Tobacco exposure and susceptibility to tuberculosis: is there a smoking gun?

Ex vivo and in vivo evidence that cigarette smoke-exposed T regulatory cells impair host immunity against Mycobacterium tuberculosis

Introduction

A strong epidemiologic link exists between cigarette smoke (CS) exposure and susceptibility to tuberculosis (TB). Macrophage and murine studies showed that CS and nicotine impair host-protective immune cells against Mycobacterium tuberculosis (MTB) infection. While CS and nicotine may activate T regulatory cells (Tregs), little is known about how CS may affect these immunosuppressive cells with MTB infection.

Methods

We investigated whether CS-exposed Tregs could exacerbate MTB infection in co-culture with human macrophages and in recipient mice that underwent adoptive transfer of Tregs from donor CS-exposed mice.

Results

We found that exposure of primary human Tregs to CS extract impaired the ability of unexposed human macrophages to control an MTB infection by inhibiting phagosome-lysosome fusion and autophagosome formation. Neutralizing CTLA-4 on the CS extract-exposed Tregs abrogated the impaired control of MTB infection in the macrophage and Treg co-cultures. In Foxp3+GFP+DTR+ (Thy1.2) mice depleted of endogenous Tregs, adoptive transfer of Tregs from donor CS-exposed B6.PL(Thy1.1) mice with subsequent MTB infection of the Thy1.2 mice resulted in a greater burden of MTB in the lungs and spleens than those that received Tregs from air-exposed mice. Mice that received Tregs from donor CS-exposed mice and infected with MTB had modest but significantly reduced numbers of interleukin-12-positive dendritic cells and interferon-gamma-positive CD4+ T cells in the lungs, and an increased number of total programmed cell death protein-1 (PD-1) positive CD4+ T cells in both the lungs and spleens.

Discussion

Previous studies demonstrated that CS impairs macrophages and host-protective T effector cells in controlling MTB infection. We now show that CS-exposed Tregs can also impair control of MTB in co-culture with macrophages and in a murine model.

Nicotine Suppresses Phagocytic Ability of Macrophages by Regulating the miR-296-3p-SIRPα Axis

Phagocytic ability of macrophage is responsible for tuberculosis infection. Nicotine has been shown to attenuate the phagocytic ability of macrophage; however, the underlying mechanism remains unclear. Here, we demonstrated that nicotine increased the message RNA (mRNA) and protein expression of signal regulatory protein alpha (SIRPα) and enhanced the stability of SIRPα mRNA in macrophage. Nicotine decreased the expression of microRNA (miR)-296-3p, which directly targeted the 3'-untranslated region (3'-UTR) of SIRPα mRNA in macrophage. Furthermore, nicotine inhibited the phagocytic ability of macrophage by regulating the miR-296-3p-SIRPα axis. Moreover, nicotine decreased miR-296-3p expression via increasing c-Myc expression in macrophage. Together, we found that nicotine attenuate the phagocytic ability of macrophage by regulating the c-Myc-miR-296-3p-SIRPα signal.

Progress on diagnosis and treatment of latent tuberculosis infection

One fourth of the global population has been infected with Mycobacterium tuberculosis, and about 5%-10% of the infected individuals with latent tuberculosis infection (LTBI) will convert to active tuberculosis (ATB). Correct diagnosis and treatment of LTBI are important in ending the tuberculosis epidemic. Current methods for diagnosing LTBI, such as tuberculin skin test (TST) and interferon-γ release assay (IGRA), have limitations. Some novel biomarkers, such as transcriptome derived host genes in peripheral blood cells, will help to distinguish LTBI from ATB. More emphasis should be placed on surveillance in high-risk groups, including patients with HIV infection, those using biological agents, organ transplant recipients and those in close contact with ATB patients. For those with LTBI, treatment should be based on the risk of progression to ATB and the potential benefit. Prophylactic LTBI regimens include isoniazid monotherapy for 6 or 9 months, rifampicin monotherapy for 4 months, weekly rifapentine plus isoniazid for 3 months (3HP regimen) and daily rifampicin plus isoniazid for 3 months (3HR regimen). The success of the one month rifapentine plus isoniazid daily regimen (1HP regimen) suggests the feasibility of an ultra-short treatment strategy although its efficacy needs further assessment. Prophylactic treatment of LTBI in close contact with MDR-TB patients is another challenge, and the regimens include new anti-tuberculosis drugs such as bedaquiline, delamanid, fluoroquinolone and their combinations, which should be carefully evaluated. This article summarizes the current status of diagnosis and treatment of LTBI and its future development direction.

P2X7 1513A/C loss-of-function polymorphism and active tuberculosis disease in a cohort of Egyptian population: a pilot study

Background

Tuberculosis (TB) is a multifactorial disease, and increasing evidence shows that genetic variants in regulating genes of immune response confer susceptibility to active TB at the individual level. We aimed to identify the contribution of P2X7 receptor 1513A/C genetic polymorphisms to different clinical forms of active tuberculosis in a cohort of Egyptian population.

Methods

A case–control study that enrolled 25 newly diagnosed pulmonary TB (PTB) patients by positive sputum for AFB or positive culture, 25 extrapulmonary TB (EPTB) diagnosed by pathological/bacteriological/immunological studies and 25 healthy controls. A blood sample was taken before starting of therapy for P2X7 1513A/C polymorphism genotyping using PCR-restriction fragment length polymorphism.

Results

Fifty-two percent of the participants were in the third decade with equal gender distribution. P2X7 receptor 1513AA (homozygote wild), AC (heterozygote) and CC (homozygote mutant) genotypes were identified. AC and CC genotypes distribution were significantly more frequent in the active TB cases (either PTB or EPTB) rather than controls (p < 0.05). Further, P2X7 1513A/C genotypes’ distribution did not associate with old TB or gender (p > 0.05), but significantly associated with history of smoking (x2 trend analysis p = 0.036).

Conclusions

There is positive association between P2X7 receptor 1513A/C polymorphism and active tuberculosis in the Egyptians.

Tobacco and nicotine use

Tobacco smoking is a major determinant of preventable morbidity and mortality worldwide. More than a billion people smoke, and without major increases in cessation, at least half will die prematurely from tobacco-related complications. In addition, people who smoke have a significant reduction in their quality of life. Neurobiological findings have identified the mechanisms by which nicotine in tobacco affects the brain reward system and causes addiction. These brain changes contribute to the maintenance of nicotine or tobacco use despite knowledge of its negative consequences, a hallmark of addiction. Effective approaches to screen, prevent and treat tobacco use can be widely implemented to limit tobacco's effect on individuals and society. The effectiveness of psychosocial and pharmacological interventions in helping people quit smoking has been demonstrated. As the majority of people who smoke ultimately relapse, it is important to enhance the reach of available interventions and to continue to develop novel interventions. These efforts associated with innovative policy regulations (aimed at reducing nicotine content or eliminating tobacco products) have the potential to reduce the prevalence of tobacco and nicotine use and their enormous adverse impact on population health.

Tuberculosis in Biologic-naïve Patients With Rheumatoid Arthritis: Risk Factors and Tuberculosis Characteristics

OBJECTIVE

To investigate risk factors and characteristics of active tuberculosis (TB) in biologic-naïve patients with rheumatoid arthritis (RA).

METHODS

We conducted a population-based case-control study using the Swedish Rheumatology Quality Register, the National Patient Register, and the Tuberculosis Register to identify RA patients with active TB and matched RA controls without TB between 2001-2014. Clinical data were obtained from medical records. TB risk was estimated as adjusted OR (aOR) with 95% CI using univariate and multivariable logistic regression analyses.

RESULTS

After validation of diagnoses, the study included 31 RA patients with TB and 122 matched RA controls. All except 3 cases had reactivation of latent TB. Pulmonary TB was most prevalent (84%). Ever use of methotrexate was not associated with increased TB risk (aOR 0.8, 95% CI 0.3-2.0), whereas ever treatment with leflunomide (aOR 6.0, 95% CI 1.5-24.7), azathioprine (aOR 3.8, 95% CI 1.1-13.8), and prednisolone (PSL; aOR 2.4, 95% CI 1.0-6.0) was. There were no significant differences between maximum dose of PSL, treatment duration with PSL before TB, or cumulative dose of PSL the year before TB diagnosis between cases and controls. Obstructive pulmonary disease was associated with an increased TB risk (aOR 3.9, 95% CI 1.5-10.7).

CONCLUSION

Several RA-associated factors may contribute to increased TB risk in biologic-naïve patients with RA, making the risk of TB activation difficult to predict in the individual patient. To further decrease TB in patients with RA, the results suggest that screening for latent TB should also be considered in biologic-naïve patients.

Smoking and COVID-19: What we know so far

The ongoing COVID-19 pandemic has placed a spotlight on infectious diseases and their associations with host factors and underlying conditions. New data on the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) virus are entering the public domain at a rapid rate such that their distillation often lags behind. To minimise weak associations becoming perceived as established paradigms, it is imperative that methodologies and outputs from different studies are appropriately critiqued and compared. In this review, we examine recent data on a potential relationship between smoking and COVID-19. While the causal role of smoking has been firmly demonstrated in regard to lung cancer and chronic obstructive pulmonary disease, such associations have the benefit of decades' worth of multi-centre epidemiological and mechanistic data. From our analysis of the available studies to date, it appears that a relationship is emerging in regard to patients with a smoking history having a higher likelihood of developing more severe symptoms of COVID-19 disease than non-smokers. Data on whether COVID-19 has a greater incidence in smokers than non-smokers is thus far, contradictory and inconclusive. There is therefore a need for some caution to be exercised until further research has been conducted in a wider range of geographical settings with sufficient numbers of patients that have been carefully phenotyped in respect of smoking status and adequate statistical control for confounding factors.

Association between household solid fuel use and tuberculosis: cross-sectional data from the Mongolian National Tuberculosis Prevalence Survey

BACKGROUND

Tuberculosis (TB) and indoor air pollution (IAP) are equally critical public health issues in the developing world. Mongolia is experiencing the double burden of TB and IAP due to solid fuel combustion. However, no study has assessed the relationship between household solid fuel use and TB in Mongolia. The present study aimed to assess the association between household solid fuel use and TB based on data from the Mongolian National Tuberculosis Prevalence Survey (MNTP Survey).

METHOD

The MNTP Survey was a nationally representative population-based cross-sectional survey targeting households in Mongolia from 2014 to 2015, with the aim of evaluating the prevalence of TB. The survey adopted a multistage cluster sampling design in accordance with the World Health Organization prevalence survey guidelines. Clusters with at least 500 residents were selected by random sampling. A sample size of 98 clusters with 54,100 participants was estimated to be required for the survey, and 41,450 participants were included in the final analysis of the present study. A structured questionnaire was used to collect information on environmental and individual factors related to TB. Physical examination, chest X-ray, and sputum examinations were also performed to diagnose TB.

RESULTS

The use of solid fuels for heating (adjusted odds ratio (aOR): 1.5; 95% confidence interval (CI): 1.1-2.1), male gender (aOR: 2.2; 95% CI: 1.6-3.2), divorced or widowed (aOR: 2.6; 95% CI: 1.7-3.8), daily smoker (aOR: 1.8; 95% CI: 1.3-2.5), contact with an active TB case (aOR: 1.7; 95% CI: 1.2-2.3), being underweight (aOR: 3.7; 95% CI: 2.4-5.7), and previous history of TB (aOR: 4.3; 95% CI: 3.0-6.1) were significantly associated with bacteriologically confirmed TB after adjusting for confounding variables.

CONCLUSION

The use of solid fuels for heating was significantly associated with active TB in Mongolian adults. Increased public awareness is needed on the use of household solid fuels, a source of IAP.

Logistic regression analysis of environmental and other variables and incidences of tuberculosis in respiratory patients

The objective of this study was to examine the association of 14 variables with TB in respiratory patients. The variables included: urban/rural, persons in 1200 sqft area, TB in family, crowding, smoking (family member), gender, age, education, smoking, workplace, kitchen location, cooking fuel, ventilation, and kerosene uses. Eight hundred respiratory patients were tested for sputum positive pulmonary TB; 500 had TB and 300 did not. An analysis of the unadjusted odds ratio (UOR) and adjusted OR (AOR) was undertaken using logistic regression to link the probability of TB incidences with the variables. There was an inconsistency in the significance of variables using UOR and AOR. A subset model of 4 variables (kerosene uses, ventilation, workplace, and gender) based on significant AOR was adjudged acceptable for estimating the probability of TB incidences. Uses of kerosene (AOR 2.62 (1.95, 3.54)) consistently related to incidences of TB. It was estimated that 50% reduction in kerosene uses could reduce the probability of TB by 13.29% in respiratory patients. The major recommendation was to replace kerosene uses from households with a supply of clean fuel like liquid petroleum or natural gas and rural electrification.

Effects of Cigarette Smoke Condensate on Growth and Biofilm Formation by Mycobacterium tuberculosis

MATERIALS AND METHODS

The planktonic and biofilm-forming cultures were prepared in Middlebrook 7H9 and Sauton broth media, respectively, using Mtb strain, H37Rv. The effects of CSC at concentrations of 0.05-3.12 mg/L on growth, biofilm formation and structure were evaluated using microplate Alamar Blue assay, spectrophotometric procedure and scanning electron microscopy (SEM), respectively. Involvement of reactive oxygen species in CSC-mediated biofilm formation was investigated by including catalase in biofilm-forming cultures.

RESULTS

CSC did not affect the growth of planktonic bacteria, but rather led to a statistically significant increase in biofilm formation at concentrations of 0.4-3.12 mg/L, as well as in the viability of biofilm-forming bacteria at CSC concentrations of 0.2-1.56 mg/L. SEM confirmed an agglomerated biofilm matrix and irregular bacterial morphology in CSC-treated biofilms. Inclusion of catalase caused significant attenuation of CSC-mediated augmentation of biofilm formation by Mtb, implying involvement of oxidative stress. These findings demonstrate that exposure of Mtb to CSC resulted in increased biofilm formation that appeared to be mediated, at least in part, by oxidative stress, while no effect on planktonic cultures was observed.

CONCLUSION

Smoking-related augmentation of biofilm formation by Mtb may contribute to persistence of the pathogen, predisposing to disease reactivation and counteracting the efficacy of antimicrobial chemotherapy.

E-cigarettes: Effects in phagocytosis and cytokines response against Mycobacterium tuberculosis

Cigarette smoking and tuberculosis are a significant cause of death worldwide. Several epidemiological studies have demonstrated cigarette smoking is a risk factor for tuberculosis. Electronic cigarettes have recently appeared as a healthier alternative to conventional smoking, although their impact in tuberculosis is not well understood. The aim of this study was to explore the effect of electronic cigarettes in phagocytosis of Mycobacterium tuberculosis and cytokines production. In vitro infection was carried out by exposing THP-1 macrophages to four electronic vapor extracts and the intracellular burden of M. tuberculosis was determined. The percentage of infection was evaluated by confocal microscopy and the cytokine production by Luminex. A reduction of intracellular M. tuberculosis burden in THP-1 macrophages was found after its exposure to electronic vapor extract; the same trend was observed by confocal microscopy when Mycobacterium bovis BCG-GFP strain was used. Electronic cigarettes stimulate a pro-inflammatory cytokine response. We conclude that electronic cigarettes impair the phagocytic function and the cytokine response to M. tuberculosis.

Indoor PM2.5, tobacco smoking and chronic lung diseases: A narrative review

The lung is one of the most important organs exposed to environmental agents. People spend approximately 90% of their time indoors, and risks to health may thus be greater from exposure to poor air quality indoors than outdoors. Multiple indoor pollutants have been linked to chronic respiratory diseases. Environmental tobacco smoke (ETS) is known as an important source of multiple pollutants, especially in indoor environments. Indoor PM_2.5 (particulate matter with aerodynamic diameter < 2.5 μm) was reported to be the most reliable marker of the presence of tobacco smoke. Recent studies have demonstrated that PM_2.5 is closely correlated with chronic lung diseases. In this paper, we reviewed the relationship of tobacco smoking and indoor PM_2.5 and the mechanism that underpin the link of tobacco smoke, indoor PM_2.5 and chronic lung diseases.

TB-diabetes co-morbidity in Ghana: The importance of Mycobacterium africanum infection

BACKGROUND

Diabetes Mellitus (DM) is a known risk factor for tuberculosis (TB) but little is known on TB-Diabetes Mellitus (TBDM) co-morbidity in Sub-Saharan Africa.

METHODS

Consecutive TB cases registered at a tertiary facility in Ghana were recruited from September 2012 to April 2016 and screened for DM using random blood glucose and glycated hemoglobin (HbA1c) level. TB patients were tested for other clinical parameters including HIV co-infection and TB lesion location. Mycobacterial isolates obtained from collected sputum samples were characterized by standard methods. Associations between TBDM patients' epidemiological as well as microbiological variables were assessed.

RESULTS

The prevalence of DM at time of diagnosis among 2990 enrolled TB cases was 9.4% (282/2990). TBDM cases were significantly associated with weight loss, poor appetite, night sweat and fatigue (p<0.001) and were more likely (p<0.001) to have lower lung cavitation 85.8% (242/282) compared to TB Non-Diabetic (TBNDM) patients 3.3% (90/2708). We observed 22.3% (63/282) treatment failures among TBDM patients compared to 3.8% (102/2708) among TBNDM patients (p<0.001). We found no significant difference in the TBDM burden attributed by M. tuberculosis sensu stricto (Mtbss) and Mycobacterium africanum (Maf) and (Mtbss; 176/1836, 9.6% and Maf; 53/468, 11.3%, p = 0.2612). We found that diabetic individuals were suggestively likely to present with TB caused by M. africanum Lineage 6 as opposed to Mtbss (odds ratio (OR) = 1.52; 95% confidence interval (CI): 0.92-2.42, p = 0.072).

CONCLUSION

Our findings confirms the importance of screening for diabetes during TB diagnosis and highlights the association between genetic diversity and diabetes. in Ghana.

Smoking in Correctional Settings Worldwide: Prevalence, Bans, and Interventions

Smoking tobacco contributes to 11.5% of deaths worldwide and, in some countries, more hospitalizations than alcohol and drugs combined. Globally in 2015, 25% of men and 5% of women smoked. In the United States, a higher proportion of people in prison smoke than do community-dwelling individuals. To determine smoking prevalence in prisons worldwide, we systematically reviewed the literature using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines; we also examined whether prisons banned smoking or treated smokers. We searched databases for articles published between 2012 and 2016 and located 85 relevant articles with data representing 73.5% of all incarcerated persons from 50 countries. In 35 of 36 nations (97%) with published prevalence data, smoking for the incarcerated exceeded community rates 1.04- to 62.6-fold. Taking a conservative estimate of a 2-fold increase, we estimated that, globally, 14.5 million male and 26,000 female smokers pass through prisons annually. Prison authorities’ responses include permitting, prohibiting, or treating tobacco use. Bans may temporarily improve health and reduce in-prison health care costs but have negligible effect after prison release. Evidence-based interventions for smoking cessation effective outside prisons are effective inside; effects persist after release. Because smoking prevalence is heightened in prisons, offering evidence-based interventions to nearly 15 million smokers passing through yearly would improve global health.

[Tobacco smoking and stopping smoking interventions in patients with TB]

Tuberculosis and tobacco smoking are two major public health problems causing significant mortality worldwide. Tobacco smoke increases the risk of Mycobacterium tuberculosis infection, severe pulmonary or extrapulmonary TB, and death of TB. In emerging countries, quitting smoking is one way to control the TB epidemic. Compared with non-smokers, smokers with tuberculosis are less observant of anti-tuberculosis treatment. Smoking abstinence improves the course of their illness, the treatment compliance and facilitates the final cure justifying smoking cessation interventions. The involvement of all healthcare professionals in helping smokers stopping smoking is required.

Tuberculosis and cigarette smoke exposure: An update of in vitro and in vivo studies

Tuberculosis (TB) has been declared the first cause of death by an infectious agent. Annually, 10.4 million people suffer active TB. Most infected individuals live in low-income countries, where social and economic conditions enhance the dissemination and progression of the disease. These countries have a high percentage of smokers. Thousands of studies have linked cigarette smoke (CS) with increased risk of many diseases, such as cancer and lung diseases. Numerous in vitro studies have been conducted to evaluate the general and specific toxic effects of CS in lung immune function. Smoke exposure increases the risk of TB development three-fold. However, until now, only few animal studies have been performed to analyze the association between smoke and TB. In the present work, we review in vitro and in vivo studies whose aim was to analyze the molecular basis of TB susceptibility caused by exposure to CS.

Risks for tuberculosis in Kazakhstan: implications for prevention

SETTING

Four regions in Kazakhstan where participants were recruited from June 2012 to May 2014.

OBJECTIVE

To examine associations between incarceration history and tobacco, alcohol, and drug consumption, and human immunodeficiency virus (HIV) infection and diabetes mellitus (DM) with TB.

DESIGN

This matched case-control study included 1600 participants who completed a survey on sociodemographics, history of incarceration, tobacco, alcohol and drug use, and HIV and DM diagnosis. Conditional logistic regression analysis was used to examine associations between a TB diagnosis and risk factors.

RESULTS

Participants who had ever smoked tobacco (aOR 1.73, 95%CI 1.23-2.43, P  0.01), ever drank alcohol (aOR 1.41, 95%CI 1.03-1.93, P  0.05), were HIV-positive (aOR 36.37, 95%CI 2.05-646.13, P  0.05) or had DM (aOR 13.96, 95%CI 6.37-30.56, P  0.01) were more likely to have TB.

CONCLUSIONS

The association between TB and tobacco use, alcohol use, HIV and DM in Kazakhstan suggests a need for comprehensive intervention and prevention approaches that also address tobacco and alcohol use, DM and HIV.

Effects of cigarette smoke on pulmonary endothelial cells

Cigarette smoking is the leading cause of preventable disease and death in the United States. Cardiovascular comorbidities associated with both active and secondhand cigarette smoking indicate the vascular toxicity of smoke exposure. Growing evidence supports the injurious effect of cigarette smoke on pulmonary endothelial cells and the roles of endothelial cell injury in development of acute respiratory distress syndrome (ARDS), emphysema, and pulmonary hypertension. This review summarizes results from studies of humans, preclinical animal models, and cultured endothelial cells that document toxicities of cigarette smoke exposure on pulmonary endothelial cell functions, including barrier dysfunction, endothelial activation and inflammation, apoptosis, and vasoactive mediator production. The discussion is focused on effects of cigarette smoke-induced endothelial injury in the development of ARDS, emphysema, and vascular remodeling in chronic obstructive pulmonary disease.

Nicotine Impairs Macrophage Control of Mycobacterium tuberculosis

Pure nicotine impairs macrophage killing of Mycobacterium tuberculosis (MTB), but it is not known whether the nicotine component in cigarette smoke (CS) plays a role. Moreover, the mechanisms by which nicotine impairs macrophage immunity against MTB have not been explored. To neutralize the effects of nicotine in CS extract, we used a competitive inhibitor to the nicotinic acetylcholine receptor (nAChR)-mecamylamine-as well as macrophages derived from mice with genetic disruption of specific subunits of nAChR. We also determined whether nicotine impaired macrophage autophagy and whether nicotine-exposed T regulatory cells (Tregs) could subvert macrophage anti-MTB immunity. Mecamylamine reduced the CS extract increase in MTB burden by 43%. CS extract increase in MTB was also significantly attenuated in macrophages from mice with genetic disruption of either the α7, β2, or β4 subunit of nAChR. Nicotine inhibited autophagosome formation in MTB-infected THP-1 cells and primary murine alveolar macrophages, as well as increased the intracellular MTB burden. Nicotine increased migration of THP-1 cells, consistent with the increased number of macrophages found in the lungs of smokers. Nicotine induced Tregs to produce transforming growth factor-β. Naive mouse macrophages co-cultured with nicotine-exposed Tregs had significantly greater numbers of viable MTB recovered with increased IL-10 production and urea production, but no difference in secreted nitric oxide as compared with macrophages cocultured with unexposed Tregs. We conclude that nicotine in CS plays an important role in subverting macrophage control of MTB infection.

Airborne Pathogens inside Automobiles for Domestic Use: Assessing In-Car Air Decontamination Devices Using Staphylococcus aureus as the Challenge Bacterium

Family cars represent ∼74% of the yearly global output of motorized vehicles. With a life expectancy of ∼8 decades in many countries, the average person spends >100 min daily inside the confined and often shared space of the car, with exposure to a mix of potentially harmful microbes. Can commercial in-car microbial air decontamination devices mitigate the risk? Three such devices (designated devices 1 to 3) with HEPA filters were tested in the modified passenger cabin (3.25 m³) of a four-door sedan housed within a biosafety level 3 containment facility. Staphylococcus aureus (ATCC 6538) was suspended in a soil load to simulate the presence of body fluids and aerosolized into the car's cabin with a 6-jet Collison nebulizer. A muffin fan (80 mm by 80 mm, with an output of 0.17 m³/min) circulated the air inside. Plates (150 mm diameter) of Trypticase soy agar (TSA), placed inside a programmable slit-to-agar sampler, were held at 36 ± 1°C for 18 to 24 h and examined for CFU. The input dose of the test bacterium, its rate of biological decay, and the log₁₀ reductions by the test devices were analyzed. The arbitrarily set performance criterion was the time in hours a device took for a 3-log₁₀ reduction in the level of airborne challenge bacterium. On average, the level of S. aureus challenge in the air varied between 4.2 log₁₀ CFU/m³ and 5.5 log₁₀ CFU/m³, and its rate of biological decay was -0.0213 ± 0.0021 log₁₀ CFU/m³/min. Devices 1 to 3 took 2.3, 1.5, and 9.7 h, respectively, to meet the performance criterion. While the experimental setup was tested using S. aureus as an archetypical airborne pathogen, it can be readily adapted to test other types of pathogens and technologies.IMPORTANCE This study was designed to test the survival of airborne pathogens in the confined and shared space of a family automobile as well as to assess claims of devices marketed for in-car air decontamination. The basic experimental setup and the test protocols reported are versatile enough for work with all major types of airborne human pathogens and for testing a wide variety of air decontamination technologies. This study could also lay the foundation for a standardized test protocol for use by device makers as well as regulators for the registration of such devices.

Airborne Infectious Agents and Other Pollutants in Automobiles for Domestic Use: Potential Health Impacts and Approaches to Risk Mitigation

The world total of passenger cars is expected to go from the current one billion to >2.5 billion by 2050. Cars for domestic use account for ~74% of the world's yearly production of motorized vehicles. In North America, ~80% of the commuters use their own car with another 5.6% travelling as passengers. With the current life-expectancy of 78.6 years, the average North American spends 4.3 years driving a car! This equates to driving 101 minutes/day with a lifetime driving distance of nearly 1.3 million km inside the confined and often shared space of the car with exposure to a mix of potentially harmful pathogens, allergens, endotoxins, particulates, and volatile organics. Such risks may increase in proportion to the unprecedented upsurge in the numbers of family cars globally. Though new technologies may reduce the levels of air pollution from car exhausts and other sources, they are unlikely to impact our in-car exposure to pathogens. Can commercial in-car air decontamination devices reduce the risk from airborne infections and other pollutants? We lack scientifically rigorous protocols to verify the claims of such devices. Here we discuss the essentials of a customized aerobiology facility and test protocols to assess such devices under field-relevant conditions.

Double-hit mouse model of cigarette smoke priming for acute lung injury

Epidemiological studies indicate that cigarette smoking (CS) increases the risk and severity of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). The mechanism is not understood, at least in part because of lack of animal models that reproduce the key features of the CS priming process. In this study, using two strains of mice, we characterized a double-hit mouse model of ALI induced by CS priming of injury caused by lipopolysaccharide (LPS). C57BL/6 and AKR mice were preexposed to CS briefly (3 h) or subacutely (3 wk) before intratracheal instillation of LPS and ALI was assessed 18 h after LPS administration by measuring lung static compliance, lung edema, vascular permeability, inflammation, and alveolar apoptosis. We found that as little as 3 h of exposure to CS enhanced LPS-induced ALI in both strains of mice. Similar exacerbating effects were observed after 3 wk of preexposure to CS. However, there was a strain difference in susceptibility to CS priming for ALI, with a greater effect in AKR mice. The key features we observed suggest that 3 wk of CS preexposure of AKR mice is a reproducible, clinically relevant animal model that is useful for studying mechanisms and treatment of CS priming for a second-hit-induced ALI. Our data also support the concept that increased susceptibility to ALI/ARDS is an important adverse health consequence of CS exposure that needs to be taken into consideration when treating critically ill individuals.

Factors Associated With Noncompletion of Latent Tuberculosis Infection Treatment: Experience From the PREVENT TB Trial in the United States and Canada

BACKGROUND

Overall rates of noncompletion of treatment (NCT) for latent tuberculosis infection (LTBI) in the PREVENT TB trial were 18% for 3 months of directly observed once-weekly rifapentine (maximum dose, 900 mg) plus isoniazid (maximum dose, 900 mg) (3HP-DOT) and 31% for 9 months of daily self-administered isoniazid (maximum dose, 300 mg; 9H-SAT). NCT for LTBI reduces its effectiveness. The study objective was to assess factors associated with NCT for LTBI among adult participants enrolled at US and Canadian sites of the PREVENT TB trial.

METHODS

This was a post hoc exploratory analysis of the randomized, open-label PREVENT TB trial. Factors were analyzed by univariate and multivariate logistic regression (with enrollment site as a random effect).

RESULTS

From 6232 participants analyzed, 1406 (22.6%) did not complete LTBI treatment (317 NCT attributed to an adverse event [NCT-AE] and 1089 NCT attributed to reasons other than an adverse event [NCT-O]). The proportion of NCT-AE was similar with both regimens (3HP-DOT = 6.4% vs 9H-SAT = 5.9%; P = .23); NCT-O was higher among participants enrolled in 9H-SAT (9H-SAT = 24.5% vs 3HP-DOT = 12.7%; P = .02). Among those in the NCT-AE group, being non-Hispanic and receiving 3HP-DOT, having cirrhosis and receiving 9H-SAT, alcohol consumption among men, and use of concomitant medication were associated with NCT-AE. Among those in the NCT-O group, receiving 9H-SAT, missing ≥1 early visit, men receiving 9H-SAT, men with a history of incarceration, alcohol abuse, use ever of intravenous drugs, younger age receiving 9H-SAT, and smoking were associated with NCT-O.

CONCLUSIONS

Factors associated with NCT, such as missing a clinic visit early during treatment, might help identify persons for whom tailored interventions could improve completion of LTBI treatment.

CLINICAL TRIALS REGISTRATION

NCT00023452.

Updates on the risk factors for latent tuberculosis reactivation and their managements

The preventive treatment of latent tuberculosis infection (LTBI) is of great importance for the elimination and control of tuberculosis (TB) worldwide, but existing screening methods for LTBI are still limited in predicting the onset of TB. Previous studies have found that some high-risk factors (including human immunodeficiency virus (HIV), organ transplantation, silicosis, tumor necrosis factor-alpha blockers, close contacts and kidney dialysis) contribute to a significantly increased TB reactivation rate. This article reviews each risk factor's association with TB and approaches to address those factors. Five regimens are currently recommended by the World Health Organization, and no regimen has shown superiority over others. In recent years, studies have gradually narrowed down to the preventive treatment of LTBI for high-risk target groups, such as silicosis patients, organ-transplantation recipients and HIV-infected patients. This review discusses regimens for each target group and compares the efficacy of different regimens. For HIV patients and transplant recipients, isoniazid monotherapy is effective in treating LTBI, but for others, little evidence is available at present.

Introducing smoking cessation to Indonesian males treated for tuberculosis: The challenges of low-moderate level smoking

There is a dearth of information about the smoking habits of people currently and formerly treated for tuberculosis (TB) in low- and middle-income countries (LMICs). In this paper we describe research carried out in Indonesia between 2007 and 2011 designed to investigate both the impact of TB-specific quit smoking messages in the TB clinic and at home, and shifts in patterns of smoking among those formerly treated for TB who continue to smoke. The results of a modest two-arm smoking cessation trial involving 87 patients undergoing Directly Observed Therapy Short course treatment (DOTS) for TB are presented. In one arm patients received a TB-specific quit smoking message delivered by doctors and a TB and smoking educational booklet and quit smoking guide. In the second, family support arm, patients also received on-going cessation messages delivered by family members trained to be DOTS supporters. The study followed patients twice during their six months of DOTS treatment and twice six months post treatment. Both arms of the study reduced rates of smoking during and following TB treatment significantly with 73% of patients in the doctor arm and 71% in the family support arm remaining quit at the end of the treatment (month 6). When complete abstinence at six months after treatment was taken as a primary outcome measure, no statistical difference was found in the effectiveness of the two arms of the intervention. Notably, 67% of higher-level smokers at baseline and 33% of low-moderate level smokers at baseline quit entirely. Many of those who resumed smoking did so at low-moderate levels (<6 cigarettes a day). Eighty-four percent of patients who quit during treatment maintained their abstinence six months after treatment, 13% resumed smoking at a low-moderate level (<6 cigarettes), and only 3% resumed smoking at a higher level. A purposeful sample of 15 patients who shifted from heavy smoking (20-40 cigarettes per day) to low-moderate levels of smoking post treatment were followed for an additional 12 months. We report on their ability to sustain lower levels of smoking and self-perceived smoking status given their dramatic reduction in cigarette consumption. This is the first study of low-moderate level smoking among patients formerly treated for TB conducted anywhere in South-East Asia.

Adverse Events in Treating Smear-Positive Tuberculosis Patients in China

This study aimed to estimate the adverse events (AE) rate during anti-tuberculosis treatment and to explore AE-related risk factors. New and previously treated smear-positive tuberculosis (TB) cases were enrolled from eight regions in China between April 2009 and October 2010. The AE rate was estimated, and AE risk factors during anti-TB treatment were assessed using Cox proportional models. Among 2091 Chinese subjects with anti-TB treatment, 462 (22.1%, 95% confidence interval (CI), 20.3–23.9) patients developed AE, with liver injury and gastrointestinal reactions constituting the most common AE. Specifically, 9.8% (95% CI, 8.5–11.1) and 6.3% (95% CI, 5.3–7.4) developed liver injuries and gastrointestinal reactions, respectively. We found that AE rate differed by regions, TB knowledge score, symptoms score and smoking status. Liver injuries were associated with age, sex and smoking status; gastrointestinal reactions were associated with education level and symptom score. Improving patients’ knowledge on TB could reduce AE rate.

The re-emergency and persistence of vaccine preventable diseases

The introduction of vaccination worldwide dramatically reduced the incidence of pathogenic bacterial and viral diseases. Despite the highly successful vaccination strategies, the number of cases among vaccine preventable diseases has increased in the last decade and several of those diseases are still endemic in different countries. Here we discuss some epidemiological aspects and possible arguments that may explain why ancient diseases such as, measles, polio, pertussis, diphtheria and tuberculosis are still with us.

Epidemiologic link between tuberculosis and cigarette/biomass smoke exposure: Limitations despite the vast literature

The geographic overlap between the prevalence of cigarette smoke (CS) exposure and tuberculosis (TB) in the world is striking. In recent years, relatively large number of studies has linked cigarette or biomass fuel smoke exposure and various aspects of TB. Our goals are to summarize the significance of the known published studies, graphically represent reports that quantified the association and discuss their potential limitations. PubMed searches were performed using the key words 'tuberculosis' with 'cigarette', 'tobacco', 'smoke' or 'biomass fuel smoke.' The references of relevant articles were examined for additional pertinent papers. A large number of mostly case-control and cross-sectional studies significantly associate both direct and second-hand smoke exposure with tuberculous infection, active TB, and/or more severe and lethal TB. Fewer link biomass fuel smoke exposure and TB. While a number of studies interpreted the association with multivariate analysis, other confounders are often not accounted for in these analyses. It is also important to emphasize that these retrospective studies can only show an association and not any causal link. We further explored the possibility that even if CS exposure is a risk factor for TB, several mechanisms may be responsible. Numerous studies associate cigarette and biomass smoke exposure with TB but the mechanism(s) remains largely unknown. While the associative link of these two health maladies is well established, more definitive, mechanistic studies are needed to cement the effect of smoke exposure on TB pathogenesis and to utilize this knowledge in empowering public health policies.