Cigarette smoking as a risk factor for tuberculosis in young adults: a case-control study

Exploring Sex Differences in Risk Factors and Quality of Life Among Tuberculosis Patients in Herat, Afghanistan: A Case-Control Study

Objectives: Tuberculosis (TB) is a significant public health concern in Afghanistan, with a high burden of disease in the western province of Herat. This study explored the risk factors of TB and TB's impact on the quality of life of patients in Herat. Methods: A total of 422 TB patients and 514 controls were recruited at Herat Regional Hospital and relevant TB laboratories between October 2020 and February 2021. Data was collected through interviews using a structured questionnaire and the SF-36 questionnaire. Descriptive statistics, chi-square tests, Multivariate General Linear Model, and logistic regression analysis were used to analyze the data. Results: The results showed that male sex (p = 0.023), chronic disease (p = 0.038), lower education levels (p < 0.001), and worse health status (p < 0.001) were significantly associated with higher odds of TB infection. The study also found that TB patients had significantly lower quality of life scores in almost all components (p < 0.05). Conclusion: This study provides important insights into the specific ways in which TB affects the wellbeing of patients in Afghanistan. The findings highlight the importance of addressing the psychological and social dimensions of TB.

Cigarette Smoking as a Risk Factor for Tuberculosis in Adults: Epidemiology and Aspects of Disease Pathogenesis

It has been noted by the World Health Organisation that cases of tuberculosis in 2022 globally numbered 10.6 million, resulting in 1.3 million deaths, such that TB is one of the infectious diseases causing the greatest morbidity and mortality worldwide. Since as early as 1918, there has been an ongoing debate as to the relationship between cigarette smoking and TB. However, numerous epidemiological studies, as well as meta-analyses, have indicated that both active and passive smoking are independent risk factors for TB infection, development of reactivation TB, progression of primary TB, increased severity of cavitary disease, and death from TB, among several other considerations. With this considerable body of evidence confirming the association between smoking and TB, it is not surprising that TB control programmes represent a key potential preventative intervention. In addition to coverage of the epidemiology of TB and its compelling causative link with smoking, the current review is also focused on evidence derived from clinical- and laboratory-based studies of disease pathogenesis, most prominently the protective anti-mycobacterial mechanisms of the alveolar macrophage, the primary intracellular refuge of M. tuberculosis. This section of the review is followed by an overview of the major strategies utilised by the pathogen to subvert these antimicrobial mechanisms in the airway, which are intensified by the suppressive effects of smoke inhalation on alveolar macrophage function. Finally, consideration is given to a somewhat under-explored, pro-infective activity of cigarette smoking, namely augmentation of antibiotic resistance due to direct effects of smoke per se on the pathogen. These include biofilm formation, induction of cellular efflux pumps, which eliminate both smoke-derived toxicants and antibiotics, as well as gene modifications that underpin antibiotic resistance.

Modeling the effects of cigarette smoke extract on influenza B virus infections in mice

Influenza B virus (IBV) is a major respiratory viral pathogen. Due to a lack of pandemic potential for IBV, there is a lag in research on IBV pathology and immunological responses compared to IAV. Therefore, the impact of various lifestyle and environmental factors on IBV infections, such as cigarette smoking (CS), remains elusive. Despite the increased risk and severity of IAV infections with CS, limited information exists on the impact of CS on IBV infections due to the absence of suitable animal models. To this end, we developed an animal model system by pre-treating mice for two weeks with cigarette smoke extract (CSE), then infected them with IBV and monitored the resulting pathological, immunological, and virological effects. Our results reveal that the CSE treatment decreased IBV specific IgG levels yet did not change viral replication in the upper airway/the lung, and weight recovery post infection. However, higher concentrations of CSE did result in higher mortality post infection. Together, this suggests that CS induced inflammation coupled with IBV infection resulted in exacerbated disease outcome.

Lifestyle Risk Factors Associated with Tuberculosis Patients in Asir Region of Saudi Arabia

Background:

Tuberculosis remains to be a major public health problem. Lifestyle factors that have indirectly influence to the burden of tuberculosis. The aim of this study is to determine the lifestyle risk factors associated with tuberculosis patients in Asir region of KSA.

Methods:

We conducted a case-control study at the military hospital of Asir region of KSA. A total of 135 sample which is divided into 67 cases and 67 controls. Cases were included from hospital database between 2017 and 2018. Control were selected from patient attending the same hospital with respiratory disease other than tuberculosis. Data collection done through interview using a structured questionnaire. Lifestyle factors and socio-demographic factors associated with tuberculosis were analyzed using logistic regression.

Results:

Mean age of study participants (cases and control) are 38.04 ± 9.66 and 40.16 ± 7.72 respectively. Most important factors associated with tuberculosis patients are overweight and obese [OR = 4.40, 95% CI 1.27-15.25 and 2.38 (1.61-9.22)], Smoker [OR = 1.34, 95% CI 0.52-3.43], abnormal sleep at night (<8 hours) [OR = 5.03, 95% CI 1.57-16.10], blue color job worker [OR = 2.69, 95% CI 1.02-7.28], physical exercise <3 days/week [OR = 1.41, 95% CI 1.21-3.47].

Conclusions:

In Saudi Arabia, a person's lifestyle and socioeconomic condition are associated with tuberculosis. Interventions focused on improving the quality of life through a reduction of risky lifestyle which prevent the spread of Tuberculosis in Saudi society and improve the efficiency of Saudi national tuberculosis control programme.

Quality of Inpatient Tuberculosis Health Care in High-Burden Resource-Limited Settings: Protocol for a Comprehensive Mixed Methods Assessment Study

Background

The quality of care for tuberculosis (TB) is deficient in high-burden countries and urgently needs improvement. However, comprehensively identifying the required improvements is challenging. Providing high-quality TB care is an important step toward improving patients’ quality of life and decreasing TB morbidity and mortality. Effective tools for assessing the quality of TB services using international standards and guidelines can identify existing gaps in services and inform improvements to ensure high-quality inpatient TB services.

Objective

This study aimed to develop evaluation instruments for defining the quality of provision of TB services.

Methods

To assess quality of services in the largest TB hospital in Armenia, we developed instruments based on the Joint Commission International Accreditation Standards for Hospitals, International Standards for TB Care, TB Laboratories Bio-Safety Standards, and the World Health Organization framework for conducting TB program reviews. A mixed methods approach was utilized, triangulating quantitative (checklists) and qualitative (in-depth interviews) results. A scoring system and strengths, weaknesses, opportunities, and treats analysis was applied to detail results for each of the 122 standards assessed. A scaling approach was used to present overall performances of inpatient services for eight patient-centered functions and five organization management functions.

Results

Overall, 40 in-depth interviews and 91 checklists (21 observations, 16 policy papers, 20 staff qualification documents, and 34 medical records) were developed, utilized, and analyzed to explore practices of health care professionals, assess inpatient treatment experience of patients and their family members, evaluate facility environmental conditions, and define the degree of compliance to standards.

Conclusions

The effective comprehensive evaluation instruments and methods developed in this study for quality of inpatient TB services support the implementation of similar effective assessments in other countries. It may also become a platform to develop similar approaches for assessing ambulatory TB services in resource-limited countries.

International Registered Report Identifier (IRRID)

DERR1-10.2196/13903

Aryl Hydrocarbon Receptor Modulation by Tuberculosis Drugs Impairs Host Defense and Treatment Outcomes

Antimicrobial resistance in tuberculosis (TB) is a public health threat of global dimension, worsened by increasing drug resistance. Host-directed therapy (HDT) is an emerging concept currently explored as an adjunct therapeutic strategy for TB. One potential host target is the ligand-activated transcription factor aryl hydrocarbon receptor (AhR), which binds TB virulence factors and controls antibacterial responses. Here, we demonstrate that in the context of therapy, the AhR binds several TB drugs, including front line drugs rifampicin (RIF) and rifabutin (RFB), resulting in altered host defense and drug metabolism. AhR sensing of TB drugs modulates host defense mechanisms, notably impairs phagocytosis, and increases TB drug metabolism. Targeting AhR in vivo with a small-molecule inhibitor increases RFB-treatment efficacy. Thus, the AhR markedly impacts TB outcome by affecting both host defense and drug metabolism. As a corollary, we propose the AhR as a potential target for HDT in TB in adjunct to canonical chemotherapy.

Lack of an Association Between Household Air Pollution Exposure and Previous Pulmonary Tuberculosis

CONTEXT

Observational studies investigating household air pollution (HAP) exposure to biomass fuel smoke as a risk factor for pulmonary tuberculosis have reported inconsistent results.

OBJECTIVE

To evaluate the association between HAP exposure and the prevalence of self-reported previous pulmonary tuberculosis.

DESIGN

We analyzed pooled data including 12,592 individuals from five population-based studies conducted in Latin America, East Africa, and Southeast Asia from 2010 to 2015. We used multivariable logistic regression to model the association between HAP exposure and self-reported previous pulmonary tuberculosis adjusted for age, sex, tobacco smoking, body mass index, secondary education, site and country of residence.

RESULTS

Mean age was 54.6 years (range of mean age across settings 43.8-59.6 years) and 48.6% were women (range of % women 38.3-54.5%). The proportion of participants reporting HAP exposure was 38.8% (range in % HAP exposure 0.48-99.4%). Prevalence of previous pulmonary tuberculosis was 2.7% (range of prevalence 0.6-6.9%). While participants with previous pulmonary tuberculosis had a lower pre-bronchodilator FEV₁ (mean - 0.7 SDs, 95% CI - 0.92 to - 0.57), FVC (- 0.52 SDs, 95% CI - 0.69 to - 0.33) and FEV₁/FVC (- 0.59 SDs, 95% CI - 0.76 to - 0.43) as compared to those who did not, we did not find an association between HAP exposure and previous pulmonary tuberculosis (adjusted odds ratio = 0.86; 95% CI 0.56-1.32).

CONCLUSIONS

There was no association between HAP exposure and self-reported previous pulmonary tuberculosis in five population-based studies conducted worldwide.

Season and size of urban particulate matter differentially affect cytotoxicity and human immune responses to Mycobacterium tuberculosis

Exposure to air pollution particulate matter (PM) and tuberculosis (TB) are two of the leading global public health challenges affecting low and middle income countries. An estimated 4.26 million premature deaths are attributable to household air pollution and an additional 4.1 million to outdoor air pollution annually. Mycobacterium tuberculosis (M.tb) infects a large proportion of the world's population with the risk for TB development increasing during immunosuppressing conditions. There is strong evidence that such immunosuppressive conditions develop during household air pollution exposure, which increases rates of TB development. Exposure to urban air pollution has been shown to alter the outcome of TB therapy. Here we examined whether in vitro exposure to urban air pollution PM alters human immune responses to M.tb. PM2.5 and PM10 (aerodynamic diameters <2.5μm, <10μm) were collected monthly from rainy, cold-dry and warm-dry seasons in Iztapalapa, a highly populated TB-endemic municipality of Mexico City with elevated outdoor air pollution levels. We evaluated the effects of seasonality and size of PM on cytotoxicity and antimycobacterial host immunity in human peripheral blood mononuclear cells (PBMC) from interferon gamma (IFN-γ) release assay (IGRA)+ and IGRA- healthy study subjects. PM10 from cold-dry and warm-dry seasons induced the highest cytotoxicity in PBMC. With the exception of PM2.5 from the cold-dry season, pre-exposure to all seasonal PM reduced M.tb phagocytosis by PBMC. Furthermore, M.tb-induced IFN-γ production was suppressed in PM2.5 and PM10-pre-exposed PBMC from IGRA+ subjects. This observation coincides with the reduced expression of M.tb-induced T-bet, a transcription factor regulating IFN-γ expression in T cells. Pre-exposure to PM10 compared to PM2.5 led to greater loss of M.tb growth control. Exposure to PM2.5 and PM10 collected in different seasons differentially impairs M.tb-induced human host immunity, suggesting biological mechanisms underlying altered M.tb infection and TB treatment outcomes during air pollution exposures.

Prevalence and molecular characterization of multidrug-resistant M. tuberculosis in Jiangxi province, China

Multidrug-resistant Mycobacterium tuberculosis (MDR-TB) is a severe health threat to human beings; however, the epidemic and molecular characteristics exist along with the change in the geographic environment and genealogy. Jiangxi province is located in southeast China, which is a high-MDR-TB burden area. Rifampin (RIF) and isoniazid (INH) are the most important first-line anti-tuberculosis drugs. The major drug target genes include rpoB for RIF and katG, inhA, and ahpC for INH. To determine the frequency and distribution of mycobacterial mutations in these genes, we sequenced specific genes of M. tuberculosis that are associated with resistance to RIF and INH in 157 phenotypic MDR isolates. At the same time, RD105 DTM-PCR and 15 loci MIRU-VNTR were performed to demonstrate the genetic lineage. It was shown that the Beijing genotype was predominant (84.1%) among these strains. The results also showed mutations within the 81 bp core region of rpoB in 93.6% of strains and mutations in a structural gene (katG) and two regulatory regions (the promoter of inhA and intergenic region of oxyR-ahpC) were shown in 88.5% of phenotypic MDR isolates. There were no significant differences in codon mutations between the Beijing and non-Beijing genotypes, as well as the clustered and no-clustered strains. The most prevalent mutations involved in RIF and INH were Ser531Leu in rpoB (55.4%) and Ser315Thr in KatG (56.1%), respectively. There was no significant difference in RIF and INH resistance between MDR-TB and other drug-resistant tuberculosis (DR-TB). The results demonstrated that some MDR-TB patients are predicted to have recent transmission.

Contribution of Smoking to Tuberculosis Incidence and Mortality in High-Tuberculosis-Burden Countries

Globally, 10 million incident cases of tuberculosis (TB) are reported annually, and 95% of TB cases and 80% of tobacco users reside in low- and middle-income countries. Smoking approximately doubles the risk of TB disease and TB mortality. We estimated the proportion of annual incident TB cases and TB mortality attributable to tobacco smoking in 32 high-TB-burden countries. We obtained country-specific estimates of TB incidence, TB mortality, and smoking prevalence from the World Health Organization Global TB Report (2017), tobacco surveillance reports (2015), and the Tobacco Atlas. Risk ratios for the effect of smoking on TB incidence and TB mortality were obtained from published meta-analyses. An estimated 17.6% (95% confidence interval (CI): 8.4, 21.4) of TB cases and 15.2% (95% CI: 1.8, 31.9) of TB mortality were attributable to smoking. Among high-TB-burden countries, Russia had the highest proportion of smoking-attributable TB disease (31.6%, 95% CI: 15.9, 37.6) and deaths (28.1%, 95% CI: 3.8, 51.4). Men had a greater proportion of TB cases attributable to smoking (30.3%, 95% CI: 14.7, 36.6) than did women (4.3, 95% CI: 1.7, 5.7). Our findings highlight the need for tobacco control in high-TB-burden countries to combat TB incidence and TB mortality.

Epidemiologic Evidence of and Potential Mechanisms by Which Second-Hand Smoke Causes Predisposition to Latent and Active Tuberculosis

Many studies have linked cigarette smoke (CS) exposure and tuberculosis (TB) infection and disease although much fewer have studied second-hand smoke (SHS) exposure. Our goal is to review the epidemiologic link between SHS and TB as well as to summarize the effects SHS and direct CS on various immune cells relevant for TB. PubMed searches were performed using the key words "tuberculosis" with "cigarette," "tobacco," or "second-hand smoke." The bibliography of relevant papers were examined for additional relevant publications. Relatively few studies associate SHS exposure with TB infection and active disease. Both SHS and direct CS can alter various components of host immunity resulting in increased vulnerability to TB. While the epidemiologic link of these 2 health maladies is robust, more definitive, mechanistic studies are required to prove that SHS and direct CS actually cause increased susceptibility to TB.

A case control study of risk factors associated with pulmonary tuberculosis in romania: experience at a clinical hospital of pneumology

BACKGROUND AND AIM

Tuberculosis (TB) remains a major public health issue in Romania. The aim of the present study was to evaluate the potential demographic, socioeconomic and behavioral risk factors for TB among hospitalized patients in Romania.

METHODS

This is a case-control study conducted between March 1st 2014 and March 30th 2015 at Leon Daniello Clinical Hospital of Pneumology, Cluj Napoca. A total of 150 TB patients defined as "cases" were matched for age, sex and county of residence to 150 controls selected from patients attending the same hospital with respiratory diseases other than TB. Data collection was obtained through patient interviews using a structured questionnaire. Factors potentially associated with TB infection were analyzed using univariate and multivariate logistic regression.

RESULTS

Factors independently associated with TB were illiteracy (OR=2.42, 95% CI 1.09-5.37), unemployment (OR=2.08, 95% CI 1.23-3.53), low household income (OR=4.12, 95% CI 2.53-6.71), smoking (more than 20 cigarettes per day) (OR=2.12, 95% CI 1.20-3.74), poor knowledge of TB (OR=3.46, 95% CI 1.97-6.07), presence of TB patient in household (OR=4.35, 95% CI 1.42-13.36), prior TB treatment (OR=2.2, 95% CI 1.93-2.5) and diabetes (OR=3.32, 95% CI 1.36-8.08).

CONCLUSION

This study provided useful information that might help to develop and adapt effective policies for TB control in Romania.

Cigarette Smoking and Its Hazards in Kidney Transplantation

Cigarette smoking affects many organs. It causes vasoconstriction through activation of sympathetic nervous system which leads to elevation of blood pressure and reduction in glomerular filtration rate and filtration pressure. It also causes thickening of renal arterioles. Cigarette smoking increases the risk of microalbuminuria and accelerates progression of microalbuminuria to macroalbuminuria. Furthermore, it causes rapid loss of glomerular filtration rate in chronic kidney disease patients. After kidney donation, these factors may be injurious to the solitary kidney. Kidney donors with history of cigarette smoking are prone to develop perioperative complications, pneumonia, and wound infection. Postkidney transplantation various stressors including warm and cold ischemia time, delayed graft function, and exposure to calcineurin inhibitors may result in poor graft function. Continuation of cigarette smoking in kidney transplant recipients will add further risk. In this review, we will specifically discuss the effects of cigarette smoking on normal kidneys, live kidney donors, and kidney transplant recipients. This will include adverse effects of cigarette smoking on graft and patient survival, cardiovascular events, rejection, infections, and cancers in kidney transplant recipients. Lastly, the impact of kidney transplantation on behavior and smoking cessation will also be discussed.

Burden and Determinants of Smoking among Prisoners with Respiratory Tract Infection: A Cross-Sectional Study of Nine Major Prison Setups in Northern Ethiopia

Background

Morbidity, mortality and a wide range of associated risk factors are disproportionately clustered among prisoners compared to the general population. Smoking is one of the risk factors for the increased burden of unfavorable health outcomes particularly among prisoners. However, little is known about the level and determinants of smoking among the incarcerated population in Ethiopia.

Methods

We collected data from 738 prisoners in nine major prison setups in Tigray region by nurses and clinical officers. Data were entered in to Epi Data 3.1 and exported to stata 13.0 for cleaning and further analysis. Multivariable logistic regression model was fitted to identify determinants of smoking at p value of less than 5%.

Result

The prevalence of smoking was 21 per cent (95%CI = 18.2%, 24.1). Urban residence (AOR = 2.15; 95%CI = 1.20, 3.84), previous history of incarceration (AOR = 1.91; 95%CI = 1.08, 3.40) and alcohol use before incarcerated (AOR = 4.20; 95%CI = 2.57, 6.87) were significantly associated with risk of smoking. In contrast, risk of smoking was significantly lower for farmers (AOR = 0.20; 95% CI = 0.08, 0.49), prisoners with family support (AOR = 0.52; 95% CI = 0.32, 0.87) and for those who were jailed in Shire prison site (AOR = 0.43; 95%CI = 0.20, 0.95).

Conclusion

Our work clearly indicates that the observed smoking prevalence calls for the need of comprehensive and interdisciplinary interventions targeting prisoners.

Factors associated with smoking among tuberculosis patients in Spain

BACKGROUND

To determine the prevalence of smoking and analyze associated factors in a cohort of patients diagnosed with tuberculosis (TB) in Spain between 2006 and 2013.

METHODS

Multicenter, cross-sectional, descriptive, observational study using a national database of TB patients, using logistic regression to calculate odds ratios (OR) and confidence intervals (CI).

RESULTS

We analyzed 5,846 cases (62 % men, mean age 39 years, 33 % foreigners). 23.4 % were alcohol abuser, 1.3 % were injected drug users (IDU), 4.6 % were co-infected with HIV, and 7.5 % had a history of TB treatment. 6.6 % and 0.8 % showed resistance to one and multiple drugs, respectively. The predominant clinical presentation was pulmonary (71 %) with a cavitary radiological pattern in 32.8 % of cases. 82 % of cases were confirmed microbiologically, and 54 % were smear-positive microscopy. 2,300 (39.3 %) patients were smokers. The following factors were associated with smoking: male sex (OR = 2.26;CI:1.97;2.60), Spanish origin (OR = 2.79;CI:2.40-3.24), alcoholism (OR = 2.85;CI:2.46;3.31), IDU (OR = 2.78;CI:1.48;5.52), homelessness (OR = 1.99;CI:1.14-3.57), pulmonary TB (OR = 1.61;CI:1.16;2.24), cavitary radiological pattern (OR = 1.99;CI:1.43;2.79) and a smear-positive microscopy at the time of diagnosis (OR = 1.39;CI:1.14;1.17).

CONCLUSIONS

The prevalence of smoking among TB patients is high. Smokers with TB have a distinct sociodemographic, clinical, radiological and microbiological profile to non-smokers.

The risk of pulmonary tuberculosis in underground copper miners in Zambia exposed to respirable silica: a cross-sectional study

Background

Pulmonary tuberculosis (PTB) among underground miners exposed to silica remains a global problem. Although well described in gold and coal mining, risk in other mining entities are not as well documented. This study aims to determine dust-related dose response risk for PTB among underground miners exposed to silica dust in Zambia's copper mines.

Methods

A cross sectional study of in-service miners (n = 357) was conducted at Occupational Health and Safety Institute (OHSI), Zambia. A systematic review of medical data over a 5-year period from assessments conducted by doctors at OHSI and statutory silica exposure data (n = 16678) from the Mine Safety Department (MSD) were analysed. Lifetime cumulative exposure metrics were calculated. Multivariate logistic regression analysis was used to determine the association between PTB and lifetime exposure to silica, while adjusting for various confounders.

Results

The median respirable silica dust level was 0.3 mg/m³ (range 0.1–1.3). The overall prevalence of PTB was 9.5 % (n = 34). High cumulative respirable silica dust category showed a statistically significant association with PTB (OR = 6.4 (95 % CI 1. 8–23)) and a significant trend of increasing disease prevalence with increasing cumulative respirable silica dust categories was observed (p_trend < 0.01). Smoking showed a statistically significant association with PTB with OR = 4.3 (95 % CI 1.9–9.9).

Conclusions

Our results demonstrate the association of increased risk for certified active TB with cumulative respirable dust in a dose related manner among this sample of copper miners. There is need to intensify dust control measures and incorporate anti-smoking interventions into TB prevention and control programmes in the mines.

Determinants of active pulmonary tuberculosis in Ambo Hospital, West Ethiopia

OBJECTIVES

The aim of this study was to determine factors associated with active pulmonary tuberculosis seen in cases in Ambo Hospital, Ethiopia.

DESIGN

A facility-based prospective case-control study.

SETTING

Patients attending Ambo Hospital from 01 December 2011 to 29 March 2012.

PARTICIPANTS

The sample included 312 adult patients attending Ambo Hospital. The main outcome measure was presence of active pulmonary tuberculosis (TB).

EXPLANATORY MEASURES

Age, gender, occupation, educational status, marital status, place of residence, patient history of TB, family history of TB, human immunodeficiency virus (HIV) infection, smoking, alcohol intake, khat chewing, body mass index (BMI), employment, diabetes, history of asthma, previous history of worm infestation, history of hospitalisation, number of adults living in the household (HH), person per room, housing condition.

RESULTS

A total of 312 study participants, including 104 active pulmonary tuberculosis (PTB) cases (cases) and 208 non-active PTB cases (controls), were recruited for the present study. Having one or more family member with a history of TB (OR = 4.4; 95% CI: 1.50–12.90), marital status (OR = 7.6; 95% CI: 2.2–12.6), male gender (OR = 3.2; 95% CI: 1.4–7), rural residence (OR = 3.3; P = 0.012), being a current or past smoker (OR = 2.8; 95% CI: 1.1–7.2), BMI < 18.5 (OR = 2.1; 95% CI: 1.03–4.2), HIV infection (OR = 8.8; 95% CI: 2.4–23.8) and a history of worm infestation (OR = 6.4; 95% CI: 2.6–15.4) remained significant independent host-related factors for active PTB.

CONCLUSION

Patients who came from a compound with more than two HHs were more likely to develop active PTB than those who came from a compound with only one HH. Those who lived in houses with no windows were more likely to develop active PTB than those who lived in houses with one or more windows, had a family history of TB, lived in rural areas. Sex of the patient was a predicting factor. Not being the owner of the house was significantly more associated with active PTB. Measures taken to reduce the prevalence and burden of active PTB should consider these determinant factors.

Second-hand smoke and the risk of tuberculosis: a systematic review and a meta-analysis

There is limited evidence and lack of consensus whether second-hand smoke (SHS) increases risk of tuberculosis (TB), which has substantial implications for unrestricted smoking indoors and TB control policies. We aimed to establish the association between SHS and the risk of acquiring and worsening of TB in non-smokers. We identified 428 articles in the initial search and 12 comparative epidemiological studies met our inclusion criteria. Exposure to SHS was found to have a higher risk of TB infection [risk ratio (RR) 1·19, 95% confidence interval (CI) 0·90–1·57] compared to non-exposure; however, this did not reach statistical significance. There was marked variability (I2 = 74%, P = 0·0008) between studies’ results, which could be explained by the differences in the diagnostic criteria used. Exposure to SHS was found to be statistically significantly associated (RR 1·59, 95% CI 1·11–2·27) with the risk of TB disease. There was significant heterogeneity (I2 = 77%, P = 0·0006) between studies’ results, which was sourced to the internal characteristics of the studies rather than combining different study designs. We did not find any studies for SHS and TB treatment-related outcomes. Thus, we conclude that SHS exposure may increase the risk of acquiring TB infection and progression to TB disease; however, the evidence remains scanty and weak.

Exposure to second-hand smoke and the risk of tuberculosis in children and adults: a systematic review and meta-analysis of 18 observational studies

BACKGROUND

According to WHO Global Health Estimates, tuberculosis (TB) is among the top ten causes of global mortality and ranks second after cardiovascular disease in most high-burden regions. In this systematic review and meta-analysis, we investigated the role of second-hand smoke (SHS) exposure as a risk factor for TB among children and adults.

METHODS AND FINDINGS

We performed a systematic literature search of PubMed, Embase, Scopus, Web of Science, and Google Scholar up to August 31, 2014. Our a priori inclusion criteria encompassed only original studies where latent TB infection (LTBI) and active TB disease were diagnosed microbiologically, clinically, histologically, or radiologically. Effect estimates were pooled using fixed- and random-effects models. We identified 18 eligible studies, with 30,757 children and 44,432 adult non-smokers, containing SHS exposure and TB outcome data for inclusion in the meta-analysis. Twelve studies assessed children and eight studies assessed adult non-smokers; two studies assessed both populations. Summary relative risk (RR) of LTBI associated with SHS exposure in children was similar to the overall effect size, with high heterogeneity (pooled RR 1.64, 95% CI 1.00-2.83). Children showed a more than 3-fold increased risk of SHS-associated active TB (pooled RR 3.41, 95% CI 1.81-6.45), which was higher than the risk in adults exposed to SHS (summary RR 1.32, 95% CI 1.04-1.68). Positive and significant exposure-response relationships were observed among children under 5 y (RR 5.88, 95% CI 2.09-16.54), children exposed to SHS through any parent (RR 4.20, 95% CI 1.92-9.20), and children living under the most crowded household conditions (RR 5.53, 95% CI 2.36-12.98). Associations for LTBI and active TB disease remained significant after adjustment for age, biomass fuel (BMF) use, and presence of a TB patient in the household, although the meta-analysis was limited to a subset of studies that adjusted for these variables. There was a loss of association with increased risk of LTBI (but not active TB) after adjustment for socioeconomic status (SES) and study quality. The major limitation of this analysis is the high heterogeneity in outcomes among studies of pediatric cases of LTBI and TB disease.

CONCLUSIONS

We found that SHS exposure is associated with an increase in the relative risk of LTBI and active TB after controlling for age, BMF use, and contact with a TB patient, and there was no significant association of SHS exposure with LTBI after adjustment for SES and study quality. Given the high heterogeneity among the primary studies, our analysis may not show sufficient evidence to confirm an association. In addition, considering that the TB burden is highest in countries with increasing SHS exposure, it is important to confirm these results with higher quality studies. Research in this area may have important implications for TB and tobacco control programs, especially for children in settings with high SHS exposure and TB burden.

First and second line drug resistance among treatment naïve pulmonary tuberculosis patients in a district under Revised National Tuberculosis Control Programme (RNTCP) in New Delhi

There is limited information of level of drug resistance to first-line and second line anti-tuberculosis agents in treatment naïve pulmonary tuberculosis (PTB) patients from the Indian region. Therefore, the present prospective study was conducted to determine the antimicrobial susceptibility to first-line and second line anti-TB drug resistance in such patients. Sputum samples from consecutive treatment naïve PTB cases registered in Lala Ram Sarup (LRS) district, under RNTCP containing 12 Directly Observed Treatment Centre’s (DOTS), were enrolled using cluster sampling technology. A total of 453 samples were received from July 2011 to June 2012. All samples were cultured on solid medium followed by drug susceptibility to first and second line anti-tubercular drugs as per RNTCP guidelines. Primary multi-drug resistance (MDR) was found to be 18/453; (4.0%). Extensively drug resistance (XDR) was found in one strain (0.2%), which was found to be resistant to other antibiotics. Data of drug resistant tuberculosis among treatment naïve TB patients are lacking in India. The presence of XDR-TB and high MDR-TB in small population studied, calls for conducting systematic multi-centric surveillance across the country.

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.

An overview of the risk factors associated with multiple oral premalignant lesions with a case report of extensive field cancerization in a female patient

BACKGROUND

Field cancerization is a well-known and well-documented process of malignant transformation first coined by Slaughter et al. in 1953. Tobacco chewing was associated with the greatest increase in the risk of multiple oral premalignant lesions and may be the major source of field cancerization of the oral cavity in the Indian population. The field cancerization will probably help clinicians in complementing evaluation of pathologic biopsy specimens.

MATERIAL AND METHODS

We present a case report of field cancerization in a 63-year-old Indian female. She presented with an intra-oral generalized hyperkeratotic verruciform type white lesions involving right and left buccal mucosa, lower labial mucosa, upper and lower vestibule, dorsal, ventral and right lateral border of the tongue, hard and soft palate. Microscopic examination revealed features of verrucous carcinoma in one area, squamous cell carcinoma in another and carcinoma in situ in other areas. Based on the overall features in various areas of the oral cavity, the lesion was diagnosed as field cancerization.

CONCLUSION

Reviewing the literature revealed the presence of a field with genetically altered cells appear to be induced by tobacco (smoking/smokeless form). The large number of premalignant cells in the fields may increase cancer risk considerably. Thus screening and monitoring of the field may have serious implications for oral cancer prevention.

TB patients learning about second hand smoke (TBLASS): a pilot individual randomised controlled trial

Background

Living with a smoker is a key determinant of exposure to Second Hand Smoke (SHS) and its exposure mainly occurs at home. Exposure to SHS from tobacco in the household predisposes to the development of tuberculosis (TB) and outcome of the disease gets worse. We aim to develop and evaluate a behavioural intervention 'Smoke Free Homes’ (SFH) for TB patients that encourages them to negotiate a smoke free environment within their homes.

Methods and design

The pilot individual randomised controlled trial of SFH will inform the design of a future definitive trial. We will first develop SFH intervention using taxonomy of behaviour change techniques aimed at encouraging families of non-smoking TB patients to implement smoking restrictions at home following a logic model of the intervention. This will be followed by conducting a pilot randomised controlled trial of intervention within the context of routine TB control programme. The eligible non-smoking TB patients will be randomised and allocated to one of the two trial arms consisting of “individual based care” and “individual based care” plus “supplementary support”. We aim to recruit 150 newly registered pulmonary TB patients from two selected TB centres with 75 cases in each arm. The Primary outcome measure will be SFH of non-smoker TB patient by validating through 'Urine Cotinine’ test. We will also determine qualitatively the barriers and key drivers to the creation of smoke free homes followed by developing a definitive trial.

Discussion

The male to female distribution of TB cases in Pakistan is almost equal whereas, tobacco use among males is much high as compared to females in Pakistan. This reflects a strong possibility that women health can be affected by men behaviour. Appropriate storage, restricted access and disposal arrangements for participant’s personal details will be implemented. All ethical issues will be addressed. There will be no extra burden, financial or otherwise, on the participants. They will not receive any financial incentive to participate in the study.

Trial registration

Trial Registration Number: ISRCTN83630841

Exposure to secondhand smoke and risk of tuberculosis: prospective cohort study

BACKGROUND

Prospective evidence on the association between secondhand-smoke exposure and tuberculosis is limited.

METHODS

We included 23,827 never smokers from two rounds (2001 and 2005) of Taiwan National Health Interview Survey. Information on exposure to secondhand smoke at home as well as other sociodemographic and behavioral factors was collected through in-person interview. The participants were prospectively followed for incidence of tuberculosis through cross-matching the survey database to the national tuberculosis registry of Taiwan.

RESULTS

A total of 85 cases of active tuberculosis were identified after a median follow-up of 7.0 years. The prevalence of exposure to secondhand smoke at home was 41.8% in the study population. In the multivariable Cox proportional hazards analysis, secondhand smoke was not associated with active tuberculosis (adjusted hazard ratio [HR], 1.03; 95% CI, 0.64 to 1.64). In the subgroup analysis, the association between secondhand smoke and tuberculosis decreased with increasing age; the adjusted HR for those <18, > = 18 and <40, > = 40 and <60, and > = 60 years old was 8.48 (0.77 to 93.56), 2.29 (0.75 to 7.01), 1.33 (0.58 to 3.01), and 0.66 (0.35 to 1.23) respectively. Results from extensive sensitivity analyses suggested that potential misclassification of secondhand-smoke exposure would not substantially affect the observed associations.

CONCLUSIONS

The results from this prospective cohort study did not support an overall association between secondhand smoke and tuberculosis. However, the finding that adolescents might be particularly susceptible to secondhand smoke's effect warrants further investigation.

Diversity of disease in childhood pulmonary tuberculosis

Many factors can influence the dynamic balance that exists between the host and the pathogen (M. tuberculosis), but the host immune response seems to be the most important. This is illustrated by the vulnerability of immune-compromised individuals to develop tuberculosis and by the age-related spectrum of disease witnessed in immune-competent children. This age-related spectrum of disease reflects the ontogeny of the host immune response towards M. tuberculosis. Renewing our focus on the ontogeny of the immune response in children might provide valuable insights to direct future research regarding tuberculosis prevention, vaccine development and treatment.

Factors that influence current tuberculosis epidemiology

According to WHO estimates, in 2010 there were 8.8 million new cases of tuberculosis (TB) and 1.5 million deaths. TB has been classically associated with poverty, overcrowding and malnutrition. Low income countries and deprived areas, within big cities in developed countries, present the highest TB incidences and TB mortality rates. These are the settings where immigration, important social inequalities, HIV infection and drug or alcohol abuse may coexist, all factors strongly associated with TB. In spite of the political, economical, research and community efforts, TB remains a major global health problem worldwide. Moreover, in this new century, new challenges such as multidrug-resistance extension, migration to big cities and the new treatments with anti-tumour necrosis alpha factor for inflammatory diseases have emerged and threaten the decreasing trend in the global number of TB cases in the last years. We must also be aware about the impact that smoking and diabetes pandemics may be having on the incidence of TB. The existence of a good TB Prevention and Control Program is essential to fight against TB. The coordination among clinicians, microbiologists, epidemiologists and others, and the link between surveillance, control and research should always be a priority for a TB Program. Each city and country should define their needs according to the epidemiological situation. Local TB control programs will have to adapt to any new challenge that arises in order to respond to the needs of their population.

Daily contact with a patient and poor housing affordability as determinants of pulmonary tuberculosis in urban Pakistan

OBJECTIVE

This study aimed to evaluate the factors associated with pulmonary tuberculosis (TB) among individuals aged 15years or more in urban Karachi, Pakistan.

DESIGN AND SETTING

A case-control design was implemented in three major tertiary-care hospitals to select cases (n=342) with active pulmonary TB (i.e. two sputum smears positive for Mycobacterium tuberculosis with clinical and radiographic evidence of current pulmonary TB and diagnosed between August 2002 and October 2003. Selected controls (n=342) were surgery patients from the same hospitals at time of recruitment of the cases, without clinical and radiographic evidence of pulmonary TB.

RESULTS

Multivariable logistic regression model showed that daily contact with a pulmonary TB patient (adjusted odds ratio [ORadj])=5.07; 95% CI: 3.31, 7.78), and poor housing affordability (i.e. rented vs. owned) (ORadj=1.59; 95% CI: 1.13, 2.26) were significantly associated with pulmonary TB status. The overall adjusted summary population attributable risk (%) for both the risk factors together was 38.7.

CONCLUSION

Reaching out to underprivileged TB patients for delivery of DOTS and focused education of patients and their contacts about M. tuberculosis transmission mode may substantially minimize pulmonary TB risk in this and similar settings.

Epidemiology of tuberculosis immunology

Immunological impairment plays a major role in the epidemiology of TB. Globally, the most common causes of immunological impairment are malnutrition, diabetes, HIV/AIDS, aging, and smoking. With the notable exception of HIV, each factor leads to relatively mild immunological impairment in individuals. However, as these conditions affect a significant proportion of the population, they contribute substantially to the incidence of TB at a global scale. Understanding immunological impairment is central to understanding the global TB pandemic, and vital to the development of effective disease control strategies.

Using System Dynamics tools to gain insight into intervention options related to the interaction between tobacco and tuberculosis

Tobacco exposure is an important risk factor for tuberculosis (TB) when considering its effects on population-level disease outcomes. If we hope to gain control over TB globally, we must begin to think ‘outside of the box’ to identify an extended and multi-faceted intervention strategy that is grounded in an understanding of the particular ways in which key risk factors worsen TB. In light of the role of tobacco exposure as an important, identifiable, modifiable, and preventable risk factor for TB, efforts aiming at reducing tobacco use merit inclusion in such a comprehensive TB control program. The goal of this paper is to share the conceptual framework we have developed using System Dynamics methodology, which diagrams the likely effects of tobacco exposure on TB dynamics in a typical low-income country setting. Using this framework as a guide, we leverage an understanding of the likely mechanisms by which tobacco exposure affects TB risk to systematically explore TB control intervention options. We hope that this paper will help inspire new approaches to extend and enhance traditional TB control efforts. We also hope that the conceptual framework will spark further discussion and research on this important and potentially explosive combination of global public health crises.

Association between tobacco smoking and active tuberculosis in Taiwan: prospective cohort study

RATIONALE

Previous case-control studies and a small number of cohort studies in high-risk populations have found an association between tobacco and active tuberculosis, but no cohort studies have been conducted in the general population on this association to date.

OBJECTIVES

To investigate the association between tobacco smoking and active tuberculosis in a cohort of a general population.

METHODS

17,699 participants (>or=12 y of age) in Taiwan National Health Interview Survey were followed up from 2001 to 2004. Smoking status and other covariates were measured by an in-person interview at baseline. Incident cases of active tuberculosis were identified from the National Health Insurance database. Multivariate logistic regression was used to estimate the association between smoking status and active tuberculosis, with adjustment for age, sex, alcohol consumption, socioeconomic status, and other covariates.

MEASUREMENTS AND MAIN RESULTS

Fifty-seven new cases of active tuberculosis occurred during the 3.3 years of follow-up. Current smoking was associated with an increased risk of active tuberculosis (adjusted odds ratio [OR], 1.94; 95% confidence interval, 1.01-3.73). The association was stronger among those less than 65 years of age (adjusted OR, 3.04) than those greater than 65 years of age (adjusted OR, 0.78; P(interaction) = 0.036). We found significant dose-response relations for cigarettes per day (P(trend) = 0.0036), years of smoking (P(trend) = 0.023), and pack-years (P(trend) = 0.0023).

CONCLUSIONS

Tobacco smoking was associated with a twofold increased risk of active tuberculosis in a representative cohort of Taiwan's population.

Association between tobacco smoking and pulmonary tuberculosis

Background/Aim. Numerous studies evaluate the influence of tobacco smoking on the tuberculosis (TB) development, with the results indicating that smoking can be also considered as important risk factor in TB. The aim of this study was to assess the influence of tobacco smoking as the risk factor in the development of TB as well as in its clinical course. Methods. We analyzed data from the medical records of 192 consecutively hospitalized TB patients (124 males and 68 females) in the Institute of Pulmonary Diseases and Tuberculosis, Clinical Center of Serbia, Belgrade in the period from 2005 to 2007. Results. Among the analyzed TB patients there were more smokers (63.5%) than nonsmokers (36.5%). The majority of the smokers (73.8%) belonged to a middle age group (35-54 years) while the majority of nonsmokers (64.3%) were older than 55 years. Sex ratio among the smokers showed the domination of males (80.3%). There were significantly more males in the smoking group and more females in the nonsmoking group (?2 = 34.402, p < 0.0001). Most smokers (68.9%) smoked more than 20 cigarettes daily. The average index of pack/years among all of the examinated patients was 32.75 ? 18.26. Cavitary pulmonary lesions were more frequently verified in the smokers (64.2%) than in the nonsmokers (35.8%). The sputum acid-fast bacillus smear-positive finding was more frequent in the smokers (78%) than in the nonsmokers (22%). The nonsmoking TB patients had more accompanied immunodeficient diseases (34%) than the smoking ones (19%). Body-mass index was lower in the smokers (21.75) than in the nonsmokers (23.80), although this difference did not reach the statistical significance. Conclusion. There are more smokers than nonsmokers in TB patients. Smokers more frequently have cavitary forms of TB with sputum acid-fast bacillus smear - positive finding than nonsmokers.

Effects of smoking and solid-fuel use on COPD, lung cancer, and tuberculosis in China: a time-based, multiple risk factor, modelling study

BACKGROUND

Chronic obstructive pulmonary disease (COPD), lung cancer, and tuberculosis are three leading causes of death in China, where prevalences of smoking and solid-fuel use are also high. We aimed to predict the effects of risk-factor trends on COPD, lung cancer, and tuberculosis.

METHODS

We used representative data sources to estimate past trends in smoking and household solid-fuel use and to construct a range of future scenarios. We obtained the aetiological effects of risk factors on diseases from meta-analyses of epidemiological studies and from large studies in China. We modelled future COPD and lung cancer mortality and tuberculosis incidence, taking into account the accumulation of hazardous effects of risk factors on COPD and lung cancer over time, and dependency of the risk of tuberculosis infection on the prevalence of disease. We quantified the sensitivity of our results to methods and data choices.

FINDINGS

If smoking and solid-fuel use remain at current levels between 2003 and 2033, 65 million deaths from COPD and 18 million deaths from lung cancer are predicted in China; 82% of COPD deaths and 75% of lung cancer deaths will be attributable to the combined effects of smoking and solid-fuel use. Complete gradual cessation of smoking and solid-fuel use by 2033 could avoid 26 million deaths from COPD and 6.3 million deaths from lung cancer; interventions of intermediate magnitude would reduce deaths by 6-31% (COPD) and 8-26% (lung cancer). Complete cessation of smoking and solid-fuel use by 2033 would reduce the projected annual tuberculosis incidence in 2033 by 14-52% if 80% DOTS coverage is sustained, 27-62% if 50% coverage is sustained, or 33-71% if 20% coverage is sustained.

INTERPRETATION

Reducing smoking and solid-fuel use can substantially lower predictions of COPD and lung cancer burden and would contribute to effective tuberculosis control in China.

Smoking increases the risk of relapse after successful tuberculosis treatment

BACKGROUND

Recent tobacco smoking has been identified as a risk factor for developing tuberculosis, and two studies which have investigated its association with relapse of tuberculosis after completion of treatment had conflicting results (and did not control for confounding). The objective of this study was to investigate risk factors for tuberculosis relapse, with emphasis on smoking.

METHODS

A cohort of newly diagnosed TB cases was followed up from their discharge after completion of treatment (in 2001-2003) until October 2006 and relapses of tuberculosis ascertained during that period. A case of relapse was defined as a patient who started a second treatment during the follow up.

RESULTS

Smoking (OR 2.53, 95% CI 1.23-5.21) and living in an area where the family health program was not implemented (OR 3.61, 95% CI 1.46-8.93) were found to be independently associated with relapse of tuberculosis.

CONCLUSIONS

Our results establish that smoking is associated with relapse of tuberculosis even after adjustment for the socioeconomic variables. Smoking cessation support should be incorporated in the strategies to improve effectiveness of Tuberculosis Control Programs.

Evaluation of a model for efficient screening of tuberculosis contact subjects

RATIONALE

Contact tracing is an important component of tuberculosis (TB) control programs. Standardization of contact investigation protocols can make them more efficient.

OBJECTIVES

To develop a model to select contact subjects for screening.

METHODS

We prospectively collected standardized data on 325 TB index cases and their 2,009 contacts. Factors that independently influenced the risk of TB infection were included in the model, which was then validated in a second prospective cohort of 88 cases of TB and their 618 contacts.

MEASUREMENTS AND MAIN RESULTS

A total of eight independent risk factors were identified (odds ratio; 95% confidence interval): age, with three subgroups: 6-14 years (3.6; 1.6-8.0); 15-29 years (3.7; 1.8-7.7); > or =30 years (4.1; 2.0-8.5); cavitation on the index case's chest radiograph (1.6; 1.1-2.2); an index case sputum smear with 100 or more acid-fast bacilli per field (1.8; 1.2-2.8); household contact at night (2.1; 1.3-3.2); first-degree family relationship with the index case (2.1; 1.3-3.3); active smoking by the contact (1.6; 1.1-2.4); free health care (2.0; 1.2-3.2); and birth in a country with TB incidence rate higher than 25 of 100,000 (2.2; 1.5-3.2). Predictive probabilities were chosen to ensure false-negative rates lower than estimated TB infection background. The number of contacts to be investigated was reduced by 26% while maintaining a false-negative rate of 8%.

CONCLUSIONS

This study provides a standardized contact screening model which reduces resources required without negatively affecting disease control.

Do mitochondrial DNA haplogroups play a role in susceptibility to tuberculosis?

BACKGROUND AND OBJECTIVES

Mitochondrial DNA has a unique role in ATP production and subsequent mitochondrial reactive oxygen species (ROS) production in eukaryotic cells and there is a potential role for ROS and oxygen burst against Mycobacterium tuberculosis, an intracellular pathogen. This study aimed to determine whether the frequency of different mitochondrial haplogroups was significantly different in patients with tuberculosis (TB) compared with a normal population.

METHODS

Mitochondrial DNA haplogroups M, N, J and K were studied by PCR-restriction fragment length polymorphism and sequencing. Cases were 54 patients with confirmed smear positive pulmonary TB. Controls were 256 healthy persons.

RESULTS

There were no statistically significant differences between those with TB and the control group.

CONCLUSIONS

There was no statistically significant association between mtDNA haplogroups and the presence of TB infection.

Acrolein: sources, metabolism, and biomolecular interactions relevant to human health and disease

Acrolein (2-propenal) is ubiquitously present in (cooked) foods and in the environment. It is formed from carbohydrates, vegetable oils and animal fats, amino acids during heating of foods, and by combustion of petroleum fuels and biodiesel. Chemical reactions responsible for release of acrolein include heat-induced dehydration of glycerol, retro-aldol cleavage of dehydrated carbohydrates, lipid peroxidation of polyunsaturated fatty acids, and Strecker degradation of methionine and threonine. Smoking of tobacco products equals or exceeds the total human exposure to acrolein from all other sources. The main endogenous sources of acrolein are myeloperoxidase-mediated degradation of threonine and amine oxidase-mediated degradation of spermine and spermidine, which may constitute a significant source of acrolein in situations of oxidative stress and inflammation. Acrolein is metabolized by conjugation with glutathione and excreted in the urine as mercapturic acid metabolites. Acrolein forms Michael adducts with ascorbic acid in vitro, but the biological relevance of this reaction is not clear. The biological effects of acrolein are a consequence of its reactivity towards biological nucleophiles such as guanine in DNA and cysteine, lysine, histidine, and arginine residues in critical regions of nuclear factors, proteases, and other proteins. Acrolein adduction disrupts the function of these biomacromolecules which may result in mutations, altered gene transcription, and modulation of apoptosis.

[Tobacco smoking and sputum smear conversion in pulmonary tuberculosis]

BACKGROUND AND OBJECTIVE

To analyze if cigarette smoking delays the sputum smear conversion in pulmonary tuberculosis.

PATIENTS AND METHOD

Ninety eight patients were diagnosed with pulmonary tuberculosis. Patients were all not immunosuppressed, infected by human immunodeficiecy virus (HIV) or drug resistant. Sixty four of them were smokers with a pack-year index (standard deviation) of 33.69 (23.12). Delayed sputum smear conversion (DC) was considered when 2 positive sputum culture results were obtained in the second month of anti-tuberculous treatment and was associated with the following variables in 2 groups: a) total group (in which all the patients were included): age, sex, smoking habits, risk factors (alcohol consumption, diabetes mellitus, immunosuppression, drug addicion, malnutrition), time with symptoms, radiologic presentation and bacterial load, and b) smokers: age, sex, risk factors, time with symptoms, radiologic presentation, bacterial load and pack-year index. For the statistical analysis, chi2 test, Student t test and logistic regression model were used, considering the dependant variable DC.

RESULTS

In the total group, 17 patients (17.3%) had DC, 16 of them had a history of smoking and in the univariate analysis it was associated with: alcohol consumption, time with symptoms, radiologic presentation as bilateral cavitary infiltrates and smoking habits. The logistic regression analysis showed an association with smoking habits (odds ratio = 9.8; p = 0.03) and bilateral cavitary infiltrates (odds ratio = 3.61; p = 0.02). In the group of smokers, DC was associated in the univariate analysis with the female sex.

CONCLUSIONS

Smoking habits delay sputum conversion in patients with pulmonary tuberculosis not associated with HIV and non-resistant bacilli. According to these results it is necessary to assist smoking cessation in patients who are receiving antituberculous treatment.

Tobacco smoke, indoor air pollution and tuberculosis: a systematic review and meta-analysis

BACKGROUND

Tobacco smoking, passive smoking, and indoor air pollution from biomass fuels have been implicated as risk factors for tuberculosis (TB) infection, disease, and death. Tobacco smoking and indoor air pollution are persistent or growing exposures in regions where TB poses a major health risk. We undertook a systematic review and meta-analysis to quantitatively assess the association between these exposures and the risk of infection, disease, and death from TB.

METHODS AND FINDINGS

We conducted a systematic review and meta-analysis of observational studies reporting effect estimates and 95% confidence intervals on how tobacco smoking, passive smoke exposure, and indoor air pollution are associated with TB. We identified 33 papers on tobacco smoking and TB, five papers on passive smoking and TB, and five on indoor air pollution and TB. We found substantial evidence that tobacco smoking is positively associated with TB, regardless of the specific TB outcomes. Compared with people who do not smoke, smokers have an increased risk of having a positive tuberculin skin test, of having active TB, and of dying from TB. Although we also found evidence that passive smoking and indoor air pollution increased the risk of TB disease, these associations are less strongly supported by the available evidence.

CONCLUSIONS

There is consistent evidence that tobacco smoking is associated with an increased risk of TB. The finding that passive smoking and biomass fuel combustion also increase TB risk should be substantiated with larger studies in future. TB control programs might benefit from a focus on interventions aimed at reducing tobacco and indoor air pollution exposures, especially among those at high risk for exposure to TB.

A chain-binomial model for intra-household spread of Mycobacterium tuberculosis in a low socio-economic setting in Pakistan

A simulation study using Greenwood's chain-binomial model was carried out to elucidate the spread and control of Mycobacterium tuberculosis among the household contacts of infectious pulmonary tuberculosis (TB) patients. Based on the observed data, the maximum-likelihood estimates (+/-S.E.) of chain-binomial probabilities of intra-household M. tuberculosis transmission from an index case in 3-person and 4-person households were 0.313+/-0.008 and 0.325+/-0.009 respectively. The chi2 goodness-of-fit test of observed and simulated mean expected frequencies of cases revealed good fit for 3-person (P=0.979) and 4-person (P=0.546) households. With the assumption of varying risk of M. tuberculosis transmission across the households under beta-distribution, goodness-of-fit tests of observed and mean simulated expected frequencies revealed the inadequacy of Greenwood's chain-binomial model both for 3-person (P=0.0185) and 4-person (P<0.001) households. Simulated M. tuberculosis control strategy comprising efficient diagnosis, segregation and prompt antibiotic therapy of index pulmonary TB patients showed a substantial reduction of new cases among the household contacts in both household sizes. In conclusion, segregation coupled with prompt antibiotic therapy of the index case, chemoprophylaxis of M. tuberculosis-exposed household contacts, and the assessment of household environmental risks to devise and implement an educational programme may help reduce the TB burden in this and similar settings.