Mycobacterium tuberculosis Transmission among Elderly Persons, Yamagata Prefecture, Japan, 2009-2015

Differences in clinical, radiological and laboratory parameters between elderly and young patients with newly diagnosed smear-positive pulmonary tuberculosis in Vietnam

OBJECTIVES

To investigate the differences in clinical, radiological and laboratory parameters between elderly and young patients with newly diagnosed smear-positive pulmonary tuberculosis in Vietnam.

METHODS

This retrospective analysis included all patients hospitalised with newly diagnosed pulmonary tuberculosis with acid-fast bacilli-positive smear. Clinical symptoms, laboratory results and chest X-ray findings were collected using a standardised questionnaire. Elderly was defined as those patients aged 65 years and older.

RESULTS

A total of 183 patients diagnosed with new acid-fast bacilli-positive pulmonary tuberculosis were included in this study, with a mean age of 56.2 ± 16.3 years (minimum = 18 and maximum = 87 years). Seventy-seven participants were aged ≥65 years, accounting for 42.1% of participants. A total of 147 (80.3%) patients were male, and the sex ratio of male/female was 4.1. Night sweats were statistically more frequent among younger patients (34.9% vs. 20.8%, p = 0.04), whereas muscle and joint pain were more predominant among the elderly (7.6% vs. 22.1%, p = 0.01). A proportion of 67.0% of younger patients and 63.6% of the elderly group were bilaterally affected. Cavitation lesions were significantly more frequent in the younger group (55.7% vs. 39.0%, p = 0.03), whereas pulmonary fibrosis occurred more frequently in elderly patients (29.3% vs. 45.4%, p = 0.02). No other significant differences in clinical symptoms, laboratory results and chest X-ray findings were observed.

CONCLUSION

These findings underscore the importance of considering age-related variations in the clinical and radiological presentation of tuberculosis, which can guide tailored approaches in diagnosis, management and treatment strategies for different age groups.

Clinical, Radiological Features and Treatment Outcomes of Tuberculosis in Patients Aged 75 Years and Older

INTRODUCTION

Tuberculosis (TB) is a significant contributor to morbidity and mortality. With a progressively aging population, TB is increasingly encountered in older adults. Understanding the clinical presentation and optimal treatment strategies for TB in this population is essential.

METHOD

Clinical, radiological features, treatment, and outcome of patients aged 75 and above who were diagnosed with tuberculosis at King Abdulaziz Medical City in Riyadh in the period between January 2015 to December 2021wereevaluated retrospectively.

RESULTS

Among 92 elderly tuberculosis patients, most were male (76.1%) with a mean age of 82.5 years. Pulmonary TB was diagnosed in 52.2% of patients, Extra Pulmonary TB in 32.6%, and Disseminated TB in 15.2%. Comorbidities included Diabetes Mellitus (59.8%) and Congestive Heart Failure (41.3%). The most common presentation symptoms included cough (51.1%), fever (43.5%), dyspnea (39.1%), and weight loss (31.5%). Delay of TB diagnosis for up to 3 months was observed in 31.5% of patients. Weight loss and male gender were significant predictors of delayed diagnosis. Laboratory findings varied among TB types, with disseminated TB showing higher eosinophilia and thrombocytopenia. Completion of an initial RIPE treatment protocol was achieved in 67.6% of patients. Mortality during treatment occurred in 23.9% of patients. Pulmonary TB was associated with higher mortality compared to extrapulmonary TB (p = 0.007).

CONCLUSION

Tuberculosis is associated with high mortality in patients above the age of 75. There is still a substantial delay in TB diagnosis in the elderly. RIPE regimen is frequently changed due to side effects. Alternative regimen choices were quite variable. More studies on tuberculosis in this patient's population are needed to define the most effective therapeutic approach.

Association of mutations in Mycobacterium tuberculosis complex (MTBC) respiration chain genes with hyper-transmission

BACKGROUND

The respiratory chain plays a key role in the growth of Mycobacterium tuberculosis complex (MTBC). However, the exact regulatory mechanisms of this system still need to be elucidated, and only a few studies have investigated the impact of genetic mutations within the respiratory chain on MTBC transmission. This study aims to explore the impact of respiratory chain gene mutations on the global spread of MTBC.

RESULTS

A total of 13,402 isolates of MTBC were included in this study. The majority of the isolates (n = 6,382, 47.62%) belonged to lineage 4, followed by lineage 2 (n = 5,123, 38.23%). Our findings revealed significant associations between Single Nucleotide Polymorphisms (SNPs) of specific genes and transmission clusters. These SNPs include Rv0087 (hycE, G178T), Rv1307 (atpH, C650T), Rv2195 (qcrA, G181C), Rv2196 (qcrB, G1250T), Rv3145 (nuoA, C35T), Rv3149 (nuoE, G121C), Rv3150 (nuoF, G700A), Rv3151 (nuoG, A1810G), Rv3152 (nuoH, G493A), and Rv3157 (nuoM, A1243G). Furthermore, our results showed that the SNPs of atpH C73G, atpA G271C, qcrA G181C, nuoJ G115A, nuoM G772A, and nuoN G1084T were positively correlated with cross-country transmission clades and cross-regional transmission clades.

CONCLUSIONS

Our study uncovered an association between mutations in respiratory chain genes and the transmission of MTBC. This important finding provides new insights for future research and will help to further explore new mechanisms of MTBC pathogenicity. By uncovering this association, we gain a more complete understanding of the processes by which MTBC increases virulence and spread, providing potential targets and strategies for preventing and treating tuberculosis.

Toxin-antitoxin system gene mutations driving Mycobacterium tuberculosis transmission revealed by whole genome sequencing

Background

The toxin-antitoxin (TA) system plays a vital role in the virulence and pathogenicity of Mycobacterium tuberculosis (M. tuberculosis). However, the regulatory mechanisms and the impact of gene mutations on M. tuberculosis transmission remain poorly understood.

Objective

To investigate the influence of gene mutations in the toxin-antitoxin system on M. tuberculosis transmission dynamics.

Method

We performed whole-genome sequencing on the analyzed strains of M. tuberculosis. The genes associated with the toxin-antitoxin system were obtained from the National Center for Biotechnology Information (NCBI) Gene database. Mutations correlating with enhanced transmission within the genes were identified by using random forest, gradient boosting decision tree, and generalized linear mixed models.

Results

A total of 13,518 M. tuberculosis isolates were analyzed, with 42.29% (n = 5,717) found to be part of genomic clusters. Lineage 4 accounted for the majority of isolates (n = 6488, 48%), followed by lineage 2 (n = 5133, 37.97%). 23 single nucleotide polymorphisms (SNPs) showed a positive correlation with clustering, including vapB1 G34A, vapB24 A76C, vapB2 T171C, mazF2 C85T, mazE2 G104A, vapB31 T112C, relB T226A, vapB11 C54T, mazE5 T344C, vapB14 A29G, parE1 (C103T, C88T), and parD1 C134T. Six SNPs, including vapB6 A29C, vapB31 T112C, parD1 C134T, vapB37 G205C, Rv2653c A80C, and vapB22 C167T, were associated with transmission clades across different countries. Notably, our findings highlighted the positive association of vapB6 A29C, vapB31 T112C, parD1 C134T, vapB37 G205C, vapB19 C188T, and Rv2653c A80C with transmission clades across diverse regions. Furthermore, our analysis identified 32 SNPs that exhibited significant associations with clade size.

Conclusion

Our study presents potential associations between mutations in genes related to the toxin-antitoxin system and the transmission dynamics of M. tuberculosis. However, it is important to acknowledge the presence of confounding factors and limitations in our study. Further research is required to establish causation and assess the functional significance of these mutations. These findings provide a foundation for future investigations and the formulation of strategies aimed at controlling TB transmission.

Iron-related gene mutations driving global Mycobacterium tuberculosis transmission revealed by whole-genome sequencing

BACKGROUND

Iron plays a crucial role in the growth of Mycobacterium tuberculosis (M. tuberculosis). However, the precise regulatory mechanism governing this system requires further elucidation. Additionally, limited studies have examined the impact of gene mutations related to iron on the transmission of M. tuberculosis globally. This research aims to investigate the correlation between mutations in iron-related genes and the worldwide transmission of M. tuberculosis.

RESULTS

A total of 13,532 isolates of M. tuberculosis were included in this study. Among them, 6,104 (45.11%) were identified as genomic clustered isolates, while 8,395 (62.04%) were classified as genomic clade isolates. Our results showed that a total of 12 single nucleotide polymorphisms (SNPs) showed a positive correlation with clustering, such as Rv1469 (ctpD, C758T), Rv3703c (etgB, G1122T), and Rv3743c (ctpJ, G676C). Additionally, seven SNPs, including Rv0104 (T167G, T478G), Rv0211 (pckA, A302C), Rv0283 (eccB3, C423T), Rv1436 (gap, G654T), ctpD C758T, and etgB C578A, demonstrated a positive correlation with transmission clades across different countries. Notably, our findings highlighted the positive association of Rv0104 T167G, pckA A302C, eccB3 C423T, ctpD C758T, and etgB C578A with transmission clades across diverse regions. Furthermore, our analysis identified 78 SNPs that exhibited significant associations with clade size.

CONCLUSIONS

Our study reveals the link between iron-related gene SNPs and M. tuberculosis transmission, offering insights into crucial factors influencing the pathogenicity of the disease. This research holds promise for targeted strategies in prevention and treatment, advancing research and interventions in this field.

Association between two-component systems gene mutation and Mycobacterium tuberculosis transmission revealed by whole genome sequencing

BACKGROUND

Two-component systems (TCSs) assume a pivotal function in Mycobacterium tuberculosis (M.tuberculosis) growth. However, the exact regulatory mechanism of this system needs to be elucidated, and only a few studies have investigated the effect of gene mutations within TCSs on M.tuberculosis transmission. This research explored the relationship between TCSs gene mutation and the global transmission of (M.tuberculosis).

RESULTS

A total of 13531 M.tuberculosis strains were enrolled in the study. Most of the M.tuberculosis strains belonged to lineage4 (n=6497,48.0%), followed by lineage2 (n=5136,38.0%). Our results showed that a total of 36 single nucleotide polymorphisms (SNPs) were positively correlated with clustering of lineage2, such as Rv0758 (phoR, C820G), Rv1747(T1102C), and Rv1057(C1168T). A total of 30 SNPs showed positive correlation with clustering of lineage4, such as phoR(C182A, C1184G, C662T, T758G), Rv3764c (tcrY, G1151T), and Rv1747 C20T. A total of 19 SNPs were positively correlated with cross-country transmission of lineage2, such as phoR A575C, Rv1028c (kdpD, G383T, G1246C), and Rv1057 G817T. A total of 41 SNPs were positively correlated with cross-country transmission of lineage4, such as phoR(T758G, T327G, C284G), kdpD(G1755A, G625C), Rv1057 C980T, and Rv1747 T373G.

CONCLUSIONS

Our study identified that SNPs in genes of two-component systems were related to the transmission of M. tuberculosis. This finding adds another layer of complexity to M. tuberculosis virulence and provides insight into future research that will help to elucidate a novel mechanism of M. tuberculosis pathogenicity.

Tuberculosis in older adults: challenges and best practices in the Western Pacific Region

The Western Pacific has one of the fastest-growing older adult populations globally, and tuberculosis (TB) remains one of the foremost infectious causes of disease and death in the region. Older adults are at higher risk of TB due to immunosenescence, comorbidities, and increased institutionalisation. Atypical symptoms and reduced access to health services may delay care-seeking and TB diagnosis, while co-morbidity and increased risk of adverse drug reactions complicate TB treatment. Post-TB sequelae and socioeconomic challenges may decrease the quality of life after TB treatment completion. Despite their high disease burden and special challenges, there is a lack of regionally coordinated policies and guidelines to manage TB among older adults. Routine TB screening at aged-care facilities, age-friendly infrastructure and services, awareness of atypical TB features, integration of TB and non-communicable diseases services, and person-centred approaches to treatment support could improve TB management among older adults. Addressing these challenges and adopting the best practices identified should inform policy formulation and implementation.

Funding

This project was funded by 1) the World Health Organization Regional Office for the Western Pacific, with financial contributions from the Government of the Republic of Korea through the Korean Disease Control and Prevention Agency and the Government of Japan through the Ministry of Health, Labour and Welfare, and 2) NUS Start-up Grant. The funders had no role in the paper design, collection, analysis, and interpretation of data and in writing of the paper.

Tuberculosis in older adults: case studies from four countries with rapidly ageing populations in the western pacific region

BACKGROUND

The Western Pacific Region has one of the fastest-growing populations of older adults (≥ 65 years) globally, among whom tuberculosis (TB) poses a particular concern. This study reports country case studies from China, Japan, the Republic of Korea, and Singapore reflecting on their experiences in managing TB among older adults.

FINDINGS

Across all four countries, TB case notification and incidence rates were highest among older adults, but clinical and public health guidance focused on this population was limited. Individual country reports illustrated a range of practices and challenges. Passive case finding remains the norm, with limited active case finding (ACF) programs implemented in China, Japan, and the Republic of Korea. Different approaches have been trialled to assist older adults in securing an early diagnosis, as well as adhering to their TB treatment. All countries emphasised the need for person-centred approaches that include the creative application of new technology and tailored incentive programs, as well as reconceptualisation of how we provide treatment support. The use of traditional medicines was found to be culturally entrenched among older adults, with a need for careful consideration of their complementary use. TB infection testing and the provision of TB preventive treatment (TPT) were underutilised with highly variable practice.

CONCLUSION

Older adults require specific consideration in TB response policies, given the burgeoning aging population and their high TB risk. Policymakers, TB programs and funders must invest in and develop locally contextualised practice guidelines to inform evidence-based TB prevention and care practices for older adults.

Epidemiological features of tuberculosis infection in a rural prefecture of Japan from 2007 to 2018

This study aimed to investigate the epidemiological features of reported tuberculosis (TB) infections in a western prefecture (Nagasaki Prefecture) from 2007 to 2018, and to identify the high-risk group for TB infection. The characteristics of 12 years of reported TB infections from the Nagasaki Prefectural Informational Center of Infectious Diseases were summarized by median (interquartile range [IQR]) and proportion; the annual TB infections’ notification rate regarding sex/age was calculated accordingly. The diagnosis of TB infection was made according to clinic symptoms and laboratory examination. In total, 4364 TB infections were reported in 2007 and 2018, with a median age (IQR) of 74 (55–84) years. The majority of TB infections were male (52.6%, 2297/4364), > 65 years (65.8%, 2869/4364), and indigenous (98.1%, 4276/4364). Among active TB, 66.9% (1833/2740) had pulmonary TB, and 25.3% (694/2740) were diagnosed as extrapulmonary TB. The highest notification rate of TB infection was observed in the elderly male population (> 85 years). The annual notification rate of TB infections ranged between 19.4/and 34.0/100,000 for 12 years. The notification rates of TB infections were high in older people of both sexes, especially in men aged > 85. Therefore, appropriate interventions and health management are essential for TB control in (and with a focus on) the elderly population.

Delayed diagnosis of active pulmonary tuberculosis - potential risk factors for patient and healthcare delays in Portugal

BACKGROUND

Early diagnosis and treatment of pulmonary tuberculosis (PTB) is essential for an effective control of the tuberculosis (TB) epidemic. Delayed diagnosis and treatment of TB increases the chance of complications and mortality for the patients, and enhances TB transmission in the population. Therefore, the aim of this study was to characterize patient, healthcare and total delay in diagnosing PTB and assess the effect of clinical and sociodemographic factors on the time until first contact with healthcare or reaching a PTB diagnosis.

METHODS

Retrospective cohort study that included active PTB patients notified in the National Tuberculosis Surveillance System (SVIG-TB), between 2008 and 2017. Descriptive statistics, Kaplan-Meier estimates, logrank test and Cox proportional hazards model were used to characterize patient, healthcare and total delay and estimate the effect of clinical and sociodemographic variables on these delays. Significance level was set at 0.05.

RESULTS

Median patient, healthcare and total delays was 37 days (Interquartile range (IQR): 19-71), 8 days (IQR: 1-32) and 62 days (IQR: 38-102), respectively. The median patient delay showed a constant increase, from 33 days in 2008 to 44 days in 2017. The median total delay presented a similar trend, increasing from 59 days in 2008 to 70 days in 2017. Healthcare delay remained constant during the study period. More than half of the PTB cases (82.9%) had a delay > 1 month between symptom onset and diagnosis. In the final Cox model, alcohol abuse, unemployment and being from a high TB incidence country were factors significantly associated with longer patient delay, while being female, having more than 45 years, oncologic and respiratory diseases were associated with longer healthcare delay. Being female, having more than 45 years and being from a high TB incidence country were associated with longer total delay.

CONCLUSIONS

Patient delay and total delay have increased in recent years. Older patients, patients with alcohol problems, other comorbidities, unemployed or from countries with high TB incidence would benefit from the development of specific public health strategies that could help reduce the delay in TB diagnosis observed in our study. This study emphasizes the need to promote awareness of TB in the general population and among the healthcare community, especially at ambulatory care level, in order to reduce the gap between beginning of symptoms and TB diagnosis.

Estimating the burden of nosocomial exposure to tuberculosis in South Korea, a nationwide population based cross-sectional study

BACKGROUND/AIMS

The aim of the study was to investigate the current nationwide burden of nosocomial exposure to tuberculosis (TB) using national health insurance claims data.

METHODS

All patients who had claims for drug susceptibility testing for TB from 2012 to 2016, which indicated culture-proven TB, were included. The first day of the infectious period was defined as 3 months before a doctor's suspicion of TB in patients with respiratory symptoms and 1 month before in patients without symptoms. The last day of the infectious period was defined as one day before the prescription of anti-TB medications. Patients hospitalized during infectious periods were investigated and their hospitalization days were calculated. Records of medical procedures which increased the risk of nosocomial transmission by generating aerosols were also investigated.

RESULTS

A total of 7,186 cases with 94,636 person-days of hospitalization with unrecognized active TB were found. Patients above 60 years of age accounted for 63.99% of the total number and 69.70% of the total duration of hospitalization. TB patients in the older age group showed a trend toward higher risks for hospitalization with unrecognized active TB. Patients in their 80s showed the highest risk (12.65%). Bronchoscopy (28.86%), nebulizer therapy (28.48%), and endotracheal intubation (13.02%) were common procedures performed in these patients during hospitalization.

CONCLUSION

The burden of nosocomial exposure to TB in South Korea is still substantial. Hospitalization with unrecognized active TB, especially among the elderly TB patients could be a serious public health issue in South Korea.

Pulmonary Tuberculosis in Older Adults: Increased Mortality Related to Tuberculosis Within Two Months of Treatment Initiation

BACKGROUND

The proportion of tuberculosis (TB) patients who are older adults is increasing worldwide. Nearly 60% of TB patients in Japan are 70 years or older, and the TB incidence rate in Japan is one of the highest among high-income countries. The previous TB treatment guidelines prior to 2018 in Japan recommended excluding pyrazinamide (PZA) from the initial regimen for patients aged over 80 years.

OBJECTIVES

We aimed to examine differences in TB treatment outcomes among different age groups, and between those who received PZA and those who did not.

METHODS

We performed a retrospective cohort study of patients with pulmonary TB who were managed at a single medical center in Japan. We compared treatment outcomes and adverse events that resulted in treatment interruption across the age groups.

RESULTS

Of 246 patients, 117 (48%) were aged 75 years or older. Compared with patients aged < 74 years, those ≥ 75 years were less likely to have PZA in the initial regimen (53.0% vs 89.9%; p < 0.0001), more likely to die during treatment (38.5% vs 6.2%; p < 0.0001), and more likely to experience adverse events (30.8% vs 19.4%; p < 0.05). The mortality rate related to TB at 2 months after TB treatment initiation was 28% in those aged ≥ 84 years. Furthermore, among patients aged ≥ 84 years, those who did not receive PZA were significantly more likely to die than those who did (65.8% vs 36.8%; p < 0.05).

CONCLUSIONS

Patients aged ≥ 75 years with pulmonary TB experienced increased mortality related to TB during treatment and more frequent adverse events than younger patients, even though PZA was often avoided among older patients.

Epidemiology of coronavirus disease 2019 in Yamagata Prefecture, Japan, January-May 2020: The importance of retrospective contact tracing

Public health interventions have served an important role in controlling coronavirus disease 2019 (COVID-19), a rapidly spreading infectious disease. To contribute to future COVID-19 countermeasures, we aimed at verifying the results of countermeasures achieved by public health centers (PHCs) against the first wave of COVID-19 in Yamagata Prefecture, Japan. During January-May 2020, 1,253 patients suspected of SARS-CoV-2 infection were invited for testing. Simultaneously, based on retrospective contact tracings, PHCs investigated the infection sources and transmission routes of laboratory-confirmed COVID-19 cases and tested 928 contacts. Consequently, 69 cases were confirmed during March 31 - May 4, 58 (84.1%; 95% confidence interval 75.5-92.7) of whom were found from contacts. The spread of infection was triggered by cases harboring epidemiological links outside of Yamagata. Then, the number of cases increased rapidly. However, PHCs identified epidemiological links in 61 (88.4%; 95% confidence interval 80.8-96.0) of the 69 cases and transmission chains up to the fifth generation. Finally, the spread of infection ended after approximately one month. Our results indicate that the identification of infection sources and active case finding from contacts based on retrospective contact tracing was likely to be an effective strategy to end the first wave of COVID-19 in Yamagata.

Tuberculosis Contact Investigations Conducted in New York City Adult Day Care and Senior Centers, 2011-2018

OBJECTIVES

Multiple tuberculosis (TB) exposures have been reported in New York City (NYC) adult day care and senior centers. Strategies to identify TB transmission at such locations are needed.

METHOD

Review of the NYC TB Registry identified 12 contact investigations (CIs) at adult day care or senior centers (2011-2018).

RESULTS

Median age of the 12 index patients was 81 years. Of 148 contacts identified who had no history of TB infection or disease, 141 (95%) were tested for TB, primarily with interferon gamma release assays; 46 (33%) tested positive. Transmission was probable (n = 3) or possible (n = 1) at 4 (33%) centers; at all of these, the index patient had an acid-fast bacilli-positive sputum smear. Transmission was not found from index patients with negative sputum smears.

DISCUSSION

We found evidence of transmission of smear-positive respiratory TB disease to contacts in adult day care or senior centers, underscoring the importance of CI.

Time to diagnosis of tuberculosis is greater in older patients: a retrospective cohort review

Introduction

Age-related immunosenescence influences the presentation of tuberculosis (TB) in older patients. Here, we explore the clinical and radiological presentation of TB in the elderly and the factors associated with time to treatment for TB.

Methods

This is a retrospective cohort study comparing the clinical, radiological and demographic characteristics of TB patients aged ≥65 years with TB patients aged 18–64 years in a large cohort of TB patients in the UK. Factors associated with the time to presentation and time to treatment were identified using a multivariable analysis model.

Results

1023 patients were included in the analyses: 679 patients aged 18–64 years and 344 patients aged ≥65 years. “Classical” symptoms of TB (cough, haemoptysis, fever, nights sweats and weight loss) were less common among older patients with pulmonary TB (PTB) (p<0.05), but dyspnoea was more common among older patients (p=0.001). Time from presenting in secondary care to starting treatment was shorter in younger compared with older patients: 3 versus 15 days (p=0.001). When adjusted for age, factors associated with shorter time to treatment from symptom onset include sex (male versus female) (hazard ratio (HR) 1.23 (95% CI 1.05–1.46)), UK born (HR 1.23 (95% CI 1.05–1.46)) and HIV (HR 2.07 (95% CI 1.30–3.29)). Only age remained an independent predictor of time to treatment in a multivariable model (HR 0.98 (95% CI 0.98–0.99)). For those with PTB, chest radiography findings showed that cavitation and lymphadenopathy were more common among younger patients (p=0.001).

Conclusions

Older patients aged ≥65 years with TB had fewer “classical” clinical and radiological presentations of TB, which may explain longer times to starting treatment from symptom onset compared with younger patients aged <65 years.

A retrospective UK study in patients with TB shows only age remains an independent predictor of time to treatment in a multivariable model. Older patients have fewer of the “classical” clinical and radiological features of TB compared with younger patients.http://bit.ly/2yHc0OL

Mathematical modelling of the impact of treating latent tuberculosis infection in the elderly in a city with intermediate tuberculosis burden

Hong Kong is a high-income city with intermediate tuberculosis (TB) burden primarily driven by endogenous reactivations. A high proportion of remote latently infected people, particularly elderly, hinders the effectiveness of current strategies focusing on passive TB detection. In this study, we developed a mathematical model to evaluate the impact of treating latent TB infection (LTBI) in the elderly in addition to current TB control strategies. The model was calibrated using the annual age-stratified TB notifications from 1965-2013 in Hong Kong. Our results showed that at present, approximately 75% of annual new notifications were from reactivations. Given the present treatment completion rate, even if only a low to moderate proportion (approximately 20% to 40%) of elderly people were screened and treated for LTBI, the overall TB incidence could be reduced by almost 50%, to reach the 2025 milestone of the global End TB Strategy. Nevertheless, due to a high risk of hepatotoxicity in elderly population, benefit-risk ratios were mostly below unity; thus, intervention programs should be carefully formulated, including prioritising LTBI treatment for high-risk elderly groups who are closely monitored for possible adverse side effects.

Nosocomial Mycobacterium tuberculosis transmission by brief casual contact identified using comparative genomics

This paper reports a case of nosocomial transmission of Mycobacterium tuberculosis by brief casual contact. Routine variable number tandem repeat typing in Yamagata Prefecture, Japan found that M. tuberculosis clinical isolates from two patients showed indistinguishable genotypes. The patients had an epidemiological relationship of sharing a waiting room in a hospital on the same day. As comparative genomics detected only two single nucleotide variants between the isolates, it was concluded that recent tuberculosis transmission occurred in the waiting room. These results indicate that the physical separation of infectious tuberculosis patients is an essential control measure for preventing unpredictable nosocomial transmission by casual contact.

Longitudinal genotyping surveillance of Mycobacterium tuberculosis in an area with high tuberculosis incidence shows high transmission rate of the modern Beijing subfamily in Japan

Tuberculosis (TB) is a severe and wide-spread infectious disease worldwide. The modern Beijing subfamily, one lineage of M. tuberculosis, reportedly has high pathogenicity and transmissibility. This study used a molecular epidemiological approach to investigate the transmissibility of the modern Beijing subfamily in the Airin area of Osaka City, Japan. During 2006-2016, we collected 596 M. tuberculosis clinical isolates in the Airin area, Osaka city, Japan. We analyzed the 24-locus variable number of tandem repeats typing optimized for the Beijing family of isolates, M. tuberculosis lineage, and patient epidemiological data. The proportion of the modern Beijing subfamily was significantly higher not only than previously obtained data for the Airin area: it was also higher than the nationwide in Japan. The rate of recent clusters, defined as a variable number of tandem repeats profile identified within two years, of the modern Beijing subfamily was significantly higher than that the rate of recent clusters of the ancient Beijing subfamily. Results suggest that TB control measures formulated with attention to the modern Beijing subfamily might be an important benchmark to understanding recent TB transmission in the area.

Reduced transmission of Mycobacterium africanum compared to Mycobacterium tuberculosis in urban West Africa

OBJECTIVE

Understanding transmission dynamics is useful for tuberculosis (TB) control. A population-based molecular epidemiological study was conducted to determine TB transmission in Ghana.

METHODS

Mycobacterium tuberculosis complex (MTBC) isolates obtained from prospectively sampled pulmonary TB patients between July 2012 and December 2015 were characterized using spoligotyping and standard 15-locus mycobacterial interspersed repetitive unit variable number tandem repeat (MIRU-VNTR) typing for transmission studies.

RESULTS

Out of 2309 MTBC isolates, 1082 (46.9%) unique cases were identified, with 1227 (53.1%) isolates belonging to one of 276 clusters. The recent TB transmission rate was estimated to be 41.2%. Whereas TB strains of lineage 4 belonging to M. tuberculosis showed a high recent transmission rate (44.9%), reduced recent transmission rates were found for lineages of Mycobacterium africanum (lineage 5, 31.8%; lineage 6, 24.7%).

CONCLUSIONS

The study findings indicate high recent TB transmission, suggesting the occurrence of unsuspected outbreaks in Ghana. The observed reduced transmission rate of M. africanum suggests other factor(s) (host/environmental) may be responsible for its continuous presence in West Africa.

Delay from symptom onset to treatment start among tuberculosis patients in England, 2012-2015

Improving access to tuberculosis (TB) care and ensuring early diagnosis are two major aims of the WHO End TB strategy and the Collaborative TB Strategy for England. This study describes risk factors associated with diagnostic delay among TB cases in England. We conducted a retrospective cohort study of TB cases notified to the Enhanced TB Surveillance System in England between 2012 and 2015. Diagnostic delay was defined as more than 4 months between symptom onset and treatment start date. Multivariable logistic regression was used to identify demographic and clinical factors associated with diagnostic delay. Between 2012 and 2015, 22 422 TB cases were notified in England and included in the study. A third (7612) of TB cases had a diagnostic delay of more than 4 months. Being female, aged 45 years and older, residing outside of London and having extra-pulmonary TB disease were significantly associated with a diagnostic delay in the multivariable model (aOR = 1.2, 1.2, 1.2, 1.3, 1.8, respectively). This study identifies demographic and clinical factors associated with diagnostic delay, which will inform targeted interventions to improve access to care and early diagnosis among these groups, with the ultimate aim of helping reduce transmission and improve treatment outcomes for TB cases in England.

Mycobacterium tuberculosis Acquires Limited Genetic Diversity in Prolonged Infections, Reactivations and Transmissions Involving Multiple Hosts

Background:Mycobacterium tuberculosis (MTB) has limited ability to acquire variability. Analysis of its microevolution might help us to evaluate the pathways followed to acquire greater infective success. Whole-genome sequencing (WGS) in the analysis of the transmission of MTB has elucidated the magnitude of variability in MTB. Analysis of transmission currently depends on the identification of clusters, according to the threshold of variability (<5 SNPs) between isolates. Objective: We evaluated whether the acquisition of variability in MTB, was more frequent in situations which could favor it, namely intrapatient, prolonged infections or reactivations and interpatient transmissions involving multiple sequential hosts. Methods: We used WGS to analyze the accumulation of variability in sequential isolates from prolonged infections or translations from latency to reactivation. We then measured microevolution in transmission clusters with prolonged transmission time, high number of involved cases, simultaneous involvement of latency and active transmission. Results: Intrapatient and interpatient acquisition of variability was limited, within the ranges expected according to the thresholds of variability proposed, even though bursts of variability were observed. Conclusions: The thresholds of variability proposed for MTB seem to be valid in most circumstances, including those theoretically favoring acquisition of variability. Our data point to multifactorial modulation of microevolution, although further studies are necessary to elucidate the factors underlying this modulation.

Convenient PCR method for variable-number tandem-repeat typing of Mycobacterium tuberculosis clinical isolates

Variable-number tandem-repeat typing for Mycobacterium tuberculosis clinical isolates contributes to evidence-based tuberculosis control. However, cumbersome PCR procedures for the typing have disturbed routine analyses. We proposed a convenient PCR method for the typing using a PCR master mix that provides rapidity and long-term stability of the frozen PCR cocktail.