the literature and discusses hypotheses for origins and epidemiological patterns of prehistoric tuberculosis. From the last decades, 24 papers about prehistoric tuberculosis were published and 133 cases were reviewed. In South America most are isolated case studies, contrary to North America where more skeletal series were analyzed. Disease was usually located at the deserts of Chile and Peru, Central Plains in USA, and Lake Ontario in Canada. Skeletal remains represent most of the cases, but 16 mummies have also been described. Thirty individuals had lung disease, 19 of them diagnosed by the ribs. More then 100 individuals had osseous tuberculosis and 26 also had it in other organs. As today, transmission of the infection and establishment of the disease were favored by cultural and life-style changes such as sedentarization, crowding, undernutrition, use of dark and insulated houses, and by the frequency of interpersonal contacts. The papers confirm that despite previous perceptions, tuberculosis seems to have occurred in America for millennia. It only had epidemiological expression when special conditions favored its expansion. Occurring as epidemic bursts or low endemic disease, it had differential impact on groups or social segments in America for at least two millennia.

DNA fngerprinting of Mycobacterium tuberculosis: lessons learned and implications for the future

DNA fingerprinting of Mycobacterium tuberculosis--a relatively new laboratory technique--offers promise as a powerful aid in the prevention and control of tuberculosis (TB). Established in 1996 by the Centers for Disease Control and Prevention (CDC), the National Tuberculosis Genotyping and Surveillance Network was a 5-year prospective, population-based study of DNA fingerprinting conducted from 1996 to 2000. The data from this study suggest multiple molecular epidemiologic and program management uses for DNA fingerprinting in TB public health practice. From these data, we also gain a clearer understanding of the overall diversity of M. tuberculosis strains as well as the presence of endemic strains in the United States. We summarize the key findings and the impact that DNA fingerprinting may have on future approaches to TB control. Although challenges and limitations to the use of DNA fingerprinting exist, the widespread implementation of the technique into routine TB prevention and control practices appears scientifically justified.

Quality assessment of Mycobacterium tuberculosis genotyping in a large laboratory network

Quality assessment exercises were conducted to evaluate the reproducibility of IS6110 DNA fingerprinting performed by eight laboratories in the National Tuberculosis Genotyping and Surveillance Network. Three panels, each with 8 to 16 isolates, were typed at all laboratories, resulting in 280 images. When the pattern obtained by the majority for each isolate was used as the standard, exact matches were obtained for 73% of patterns; 90% and 97% of patterns matched within one- and two-band differences, respectively. A second approach involved retyping of randomly selected isolates at the Centers for Disease Control and Prevention. Retyping was done for 8-19 isolates per laboratory (76 total). Paired images matched exactly for 54% of isolates and within one and two band differences, 78% and 93%, respectively. We evaluated reasons for mismatching. We also evaluated the reproducibility of spoligotyping using a test panel of 13 isolates; a discrepancy of 1 in 91 results was noted.

Cross-jurisdictional transmission of Mycobacterium tuberculosis in Maryland and Washington, D C, 1996-2000, linked to the homeless

From 1996 to 2000, 23 Maryland and Washington, D.C., tuberculosis cases were identified in one six-band DNA cluster. Cases were clustered on the basis of their Mycobacterium tuberculosis isolates. Medical record reviews and interviews were conducted to identify epidemiologic linkages. Eighteen (78%) of the 23 case-patients with identical restriction fragment length polymorphism patterns were linked to another member; half the patients were associated with a Washington, D.C., homeless shelter. Molecular epidemiology defined the extent of this large, cross-jurisdictional outbreak.

Genetic diversity and evidence for acquired antimicrobial resistance in Mycobacterium tuberculosis at a large hospital in South India

OBJECTIVE

To assess genetic diversity and drug resistance of Mycobacterium tuberculosis isolates collected at Christian Medical College Hospital (CMCH), Vellore, India, between July 1995 and May 1996.

MATERIALS AND METHODS

Isolates were subjected to IS6110-based restriction fragment length polymorphism (RFLP) analysis and tested for resistance to isoniazid, rifampin, ethambutol, streptomycin, and pyrazinamide, and DNA from selected strains was sequenced in regions associated with drug resistance.

RESULTS

One hundred and one M. tuberculosis isolates were collected from 87 patients with pulmonary tuberculosis. Charts of 69 patients were reviewed for history of tuberculosis illness and treatment. DNA from 29 strains was sequenced in katG, rpoB, and gyrA, and sometimes pncA regions. Analysis by RFLP revealed a high degree of genetic diversity, with no identifiable clusters of infection. Of the strains tested, 51% were resistant to at least one antibiotic, and 43% were resistant to more than one drug. There was a high rate of resistance observed in patients whose charts indicated a history of improperly administered tuberculosis treatment, whereas little drug resistance was observed in patients never previously treated for tuberculosis. Sequencing of genes associated with drug resistance revealed several previously unreported mutations in resistant strains.

CONCLUSIONS

This analysis suggests that the cases of tuberculosis in the sample are largely reactivation of long-standing infections and that the drug resistance among patients in CMCH is largely acquired or secondary rather than attributable to the spread of drug-resistant strains.

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

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

Genotypic characterization of drug-resistant Mycobacterium tuberculosis isolates from Peru

SETTING

Twenty-nine epidemiological unrelated and mostly multidrug-resistant Mycobacterium tuberculosis (MDR-TB) strains from Peruvian patients.

OBJECTIVE

To investigate the molecular genetics of MDR-TB strains recovered in a Latin American country.

DESIGN

Antimicrobial agent susceptibility testing, major genetic group designation, IS6110 fingerprinting, spoligotyping, and automated deoxyribonucleic acid sequencing of regions of the katG, rpoB, embB, gyrA, and pncA genes with mutations commonly associated with drug resistance.

RESULTS

Nineteen isolates were found to be multidrug-resistant by susceptibility testing. IS6110 typing showed that virtually all isolates were unique and therefore had independently acquired drug resistance. Seventy-nine percent of isoniazid-resistant strains had a Ser315Thr amino acid change in KatG. Ninety-five percent of rifampin-resistant isolates had amino acid replacements in the rifampin-resistance determining region of RpoB. Six of 11 ethambutol-resistant strains had EmbB alterations. Eleven pyrazinamide-resistant strains had distinct mutations in pncA.

CONCLUSION

Virtually all organisms evolved drug resistance independently. The types of drug resistance-associated mutations identified were very similar to changes occurring in isolates from other areas of the world. Nucleotide sequence-based strategies for rapid detection of drug resistance-conferring mutants will be applicable to organisms recovered in Peru, and potentially other areas of Latin America.

Transmission of Mycobacterium tuberculosis from patients smear-negative for acid-fast bacilli

BACKGROUND

The microscopic examination of sputum for acid-fast bacilli, is a simple and rapid test that is used to provide a presumptive diagnosis of infectious tuberculosis. While patients with tuberculosis with sputum smears negative for acid-fast bacilli are less infectious than those with positive smears, both theoretical and empirical evidence suggest that they can still transmit Mycobacterium tuberculosis. We aimed to estimate the risk of transmission from smear-negative individuals.

METHODS

As part of an ongoing study of the molecular epidemiology of tuberculosis in San Francisco, patients with tuberculosis with mycobacterial isolates with the same DNA fingerprint were assigned to clusters that were assumed to have involved recent transmission. Secondary cases with tuberculosis, whose mycobacterial isolates had the same DNA, were linked to their presumed source case to estimate transmission from smear-negative patients. Sensitivity analyses were done to assess potential bias due to misclassification of source cases, unidentified source cases, and HIV-1 co-infection.

FINDINGS

1574 patients with culture-positive tuberculosis were reported and DNA fingerprints were available for 1359 (86%) of these patients. Of the 71 clusters of patients infected with strains that had matching fingerprints, 28 (39% [95% CI 28-52]) had a smear-negative putative source. There were 183 secondary cases in these 71 clusters, of whom a minimum of 32 were attributed to infection by smear-negative patients (17% [12-24]). The relative transmission rate of smear-negative compared with smear-positive patients was calculated as 0.22 (95% CI 0.16-0.32). Sensitivity analyses and stratification for HIV-1 status had no impact on these estimates.

INTERPRETATION

In San Francisco, the acid-fast-bacilli smear identifies the most infectious patients, but patients with smear-negative culture-positive tuberculosis appear responsible for about 17% of tuberculosis transmission.

Population biology, evolution, and infectious disease: convergence and synthesis

Traditionally, the interest of population and evolutionary biologists in infectious diseases has been almost exclusively in their role as agents of natural selection in higher organisms. Recently, this interest has expanded to include the genetic structure and evolution of microparasite populations, the mechanisms of pathogenesis and the immune response, and the population biology, ecology, and evolutionary consequences of medical and public health interventions. This article describes recent work in these areas, emphasizing the ways in which quantitative, population-biological approaches have been contributing to the understanding of infectious disease and the design and evaluation of interventions for their treatment and prevention.

Mycobacterium tuberculosis infection after travel to or contact with visitors from countries with a high prevalence of tuberculosis

To assess whether there is increased risk of tuberculous infection in children who traveled to or had a household visitor from a country having a high prevalence of tuberculosis, we conducted a case-control study. Children younger than 6 yr of age who had a tuberculin skin test read at public health clinics in areas of California that have a high prevalence of tuberculosis were enrolled. Of the 953 children who had a skin test read, 72 (7.6%) had a positive reaction. By multiple logistic regression analysis, children who had traveled in the 12 mo before the skin test were 3.9 times more likely to have a positive skin test than were children who had not traveled (95% confidence interval [CI], 1.9 to 7.9). Among children born in the United States, those who had traveled were 4.7 times more likely to have a positive skin test (95% CI, 2.0 to 11.2). Children who had a household visitor from a country having a high prevalence of tuberculosis were 2.4 times more likely to have a positive skin test than were those who did not have a visitor (95% CI, 1.0 to 5.5). These data indicate that travel to a country that has a high prevalence of tuberculosis or having a visitor from such countries increase the risk of tuberculous infection among young children. Physicians and tuberculosis control programs should incorporate questions about travel and visitors into their evaluations, and children with a history of extended travel should have a tuberculin skin test.

The tuberculosis epidemic. Scientific challenges and opportunities

One in every three people on Earth is believed to be infected with Mycobacterium tuberculosis, leading to seven to eight million cases of active tuberculosis (TB) per year and approximately three million deaths annually. this epidemic, like those of most infectious diseases, creates scientific challenges and opportunities as it raises the demand for public health solutions. The currently available weapons for fighting TB are inadequate. The ultimate goal of biomedical TB research is to lessen the public health burden of this disease by developing improved diagnostic, therapeutic, and intervention strategies. Achieving this goal requires a base of knowledge about the biology of M. tuberculosis and related mycobacteria, their interactions with human and animal hosts, and the nature of an effective host-protective immune response. TB researchers are applying this accumulating base of knowledge to developing rapid, easy-to-use diagnostic assays appropriate for low-as well as high-income countries, improving the current complicated therapeutic regimen, identifying potential new drugs to combat multidrug-resistant TB, and creating more effective vaccines.

Susceptibility to levofloxacin of Myocobacterium tuberculosis isolates from patients with HIV-related tuberculosis and characterization of a strain with levofloxacin monoresistance. Community Programs for Clinical Research on AIDS 019 and the AIDS Clinical Trials Group 222 Protocol Team

OBJECTIVE

To characterize the susceptibility to levofloxacin of clinical isolates of Mycobacterium tuberculosis (MTB) obtained from patients with HIV-related tuberculosis and to characterize the molecular genetics of levofloxacin resistance.

DESIGN AND METHODS

Isolates from culture-positive patients in a United States multicenter trial of HIV-related TB were tested for susceptibility to levofloxacin by minimum inhibitory concentration (MIC) determinations in Bactec 7H12 broth. Automated sequencing of the resistance determining region of gyrA was performed.

RESULTS

Of the 135 baseline MTB isolates tested, 134 (99%; 95% exact binomial confidence interval, 95.9-99.9%) were susceptible to levofloxacin with an MIC < or = 1.0 microg/ml. We identified a previously unrecognized mis-sense mutation occurring at codon 88 of gyrA in a levofloxacin mono-resistant MTB isolate obtained from a patient with AIDS who had received ofloxacin for 8 months prior to the diagnosis of tuberculosis.

CONCLUSIONS

Clinical MTB isolates from HIV-infected patients were generally susceptible to levofloxacin. However, the identification of a clinical isolate with mono-resistance to levofloxacin highlights the need for circumspection in the use of fluoroquinolones in the setting of potential HIV-related tuberculosis and for monitoring of rates of resistance of MTB isolates to fluoroquinolones.

DNA fingerprints from Mycobacterium tuberculosis isolates of patients confined for therapy noncompliance show frequent clustering

STUDY OBJECTIVE

To test the hypothesis that individuals chronically noncompliant with antituberculous chemotherapy are vectors for ongoing transmission of the disease in the community.

DESIGN

Cohort study.

SETTING

A large public hospital with a tuberculosis detention unit for patients with repeated and prolonged nonadherence to therapy.

PATIENTS

Mycobacterium tuberculosis isolates from patients confined on the detention unit were obtained from the hospital's mycobacteriology laboratory.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

A standardized IS6110-based Southern blot hybridization protocol was used to genotype M tuberculosis isolates recovered from patients confined on the detention unit at the hospital. Each DNA fingerprint pattern was compared with the IS6110-fingerprint database at the Public Health Research Institute Tuberculosis Center, which has archived fingerprint patterns from over 2,500 M tuberculosis isolates collected from New York City patients in the past 5 years. Eighty percent of available isolates from detained patients belonged to an identifiable DNA fingerprint cluster, suggesting an epidemiologic link between the detainees and other New York City tuberculosis patients.

CONCLUSIONS

Chronic noncompliance with therapy is associated with ongoing spread of tuberculosis in the community. Aggressive measures, including detention, for the small number of recalcitrant, noncompliant patients may interrupt a chain of transmission and contribute to a decline in the spread of tuberculosis in urban areas.