Epidemiology of Tuberculosis in the United States

Social Disparities in Benign Lung Diseases

The many socioeconomic disparities in the myriad of diagnoses that make up benign lung diseases are unfortunately a global issue that was most recently highlighted by the COVID-19 pandemic of 2020. In this chapter, we will be reviewing the socioeconomic disparities in benign lung disease from both a United States perspective as well as a global perspective. We will cover the spectrum of infectious, obstructive, and restrictive lung disease and review the evidence on how social disparities affect these populations and their access to medical care.

Making the invisible visible: the current face of tuberculosis in Detroit, Michigan, USA

Objectives

The objective of this study was to describe the socioeconomic inequities among individuals with tuberculosis (TB) in metropolitan Detroit.

Methods

We used data from the TB Social Survey to examine socioeconomic and demographic characteristics among individuals diagnosed with TB in one of three metropolitan Detroit health departments. We then examined mean levels of both economic disadvantage and socioeconomic instability across levels of race/ethnicity, nativity, and health department.

Results

Sixty-seven percent of individuals with TB in Detroit City were non-Hispanic Black, compared to 27% and 25% in Oakland County and Wayne County (excluding Detroit), respectively. Non-Hispanic Blacks, U.S.-born individuals, and those living in Detroit City had higher mean levels of both economic disadvantage and socioeconomic instability compared to non-Hispanic Whites, foreign-born individuals and those living in Wayne (excluding Detroit City) or Oakland County.

Conclusions

The findings from this study highlight the ways in which TB is distributed along lines of socioeconomic disadvantage. This suggests that enduring inequities in socioeconomic resources may be contributing to inequities in TB disease, a trend that is likely to continue with worsening socioeconomic disparities in the U.S.

Silver Nanoparticles for the Therapy of Tuberculosis

Rapid emergence of aggressive, multidrug-resistant Mycobacteria strain represents the main cause of the current antimycobacterial-drug crisis and status of tuberculosis (TB) as a major global health problem. The relatively low-output of newly approved antibiotics contributes to the current orientation of research towards alternative antibacterial molecules such as advanced materials. Nanotechnology and nanoparticle research offers several exciting new-concepts and strategies which may prove to be valuable tools in improving the TB therapy. A new paradigm in antituberculous therapy using silver nanoparticles has the potential to overcome the medical limitations imposed in TB treatment by the drug resistance which is commonly reported for most of the current organic antibiotics. There is no doubt that AgNPs are promising future therapeutics for the medication of mycobacterial-induced diseases but the viability of this complementary strategy depends on overcoming several critical therapeutic issues as, poor delivery, variable intramacrophagic antimycobacterial efficiency, and residual toxicity. In this paper, we provide an overview of the pathology of mycobacterial-induced diseases, andhighlight the advantages and limitations of silver nanoparticles (AgNPs) in TB treatment.

Population Genetics Based Phylogenetics Under Stabilizing Selection for an Optimal Amino Acid Sequence: A Nested Modeling Approach

We present a new phylogenetic approach, selection on amino acids and codons (SelAC), whose substitution rates are based on a nested model linking protein expression to population genetics. Unlike simpler codon models that assume a single substitution matrix for all sites, our model more realistically represents the evolution of protein-coding DNA under the assumption of consistent, stabilizing selection using a cost-benefit approach. This cost-benefit approach allows us to generate a set of 20 optimal amino acid-specific matrix families using just a handful of parameters and naturally links the strength of stabilizing selection to protein synthesis levels, which we can estimate. Using a yeast data set of 100 orthologs for 6 taxa, we find SelAC fits the data much better than popular models by 104-105 Akike information criterion units adjusted for small sample bias. Our results also indicated that nested, mechanistic models better predict observed data patterns highlighting the improvement in biological realism in amino acid sequence evolution that our model provides. Additional parameters estimated by SelAC indicate that a large amount of nonphylogenetic, but biologically meaningful, information can be inferred from existing data. For example, SelAC prediction of gene-specific protein synthesis rates correlates well with both empirical (r=0.33-0.48) and other theoretical predictions (r=0.45-0.64) for multiple yeast species. SelAC also provides estimates of the optimal amino acid at each site. Finally, because SelAC is a nested approach based on clearly stated biological assumptions, future modifications, such as including shifts in the optimal amino acid sequence within or across lineages, are possible.

Race and nativity are major determinants of tuberculosis in the U.S.: evidence of health disparities in tuberculosis incidence in Michigan, 2004-2012

Background

The incidence of TB in Michigan was 1.5 per 100,000 people in 2012, roughly half the U.S. incidence. Despite successes in TB control, disparities in TB still exist in Michigan, particularly by race, age, and nativity. A major challenge in understanding disparities in TB burden is distinguishing between TB cases resulting from recent transmission and those resulting from reactivation of latent TB infection, information critical to tailoring control strategies. We examined nine-year trends in tuberculosis (TB) incidence patterns for the entire population of Michigan, and within demographic subgroups.

Methods

Using a cross-sectional study of TB surveillance data, we analyzed 1254 TB cases reported in Michigan during 2004–2012. Cases included were those for whom both spoligotyping and 12-locus-MIRU-VNTR results were available. Using a combination of the genotyping information and time of diagnosis, we then classified cases as resulting from either recent transmission or reactivation of latent TB infection. We used multivariable negative binomial regression models to study trends in the TB incidence rate for the entire population and by race, nativity, gender, and age.

Results

Overall, the incidence rate of TB declined by an average of 8% per year—11% among recently transmitted cases, and 9% among reactivation cases. For recently transmitted disease, Blacks had an average incidence rate 25 times greater than Whites, after controlling for nativity, gender, and age. For disease resulting from latent TB infection Asians had an average incidence rate 24 times greater than Whites, after controlling for nativity, gender, and age.

Conclusions

Disparities in incidence persist despite ongoing TB control efforts. Greater disparities were observed by race and nativity demonstrating some of the ways that TB incidence is socially patterned. Reducing these disparities will require a multi-faceted approach encompassing the social and environmental contexts of high-risk populations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-017-4461-y) contains supplementary material, which is available to authorized users.

Mycobacteria

The immunocompromised host is at increased risk of Mycobacterium tuberculosis complex and nontuberculous mycobacteria infection. Although Mycobacterium tuberculosis complex is a significant mycobacterial pathogen, nontuberculous mycobacteria causes substantial disease in those with suppressed immune responses. Mycobacterial infections can cause significant morbidity and mortality in this patient population, and rapid identification and susceptibility testing of the mycobacterial species is paramount to patient management and outcomes. Mycobacterial diagnostics has undergone some significant advances in the last two decades with immunodiagnostics (interferon gamma release assay), microscopy (light-emitting diode), culture (automated broth-based systems), identification (direct PCR, sequencing and matrix-assisted laser-desorption ionization–time of flight mass spectrometry) and susceptibility testing (molecular detection of drug resistance from direct specimens or positive cultures). Employing the most rapid and sensitive methods in the mycobacterial laboratory will have a tremendous impact on patient care and, in the case of Mycobacterium tuberculosis complex, in the control of tuberculosis.

Recent Transmission of Tuberculosis - United States, 2011-2014

Tuberculosis is an infectious disease that may result from recent transmission or from an infection acquired many years in the past; there is no diagnostic test to distinguish the two causes. Cases resulting from recent transmission are particularly concerning from a public health standpoint. To describe recent tuberculosis transmission in the United States, we used a field-validated plausible source-case method to estimate cases likely resulting from recent transmission during January 2011-September 2014. We classified cases as resulting from either limited or extensive recent transmission based on transmission cluster size. We used logistic regression to analyze patient characteristics associated with recent transmission. Of 26,586 genotyped cases, 14% were attributable to recent transmission, 39% of which were attributable to extensive recent transmission. The burden of cases attributed to recent transmission was geographically heterogeneous and poorly predicted by tuberculosis incidence. Extensive recent transmission was positively associated with American Indian/Alaska Native (adjusted prevalence ratio [aPR] = 3.6 (95% confidence interval [CI] 2.9-4.4), Native Hawaiian/Pacific Islander (aPR = 3.2, 95% CI 2.3-4.5), and black (aPR = 3.0, 95% CI 2.6-3.5) race, and homelessness (aPR = 2.3, 95% CI 2.0-2.5). Extensive recent transmission was negatively associated with foreign birth (aPR = 0.2, 95% CI 0.2-0.2). Tuberculosis control efforts should prioritize reducing transmission among higher-risk populations.

Radiologic manifestations of pulmonary tuberculosis in patients of intensive care units

BACKGROUND

Tuberculosis (TB) is a serpent disease with various pulmonary manifestations, and timely diagnosis of the disease is paramount, since delayed treatment is associated with severe morbidity, particularly in intensive care units (ICU). Therefore, it is imperative that intensivists understand the typical distribution, patterns, and imaging manifestations of TB.

AIM

To describe different manifestations of pulmonary TB in patients in the ICU.

METHODS

In a retrospective study, all patients with a clinical and a laboratory-confirmed diagnosis of TB who were admitted to the ICU were entered in the study. All patients had a confirmatory laboratory diagnosis of TB including positive smears. The patterns of parenchymal lesions, involved segments and presence of cavity, bronchiectasis and bronchogenic spread of the lesions with computed tomography (CT) and chest/X-ray (CXR) were recorded and analyzed.

RESULTS

Data of 146 patients with TB were entered in the study. The most common finding in CT was acute respiratory distress syndrome (ARDS)-like radiologic manifestations (17.1%), followed by parenchymal nodular infiltration (13.6%) and cavitation (10.9%), consolidation (10.2%), interstitial involvement (9.5%), calcified parenchymal mass (8.3%), ground-glass opacities (7.5%), and pleural effusion or thickening (6.9%). Radiologic evidence of lymphadenopathy was seen in up to 43% of adults. Miliary TB was observed in 2.3% of patients, mostly in those older than 60years of age. ARDS-like (64.5%) manifestations on CT and miliary TB (85.5%) had the highest mortality rates among other pulmonary manifestations.

CONCLUSION

ARDS, interstitial involvement, and Parenchymal nodular infiltration are the most common manifestations of pulmonary TB. Various features of TB in ICU patients could be misleading for intensivists.

Evaluation of the relationship between smear positivity and high-resolution CT findings in children with pulmonary tuberculosis

Background

The aim of this study is to find a relationship between the radiological manifestations of childhood tuberculosis on a high-resolution computed tomography (HRCT) and the results of sputum smear. This study aims to propose an alternative indicator of infectivity in terms of prevention of disease transmission through selective isolation policy in children whose clinical condition is highly suggestive of tuberculosis.

Material/Methods

This retrospective comparative study was performed on 95 children under 15 years of age diagnosed with tuberculosis based on both WHO criteria and positive sputum culture for mycobacterium Tuberculosis. The children were admitted for TB screening in the pediatric department of national research institute of tuberculosis and lung disease (NRITLD) between 2008–2012. Direct smear collected from sputum or gastric lavage, as well as HRCT were performed in all children prior to administration of medical therapy. Children were divided into 2 groups based on positive and negative smear results. HRCT abnormalities, as well as their anatomical distribution were compared between these 2 groups using multivariate analytic model.

Results

The most prevalent abnormalities in the positive smear group were consolidation, tree-in-bud pattern, upper lobe nodular infiltration and cavitation. The negative smear group featured lymphadenopathy, consolidation, collapse and nodular infiltration in the upper lobe. Cavity, tree- in-bud pattern and upper lobe nodular infiltration were highly associated with smear positivity in children. Conversely, lymphadenopathy and collapse had significant association with a negative smear.

Conclusions

This study revealed that cavity, tree-in-bud and upper lobe nodular infiltration has significant association with smear positivity in childhood tuberculosis. On the other hand, lymphadenopathy and collapse were closely associated with smear negativity in this age group. It was also demonstrated that children with a positive smear most likely presented with radiological features of post primary tuberculosis, while the negative smear group most often manifested with primary tuberculosis.

Tuberculous pleural effusion

Tuberculous pleural effusion (TBPE) is the most common form of extrapulmonary tuberculosis (TB) in Spain, and is one of the most frequent causes of pleural effusion. Although the incidence has steadily declined (4.8 cases/100,000population in 2009), the percentage of TBPE remains steady with respect to the total number of TB cases (14.3%-19.3%). Almost two thirds are men, more than 60% are aged between 15-44years, and it is more common in patients with human immunodeficiency virus. The pathogenesis is usually a delayed hypersensitivity reaction. Symptoms vary depending on the population (more acute in young people and more prolonged in the elderly). The effusion is almost invariably a unilateral exudate (according to Light's criteria), more often on the right side, and the tuberculin test is negative in one third of cases. There are limitations in making a definitive diagnosis, so various pleural fluid biomarkers have been used for this. The combination of adenosine deaminase and lymphocyte percentage may be useful in this respect. Treatment is the same as for any TB. The addition of corticosteroids is not advisable, and chest drainage could help to improve symptoms more rapidly in large effusions.

The impact of migrant workers on the tuberculosis transmission: general models and a case study for China

A tuberculosis (TB) transmission model involving migrant workers is proposed and investigated. The basic reproduction number R0 is calculated, and is shown to be a threshold parameter for the disease to persist or become extinct in the population. The existence and global attractivity of an endemic equilibrium, if R0 > 1, is also established under some technical conditions. A case study, based on the TB epidemiological and other statistical data in China, indicates that the disease spread can be controlled if effective measures are taken to reduce the reactivation rate of exposed/latent migrant workers. Impact of the migration rate and direction, as well as the duration of home visit stay, on the control of disease spread is also examined numerically.

Non-hispanic whites have higher risk for pulmonary impairment from pulmonary tuberculosis

BACKGROUND

Disparities in outcomes associated with race and ethnicity are well documented for many diseases and patient populations. Tuberculosis (TB) disproportionately affects economically disadvantaged, racial and ethnic minority populations. Pulmonary impairment after tuberculosis (PIAT) contributes heavily to the societal burden of TB. Individual impacts associated with PIAT may vary by race/ethnicity or socioeconomic status.

METHODS

We analyzed the pulmonary function of 320 prospectively identified patients with pulmonary tuberculosis who had completed at least 20 weeks standard anti-TB regimes by directly observed therapy. We compared frequency and severity of spirometry-defined PIAT in groups stratified by demographics, pulmonary risk factors, and race/ethnicity, and examined clinical correlates to pulmonary function deficits.

RESULTS

Pulmonary impairment after tuberculosis was identified in 71% of non-Hispanic Whites, 58% of non-Hispanic Blacks, 49% of Asians and 32% of Hispanics (p < 0.001). Predictors for PIAT varied between race/ethnicity. PIAT was evenly distributed across all levels of socioeconomic status suggesting that PIAT and socioeconomic status are not related. PIAT and its severity were significantly associated with abnormal chest x-ray, p < 0.0001. There was no association between race/ethnicity and time to beginning TB treatment, p = 0.978.

CONCLUSIONS

Despite controlling for cigarette smoking, socioeconomic status and time to beginning TB treatment, non-Hispanic White race/ethnicity remained an independent predictor for disproportionately frequent and severe pulmonary impairment after tuberculosis relative to other race/ethnic groups. Since race/ethnicity was self reported and that race is not a biological construct: these findings must be interpreted with caution. However, because race/ethnicity is a proxy for several other unmeasured host, pathogen or environment factors that may contribute to disparate health outcomes, these results are meant to suggest hypotheses for further research.

Heightened vulnerability to MDR-TB epidemics after controlling drug-susceptible TB

BACKGROUND

Prior infection with one strain TB has been linked with diminished likelihood of re-infection by a new strain. This paper attempts to determine the role of declining prevalence of drug-susceptible TB in enabling future epidemics of MDR-TB.

METHODS

A computer simulation of MDR-TB epidemics was developed using an agent-based model platform programmed in NetLogo (See http://mdr.tbtools.org/). Eighty-one scenarios were created, varying levels of treatment quality, diagnostic accuracy, microbial fitness cost, and the degree of immunogenicity elicited by drug-susceptible TB. Outcome measures were the number of independent MDR-TB cases per trial and the proportion of trials resulting in MDR-TB epidemics for a 500 year period after drug therapy for TB is introduced.

RESULTS

MDR-TB epidemics propagated more extensively after TB prevalence had fallen. At a case detection rate of 75%, improving therapeutic compliance from 50% to 75% can reduce the probability of an epidemic from 45% to 15%. Paradoxically, improving the case-detection rate from 50% to 75% when compliance with DOT is constant at 75% increases the probability of MDR-TB epidemics from 3% to 45%.

CONCLUSIONS

The ability of MDR-TB to spread depends on the prevalence of drug-susceptible TB. Immunologic protection conferred by exposure to drug-susceptible TB can be a crucial factor that prevents MDR-TB epidemics when TB treatment is poor. Any single population that successfully reduces its burden of drug-susceptible TB will have reduced herd immunity to externally or internally introduced strains of MDR-TB and can experience heightened vulnerability to an epidemic. Since countries with good TB control may be more vulnerable, their self interest dictates greater promotion of case detection and DOTS implementation in countries with poor control to control their risk of MDR-TB.

A new paradigm for quarantine and public health activities at land borders: opportunities and challenges

The Institute of Medicine (IOM) report Quarantine Stations at Ports of Entry: Protecting the Public's Health focused almost exclusively on U.S. airports and seaports, which served 106 million entries in 2005. IOM concluded that the primary function of these quarantine stations (QSs) should shift from providing inspection to providing strategic national public health leadership. The large expanse of our national borders, large number of crossings, sparse federal resources, and decreased regulation regarding conveyances crossing these borders make land borders more permeable to a variety of threats. To address the health challenges related to land borders, the QSs serving such borders must assume unique roles and partnerships to achieve the strategic leadership and public health research roles envisioned by the IOM. In this article, we examine how the IOM recommendations apply to the QSs that serve the land borders through which more than 319 million travelers, immigrants, and refugees entered the U.S. in 2005.

Communicable Diseases, Globalization of

This article examines the spatial distribution of leading infectious causes of morbidity and mortality worldwide. Beginning with simple models explaining the spatial pattern of infectious diseases, the epidemiologic transition, and disease ecology models, the article focuses on HIV/AIDS, tuberculosis, polio, SARS, and influenza as well as sexually transmitted infections such as gonorrhea. It addresses the problem of disease strain mutation and especially drug resistance, and argues for the application of genotyping in medical geography research. The article emphasizes how migration and increased global interaction are producing a globalization of infectious diseases while at the same time, ethnic residential segregation is producing spatial concentrations of infectious disease or different strains of disease.

Presentation and outcome of tuberculous meningitis in adults in the province of Castellon, Spain: a retrospective study

The aim of this study was to describe the epidemiological and clinical features of tuberculous meningitis in the province of Castellon, Spain. Retrospective analysis was done of all cases attended during the last 15 years. The following groups of variables were assessed: sociodemographic data, medical antecedents, clinical presentation, imaging study results, analyses, cerebrospinal fluid microbiology, treatment, and outcome. Twenty-nine cases were included. Median of age of patients was 34 years, and 17 (59%) were males. HIV infection was present in 15 cases (52%), fever, the most common symptom, occurred in 27 (93%), nuchal rigidity was noted in only 16 (55%), and syndrome of inappropriate ADH secretion (SIADH) occurred in 13 cases (45%). Chest radiograph was abnormal in 15 cases (52%). Anaemia was found in 22 subjects (76%), hypoalbuminaemia in 18 (62%) and hyponatraemia in 15 (52%). Macroscopic aspect of cerebrospinal fluid was normal in 17 cases (65%). Acid-fast stain was positive in only one case (4%). Two patients presented resistance to anti-tuberculous medications. Twelve patients (41%) died and eight (28%) presented sequelae. An association was found between death as outcome and presence of SIADH and lower level of serum cholesterol. Tuberculous meningitis is a rare and frequently difficult to recognize disease, which results in significant morbidity and mortality. We found an association of mortality with SIADH and lower level of serum cholesterol.

Infection in the elderly

Many functional, demographic, and immunologic changes associated with aging are responsible for increasing the incidence and severity of infectious diseases in the elderly. Management is complicated by age-related organ system changes. Because many of the elderly are on multiple medications for underlying illnesses, antimicrobial therapy needs to be chosen keeping drug interactions and adverse events in mind. Common infections seen in the elderly are infections of skin and soft tissue, urinary tract, respiratory tract, and gastrointestinal tract. Organized and well-funded programs to address infectious disease issues in the elderly are the only way to improve care.

Orbital tuberculosis: a review of the literature

PURPOSE

To provide an up-to-date review of the clinical presentations, investigations, and management of orbital tuberculosis (OTB).

METHODS

Systematic review of the literature concerning OTB, limiting the results to English-language peer-reviewed journals.

RESULTS

Seventy-nine patients from 39 publications were identified as cases of OTB. The condition presents in one of five forms: classical periostitis; orbital soft tissue tuberculoma or cold abscess, with no bony involvement; OTB with bony involvement; spread from the paranasal sinuses; and tuberculous dacryoadenitis. The ocular adnexa, including the nasolacrimal system and overlying skin, may also be involved.

CONCLUSIONS

Diagnosis can be difficult and may necessitate an orbital biopsy, in which acid-fast bacilli (AFB) and characteristic histopathology may be seen. Growth of Mycobacterium tuberculosis (mTB) from such a specimen remains the gold standard for diagnosis. Ancillary investigations include tuberculin skin tests and chest radiography, but more recently alternatives such as whole blood interferon-gamma immunological tests and PCR-based tests of pathological specimens have proven useful. The management of OTB is complex, requiring a stringent public health strategy and high levels of patient adherence, combined with long courses of multiple anti-tuberculous medications. The interaction of the human immunodeficiency virus (HIV) with TB may further complicate management.

Foreign-Born Status and Geographic Patterns of Tuberculosis Genotypes in Tarrant County, Texas

Regardless of destination, immigrants arrive with health profiles typical of people in their previous surroundings. Thus, immigrants change the epidemiological profile of destination communities, and immigrant neighborhoods may represent islands of infectious disease. Genotyping has emerged as a useful surveillance tool to track the spread of disease at the molecular level. Yet the spatial distribution of infectious disease at the molecular level associated with migration and immigrant neighborhoods has received little attention. Using molecular genotyping to characterize M. tuberculosis isolated from tuberculosis cases, this article analyzes spatial variations of unique molecular M. tuberculosis strains by zip code in Tarrant County, Texas. The results suggest that immigrant neighborhoods have higher rates of unique isolates of tuberculosis (suggestive of remote transmission) compared to neighborhoods occupied by the native-born. Neighborhoods dominated by the native-born have higher rates of clustered isolates (suggestive of recent transmission). Therefore, in addition to being culturally distinct, immigrant neighborhoods may also be pathogenically distinct from surrounding neighborhoods.

Tuberculosis: a radiologic review

Tuberculosis has shown a resurgence in nonendemic populations in recent years, a phenomenon that has been attributed to factors such as increased migration and the human immunodeficiency virus epidemic. Although the thorax is most frequently involved, tuberculosis may involve any of a number of organ systems (eg, the respiratory, cardiac, central nervous, musculoskeletal, gastrointestinal, and genitourinary systems), and timely diagnosis of the disease is paramount, since delayed treatment is associated with severe morbidity. Unfortunately, a history of infection with or exposure to tuberculosis may or may not be present, and evidence of active tuberculosis is present in less than 50% of cases. A negative tuberculin skin test does not in itself exclude infection. Furthermore, the clinical and radiologic features of tuberculosis may mimic those of many other diseases. Therefore, although in many cases biopsy or culture specimens are required to make the definitive diagnosis, it is imperative that radiologists and clinicians understand the typical distribution, patterns, and imaging manifestations of tuberculosis.

Investigating the metabolic capabilities of Mycobacterium tuberculosis H37Rv using the in silico strain iNJ661 and proposing alternative drug targets

Background:

Mycobacterium tuberculosis continues to be a major pathogen in the third world, killing almost 2 million people a year by the most recent estimates. Even in industrialized countries, the emergence of multi-drug resistant (MDR) strains of tuberculosis hails the need to develop additional medications for treatment. Many of the drugs used for treatment of tuberculosis target metabolic enzymes. Genome-scale models can be used for analysis, discovery, and as hypothesis generating tools, which will hopefully assist the rational drug development process. These models need to be able to assimilate data from large datasets and analyze them.

Results:

We completed a bottom up reconstruction of the metabolic network of Mycobacterium tuberculosis H37Rv. This functional in silico bacterium, iNJ661, contains 661 genes and 939 reactions and can produce many of the complex compounds characteristic to tuberculosis, such as mycolic acids and mycocerosates. We grew this bacterium in silico on various media, analyzed the model in the context of multiple high-throughput data sets, and finally we analyzed the network in an 'unbiased' manner by calculating the Hard Coupled Reaction (HCR) sets, groups of reactions that are forced to operate in unison due to mass conservation and connectivity constraints.

Conclusion:

Although we observed growth rates comparable to experimental observations (doubling times ranging from about 12 to 24 hours) in different media, comparisons of gene essentiality with experimental data were less encouraging (generally about 55%). The reasons for the often conflicting results were multi-fold, including gene expression variability under different conditions and lack of complete biological knowledge. Some of the inconsistencies between in vitro and in silico or in vivo and in silico results highlight specific loci that are worth further experimental investigations. Finally, by considering the HCR sets in the context of known drug targets for tuberculosis treatment we proposed new alternative, but equivalent drug targets.

Pleural tuberculosis in the United States: incidence and drug resistance

BACKGROUND

Pleural tuberculosis (TB) should be considered in any patient with a lymphocytic pleural effusion. The diagnostic approach is under debate. Knowledge of pleural TB epidemiology would be beneficial. To help clarify pleural TB epidemiology, we analyzed US national TB surveillance data for 1993 to 2003.

METHODS

We compared pleural TB to pulmonary TB (where each was reported as the major site of TB disease, and no additional sites of disease were reported). Applicable statistical tests were performed; p < 0.05 was considered to be significant.

RESULTS

From 1993 through 2003, 7,549 cases of pleural TB and 156,779 cases of pulmonary TB were reported (in 2003: pleural TB, 536 cases; pulmonary TB, 10,551 cases). The annual proportion of pleural TB was relatively stable (median rate, 3.6%; range, 3.3 to 4.0%) compared to that for pulmonary TB, which steadily decreased (average annual decrease, 0.9%; p < 0.01). Pleural TB occurred significantly more often than pulmonary TB among persons >/= 65 years old (30.4% vs 23.3%, respectively; p < 0.01), and it occurred significantly less often among children < 15 years old (1.8% vs 6.1%, respectively; p < 0.01) and persons 45 to 64 years old (22.9% vs 27.9%, respectively; p < 0.01). Pleural TB patients (63.4%) were born slightly more often in the United States than were pulmonary TB patients (60.9%; p < 0.01). Drug-resistance patterns of pleural TB broadly reflected those of pulmonary TB. However, isolates from pleural TB patients were less often resistant to at least isoniazid (6.0% vs 7.8%, respectively; p < 0.01) and to at least one first-line TB drug (9.9% vs 11.9%, respectively; p < 0.01) compared with pulmonary TB patients.

CONCLUSIONS

Knowledge of pleural TB demographic, clinical, and drug-resistance patterns may assist clinicians in making diagnostic and therapeutic decisions.