Tuberculosis in ageing: high rates, complex diagnosis and poor clinical outcomes

BACKGROUND

worldwide, the frequency of tuberculosis among older people almost triples that observed among young adults.

OBJECTIVE

to describe clinical and epidemiological consequences of pulmonary tuberculosis among older people.

METHODS

we screened persons with a cough lasting more than 2 weeks in Southern Mexico from March 1995 to February 2007. We collected clinical and mycobacteriological information (isolation, identification, drug-susceptibility testing and IS6110-based genotyping and spoligotyping) from individuals with bacteriologically confirmed pulmonary tuberculosis. Patients were treated in accordance with official norms and followed to ascertain treatment outcomes, retreatment, and vital status.

RESULTS

eight hundred ninety-three tuberculosis patients were older than 15 years of age; of these, 147 (16.5%) were 65 years of age or older. Individuals ≥ 65 years had significantly higher rates of recently transmitted and reactivated tuberculosis. Older age was associated with treatment failure (OR=5.37; 95% CI: 1.06-27.23; P=0.042), and death due to tuberculosis (HR=3.52; 95% CI: 1.78-6.96; P<0.001) adjusting for sociodemographic and clinical variables.

CONCLUSIONS

community-dwelling older individuals participate in chains of transmission indicating that tuberculosis is not solely due to the reactivation of latent disease. Untimely and difficult diagnosis and a higher risk of poor outcomes even after treatment completion emphasise the need for specific strategies for this vulnerable group.

Surveillance of nosocomial infections in a Mexican community hospital. How are we doing?

OBJECTIVE

To compare the nosocomial infection (NI) rate obtained from a retrospective review of clinical charts with that from the routine nosocomial infection surveillance system in a community hospital.

MATERIAL AND METHODS

Retrospective review of a randomized sample of clinical charts.Results were compared to standard surveillance using crude and adjusted analyses.

RESULTS

A total of 440 discharges were reviewed, there were 27 episodes of NIs among 22 patients. Cumulated incidence was 6.13 NI per 100 discharges. Diarrhea, pneumonia and peritonitis were the most common infections. Predictors of NI by Cox regression analysis included pleural catheter (HR 16.38), entry through the emergency ward, hospitalization in the intensive care unit (HR 7.19), and placement of orotracheal tube (HR 5.54).

CONCLUSIONS

Frequency of NIs in this community hospital was high and underestimated. We identified urgent needs in the areas of training and monitoring.

Partial protection of seasonal trivalent inactivated vaccine against novel pandemic influenza A/H1N1 2009: case-control study in Mexico City

OBJECTIVE

To evaluate the association of 2008-9 seasonal trivalent inactivated vaccine with cases of influenza A/H1N1 during the epidemic in Mexico.

DESIGN

Frequency matched case-control study.

SETTING

Specialty hospital in Mexico City, March to May 2009.

PARTICIPANTS

60 patients with laboratory confirmed influenza A/H1N1 and 180 controls with other diseases (not influenza-like illness or pneumonia) living in Mexico City or the State of Mexico and matched for age and socioeconomic status.

MAIN OUTCOME MEASURES

Odds ratio and effectiveness of trivalent inactivated vaccine against influenza A/H1N1.

RESULTS

Cases were more likely than controls to be admitted to hospital, undergo invasive mechanical ventilation, and die. Controls were more likely than cases to have chronic conditions that conferred a higher risk of influenza related complications. In the multivariate model, influenza A/H1N1 was independently associated with trivalent inactivated vaccine (odds ratio 0.27, 95% confidence interval 0.11 to 0.66) and underlying conditions (0.15, 0.08 to 0.30). Vaccine effectiveness was 73% (95% confidence interval 34% to 89%). None of the eight vaccinated cases died.

CONCLUSIONS

Preliminary evidence suggests some protection from the 2008-9 trivalent inactivated vaccine against pandemic influenza A/H1N1 2009, particularly severe forms of the disease, diagnosed in a specialty hospital during the influenza epidemic in Mexico City.

Indoor pollution as an occupational risk factor for tuberculosis among women: a population-based, gender oriented, case-control study in Southern Mexico

BACKGROUND

Indoor air pollution produced by biomass cooking fuels in developing countries has been associated with acute and chronic lower respiratory diseases, but has not been identified as an occupational exposure among women.

OBJECTIVE

To examine the relationship between the use of biomass cooking fuels (mainly wood) and tuberculosis (TB) among women living in rural areas in Southern Mexico.

METHODS

We conducted a population based case-control study in the health jurisdiction of Orizaba, Mexico. Cases were all incident female pulmonary TB patients, with Mycobacterium tuberculosis in sputum, living in communities with fewer than 15,000 inhabitants, diagnosed between March 1995 and April 2003. Woodsmoke exposure was assessed by applying a standardized questionnaire (ATS-DLD-78 questionnaire). Controls were randomly selected from sex-matched neighbors. Appropriate IRB approval was obtained.

RESULTS

42 TB cases and 84 community controls were recruited. Multivariate assessment showed that more than 20 years of exposure to smoke from biomass fuels was three times more frequent among cases than among controls [Odds ratio (OR): 3.3, 95% confidence interval (CI):1.06-10.30, p = 0.03], after controlling for age, body mass, household crowding, years of formal education and tobacco use.

CONCLUSIONS

We found a strong association between the use of biomass cooking fuels and tuberculosis among women in a community-based, case-control study. Results of this study are intended to provide evidence to policy makers, community leaders and the general public on the importance of implementing gender oriented interventions that decrease the use of biomass fuels in poor communities in developing countries.

[Research on conventional and molecular epidemiology of tuberculosis in Orizaba, Veracruz, 1995-2008]

This study describes the achievements of the Mexican Consortium against Tuberculosis, in the Sanitary District of Orizaba, Veracruz, Mexico between 1995 and 2008. In brief, the main results can be classified as follows: 1) Conventional and molecular epidemiology (measurement of burden of disease, trends, risk factors and vulnerable groups, consequences of drug resistance, identification of factors that favor nosocomial and community transmission); 2) Development of diagnostic techniques to detect drug resistance, description of circulating clones and adaptation of simple techniques to be used in the field; 3) Evaluation of usefulness of tuberculin skin test, immunologic responses to BCG, impact of directly observed therapy for tuberculosis (DOTS), and study of immunological biomarkers and 4) Comments on ethical aspects of tuberculosis research. Additionally, we describe the impact on public policies, transference of technology, capacity building and future perspectives.

Virulence, immunopathology and transmissibility of selected strains of Mycobacterium tuberculosis in a murine model

After encounter with Mycobacterium tuberculosis, a series of non-uniform immune responses are triggered that define the course of the infection. Eight M. tuberculosis strains were selected from a prospective population-based study of pulmonary tuberculosis patients (1995-2003) based on relevant clinical/epidemiological patterns and tested in a well-characterized BALB/c mouse model of progressive pulmonary tuberculosis. In addition, a new mouse model of transmissibility consisting of prolonged cohousing (up to 60 days) of infected and naïve animals was tested. Four phenotypes were defined based on strain virulence (mouse survival, lung bacillary load and tissue damage), immunology response (cytokine expression determined by real-time polymerase chain reaction) and transmissibility (lung bacillary loads and cutaneous delayed-type hypersensitivity in naïve animals).We identified four clearly defined strain phenotypes: (1) hypervirulent strain with non-protective immune response and highly transmissible; (2) virulent strain, associated with high expression of proinflammatory cytokines (tumour necrosis factor and interferon) and very low anti-inflammatory cytokine expression (interleukins 4 and 10), which induced accelerated death by immunopathology; (3) strain inducing efficient protective immunity with lower virulence, and (4) strain demonstrating strong and early macrophage activation (innate immunity) with delayed participation of acquired immunity (interferon expression). We were able to correlate virulent and transmissible phenotypes in the mouse model and markers of community transmission such as tuberculin reactivity among contacts, rapid progression to disease and cluster status. However, we were not able to find correlation with the other two phenotypes. Our new transmission model supported the hypothesis that among these strains increased virulence was linked to increased transmission.

Is tuberculin skin testing useful to diagnose latent tuberculosis in BCG-vaccinated children?

BACKGROUND

The tuberculin skin test (TST) is the most commonly used tool to detect infection with Mycobacterium tuberculosis. We sought to determine whether tuberculin skin testing is useful to detect latent infection by M. tuberculosis in a population that was vaccinated with the Bacille Calmette Guérin (BCG) vaccine.

METHODS

We performed a cross-sectional study during October 2000-February 2001, enrolling first and sixth graders from a random, stratified sample of public elementary schools in Orizaba, Veracruz, Mexico. We assessed the relationship between sociodemographic and epidemiological information, BCG scars, and TST reactivity.

RESULTS

There were 858 children enrolled in the study with a completed questionnaire and TST result. The prevalence of a positive TST result (> or =10 mm) was 12.4%. Controlling for BCG scar, age, and other characteristics, close contact with pulmonary tuberculosis patients (odds ratio 6.56, 95% confidence interval 2.05-21.07, P = 0.001) was independently associated with TST reactivity.

CONCLUSIONS

TST results helped identify children in a BCG-vaccinated population who had recent exposure to persons with pulmonary tuberculosis, were probably infected with M. tuberculosis, and could benefit from treatment for their latent tuberculosis infection.

Gender differentials of pulmonary tuberculosis transmission and reactivation in an endemic area

BACKGROUND

In most low income countries there are twice as many cases of tuberculosis (TB) reported among men than among women, a difference commonly attributed to biological and epidemiological characteristics as well as socioeconomic and cultural barriers in access to health care. The World Health Organization has encouraged gender specific comparisons in TB rates to determine whether women with TB are less likely than men with TB to be diagnosed, reported, and treated. A study was undertaken to identify gender based differences in patients with pulmonary TB and to use this information to improve TB control efforts.

METHODS

Individuals with a cough for more than 2 weeks in southern Mexico were screened from March 1995 to April 2003. Clinical and mycobacteriological information (isolation, identification, drug susceptibility testing and IS6110 based genotyping, and spoligotyping) was collected from those with bacteriologically confirmed pulmonary TB. Patients were treated in accordance with official norms and followed to ascertain treatment outcome, retreatment, and vital status.

RESULTS

623 patients with pulmonary TB were enrolled. The male:female incidence rate ratio for overall, reactivated, and recently transmitted disease was 1.58 (95% CI 1.34 to 1.86), 1.64 (95% CI 1.36 to 1.98), and 1.41 (95% CI 1.01 to 1.96), respectively. Men were more likely than women to default from treatment (adjusted OR 3.30, 95% CI 1.46 to 7.43), to be retreated (hazard ratio (HR) 3.15, 95% CI 1.38 to 7.22), and to die from TB (HR 2.23, 95% CI 1.25 to 3.99).

CONCLUSIONS

Higher rates of transmitted and reactivated disease and poorer treatment outcomes among men are indicators of gender differentials in the diagnosis and treatment of pulmonary TB, and suggest specific strategies in endemic settings.

Changes in the geographical distribution of tuberculosis patients in Veracruz, Mexico, after reinforcement of a tuberculosis control programme

OBJECTIVE

Geographical information systems are valuable tools for studying tuberculosis (TB) epidemiology, but have been underused for the evaluation of TB control programs. We aimed to compare the geographical distribution of TB before and after the five elements of directly observed therapy, short course (DOTS) were strengthened in a Health Jurisdiction in Mexico in response to recommendations made by the WHO Global Tuberculosis Program.

METHODS

All consenting persons detected by passive case finding between March 1995 and February 2000 who were confirmed to have acid-fast bacilli (AFB) in sputum underwent clinical and laboratory evaluation. A TB 'episode' was defined as the period of time between bacteriological diagnosis and treatment discharge by the local control programme. Distances of TB episodes from the nearest urban centre were determined according to recent transmission and multidrug resistance (MDR).

RESULTS

During the first half of the study period, MDR episodes were located a median distance of 1.24 km from urban centres, which did not differ significantly from non-MDR episodes (1.14 km, P=0.56). In contrast, the median distance of MDR episodes increased 55% to 1.92 km during the second half, which placed them significantly further away out than non-MDR episodes (1.08 km, P=0.01). No changes in location were detected for recent transmission.

CONCLUSION

While reinforcing the TB control programme reduced the incidence of MDR, the remaining episodes were located in poorer and more remote areas.

Tuberculosis and diabetes in southern Mexico

OBJECTIVE

To determine the impact of diabetes on the rates of tuberculosis in a region where both diseases are prevalent.

RESEARCH DESIGN AND METHODS

Data from a population-based cohort of patients with pulmonary tuberculosis undergoing clinical and mycobacteriologic evaluation (isolation, identification, drug-susceptibility testing, and IS6110-based genotyping and spoligotyping) were linked to the 2000 National Health Survey (ENSA2000), a national probabilistic, polystage, stratified, cluster household survey of the civilian, noninstitutionalized population of Mexico.

RESULTS

From March 1995 to March 2003, 581 patients with Mycobacterium tuberculosis culture and fingerprint were diagnosed, 29.6% of whom had been diagnosed previously with diabetes by a physician. According to the ENSA2000, the estimated prevalence of diabetes in the study area was 5.3% (95% CI 4.1-6.5). The estimated rates of tuberculosis for the study area were greater for patients with diabetes than for nondiabetic individuals (209.5 vs. 30.7 per 100000 person-years, P < 0.0001).

CONCLUSIONS

In this setting, the rate of tuberculosis was increased 6.8-fold (95% CI 5.7-8.2, P < 0.0001) in patients with diabetes due to increases in both reactivated and recently transmitted infection. Comorbidity with diabetes may increase tuberculosis rates as much as coinfection with human immunodeficiency virus (HIV), with important implications for the allocation of health care resources.