Transmission of drug-susceptible and drug-resistant tuberculosis and the critical importance of airborne infection control in the era of HIV infection and highly active antiretroviral therapy rollouts

Addressing the challenges in implementing airborne infection control guidelines and embracing the policies

Airborne pathogens not only lead to epidemics and pandemics, but are associated with morbidity and mortality. Administrative or managerial control, environmental control and use of personal protective equipments are the three components in airborne infection control. National and international guidelines for ideal airborne infection control (AIC) practices are available for more than a decade; however the implementation of these need to be looked into, challenges identified and addressed for effective prevention of airborne disease transmission. Commitment of multiple stakeholders from policy makers to patients, budget allocation and adequate fund flow, functioning AIC committees at multiple levels with an inbuilt reporting and monitoring mechanism, adaptation of the AIC practices at various health care levels, supportive supervision, training and ongoing education for health care providers, behaviour change communication to patients to adapt the practices at health care facility level, by health care personnel and patients will facilitate health system preparedness for handling any emergencies, but will also help in reducing the burden of persisting airborne diseases such as tuberculosis. Operational research in this least focused area will also help to identify and address the challenges.

Particle Dynamics and Bioaerosol Viability of Aerosolized Bacillus Calmette-Guérin Vaccine Using Jet and Vibrating Mesh Clinical Nebulizers

Background: Bacillus Calmette-Guérin (BCG) is a vaccine used to protect against tuberculosis primarily in infants to stop early infection in areas of the world where the disease is endemic. Normally administered as a percutaneous injection, BCG is a live significantly attenuated bacteria that is now being investigated for its potential within an inhalable vaccine formulation. This study investigates the feasibility and performance of two jet and two vibrating mesh nebulizers aerosolizing BCG and the resulting particle characteristics and residual viability of the bacteria postaerosolization. Methods: A jet nebulizer (Collison), outfitted either with a 3- or 6-jet head, was compared with two clinical nebulizers, the vibrating mesh Omron MicroAir and Aerogen Solo devices. Particle characteristics, including aerodynamic particle sizing, was performed on all devices within a common aerosol chamber configuration and comparable BCG innocula concentrations. Integrated aerosol samples were collected for each generator and assayed for bacterial viability using conventional microbiological technique. Results: A batch lot of BCG (Danish) was grown to titer and used in all generator assessments. Aerosol particles within the respirable range were generated from all nebulizers at four different concentrations of BCG. The jet nebulizers produced a uniformly smaller particle size than the vibrating mesh devices, although particle concentrations by mass were similar across all devices tested with the exception of the Aerogen Solo, which resulted in a low concentration of BCG aerosols. Conclusions: The resulting measured viable BCG aerosol concentration fraction produced by each device approximated one another; however, a measurable decrease of efficiency and overall viability reduction in the jet nebulizer was observed in higher BCG inoculum starting concentrations, whereas the vibrating mesh nebulizer returned a remarkably stable viable aerosol fraction irrespective of inoculum concentration.

Occupational Risk of Airborne Mycobacterium tuberculosis Exposure: A Situational Analysis in a Three-Tier Public Healthcare System in South Africa

This study aimed to detect airborne Mycobacterium tuberculosis (MTB) at nine public health facilities in three provinces of South Africa and determine possible risk factors that may contribute to airborne transmission. Personal samples (n = 264) and stationary samples (n = 327) were collected from perceived high-risk areas in district, primary health clinics (PHCs) and TB facilities. Quantitative real-time (RT) polymerase chain reaction (PCR) was used for TB analysis. Walkabout observations and work practices through the infection prevention and control (IPC) questionnaire were documented. Statistical analysis was carried out using Stata version 15.2 software. Airborne MTB was detected in 2.2% of samples (13/572), and 97.8% were negative. District hospitals and Western Cape province had the most TB-positive samples and identified risk areas included medical wards, casualty, and TB wards. MTB-positive samples were not detected in PHCs and during the summer season. All facilities reported training healthcare workers (HCWs) on TB IPC. The risk factors for airborne MTB included province, type of facility, area or section, season, lack of UVGI, and ineffective ventilation. Environmental monitoring, PCR, IPC questionnaire, and walkabout observations can estimate the risk of TB transmission in various settings. These findings can be used to inform management and staff to improve the TB IPC programmes.

Projecting the impact of variable MDR-TB transmission efficiency on long-term epidemic trends in South Africa and Vietnam

Whether multidrug-resistant tuberculosis (MDR-TB) is less transmissible than drug-susceptible (DS-)TB on a population level is uncertain. Even in the absence of a genetic fitness cost, the transmission potential of individuals with MDR-TB may vary by infectiousness, frequency of contact, or duration of disease. We used a compartmental model to project the progression of MDR-TB epidemics in South Africa and Vietnam under alternative assumptions about the relative transmission efficiency of MDR-TB. Specifically, we considered three scenarios: consistently lower transmission efficiency for MDR-TB than for DS-TB; equal transmission efficiency; and an initial deficit in the transmission efficiency of MDR-TB that closes over time. We calibrated these scenarios with data from drug resistance surveys and projected epidemic trends to 2040. The incidence of MDR-TB was projected to expand in most scenarios, but the degree of expansion depended greatly on the future transmission efficiency of MDR-TB. For example, by 2040, we projected absolute MDR-TB incidence to account for 5% (IQR: 4–9%) of incident TB in South Africa and 14% (IQR: 9–26%) in Vietnam assuming consistently lower MDR-TB transmission efficiency, versus 15% (IQR: 8–27%)and 41% (IQR: 23–62%), respectively, assuming shrinking transmission efficiency deficits. Given future uncertainty, specific responses to halt MDR-TB transmission should be prioritized.

Assessment of Health Facilities for Airborne Infection Control Practices and Adherence to National Airborne Infection Control Guidelines: A Study from Kerala, Southern India

INTRODUCTION

Nosocomial transmission of airborne infections, such as H1N1, drug-resistant tuberculosis, and Nipah virus disease, has been reported recently and has been linked to the limited airborne infection control strategies. The objective of the current study was to assess the health facilities for airborne infection control (AIC) practices and adherence to the National AIC (NAIC) guidelines, 2010.

MATERIALS AND METHODS

A cross-sectional study was conducted in 25 public and 25 private hospitals selected from five randomly selected districts in the state of Kerala. A checklist with 62 components was developed based on the NAIC guidelines. Frequencies, percentages, and mean with standard deviation were used to summarize facility risk assessment and compliance to guidelines.

RESULTS

Most of the facilities had infection control committees 35 (70%). Annual infection control trainings were held for staff in 21 (42%) facilities. Twenty (40%) facilities were not familiar with NAIC guidelines. Counseling on cough etiquette at registration was practiced in 5 (10%) institutions. Cross ventilation was present in outpatient departments in 27 (54%) institutions. Sputum was disposed properly in 43 (86%) institutions. N95 masks were available in high-risk settings in 7 (14%) health facilities.

CONCLUSION

There exist deficiencies in adherence to all components of NAIC guidelines including administrative, environmental, and use of personal protective equipment in both government and private hospitals in the state.

Cartridge-based nucleic acid amplification test: a novel rapid diagnostic tool to study the burden of tuberculosis from a tertiary care hospital

Despite efforts to limit the morbidity and mortality from tuberculosis (TB), it continues to be an important cause of death. There is an urgent need for a diagnostic test that accurately and quickly diagnoses TB, especially if it is also a near-point-of-care test. The GeneXpert polymerase chain reaction test (known in India as CBNAAT [cartridge-based nucleic acid amplification test] and is capable of diagnosing TB and rifampicin resistance within 2 h) is a promising tool. The duration of our study was two years and was carried out in the DOTS centre of a tertiary care hospital in India. A total of 5449 samples were processed using CBNAAT. Of the total samples tested, 2068 were extra-pulmonary. The following information was collected: number of extra-pulmonary samples processed; number of Mycobacterium tuberculosis (M. tuberculosis)-positive samples; patterns of rifampicin sensitivity; number of people living with HIV (PLHIV); and number of children. Of the samples, 62.1% were from suspected pulmonary TB patients. Out of the total samples tested using CBNAAT, 21.8% were positive for M. tuberculosis. Rifampicin resistance was seen in 9.2%, 8.5% and 10.3% of the total, pulmonary and extra-pulmonary samples, respectively, in M. tuberculosis-positive samples. Overall, 36.9% samples were from the paediatric population and 5.7% belonged to PLHIV. Rifampicin resistance was seen in 8.8% and 8.3% of the M. tuberculosis-positive paediatric and PLHIV samples, respectively.

Reducing tuberculosis transmission: a consensus document from the World Health Organization Regional Office for Europe

Evidence-based guidance is needed on 1) how tuberculosis (TB) infectiousness evolves in response to effective treatment and 2) how the TB infection risk can be minimised to help countries to implement community-based, outpatient-based care.This document aims to 1) review the available evidence on how quickly TB infectiousness responds to effective treatment (and which factors can lower or boost infectiousness), 2) review policy options on the infectiousness of TB patients relevant to the World Health Organization European Region, 3) define limitations of the available evidence and 4) provide recommendations for further research.The consensus document aims to target all professionals dealing with TB (e.g TB specialists, pulmonologists, infectious disease specialists, primary healthcare professionals, and other clinical and public health professionals), as well as health staff working in settings where TB infection is prevalent.

Unsuccessful Xpert® MTB/RIF results: the Nigerian experience

Setting: Nigeria, a high tuberculosis (TB) burden country. Objective: To study the rate, distribution and causes of unsuccessful Xpert^® MTB/RIF test outcomes, with the aim of identifying key areas that need to be strengthened for optimal performance of the assay. Design: This was a retrospective analysis of data uploaded between January and December 2015 from Xpert facilities to the central server using GXAlert. Result: Of 52 219 test results uploaded from 176 Xpert machines, 22.5% were positive for Mycobacterium tuberculosis, 10.8% of which were rifampicin-resistant; 4.7% of the total number of results were invalid, 4.2% had error results and 2.1% no result outcomes. Technical errors were most frequent (69%); these were non-seasonal and occurred in all geopolitical regions and at all health facility levels. Temperature-related errors were more prevalent in the North-West Region, with peaks in April to June. Peak periods for temperature and machine malfunction errors coincided with the periods of low utilisation of the assay. Conclusion: The key challenge affecting performance was poor adherence to standard operating procedures. Periodic refresher training courses, regular supervision, preventive maintenance of Xpert machines and proper storage of cartridges are strategies that could improve Xpert performance.

Protecting Our Front-liners: Occupational Tuberculosis Prevention Through Infection Control Strategies

Healthcare workers (HCWs) in low- and middle-income countries with high tuberculosis prevalence are at increased risk of tuberculosis infection; however, tuberculosis infection control (TBIC) measures are often poorly implemented. The World Health Organization recommends 4 levels of TBIC: managerial (establishment and oversight of TBIC policies), administrative controls (reducing HCWs' exposure to tuberculosis), environmental controls (reducing the concentration of infectious respiratory aerosols in the air), and personal respiratory protection. This article will discuss each of these levels of TBIC, and review the available data on the implementation of each in sub-Saharan African countries. In addition, we review the attitudes and motivation of HCWs regarding TBIC measures, and the impact of stigma on infection control practices and implementation. After summarizing the challenges facing effective TBIC implementation, we will discuss possible solutions and recommendations. Last, we present a case study of how a clinic effectively addressed some of the challenges of TBIC implementation.

Epidemiology of Drug-Resistant Tuberculosis

As we move into the era of the Sustainable Development Goals (SDGs), the World Health Organization (WHO) has developed the End TB strategy 2016-2035 with a goal to end the global epidemic of tuberculosis (TB) by 2035. Achieving the targets laid out in the Strategy will require strengthening of the whole TB diagnosis and treatment cascade, including improved case detection, the establishment of universal drug susceptibility testing and rapid treatment initiation. An estimated 3.9% of new TB cases and 21% of previously treated cases had rifampicin-resistant (RR) or multidrug-resistant (MDR) TB in 2015. These levels have remained stable over time, although limited data are available from major high burden settings. In addition to the emergence of drug resistance due to inadequate treatment, there is growing evidence that direct transmission is a large contributor to the RR/MDR-TB epidemic. Only 340,000 of the estimated 580,000 incident cases of RR/MDR-TB were notified to WHO in 2015. Among these, only 125,000 were initiated on second-line treatment. RR/MDR-TB epidemics are likely to be driven by direct transmission. The most important risk factor for MDR-TB is a history of previous treatment. Other risk factors vary according to setting but can include hospitalisation, incarceration and HIV infection. Children have the same risk of MDR-TB as adults and represent a diagnostic and treatment challenge. Rapid molecular technologies have revolutionized the diagnosis of drug-resistant TB. Until capacity can be established to test every TB patient for rifampicin resistance, countries should focus on gradually expanding their coverage of testing. DNA sequencing technologies are being increasingly incorporated into patient management and drug resistance surveillance. They offer additional benefits over conventional culture-based phenotypic testing, including a faster turn-around time for results, assessment of resistance patterns to a range of drugs, and investigation of strain clustering and transmission.

Infection Control for Drug-Resistant Tuberculosis: Early Diagnosis and Treatment Is the Key

Multidrug-resistant (MDR) tuberculosis, "Ebola with wings," is a significant threat to tuberculosis control efforts. Previous prevailing views that resistance was mainly acquired through poor treatment led to decades of focus on drug-sensitive rather than drug-resistant (DR) tuberculosis, driven by the World Health Organization's directly observed therapy, short course strategy. The paradigm has shifted toward recognition that most DR tuberculosis is transmitted and that there is a need for increased efforts to control DR tuberculosis. Yet most people with DR tuberculosis are untested and untreated, driving transmission in the community and in health systems in high-burden settings. The risk of nosocomial transmission is high for patients and staff alike. Lowering transmission risk for MDR tuberculosis requires a combination approach centered on rapid identification of active tuberculosis disease and tuberculosis drug resistance, followed by rapid initiation of appropriate treatment and adherence support, complemented by universal tuberculosis infection control measures in healthcare facilities. It also requires a second paradigm shift, from the classic infection control hierarchy to a novel, decentralized approach across the continuum from early diagnosis and treatment to community awareness and support. A massive scale-up of rapid diagnosis and treatment is necessary to control the MDR tuberculosis epidemic. This will not be possible without intense efforts toward the implementation of decentralized, ambulatory models of care. Increasing political will and resources need to be accompanied by a paradigm shift. Instead of focusing on diagnosed cases, recognition that transmission is driven largely by undiagnosed, untreated cases, both in the community and in healthcare settings, is necessary. This article discusses this comprehensive approach, strategies available, and associated challenges.

Extensively Drug-Resistant Tuberculosis: Principles of Resistance, Diagnosis, and Management

Extensively drug-resistant (XDR) tuberculosis (TB) is an unfortunate by-product of mankind's medical and pharmaceutical ingenuity during the past 60 years. Although new drug developments have enabled TB to be more readily curable, inappropriate TB management has led to the emergence of drug-resistant disease. Extensively drug-resistant TB describes Mycobacterium tuberculosis that is collectively resistant to isoniazid, rifampin, a fluoroquinolone, and an injectable agent. It proliferates when established case management and infection control procedures are not followed. Optimized treatment outcomes necessitate time-sensitive diagnoses, along with expanded combinations and prolonged durations of antimicrobial drug therapy. The challenges to public health institutions are immense and most noteworthy in underresourced communities and in patients coinfected with human immunodeficiency virus. A comprehensive and multidisciplinary case management approach is required to optimize outcomes. We review the principles of TB drug resistance and the risk factors, diagnosis, and managerial approaches for extensively drug-resistant TB. Treatment outcomes, cost, and unresolved medical issues are also discussed.

Tuberculosis infection control measures in health care facilities offering tb services in Ikeja local government area, Lagos, South West, Nigeria

Background

Tuberculosis infection among health care workers is capable of worsening the existing health human resource problems of low - and middle-income countries. Tuberculosis infection control is often weakly implemented in these parts of the world therefore, understanding the reasons for poor implementation of tuberculosis infection control guidelines are important. This study was aimed at assessing tuberculosis infection control practices and barriers to its implementation in Ikeja, Nigeria.

Methods

A cross-sectional study in 20 tuberculosis care facilities (16 public and 4 private) in Ikeja, Lagos was conducted. The study included a facility survey to assess the availability of tuberculosis infection control guidelines, the adequacy of facilities to prevent transmission of tuberculosis and observations of practices to assess the implementation of tuberculosis infection control guidelines. Four focus group discussions were carried out to highlight HCWs’ perceptions on tuberculosis infection control guidelines and barriers to its implementation.

Results

The observational study showed that none of the clinics had a tuberculosis infection control plan. No clinic was consistently screening patients for cough. Twelve facilities (60 %) consistently provided masks to patients who were coughing. Ventilation in the waiting areas was assessed to be adequate in 60 % of the clinics while four clinics (20 %) possessed N-95 respirators. Findings from the focus group discussions showed weak managerial support, poor funding, under-staffing, lack of space and not wanting to be seen as stigmatizing against tuberculosis patients as barriers that hindered the implementation of TB infection control measures.

Conclusion

Tuberculosis infection control measures were not adequately implemented in health facilities in Ikeja, Nigeria. A multi-pronged approach is required to address the identified barriers to the implementation of tuberculosis infection control guidelines.

The transmission of Mycobacterium tuberculosis in high burden settings

Unacceptable levels of Mycobacterium tuberculosis transmission are noted in high burden settings and a renewed focus on reducing person-to-person transmission in these communities is needed. We review recent developments in the understanding of airborne transmission. We outline approaches to measure transmission in populations and trials and describe the Wells-Riley equation, which is used to estimate transmission risk in indoor spaces. Present research priorities include the identification of effective strategies for tuberculosis infection control, improved understanding of where transmission occurs and the transmissibility of drug-resistant strains, and estimates of the effect of HIV and antiretroviral therapy on transmission dynamics. When research is planned and interventions are designed to interrupt transmission, resource constraints that are common in high burden settings-including shortages of health-care workers-must be considered.

Airborne infection control in India: Baseline assessment of health facilities

BACKGROUND

Tuberculosis transmission in health care settings represents a major public health problem. In 2010, national airborne infection control (AIC) guidelines were adopted in India. These guidelines included specific policies for TB prevention and control in health care settings. However, the feasibility and effectiveness of these guidelines have not been assessed in routine practice. This study aimed to conduct baseline assessments of AIC policies and practices within a convenience sample of 35 health care settings across 3 states in India and to assess the level of implementation at each facility after one year.

METHOD

A multi-agency, multidisciplinary panel of experts performed site visits using a standardized risk assessment tool to document current practices and review resource capacity. At the conclusion of each assessment, facility-specific recommendations were provided to improve AIC performance to align with national guidelines.

RESULT

Upon initial assessment, AIC systems were found to be poorly developed and implemented. Administrative controls were not commonly practiced and many departments needed renovation to achieve minimum environmental standards. One year after the baseline assessments, there were substantial improvements in both policy and practice.

CONCLUSION

A package of capacity building and systems development that followed national guidelines substantially improved implementation of AIC policies and practice.

Evaluating the Diagnostic Accuracy of Xpert MTB/RIF Assay in Pulmonary Tuberculosis

Pulmonary tuberculosis still remains a major communicable disease worldwide. In 2013, 9 million people developed TB and 1.5 million people died from the disease. India constitutes 24% of the total TB burden. Early detection of TB cases is the key to successful treatment and reduction of disease transmission. Xpert MTB/RIF, an automated cartridge-based molecular technique detects Mycobacterium tuberculosis and rifampicin resistance within two hours has been endorsed by WHO for rapid diagnosis of TB. Our study is the first study from India with a large sample size to evaluate the performance of Xpert MTB/RIF assay in PTB samples. The test showed an overall sensitivity and specificity of 95.7% (430/449) and 99.3% (984/990) respectively. In smear negative-culture positive cases, the test had a sensitivity of 77.7%. The sensitivity and specificity for detecting rifampicin resistance was 94.5% and 97.7% respectively with respect to culture as reference standard. However, after resolving the discrepant samples with gene sequencing, the sensitivity and specificity rose to 99.0% and 99.3% respectively. Hence, while solid culture still forms the foundation of TB diagnosis, Xpert MTB/RIF proposes to be a strong first line diagnostic tool for pulmonary TB cases.

Development of tuberculosis infection control guidelines in a pediatric HIV clinic in sub-Saharan Africa

SETTING

A well-established pediatric human immunodeficiency virus (HIV) clinic in Lesotho with initial infection control (IC) measures prioritizing blood-borne disease. In line with international recommendations, services have been expanded to include the management of patients with tuberculosis (TB). The creation of comprehensive IC guidelines with an emphasis on TB has become a priority.

OBJECTIVE

To provide a model for developing and implementing IC guidelines in ambulatory care facilities in limited-resource settings with high HIV and TB prevalence. Activities: An IC plan that includes guidance covering both general IC measures and TB-specific guidelines was created by integrating local and international recommendations and emphasizing the importance of administrative measures, environmental controls, and disease-specific precautions. An interdisciplinary committee was established to oversee its implementation, monitoring, and evaluation.

DISCUSSION

Development and implementation of IC guidelines in resource-limited settings are feasible and should be a priority in high HIV and TB prevalence areas. Education should be the cornerstone of such endeavors. Many interventions can be implemented with minimal expertise and material resources. Administrative support and institutional investment are essential to the sustainability of an effective IC program.

Tuberculosis in health care workers in Belarus

SETTING

Tuberculosis (TB), including drug-resistant TB, is a serious problem in Belarus.

OBJECTIVES

To determine the prevalence of TB among health care workers (HCWs) along with patient characteristics, treatment outcomes and drug resistance patterns between 2008 and 2012.

DESIGN

A retrospective national record review.

RESULTS

There were 116 HCWs with TB. Case notification rates were higher among HCWs than in the general population (349 vs. 40/100 000 in 2012). Most HCWs with TB were nurses (n = 46, 40%) or nurse assistants (n = 37, 32%), female (n = 100, 86%) and aged 25-44 years (n = 84, 72%). Most common places of work for HCWs with TB were multidrug-resistant (MDR-) and extensively drug-resistant (XDR-TB) wards (n = 23, 20%), general medical (n = 26, 22%) and non-medical (n = 34, 29%) departments. All HCWs had pulmonary TB, 107 (92%) had new TB and 103 (89%) had negative sputum smears. Of the 38 (33%) with culture and drug susceptibility testing (DST), 28 (74%) had MDR-/XDR-TB. In 109 HCWs evaluated for final treatment outcomes, 97 (89%) were successfully treated, and their results were not affected by DST status.

CONCLUSION

This study highlights the high prevalence of recorded TB in HCWs in TB health facilities in Belarus: there is a need to better understand and rectify this problem.

Outcomes of on-site antiretroviral therapy provision in a South African correctional facility

We evaluated a novel on-site antiretroviral therapy (ART) programme in a South African correctional facility using routinely collected programme data, from a retrospective cohort of adult inmates starting ART between 03/2007 and 03/2009 followed-up to 09/2009. We report (1) mortality (using survival analysis); (2) retention in the programme (to 09/2009); and (3) virological suppression at six and 12 months (<400 copies/ml) following ART initiation. In total, 404 started ART (median age 33 years; 91.3% men; median baseline CD4 cell count 152 cells/µl [interquartile range 85-225]). Among 299 starting ART for the first time (ART-naïve), 23 deaths occurred during 252 person-years (median follow-up nine months). Mortality rates were 17.2 at 0-6 months (95% confidence interval 10.9-26.9) and 2.8 at >6 months (95% confidence interval 1.1-7.5)/100 person-years; p < 0.001. At 09/2009, 35.6% (144/404) remained in the correctional facility, with 94.4% (136/144) retained in the programme; 38.4% (155/404) were released; and 20.0% (81/404) transferred to another facility. ART-naïve patients in care six and 12 months after ART initiation, 94.7% (124/131) and 92.5% (74/80) were virologically suppressed, respectively. High early mortality warrants the early identification and management of HIV-positive inmates. The high mobility of inmates necessitates systems for facilitating continuity of care. Good virological responses and retention supports decentralising HIV care to correctional facilities.

Significant clinical impact of a rapid molecular diagnostic test (Genotype MTBDRplus assay) to detect multidrug-resistant tuberculosis

BACKGROUND

There are limited data on the clinical impact of rapid diagnostic tests to detect multidrug-resistant tuberculosis (MDR-TB). We sought to determine whether the use of a molecular diagnostic test to detect MDR-TB improves clinical outcomes.

METHODS

A quasi-experimental study was conducted to analyze the impact of the Genotype MTBDRplus assay on clinical outcomes among patients with culture-confirmed pulmonary MDR-TB. Patients received treatment at the National Center for Tuberculosis and Lung Diseases in Tbilisi, Georgia. Time to MDR-TB treatment initiation, culture conversion, and infection control measures were compared to a time period prior to the implementation of the molecular test.

RESULTS

Of 152 MDR-TB patients, 72 (47%) were from prior to and 80 (53%) following implementation of the MTBDRplus assay ("post-implementation group"). Patients in the post-implementation group initiated a second-line treatment regimen more rapidly than those in the pre-implementation group (18.2 vs 83.9 days, P < .01). Among patients admitted to a "drug-susceptible" tuberculosis ward, those from the post-implementation group spent significantly fewer days on the drug-susceptible ward compared to patients in the pre-implementation group (10.0 vs 58.3 days, P < .01). Among patients with 24 weeks follow-up (n = 119), those in the post-implementation group had a higher rate of culture conversion at 24 weeks (86% vs 63%, P < .01) and a more rapid rate of time to culture conversion (adjusted hazard ratio [aHR] 4.15, 95% confidence interval [CI], 2.5-6.9).

CONCLUSIONS

The implementation of a rapid molecular diagnostic test led to significant clinical improvements including reduced time to initiation of MDR-TB treatment, culture conversion, and improved infection control practices.

A study of Mycobacterium tuberculosis genotypic diversity & drug resistance mutations in Varanasi, north India

BACKGROUND & OBJECTIVES

One-fifth of the world's new tuberculosis (TB) cases and two-thirds of cases in the South East Asian region occur in India. Molecular typing of Mycobacterium tuberculosis isolates has greatly facilitated to understand the transmission of TB. This study was aimed to investigate the molecular epidemiology of M. tuberculosis genotypes in Varanasi, north India, and their association with clinical presentation among patients with pulmonary TB.

METHODS

M. tuberculosis isolates from 104 TB patients attending a tertiary referral hospital of north India were screened for susceptibility to isoniazid (INH), rifampicin (RIF), ethambutol (EMB) and streptomycin (STR) by proportion method and multiplex-allele-specific-polymerase chain reaction (MAS-PCR). These were genotyped by spoligotyping. The spoligotype patterns were compared with those in the international SITVIT2 spoligotyping database.

RESULTS

Eighty three of 104 isolates were distributed in 38 SITs, of which SIT3366 was newly created within the present study. The mass of ongoing transmission with MDR-TB isolates in Varanasi, northern India, was linked to Beijing genotype followed by the CAS1_Delhi lineage. HIV-seropositive patients had a significantly higher proportion of clustered isolates than HIV-seronegative patients and compared with the wild type(wt) isolates, the isolates with katG315Thr mutation were considerably more likely to be clustered.

INTERPRETATION & CONCLUSIONS

This study gives an insight into the M. tuberculosis genetic biodiversity in Varanasi, north India, the predominant spoligotypes and their impact on disease transmission. In this region of north India, TB is caused by a wide diversity of spoligotypes with predominance of four genotype lineages: Beijing, CAS, EAI and T. The Beijing genotype was the most frequent single spoligotype and strongly associated with multi drug resistant (MDR)-TB isolates. These findings may have important implications for control and prevention of TB in north India.

Transmission of tuberculosis in resource-limited settings

Unrecognized transmission is a major contributor to ongoing TB epidemics in high-burden, resource-constrained settings. Limitations in diagnosis, treatment, and infection control in health-care and community settings allow for continued transmission of drug-sensitive and drug-resistant TB, particularly in regions of high HIV prevalence. Health-care facilities are common sites of TB transmission. Improved implementation of infection control practices appropriate for the local setting and in combination, has been associated with reduced transmission. Community settings account for the majority of TB transmission and deserve increased focus. Strengthening and intensifying existing high-yield strategies, including household contact tracing, can reduce onward TB transmission. Recent studies documenting high transmission risk community sites and strategies for community-based intensive case finding hold promise for feasible, effective transmission reduction. Infection control in community settings has been neglected and requires urgent attention. Developing and implementing improved strategies for decreasing transmission to children, within prisons and of drug-resistant TB are needed.

Estimating potential infection transmission routes in hospital wards using wearable proximity sensors

Background

Contacts between patients, patients and health care workers (HCWs) and among HCWs represent one of the important routes of transmission of hospital-acquired infections (HAI). A detailed description and quantification of contacts in hospitals provides key information for HAIs epidemiology and for the design and validation of control measures.

Methods and Findings

We used wearable sensors to detect close-range interactions (“contacts”) between individuals in the geriatric unit of a university hospital. Contact events were measured with a spatial resolution of about 1.5 meters and a temporal resolution of 20 seconds. The study included 46 HCWs and 29 patients and lasted for 4 days and 4 nights. 14,037 contacts were recorded overall, 94.1% of which during daytime. The number and duration of contacts varied between mornings, afternoons and nights, and contact matrices describing the mixing patterns between HCW and patients were built for each time period. Contact patterns were qualitatively similar from one day to the next. 38% of the contacts occurred between pairs of HCWs and 6 HCWs accounted for 42% of all the contacts including at least one patient, suggesting a population of individuals who could potentially act as super-spreaders.

Conclusions

Wearable sensors represent a novel tool for the measurement of contact patterns in hospitals. The collected data can provide information on important aspects that impact the spreading patterns of infectious diseases, such as the strong heterogeneity of contact numbers and durations across individuals, the variability in the number of contacts during a day, and the fraction of repeated contacts across days. This variability is however associated with a marked statistical stability of contact and mixing patterns across days. Our results highlight the need for such measurement efforts in order to correctly inform mathematical models of HAIs and use them to inform the design and evaluation of prevention strategies.

Implementation of tuberculosis infection control in health facilities in Mukono and Wakiso districts, Uganda

Background

Tuberculosis infection control (TBIC) is rarely implemented in the health facilities in resource limited settings. Understanding the reasons for low level of implementation is critical. The study aim was to assess TBIC practices and barriers to implementation in two districts in Uganda.

Methods

We conducted a cross-sectional study in 51 health facilities in districts of Mukono and Wakiso. The study included: a facility survey, observations of practices and eight focus group discussions with health workers.

Results

Quantitative: Only 16 facilities (31%) had a TBIC plan. Five facilities (10%) were screening patients for cough. Two facilities (4%) reported providing masks to patients with cough. Ventilation in the waiting areas was inadequate for TBIC in 43% (22/51) of the facilities. No facility possessed N95 particulate respirators.

Qualitative: Barriers that hamper implementation of TBIC elicited included: under-staffing, lack of space for patient separation, lack of funds to purchase masks, and health workers not appreciating the importance of TBIC.

Conclusion

TBIC measures were not implemented in health facilities in the two Ugandan districts where the survey was done. Health system factors like lack of staff, space and funds are barriers to implement TBIC. Effective implementation of TBIC measures occurs when the fundamental health system building blocks -governance and stewardship, financing, infrastructure, procurement and supply chain management are in place and functioning appropriately.

Natural ventilation reduces high TB transmission risk in traditional homes in rural KwaZulu-Natal, South Africa

BACKGROUND

Transmission of drug susceptible and drug resistant TB occurs in health care facilities, and community and households settings, particularly in highly prevalent TB and HIV areas. There is a paucity of data regarding factors that may affect TB transmission risk in household settings. We evaluated air exchange and the impact of natural ventilation on estimated TB transmission risk in traditional Zulu homes in rural South Africa.

METHODS

We utilized a carbon dioxide decay technique to measure ventilation in air changes per hour (ACH). We evaluated predominant home types to determine factors affecting ACH and used the Wells-Riley equation to estimate TB transmission risk.

RESULTS

Two hundred eighteen ventilation measurements were taken in 24 traditional homes. All had low ventilation at baseline when windows were closed (mean ACH = 3, SD = 3.0), with estimated TB transmission risk of 55.4% over a ten hour period of exposure to an infectious TB patient. There was significant improvement with opening windows and door, reaching a mean ACH of 20 (SD = 13.1, p < 0.0001) resulting in significant decrease in estimated TB transmission risk to 9.6% (p < 0.0001). Multivariate analysis identified factors predicting ACH, including ventilation conditions (windows/doors open) and window to volume ratio. Expanding ventilation increased the odds of achieving ≥12 ACH by 60-fold.

CONCLUSIONS

There is high estimated risk of TB transmission in traditional homes of infectious TB patients in rural South Africa. Improving natural ventilation may decrease household TB transmission risk and, combined with other strategies, may enhance TB control efforts.

Management of difficult multidrug-resistant tuberculosis and extensively drug-resistant tuberculosis: update 2012

Multidrug-resistant (MDR) tuberculosis (TB) denotes bacillary resistance to at least isoniazid and rifampicin. Extensively drug-resistant (XDR) TB is MDR-TB with additional bacillary resistance to any fluoroquinolone and at least one second-line injectable drugs. Rooted in inadequate TB treatment and compounded by a vicious circle of diagnostic delay and improper treatment, MDR-TB/XDR-TB has become a global epidemic that is fuelled by poverty, human immunodeficiency virus (HIV) and neglect of airborne infection control. The majority of MDR-TB cases in some settings with high prevalence of MDR-TB are due to transmission of drug-resistant bacillary strains to previously untreated patients. Global efforts in controlling MDR-TB/XDR-TB can no longer focus solely on high-risk patients. It is difficult and costly to treat MDR-TB/XDR-TB. Without timely implementation of preventive and management strategies, difficult MDR-TB/XDR-TB can cripple global TB control efforts. Preventive strategies include prompt diagnosis with adequate TB treatment using the directly observed therapy, short-course (DOTS) strategy and drug-resistance programmes, airborne infection control, preventive treatment of TB/HIV, and optimal use of antiretroviral therapy. Management strategies for established cases of difficult MDR-TB/XDR-TB rely on harnessing existing drugs (notably newer generation fluoroquinolones, high-dose isoniazid, linezolid and pyrazinamide with in vitro activity) in the best combinations and dosing schedules, together with adjunctive surgery in carefully selected cases. Immunotherapy may also have a role in the future. New diagnostics, drugs and vaccines are required to meet the challenge, but science alone is insufficient. Difficult MDR-TB/XDR-TB cannot be tackled without achieving high cure rates with quality DOTS and beyond, and concurrently addressing poverty and HIV.

Aerobiology and its role in the transmission of infectious diseases

Aerobiology plays a fundamental role in the transmission of infectious diseases. As infectious disease and infection control practitioners continue employing contemporary techniques (e.g., computational fluid dynamics to study particle flow, polymerase chain reaction methodologies to quantify particle concentrations in various settings, and epidemiology to track the spread of disease), the central variables affecting the airborne transmission of pathogens are becoming better known. This paper reviews many of these aerobiological variables (e.g., particle size, particle type, the duration that particles can remain airborne, the distance that particles can travel, and meteorological and environmental factors), as well as the common origins of these infectious particles. We then review several real-world settings with known difficulties controlling the airborne transmission of infectious particles (e.g., office buildings, healthcare facilities, and commercial airplanes), while detailing the respective measures each of these industries is undertaking in its effort to ameliorate the transmission of airborne infectious diseases.

Indoor social networks in a South African township: potential contribution of location to tuberculosis transmission

BACKGROUND

We hypothesized that in South Africa, with a generalized tuberculosis (TB) epidemic, TB infection is predominantly acquired indoors and transmission potential is determined by the number and duration of social contacts made in locations that are conducive to TB transmission. We therefore quantified time spent and contacts met in indoor locations and public transport by residents of a South African township with a very high TB burden.

METHODS

A diary-based community social mixing survey was performed in 2010. Randomly selected participants (n = 571) prospectively recorded numbers of contacts and time spent in specified locations over 24-hour periods. To better characterize age-related social networks, participants were stratified into ten 5-year age strata and locations were classified into 11 types.

RESULTS

Five location types (own-household, other-households, transport, crèche/school, and work) contributed 97.2% of total indoor time and 80.4% of total indoor contacts. Median time spent indoors was 19.1 hours/day (IQR:14.3-22.7), which was consistent across age strata. Median daily contacts increased from 16 (IQR:9-40) in 0-4 year-olds to 40 (IQR:18-60) in 15-19 year-olds and declined to 18 (IQR:10-41) in ≥45 year-olds. Mean daily own-household contacts was 8.8 (95%CI:8.2-9.4), which decreased with increasing age. Mean crèche/school contacts increased from 6.2/day (95%CI:2.7-9.7) in 0-4 year-olds to 28.1/day (95%CI:8.1-48.1) in 15-19 year-olds. Mean transport contacts increased from 4.9/day (95%CI:1.6-8.2) in 0-4 year-olds to 25.5/day (95%CI:12.1-38.9) in 25-29 year-olds.

CONCLUSIONS

A limited number of location types contributed the majority of indoor social contacts in this community. Increasing numbers of social contacts occurred throughout childhood, adolescence, and young adulthood, predominantly in school and public transport. This rapid increase in non-home socialization parallels the increasing TB infection rates during childhood and young adulthood reported in this community. Further studies of the environmental conditions in schools and public transport, as potentially important locations for ongoing TB infection, are indicated.

Survival from XDR-TB is associated with modifiable clinical characteristics in rural South Africa

BACKGROUND

Drug-resistant tuberculosis (TB) is a major threat to global public health. Patients with extensively drug-resistant TB (XDR-TB), particularly those with HIV-coinfection, experience high and accelerated mortality with limited available interventions. To determine modifiable factors associated with survival, we evaluated XDR-TB patients from a community-based hospital in rural South Africa where a large number of XDR-TB cases were first detected.

METHODOLOGY/PRINCIPAL FINDINGS

A retrospective case control study was conducted of XDR-TB patients diagnosed from 2005-2008. Survivors, those alive at 180 days from diagnostic sputum collection date, were compared with controls who died within 180 days. Clinical, laboratory and microbiological correlates of survival were assessed in 69 survivors (median survival 565 days [IQR 384-774] and 73 non-survivors (median survival 34 days [IQR 18-90]). Among 129 HIV+ patients, multivariate analyses of modifiable factors demonstrated that negative AFB smear (AOR 8.4, CI 1.84-38.21), a lower laboratory index of routine laboratory findings (AOR 0.48, CI 0.22-1.02), CD4>200 cells/mm(3) (AOR 11.53, 1.1-119.32), and receipt of antiretroviral therapy (AOR 20.9, CI 1.16-376.83) were independently associated with survival from XDR-TB.

CONCLUSIONS/SIGNIFICANCE

Survival from XDR-TB with HIV-coinfection is associated with less advanced stages of both diseases at time of diagnosis, absence of laboratory markers indicative of multiorgan dysfunction, and provision of antiretroviral therapy. Survival can be increased by addressing these modifiable risk factors through policy changes and improved clinical management. Health planners and clinicians should develop programmes focusing on earlier case finding and integration of HIV and drug-resistant TB diagnostic, therapeutic, and preventive activities.

Tuberculosis infection control in a high drug-resistance setting in rural South Africa: information, motivation, and behavioral skills

BACKGROUND

Tuberculosis (TB) is transmitted in resource-limited facilities where TB infection control (IC) is poorly implemented. Theory-based behavioral models can potentially improve IC practices.

METHODS

The present study used an anonymous questionnaire to assess healthcare worker (HCW) TB IC information, motivation, and behavioral skills (IMB) and implementation in two resource-limited rural South African hospitals with prevalent drug-resistant TB.

RESULTS

Between June and August 2010, 198 surveys were completed. Although the respondents demonstrated information proficiency and positive motivation, 22.8% did not consider TB IC to be worthwhile. Most tasks were rated as easy by survey participants, but responding HCWs highlighted challenges in discrete behavioral skills. The majority of responding HCWs reported that they always wore respirators (54.3%), instructed patients on cough hygiene (63.0%), and ensured natural ventilation (67.4%) in high-risk areas. Most respondents (74.0%) knew their HIV status. Social support items correlated with the implementation of the first three aforementioned practices but not with the respondents' knowledge of their HIV status. In most cases, motivation and behavioral skills, but not information, were associated with implementation.

CONCLUSION

HCWs in rural South African hospitals with high drug-resistance demonstrated moderate IMB and implementation of TB IC. Improvement efforts should emphasize the development of HCW motivation and behavioral skills as well as social support from colleagues and supervisors. Such interventions should be informed by baseline IMB assessments. In the present study, a trimmed/modified IMB model helped characterize TB IC implementation.

Tuberculosis infection control in rural South Africa: survey of knowledge, attitude and practice in hospital staff

A baseline assessment of tuberculosis infection control (TB IC) knowledge, attitude and practice (KAP) was conducted among staff in a resource-limited rural South African hospital where nosocomially transmitted multi- and extensively drug-resistant (M/XDR) TB had been reported. Assessment consisted of anonymous questionnaires and direct observation during July-September 2007, soon after the report of M/XDR-TB. Data were obtained from 57 questionnaires and 10h of direct observation. While knowledge and attitudes were generally supportive of TB IC implementation, 49.1% of staff felt that the hospital did not care about them and/or was not working to prevent staff TB infections, and 42.9% were less willing to continue as a healthcare worker because of staff TB/MDR-TB/XDR-TB deaths. Practices were variable. The recent appointment of an IC officer and implementation of natural ventilation were strengths, but the facility lacked a TB IC policy, the patient TB screening process was inadequate, and 41.5% of respondents were unaware of their personal human immunodeficiency virus (HIV) status. Respondents reported a number of barriers to TB IC implementation such as concerns about the confidentiality of staff health information, the stigma of TB and HIV, inadequate resources, and patient non-compliance. Assessment of staff KAP provided useful data regarding deficits and barriers to TB IC, and helped to focus subsequent IC strategies. Given the critical importance of reducing nosocomial TB transmission, it is recommended that facilities should conduct simplified TB IC assessment, ensure the confidentiality of staff health information, address the stigma of TB/HIV, and implement multi-faceted TB IC facility and behavioural change interventions. Behavioural science methods have the potential to improve TB IC research and implementation.

Transmission pattern of drug-resistant tuberculosis and its implication for tuberculosis control in eastern rural China

OBJECTIVE

Transmission patterns of drug-resistant Mycobacterium tuberculosis (MTB) may be influenced by differences in socio-demographics, local tuberculosis (TB) endemicity and efficaciousness of TB control programs. This study aimed to investigate the impact of DOTS on the transmission of drug-resistant TB in eastern rural China.

METHODS

We conducted a cross-sectional study of all patients diagnosed with drug-resistant TB over a one-year period in two rural Chinese counties with varying lengths of DOTS implementation. Counties included Deqing, with over 11 years' DOTS implementation and Guanyun, where DOTS was introduced 1 year prior to start of this study. We combined demographic, clinical and epidemiologic information with IS6110-based restricted fragment length polymorphism (RFLP) and Spoligotyping analysis of MTB isolates. In addition, we conducted DNA sequencing of resistance determining regions to first-line anti-tuberculosis agents.

RESULTS

Of the 223 drug-resistant isolates, 73(32.7%) isolates were identified with clustered IS6110RFLP patterns. The clustering proportion among total drug-resistant TB was higher in Guanyun than Deqing (26/101.vs.47/122; p,0.04), but not significantly different among the 53 multidrug-resistant isolates (10/18.vs.24/35; p,0.35). Patients with cavitary had increased risk of clustering in both counties. In Guanyun, patients with positive smear test or previous treatment history had a higher clustering proportion. Beijing genotype and isolates resistant to isoniazid and/or rifampicin were more likely to be clustered. Of the 73 patients with clustered drug-resistant isolates, 71.2% lived in the same or neighboring villages. Epidemiological link (household and social contact) was confirmed in 12.3% of the clustered isolates.

CONCLUSION

Transmission of drug-resistant TB in eastern rural China is characterized by small clusters and limited geographic spread. Our observations highlight the need for supplementing DOTS with additional strategies, including active case finding at the village level, effective treatment for patients with cavities and drug susceptibility testing for patients at increased risk for drug-resistance.

Predictors of multidrug- and extensively drug-resistant tuberculosis in a high HIV prevalence community

Background

Multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB) have emerged in high-HIV-prevalence settings, which generally lack laboratory infrastructure for diagnosing TB drug resistance. Even where available, inherent delays with current drug-susceptibility testing (DST) methods result in clinical deterioration and ongoing transmission of MDR and XDR-TB. Identifying clinical predictors of drug resistance may aid in risk stratification for earlier treatment and infection control.

Methods

We performed a retrospective case-control study of patients with MDR (cases), XDR (cases) and drug-susceptible (controls) TB in a high-HIV-prevalence setting in South Africa to identify clinical and demographic risk factors for drug-resistant TB. Controls were selected in a 1∶1∶1 ratio and were not matched. We calculated odds ratios (OR) and performed multivariate logistic regression to identify independent predictors.

Results

We enrolled 116, 123 and 139 patients with drug-susceptible, MDR, and XDR-TB. More than 85% in all three patient groups were HIV-infected. In multivariate analysis, MDR and XDR-TB were each strongly associated with history of TB treatment failure (adjusted OR 51.7 [CI 6.6-403.7] and 51.5 [CI 6.4–414.0], respectively) and hospitalization more than 14 days (aOR 3.8 [CI 1.1–13.3] and 6.1 [CI 1.8–21.0], respectively). Prior default from TB treatment was not a risk factor for MDR or XDR-TB. HIV was a risk factor for XDR (aOR 8.2, CI 1.3–52.6), but not MDR-TB. Comparing XDR with MDR-TB patients, the only significant risk factor for XDR-TB was HIV infection (aOR 5.3, CI 1.0–27.6).

Discussion

In this high-HIV-prevalence and drug-resistant TB setting, a history of prolonged hospitalization and previous TB treatment failure were strong risk factors for both MDR and XDR-TB. Given high mortality observed among patients with HIV and drug-resistant TB co-infection, previously treated and hospitalized patients should be considered for empiric second-line TB therapy while awaiting confirmatory DST results in settings with a high-burden of MDR/XDR-TB.

Keeping health facilities safe: one way of strengthening the interaction between disease-specific programmes and health systems

The debate on the interaction between disease-specific programmes and health system strengthening in the last few years has intensified as experts seek to tease out common ground and find solutions and synergies to bridge the divide. Unfortunately, the debate continues to be largely academic and devoid of specificity, resulting in the issues being irrelevant to health care workers on the ground. Taking the theme 'What would entice HIV- and tuberculosis (TB)-programme managers to sit around the table on a Monday morning with health system experts', this viewpoint focuses on infection control and health facility safety as an important and highly relevant practical topic for both disease-specific programmes and health system strengthening. Our attentions, and the examples and lessons we draw on, are largely aimed at sub-Saharan Africa where the great burden of TB and HIV ⁄ AIDS resides, although the principles we outline would apply to other parts of the world as well. Health care infections, caused for example by poor hand hygiene, inadequate testing of donated blood, unsafe disposal of needles and syringes, poorly sterilized medical and surgical equipment and lack of adequate airborne infection control procedures, are responsible for a considerable burden of illness amongst patients and health care personnel, especially in resource-poor countries. Effective infection control in a district hospital requires that all the components of a health system function well: governance and stewardship, financing,infrastructure, procurement and supply chain management, human resources, health information systems, service delivery and finally supervision. We argue in this article that proper attention to infection control and an emphasis on safe health facilities is a concrete first step towards strengthening the interaction between disease-specific programmes and health systems where it really matters – for patients who are sick and for the health care workforce who provide the care and treatment.

Infectious disease comorbidities adversely affecting substance users with HIV: hepatitis C and tuberculosis

The linkage between drug use, particularly injection drug use, and HIV/AIDS, hepatitis C (HCV), and tuberculosis (TB) has been recognized since the beginning of the HIV pandemic. These comorbid conditions affect drug users worldwide and act synergistically, with resultant adverse biologic, epidemiologic, and clinical consequences. Prevention, care, and treatment of TB and HCV can be successful, and both diseases can be cured. Special clinical challenges among drug users, however, can result in increased morbidity, mortality, and decreased therapeutic success. Among these are limited disease screening, inadequate and insensitive diagnostics, difficult treatment regimens with varying toxicities, and complicated pharmacokinetic and pharmacodynamic drug interactions. These may result in delayed diagnosis, deferred treatment initiation, and low completion rates, with the potential for generation and transmission of drug resistant organisms. Strategies to address these challenges include outreach programs to engage substance abusers in nonmedical settings, such as prisons and the streets, active screening programs for HIV, HCV, and TB, increased and broadened clinician expertise, knowledge and avoidance of drug interactions, attention to infection control, use of isoniazid preventive therapy, and creative strategies to insure medication adherence. All of these require structural changes directed at comprehensive prevention and treatment programs and increased collaboration and integration of needed services for substance abusers.

Human lung immunity against Mycobacterium tuberculosis: insights into pathogenesis and protection

The study of human pulmonary immunity against Mycobacterium tuberculosis (M.tb) provides a unique window into the biological interactions between the human host and M.tb within the broncho-alveolar microenvironment, the site of natural infection. Studies of bronchoalveolar cells (BACs) and lung tissue evaluate innate, adaptive, and regulatory immune mechanisms that collectively contribute to immunological protection or its failure. In aerogenically M.tb-exposed healthy persons lung immune responses reflect early host pathogen interactions that may contribute to sterilization, the development of latent M.tb infection, or progression to active disease. Studies in these persons may allow the identification of biomarkers of protective immunity before the initiation of inflammatory and disease-associated immunopathological changes. In healthy close contacts of patients with tuberculosis (TB) and during active pulmonary TB, immune responses are compartmentalized to the lungs and characterized by an exuberant helper T-cell type 1 response, which as suggested by recent evidence is counteracted by local suppressive immune mechanisms. Here we discuss how exploring human lung immunity may provide insights into disease progression and mechanisms of failure of immunological protection at the site of the initial host-pathogen interaction. These findings may also aid in the identification of new biomarkers of protective immunity that are urgently needed for the development of new and the improvement of current TB vaccines, adjuvant immunotherapies, and diagnostic technologies. To facilitate further work in this area, methodological and procedural approaches for bronchoalveolar lavage studies and their limitations are also discussed.

Comparison of two active case-finding strategies for community-based diagnosis of symptomatic smear-positive tuberculosis and control of infectious tuberculosis in Harare, Zimbabwe (DETECTB): a cluster-randomised trial

BACKGROUND

Control of tuberculosis in settings with high HIV prevalence is a pressing public health priority. We tested two active case-finding strategies to target long periods of infectiousness before diagnosis, which is typical of HIV-negative tuberculosis and is a key driver of transmission.

METHODS

Clusters of neighbourhoods in the high-density residential suburbs of Harare, Zimbabwe, were randomised to receive six rounds of active case finding at 6-monthly intervals by either mobile van or door-to-door visits. Randomisation was done by selection of discs of two colours from an opaque bag, with one disc to represent every cluster, and one colour allocated to each intervention group before selection began. In both groups, adult (≥16 years) residents volunteering chronic cough (≥2 weeks) had two sputum specimens collected for fluorescence microscopy. Community health workers and cluster residents were not masked to intervention allocation, but investigators and laboratory staff were masked to allocation until final analysis. The primary outcome was the cumulative yield of smear-positive tuberculosis per 1000 adult residents, compared between intervention groups; analysis was by intention to treat. The secondary outcome was change in prevalence of culture-positive tuberculosis from before intervention to before round six of intervention in 12% of randomly selected households from the two intervention groups combined; analysis was based on participants who provided sputum in the two prevalence surveys. This trial is registered, number ISRCTN84352452.

FINDINGS

46 study clusters were identified and randomly allocated equally between intervention groups, with 55 741 adults in the mobile van group and 54,691 in the door-to-door group at baseline. HIV prevalence was 21% (1916/9060) and in the 6 months before intervention the smear-positive case notification rate was 2·8 per 1000 adults per year. The trial was completed as planned with no adverse events. The mobile van detected 255 smear-positive patients from 5466 participants submitting sputum compared with 137 of 4711 participants identified through door-to-door visits (adjusted risk ratio 1·48, 95% CI 1·11-1·96, p=0·0087). The overall prevalence of culture-positive tuberculosis declined from 6·5 per 1000 adults (95% CI 5·1-8·3) to 3·7 per 1000 adults (2·6-5·0; adjusted risk ratio 0·59, 95% CI 0·40-0·89, p=0·0112).

INTERPRETATION

Wide implementation of active case finding, particularly with a mobile van approach, could have rapid effects on tuberculosis transmission and disease.

FUNDING

Wellcome Trust.