Anti-tuberculosis Drug Resistance Surveillance Research Articles

The Emergence of Novel Spoligotypes of Highly Drug-Resistant Mycobacterium tuberculosis Isolates in Fujian, China.

BackgroundHere, we aimed to determine the population structure of Mycobacterium tuberculosis (MTB) genotypes in Fujian and explore risk factors associated with infection with the Beijing genotype. We also explored the association between Beijing genotype and drug resistance.MethodsRepresentative MTB isolates obtained during provincial-level routine anti-tuberculosis drug resistance surveillance conducted since 2013 in 11 Fujian counties were analyzed using McSpoligotyping. In vitro drug susceptibilities to anti-tuberculosis drugs were determined using the standard Löwenstein–Jensen proportion method.ResultsOverall, 477 MTB isolates were included in the study, of which 245 isolates belonged to the Beijing genotype family and 232 possessed non-Beijing genotypes. Ultimately, a total of 204 spoligotypes were identified that included 58 spoligotype international types (SITs) from the SITVITWEB database and 146 novel spoligotypes. As compared to patients <25 years of age (control group), elderly patients (≥65 years of age) were more likely to be infected with non-Beijing genotypes [aOR 18.69, 95% CI (5.80–60.26)], with risk of infection with non-Beijing genotypes increasing with age [aOR 3.73, 95% CI (1.67–8.30) for patients 45–64 years of age]. Additionally, as compared to isolates with Beijing and other non-Beijing genotypes, significantly greater proportions of isolates with novel spoligotypes exhibited PTO- and PAS-resistance. Moreover, a markedly higher proportion of isolates with novel spoligotypes exhibited OFX-resistance as compared to isolates with other non-Beijing genotypes.ConclusionOur data demonstrated that the Beijing genotype is the predominant MTB sublineage in Fujian and that the prevalence rate of infection with this MTB genotype decreases with advancing patient age. Notably, the prevalence rate of this genotype in Fujian TB patients is relatively lower than in other regions of China. In addition, the emergence of novel spoligotypes of highly drug-resistant MTB isolates highlights the urgent need for ongoing molecular genotyping surveillance in Fujian.

Multidrug Resistant Tuberculosis: Trends and Control

Multidrug resistant tuberculosis (MDR-TB) has been an area of growing concern and is posing a threat to the control of tuberculosis (TB). The exact magnitude of problem of resistance to anti-tuberculosis drugs worldwide was not known till the 1994-97 global project on anti-tuberculosis drug resistance surveillance initiated by the World Health Organization (WHO) and International Union Against Tuberculosis and Lung Diseases (IUATLD). The Global Tuberculosis Report 2014 estimated that an 3.5% of newly diagnosed and 20.5% of previously treated.TB cases had MDR-TB. It has been estimated that 480,000 cases emerged and 210,000 deaths occurred due to MDR-TB globally in 2013. In India, estimates showed that the prevalence of MDR-TB among new and previously treated patients was 2.2% and 15%, respectively. It is estimated that 99,000 cases of MDR-TB emerge every year of which 62,000 were among notified cases of TB in 2013. The MDR-TB is a human-made problem and results largely from poorly managed cases of TB. Adequate, timely diagnosis and optimal treatment of MDR-TB will help curb the epidemic. Efforts must be focused on the effective use of anti-tuberculosis drugs in every new patient, so as to prevent the emergence of MDR-TB.

Application of generalized estimation equations to establish prediction equation for tuberculosis drug resistance in Zhejiang province

Objective: Drug-resistant tuberculosis (TB) may be resistant to one or multiple anti-TB drugs. We used generalized estimation equations to analysis the risk factors of drug-resistant TB and provide information for the establishment of a warning model for these non-independent data. Methods: The drug susceptibility test and questionnaire survey were performed in sputum positive TB patients from 30 anti TB drug-resistance surveillance sites in Zhejiang province. The generalized estimation model was established by the GENMOD module of SAS, with resistance to 13 kinds of anti-TB drugs as dependent variables and possible influencing factors, such as age, having insurance, HBV infection status, and history of anti-TB drug intake, as independent variables. Results: In this study, the probability of drug resistance at baseline level was 20.26%. Age, insurance, whether being co-infected with HBV, and treatment history or treatment withdrawal were statistically significantly correlated with anti-TB drug resistance. The prediction equation was established according to the influence degree of the factors mentioned above on drug resistance. Conclusion: The generalized estimation equations can effectively and robustly analyze the correlated binary outcomes, and thus provide more comprehensive information for drug resistance risk factor evaluation and warning model establishment.

Antituberculosis Drug Resistance in Pulmonary Isolates of Mycobacterium tuberculosis, Cuba 2012–2014

ABSTRACT INTRODUCTION Systematic surveillance of antituberculosis drug resistance allows identification of multidrug-resistant and extensively drug-resistant isolates of Mycobacterium tuberculosis. Surveillance studies of antituberculosis drug resistance systematically conducted in Cuba for over 15 years have revealed low circulation of multidrug-resistant tuberculosis, under 1% in new cases. OBJECTIVE Characterize antituberculosis drug resistance in isolates of M. tuberculosis recovered from patients with pulmonary tuberculosis in Cuba in 2012–2014. METHODS The nitrate reductase assay was used to test 997 isolates of M. tuberculosis for sensitivity to isoniazid and rifampicin. Isolates identified as multidrug resistant were tested for sensitivity to isoniazid, rifampicin, streptomycin, ethambutol, ofloxacin, amikacin, kanamycin and capreomycin by the proportion method, as well as genetic resistance mutations in rpoB, katG, inhA, gyrA, rrs and embB genes, using GenoType MTBDRplus and MTBDRsl commercial kits. RESULTS Some 95.6% of isolates from new cases and 89.6% of isolates from previously treated patients were sensitive to isoniazid and rifampicin. Multidrug resistance was found in 0.8% of new and 5.2% of previously treated patients, a statistically significant difference. One extensively drug-resistant isolate was detected among previously treated cases. All isolates examined with the molecular method had mutations in the rpoB gene, which is associated with resistance to rifampicin; only seven showed mutations in the katG gene and one in the inhA gene associated with isoniazid resistance. In one isolate, we found mutations in both gyrA and rrs genes, which are associated with resistance to fluoroquinolones and second-line injectable drugs and therefore, extensive resistance. CONCLUSIONS Results corroborate the low frequency of multidrug-resistant and extensively resistant M. tuberculosis strains in Cuba and highlight the need for continuous improvement of surveillance of antituberculosis drug resistance in Cuba.

Antituberculosis Drug Resistance in Pulmonary Isolates of Mycobacterium tuberculosis, Cuba 2012-2014.

INTRODUCTION Systematic surveillance of antituberculosis drug resistance allows identification of multidrug-resistant and extensively drug-resistant isolates of Mycobacterium tuberculosis. Surveillance studies of antituberculosis drug resistance systematically conducted in Cuba for over 15 years have revealed low circulation of multidrug-resistant tuberculosis, under 1% in new cases. OBJECTIVE Characterize antituberculosis drug resistance in isolates of M. tuberculosis recovered from patients with pulmonary tuberculosis in Cuba in 2012-2014. METHODS The nitrate reductase assay was used to test 997 isolates of M. tuberculosis for sensitivity to isoniazid and rifampicin. Isolates identified as multidrug resistant were tested for sensitivity to isoniazid, rifampicin, streptomycin, ethambutol, ofloxacin, amikacin, kanamycin and capreomycin by the proportion method, as well as genetic resistance mutations in rpoB, katG, inhA, gyrA, rrs and embB genes, using GenoType MTBDRplus and MTBDRsl commercial kits. RESULTS Some 95.6% of isolates from new cases and 89.6% of isolates from previously treated patients were sensitive to isoniazid and rifampicin. Multidrug resistance was found in 0.8% of new and 5.2% of previously treated patients, a statistically significant difference. One extensively drug-resistant isolate was detected among previously treated cases. All isolates examined with the molecular method had mutations in the rpoB gene, which is associated with resistance to rifampicin; only seven showed mutations in the katG gene and one in the inhA gene associated with isoniazid resistance. In one isolate, we found mutations in both gyrA and rrs genes, which are associated with resistance to fluoroquinolones and second-line injectable drugs and therefore, extensive resistance. CONCLUSIONS Results corroborate the low frequency of multidrug-resistant and extensively resistant M. tuberculosis strains in Cuba and highlight the need for continuous improvement of surveillance of antituberculosis drug resistance in Cuba. KEYWORDS Mycobacterium tuberculosis, multidrug resistance, extensively drug-resistant tuberculosis, Cuba.

Global burden of drug-resistant tuberculosis in children: a mathematical modelling study

After infection with Mycobacterium tuberculosis, children are at an increased risk of progression to tuberculosis disease; a condition that can be challenging to diagnose. New estimation approaches for children have highlighted the gap between incidence and notifications of M tuberculosis, and suggest there are more cases of isoniazid-resistant and multidrug-resistant (MDR) disease than are identified. No work has yet quantified the burden of drug-resistant infection, or accounted for other types of drug resistance or sampling uncertainty. We combined a mathematical model of tuberculosis in children with an analysis of drug-resistance patterns to produce country-level, regional, and global estimates of drug-resistant infection and disease. We determined drug resistance using data from the Global Project on Antituberculosis Drug Resistance Surveillance at WHO, from surveys and surveillance reported between 1988 and 2014. We combined 1000 sampled proportions for each country from a Bayesian approach with 10 000 sampled country estimates of tuberculosis disease incidence and M tuberculosis infection prevalence. We estimated the proportions of tuberculosis cases at a country level with isoniazid monoresistance, rifampicin monoresistance, multidrug resistance (MDR), fluoroquinolone-resistant multidrug resistance, second-line injectable-resistant multidrug resistance, and extensive multidrug resistance with resistance to both a fluoroquinolone and a second-line injectable (XDR). We estimated that 850 000 children developed tuberculosis in 2014; 58 000 with isoniazid-monoresistant tuberculosis, 25 000 with MDR tuberculosis, and 1200 with XDR tuberculosis. We estimate 67 million children are infected with M tuberculosis; 5 million with isoniazid monoresistance, 2 million with MDR, and 100 000 with XDR. Africa and southeast Asia have the highest numbers of children with tuberculosis, but the WHO Eastern Mediterranean region, European region, and Western Pacific region also contribute substantially to the burden of drug-resistant tuberculosis because of their much higher proportions of resistance. Far more drug-resistant tuberculosis occurs in children than is diagnosed, and there is a large pool of drug-resistant infection. This finding has implications for approaches to empirical treatment and preventive therapy in some regions of the world. UNITAID.

On the spread and control of MDR-TB epidemics: an examination of trends in anti-tuberculosis drug resistance surveillance data.

Multidrug resistant tuberculosis (MDR-TB) poses serious challenges for tuberculosis control in many settings, but trends of MDR-TB have been difficult to measure. We analyzed surveillance and population-representative survey data collected worldwide by the World Health Organization between 1993 and 2012. We examined setting-specific patterns associated with linear trends in the estimated per capita rate of MDR-TB among new notified TB cases to generate hypotheses about factors associated with trends in the transmission of highly drug resistant tuberculosis. 59 countries and 39 sub-national settings had at least three years of data, but less than 10% of the population in the WHO-designated 27-high MDR-TB burden settings were in areas with sufficient data to track trends. Among settings in which the majority of MDR-TB was autochthonous, we found 10 settings with statistically significant linear trends in per capita rates of MDR-TB among new notified TB cases. Five of these settings had declining trends (Estonia, Latvia, Macao, Hong Kong, and Portugal) ranging from decreases of 3% to 14% annually, while five had increasing trends (four individual oblasts of the Russian Federation and Botswana) ranging from 14% to 20% annually. In unadjusted analysis, better surveillance indicators and higher GDP per capita were associated with declining MDR-TB, while a higher existing absolute burden of MDR-TB was associated with an increasing trend. Only a small fraction of countries in which the burden of MDR-TB is concentrated currently have sufficient surveillance data to estimate trends in drug-resistant TB. Where trend analysis was possible, smaller absolute burdens of MDR-TB and more robust surveillance systems were associated with declining per capita rates of MDR-TB among new notified cases.

Vigilancia de la resistencia a los medicamentos antituberculosos en Cuba, 2010-2011

Introduction: Antituberculosis-drug resistance surveillance is very important to identify multidrug-resistant and extensively drug-resistant Mycobacterium tuberculosis isolates.Objective: To determine the prevalence of resistance in M. tuberculosis strains isolated between 2010 and 2011, and to demonstrate the laboratory performance in the external quality control of drug susceptibility testing.Materials and methods: A prospective longitudinal study was carried out to determine antituberculosis-drug resistance in 657 M. tuberculosis isolates obtained throughout the country. The nitrate reductase assay was used to detect resistance to isoniazid and rifampin. The proportion method was performed to confirm resistance to these drugs and to further investigate in multidrug-resistant isolates their susceptibility to streptomycin, ethambutol, ofloxacin, kanamycin and capreomycin. Additionally, as part of external quality control, susceptibility was evaluated in two M. tuberculosis strain panels.Results: In 95.69% of the isolates recovered from new tuberculosis cases, and in 72.64% of isolates from previously treated patients we found susceptibility to isoniazid and rifampicin; multidrug resistance was 1,03 and 10.38%, respectively. We found two extensively resistant isolates. Except for ethambutol and capreomycin, the efficiency of all other drugs was 100% in the external quality control.Conclusion: The study confirmed the low prevalence of M. tuberculosis multidrug-resistant isolates in Cuba. This result was confirmed by the external quality control of drug susceptibility testing.

Surveillance of antituberculosis-drug resistance in Cuba, 2010-2011

Antituberculosis-drug resistance surveillance is very important to identify multidrug-resistant and extensively drug-resistant Mycobacterium tuberculosis isolates. To determine the prevalence of resistance in M. tuberculosis strains isolated between 2010 and 2011, and to demonstrate the laboratory performance in the external quality control of drug susceptibility testing. A prospective longitudinal study was carried out to determine antituberculosis-drug resistance in 657 M. tuberculosis isolates obtained throughout the country. The nitrate reductase assay was used to detect resistance to isoniazid and rifampin. The proportion method was performed to confirm resistance to these drugs and to further investigate in multidrug-resistant isolates their susceptibility to streptomycin, ethambutol, ofloxacin, kanamycin and capreomycin. Additionally, as part of external quality control, susceptibility was evaluated in two M. tuberculosis strain panels. In 95.69% of the isolates recovered from new tuberculosis cases, and in 72.64 % of isolates from previously treated patients we found susceptibility to isoniazid and rifampicin; multidrug resistance was 1,03 and 10.38%, respectively. We found two extensively resistant isolates. Except for ethambutol and capreomycin, the efficiency of all other drugs was 100% in the external quality control. The study confirmed the low prevalence of M. tuberculosis multidrug-resistant isolates in Cuba. This result was confirmed by the external quality control of drug susceptibility testing.

Multidrug resistance in new tuberculosis patients: burden and implications [Short communication

In 2010, 30 countries with anti-tuberculosis drug resistance surveillance data were each estimated to have more than 700 multidrug-resistant tuberculosis (MDR-TB) cases among their notified TB cases. New TB patients comprised a median of 54% (interquartile range 45-67) of the MDR-TB cases. The occurrence of MDR-TB in a new TB patient is a warning sign that MDR-TB is spreading in a community. While MDR-TB case-finding efforts should first prioritize previously treated patients, reaching universal access requires rapidly adding other risk groups, and then all new TB patients. Epidemiological data as presented in this paper can help inform country scale-up plans.

Evaluation of DNA microarray for detection of rifampin and isoniazid resistance in Mycobacterium tuberculosis isolates

Objective To evaluate the performance of DNA microarray for rapid detection resistance to rifampin and isoniazid in Mycobacterium tuberculosis clinical isolates and identify suitable target sites for molecular genetic test. Methods Twenty-four clinical Mycobacterium tuberculosis isolates were collected retrospectively from Shenzhen Center for Chronic Disease Control in 2009 and 127 isolates from project on anti-tuberculosis drug resistance surveillance in Shenzhen during 2007 to 2009.Drug susceptibility to rifampin and isoniazid of the stains were determined by DNA microarray, and results were compared to that obtained with reference proportion method drug susceptibility testing for sensitivity, specificity and accuracy.The consistency of microarray and phenotypic susceptibility testing was evaluated by Kappa test.Genetic mutations in rpoB, katG, inhA，regulatory region of inhA, and regulatory region of ahpC were investigated by DNA sequencing to assess proper loci for rapid molecular diagnosis. Results Compared against results of proportion method, the sensitivity, specificity and accuracy of the DNA microarray assay for rifampin resistance were 94.4%, 97.5% and 96.0% respectively, and for isoniazid resistance were 79.1%, 100% and 86.8% respectively.Mutations in resistance-determining region of rpoB were observed in 97.2%（70/72） of the isolates resistant to rifampin, which contributed in the 531, 526, 516, 511 and 533 codon region.Mutations in katG315 codon, inhA-15, and ahpC regulatory region were found in 70.3%（64/91）, 11.0%（10/91） and 9.9%（9/90） of the isolates resistant to isoniazid, respectively.Mutations of ahpC promoter region consists of ahpC-9 (4 strains), ahpC-10 (2 strains), ahpC-6 (2 strains), ahpC-12 (1 strain), and ahpC-32 (1 strain). Conclusions DNA microarray provided a rapid method for the detection of drug-resistant Mycobacterium tuberculosis isolates, and demonstrated good performance except less sensitive for isoniazid resistance.The mutations in ahpC regulatory region might be good target loci for detection of isoniazid-resistant Mycobacterium tuberculosis, so screening the region may significantly improve the sensitivity for molecular genetic tests.（Chin J Lab Med,2012,35:1125-1129） Key words: Mycobacterium tuberculosis; Drug resistance; bacterial; Rifampin; Isoniazid; Oligonucleotide array sequence analysis

Prevalence of Anti-Tuberculosis Drug Resistance in Foreign-Born Tuberculosis Cases in the U.S. and in Their Countries of Origin

BackgroundForeign-born individuals comprise >50% of tuberculosis (TB) cases in the U.S. Since anti-TB drug resistance is more common in most other countries, when evaluating a foreign-born individual for TB, one must consider the risk of drug resistance. Naturally, clinicians query The Global Project on Anti-tuberculosis Drug Resistance Surveillance (Global DRS) which provides population-based data on the prevalence of anti-TB drug resistance in 127 countries starting in 1994. However, foreign-born persons in the U.S. are a biased sample of the population of their countries of origin, and Global DRS data may not accurately predict their risk of drug resistance. Since implementing drug resistance surveillance in 1993, the U.S. National TB Surveillance System (NTSS) has accumulated systematic data on over 130,000 foreign-born TB cases from more than 200 countries and territories. Our objective was to determine whether the prevalence of drug resistance among foreign-born TB cases correlates better with data from the Global DRS or with data on foreign-born TB cases in the NTSS.Methods and FindingsWe compared the prevalence of resistance to isoniazid and rifampin among foreign-born TB cases in the U.S., 2007–2009, with US NTSS data from 1993 to 2006 and with Global DRS data from 1994–2007 visually with scatterplots and statistically with correlation and linear regression analyses. Among foreign-born TB cases in the U.S., 2007–2009, the prevalence of isoniazid resistance and multidrug resistance (MDR, i.e. resistance to isoniazid and rifampin), correlated much better with 1993–2006 US surveillance data (isoniazid: r = 0.95, P<.001, MDR: r = 0.75, P<.001) than with Global DRS data, 1994–2007 (isoniazid: r = 0.55, P = .001; MDR: r = 0.50, P<.001).ConclusionSince 1993, the US NTSS has accumulated sufficient data on foreign-born TB cases to estimate the risk of drug resistance among such individuals better than data from the Global DRS.

An In Vivo Platform for Rapid High-Throughput Antitubercular Drug Discovery

Treatment of tuberculosis, like other infectious diseases, is increasingly hindered by the emergence of drug resistance. Drug discovery efforts would be facilitated by facile screening tools that incorporate the complexities of human disease. Mycobacterium marinum-infected zebrafish larvae recapitulate key aspects of tuberculosis pathogenesis and drug treatment. Here, we develop a model for rapid in vivo drug screening using fluorescence-based methods for serial quantitative assessment of drug efficacy and toxicity. We provide proof-of-concept that both traditional bacterial-targeting antitubercular drugs and newly identified host-targeting drugs would be discovered through the use of this model. We demonstrate the model's utility for the identification of synergistic combinations of antibacterial drugs and demonstrate synergy between bacterial- and host-targeting compounds. Thus, the platform can be used to identify new antibacterial agents and entirely new classes of drugs that thwart infection by targeting host pathways. The methods developed here should be widely applicable to small-molecule screens for other infectious and noninfectious diseases.

Effective Interventions and Decline of Antituberculosis Drug Resistance in Eastern Taiwan, 2004–2008

BackgroundThe Taiwan health authority recently launched several tuberculosis (TB) control interventions, which may have an impact on the epidemic of drug-resistant TB. We conducted a population-based antituberculosis drug resistance surveillance program in Eastern Taiwan to measure the proportions of notified TB patients with anti-TB drug resistance and the trend from 2004 to 2008.Methods and FindingsAll culture-positive TB patients were enrolled. Drug susceptibility testing results of the first isolate of each TB patient in each treatment course were analyzed. In total, 2688 patients were included, of which 2176 (81.0%) were new TB cases and 512 (19.0%) were previously treated cases. Among the 2176 new TB cases, 97 (4.5%) were retreated after the first episode of TB treatment within the study period. The proportion of new patients with any resistance, isoniazid resistance but not multidrug-resistant TB (resistant to at least isoniazid and rifampin, MDR-TB), and MDR-TB was 16.4%, 7.5%, and 4.0%, respectively, and that among previously treated cases was 30.9%, 7.9%, and 17.6%, respectively. The combined proportion of any resistance decreased from 23.3% in 2004 to 14.3% in 2008, and that of MDR-TB from 11.5% to 2.4%.ConclusionsThe proportion of TB patients with drug-resistant TB in Eastern Taiwan remains substantial. However, an effective TB control program has successfully driven the proportion of drug resistance among TB patients downward.

Multidrug-resistant tuberculosis today

The World Health Organization (WHO) and its partners have long conducted efforts to improve tuberculosis (TB) case surveillance and programme monitoring and evaluation. WHO’s 2011 report on global TB control1 provided the most reliable information ever generated on the burden of disease and death caused by TB and multidrug-resistant TB (i.e. disease marked by in vitro resistance to at least isoniazid and rifampicin), treatment outcomes, financing mechanisms and new TB diagnostics, drugs and vaccines. The Global Project on Anti-tuberculosis Drug Resistance Surveillance, launched in 1994, has generated reliable drug resistance estimates for 127 countries based on representative studies that followed standard methods and separately looked at resistance among new and retreatment cases.2 The article by Zignol et al. in this issue of the Bulletin3 draws on those estimates to portray the best of current knowledge on anti-TB drug resistance, multidrug-resistant TB (MDR-TB) and extensively-drug-resistant TB (XDR-TB) (i.e. MDR-TB disease marked by additional in vitro resistance to at least one fluoroquinolone and one injectable drug). Zignol et al.’s report confirms that a belt of MDR-TB exists in eastern Europe and central Asia, as suggested by a recent study describing record rates of MDR-TB in Minsk, Belarus,4 where about half of all TB cases harbour MDR-TB strains. The finding that many countries in the same area still lack reliable MDR-TB surveillance systems is therefore highly worrisome. Efforts to understand how MDR-TB is evolving in African countries, India and the Russian Federation are also critically important. XDR-TB has been identified wherever it has been studied. In countries reporting nationally representative data, 10% of MDR-TB cases are extensively drug-resistant. The availability of good data for multiple years from 51 countries has finally made it possible to study trends in anti-TB drug resistance and to objectively examine why MDR-TB is increasing in some parts of the world and decreasing in others. We must now explore the determinants of these trends, learn from model programmes and delve into poorly understood areas and into the factors that influence how fast MDR-TB is declining in different places – slowly in Russian Federation oblasts, moderately fast in Estonia and Latvia, and fast in the United States of America. Furthermore, Zignol et al.’s suggestion that in the Republic of Korea therapeutic practices within the private sector may explain the increase in MDR-TB raises challenging questions. Finally, Zignol et al.’s report shows that MDR-TB surveillance is improving and is a useful source of data for investigating the basic determinants of MDR-TB. Sex did not emerge as an important determinant, and the long-feared association between MDR-TB and human immunodeficiency virus (HIV) infection was not supported by the study findings. However, the unavailability of data on HIV serostatus for many countries – not surprising since only 34% of the world’s confirmed TB cases are tested for HIV1 – dictates caution in interpreting this finding. It also reminds us of how difficult it is to incorporate HIV testing in TB drug resistance surveys and of how far away we are from fully implementing the 12 activities for collaborative control of TB and HIV infection recommended by WHO.5,6 The mismanagement of non-drug-resistant TB cases, which leads to drug resistance, is a continuing problem everywhere, even in high-income European countries with low TB incidence.7 The resulting growing reservoir of difficult-to-treat cases poses a challenge to national TB programmes and health systems all over the world.8 The number of incurable XDR-TB cases is on the rise in several countries, and properly caring for these cases, and especially for those experiencing treatment failure, is difficult and has obvious logistical, ethical and economic implications.8 Zignol et al.’s lucid report paves the way for targeted public health action in MDR-TB prevention and control. Although new molecular technologies, including line probe assays and Xpert® MTB/RIF, can allow the rapid diagnosis of thousands of MDR-TB cases, not all countries will be ready to treat those cases in compliance with appropriate guidelines. This obviously poses some risk of generating new super-resistant strains. On the positive side, at least two new forthcoming drugs – bedaquiline and delamanid – will reinforce our treatment armamentarium. The data presented by Zignol et al. should prompt us to make every effort to ensure their proper use.

Surveillance of anti-tuberculosis drug resistance in the world: an updated analysis, 2007–2010

To present a global update of drug-resistant tuberculosis (TB) and explore trends in 1994-2010. Data on drug resistance among new and previously treated TB patients, as reported by countries to the World Health Organization, were analysed. Such data are collected through surveys of a representative sample of TB patients or surveillance systems based on routine drug susceptibility testing. Associations between multidrug-resistant TB (MDR-TB) and human immunodeficiency virus (HIV) infection and sex were explored through logistic regression. In 2007-2010, 80 countries and 8 territories reported surveillance data. MDR-TB among new and previously treated cases was highest in the Russian Federation (Murmansk oblast, 28.9%) and the Republic of Moldova (65.1%), respectively. In three former Soviet Union countries and South Africa, more than 10% of the cases of MDR-TB were extensively drug-resistant. Globally, in 1994 to 2010 multidrug resistance was observed in 3.4% (95% confidence interval, CI: 1.9-5.0) of all new TB cases and in 19.8% (95% CI: 14.4-25.1) of previously treated TB cases. No overall associations between MDR-TB and HIV infection (odds ratio, OR: 1.4; 95% CI: 0.7-3.0) or sex (OR: 1.1; 95% CI: 0.8-1.4) were found. Between 1994 and 2010, MDR-TB rates in the general population increased in Botswana, Peru, the Republic of Korea and declined in Estonia, Latvia and the United States of America. The highest global rates of MDR-TB ever reported were documented in 2009 and 2010. Trends in MDR-TB are still unclear in most settings. Better surveillance or survey data are required, especially from Africa and India.

Spatial epidemiology and spatial ecology study of worldwide drug-resistant tuberculosis.

BackgroundDrug-resistant tuberculosis (DR-TB) is a major public health problem caused by various factors. It is essential to systematically investigate the epidemiological and, in particular, the ecological factors of DR-TB for its prevention and control. Studies of the ecological factors can provide information on etiology, and assist in the effective prevention and control of disease. So it is of great significance for public health to explore the ecological factors of DR-TB, which can provide guidance for formulating regional prevention and control strategies.MethodsAnti-TB drug resistance data were obtained from the World Health Organization/International Union Against Tuberculosis and Lung Disease (WHO/UNION) Global Project on Anti-Tuberculosis Drug Resistance Surveillance, and data on ecological factors were collected to explore the ecological factors for DR-TB. Partial least square path modeling (PLS-PM), in combination with ordinary least squares (OLS) regression, as well as geographically weighted regression (GWR), were used to build a global and local spatial regression model between the latent synthetic DR-TB factor ("DR-TB") and latent synthetic risk factors.ResultsOLS regression and PLS-PM indicated a significant globally linear spatial association between "DR-TB" and its latent synthetic risk factors. However, the GWR model showed marked spatial variability across the study regions. The "TB Epidemic", "Health Service" and "DOTS (directly-observed treatment strategy) Effect" factors were all positively related to "DR-TB" in most regions of the world, while "Health Expenditure" and "Temperature" factors were negatively related in most areas of the world, and the "Humidity" factor had a negative influence on "DR-TB" in all regions of the world.ConclusionsIn summary, the influences of the latent synthetic risk factors on DR-TB presented spatial variability. We should formulate regional DR-TB monitoring planning and prevention and control strategies, based on the spatial characteristics of the latent synthetic risk factors and spatial variability of the local relationship between DR-TB and latent synthetic risk factors.

Anti-tuberculosis drug resistance in Japan and in the world

In 1994, the World Health Organization (WHO) and the International Union against Tuberculosis and Lung Disease (IUATLD) launched a global project on anti-tuberculosis drug resistance surveillance. The results from the first 4 years (1994-1997) and the second 4 years (1996-1999) of the projects were reported in 1998 and 2000, respectively. These surveillance results showed that resistance to anti-tuberculosis drugs is a global problem. The reports also showed that there were several hot spots around the world where prevalence of multidrug resistant tuberculosis (MDR-TB, defined as resistance to at least isoniazid and rifampin) was particularly high and could possibly threaten control programs. The Tuberculosis Research Committee of Japan (Ryoken) has conducted nationwide surveys for drug resistant tuberculosis at 2- or 5-yearly intervals since 1957. The 1997 survey showed that among patients with no prior treatment, resistance to any of the four drugs was found in 10.3%, and the prevalence of primary MDR was 0.8%. The prevalence of drug resistance in the previously treated cases was 42.4% for any of the four drugs and 19.7% for MDR, indicating a high prevalence rate compared with those reported in the global project. Compared with the previous survey in 1992, the current survey shows increased prevalence of drug resistance in both new and re-treatment cases. No significant differences in resistance rates by sex, age group, nationality, district, and/or accompanying diseases were observed in any of the new or re-treatment cases. Other factors associated with the high prevalence in re-treatment cases remain to be determined. A total of 78 hospitals in various districts of Japan participated the cooperative study. Each collaborating laboratory sent all the isolated mycobacterial cultures to the Research Institute of Tuberculosis (RIT). In the local laboratories, the absolute concentration method using 1% Ogawa egg slant, its modified methods using a 48-well plate and a 16-well plate, combination of above 2 or 3 methods, and other method were used for drugsusceptibility testing, and the proportion method using 1% Ogawa egg slant was used in the RIT. The results in the local laboratories were compared with those in the RIT. There was no significant difference in the concordance rates according to the test drugs among methods for drug susceptibility testing used in the local laboratories. Relatively lower concordance rates were seen in the laboratories using the Microtiter method related to high overestimation rates, compared with those in the laboratories using the standard method and Well-pack method. However, relatively lower concordance rates (less than 90%) were seen in the laboratories using any of the three methods, indicating that there are variations among facilities.

Standardization of laboratory tests for tuberculosis and their proficiency testing

Explanations of proper collection procedures are imperative for accurate laboratory analysis. The quality of specimens collected and the proper transport of those specimens to the laboratory are critical to successful isolation of etiological agents. Most mycobacteria grow at a relatively slow rate. Therefore, the acid-fast smear plays an important role in the early diagnosis of mycobacterial infection. There are several methods of determining the acid-fast nature of an organism. In the carbolfuchsin procedures (Ziehl-Neelsen, Kinyoun), acid-fast organisms appear red, and in the fluorochrome procedures (auramine O, auramine-rhodamine, acridine orange), the acid-fast organisms fluoresce yellow to orange. Fluorochrome-stained slides may be directly restained with any of the carbolfuchsin staining procedures. This may be done to confirm a positive fluorochrome slide and to study organism morphology. In the last 10 years, there were many advances in the culture examinations of mycobacteria. The newly developed Mycobacteria Growth Indicator Tube (MGIT), BacT/Alert, ESP Myco, MB Redox and KRD "Nichi B", biphasic Septi-Chek AFB and Myco-Acid, and radiometric BACTEC 460TB systems based on liquid media, proved to be significantly better than the egg-based solid media for the isolation of mycobacteria from clinical specimens. In addition to liquid-based medium, agar (Middlebrook 7H10 or 7H11)- or egg (Ogawa or Löwenstein-Jensen)-based media should be used in the primary isolation of mycobacteria. To identify mycobacteria, conventional biochemical tests are traditionally used. Key test can be used to identify species, or further preliminary grouping may be used. Other approaches to identifying some species of mycobacteria are available. They include niacin accumulation, p-nitrobenzoic acid and p-nitro-alpha-acetylamino-beta-hydroxypropiophenone tests for discrimination of the Mycobacterium tuberculosis complex from mycobacteria other than M. tuberculosis (MOTT); DNA probe methods for identification or confirmation of the M. tuberculosis complex, M. avium complex, M. kansasii, and M. gordonae; DNA-DNA hybridization method for identification of 22 Mycobacterium species; and gas-liquid chromatography or high performance liquid chromatography analyses for recognizing the patterns of the mycobacterial cell wall fatty acids or mycolic acids. The advantages of the last four methods are that they are capable of providing definitive identification within 2 to 5 h after adequate growth. Capilia TB is the newly developed immunochromatographic assay for rapid discrimination between the M. tuberculosis complex and MOTT bacilli. The kit can be easily used for rapid identification of the M. tuberculosis complex in combination with the culture systems based on liquid media. In addition, Capilia TB could correctly detect the M. tuberculosis complex from mixed cultures with the M. tuberculosis complex and MOTT bacilli. The WHO/IUATLD supranational reference laboratory (SRL) network was created in 1994, to ascertain the accuracy of the susceptibility test methods used in different laboratories across the world, and to allow comparability of the surveillance data gathered in countries participating in the Global Project on Anti-tuberculosis Drug Resistance Surveillance. Today, the network has evolved and 23 SRLs actively participate. Results of five rounds of proficiency testing in the SRL network suggest that performance of the network has improved substantially through the years. This progress has been particularly evident for streptomycin and ethambutol sensitivity, which was very low in the first rounds of proficiency testing. In 1998 sensitivity for these two drugs was higher than 95%. For isoniazid and rifampin, sensitivity has been consistently high since the beginning of the Global Project. This indeed reflects the enhanced efforts made by the SRLs to improve their individual performance.

Modernizing Surveillance of Antituberculosis Drug Resistance: From Special Surveys to Routine Testing

Resistance to antituberculosis drugs has been documented since the 1940s, when the first medicines for tuberculosis were introduced. Since the initiation in 1994 of a global project to monitor the development of drug-resistant tuberculosis, nearly 60% of all countries in the world have implemented surveillance activities. In the past 15 years, special surveys have been the most common approach to investigate the frequency and patterns of drug-resistant tuberculosis. The major obstacle to the expansion of routine surveillance activities has been the lack of laboratory capacity needed to detect resistance. We are now in a new era for antituberculosis drug resistance surveillance due to the advent of new diagnostic tools and global commitment towards universal access to care for all patients with tuberculosis, including those with drug-resistant disease. Routine surveillance linked to patient care, which represents the best approach to monitor drug resistance, now has the possibility of becoming a reality even in resource-limited countries.