Induced sputum is safe and well-tolerated for TB diagnosis in a resource-poor primary healthcare setting

The spectrum of tuberculosis described as differential DNA methylation patterns in alveolar macrophages and alveolar T cells

BACKGROUND

Host innate immune cells have been identified as key players in the early eradication of Mycobacterium tuberculosis and in the maintenance of an anti-mycobacterial immune memory, which we and others have shown are induced through epigenetic reprogramming. Studies on human tuberculosis immunity are dominated by those using peripheral blood as surrogate markers for immunity. We aimed to investigate DNA methylation patterns in immune cells of the lung compartment by obtaining induced sputum from M. tuberculosis- exposed subjects including symptom-free subjects testing positively and negatively for latent tuberculosis as well as patients diagnosed with active tuberculosis. Alveolar macrophages and alveolar T cells were isolated from the collected sputum and DNA methylome analyses performed (Illumina Infinium Human Methylation 450 k).

RESULTS

Multidimensional scaling analysis revealed that DNA methylomes of cells from the tuberculosis-exposed subjects and controls appeared as separate clusters. The numerous genes that were differentially methylated between the groups were functionally connected and overlapped with previous findings of trained immunity and tuberculosis. In addition, analysis of the interferon-gamma release assay (IGRA) status of the subjects demonstrated that the IGRA status was reflected in the DNA methylome by a unique signature.

CONCLUSIONS

This pilot study suggests that M. tuberculosis induces epigenetic reprogramming in immune cells of the lung compartment, reflected as a specific DNA methylation pattern. The DNA methylation signature emerging from the comparison of IGRA-negative and IGRA-positive subjects revealed a spectrum of signature strength with the TB patients grouping together at one end of the spectrum, both in alveolar macrophages and T cells. DNA methylation-based biosignatures could be considered for further development towards a clinically useful tool for determining tuberculosis infection status and the level of tuberculosis exposure.

Gastric specimens for diagnosing tuberculosis in adults unable to expectorate in Rawalpindi, Pakistan

Setting: Adult pulmonary tuberculosis (TB) patients unable to expectorate quality sputum represent a diagnostic challenge. A private hospital in Pakistan routinely performs gastric aspiration in adults with difficulties expectorating. Objective: To assess the usefulness of gastric specimens (GS) in diagnosing pulmonary TB (PTB) and drug-resistant TB in adult presumptive TB patients unable to expectorate, and to compare the diagnostic yield and sensitivity of smear, culture and the Xpert^® MTB/RIF assay. Design: This was a comparative cross-sectional study based on retrospective record review. Results: Of 900, 885 and 877 GS tested by smear, Xpert and culture, respectively, interpretable results were obtained for respectively 900 (100%), 859 (97.1%) and 754 (86.0%), with a diagnostic yield of respectively 23.6%, 30.3% and 24.9%. The yield was significantly higher for Xpert in previously treated patients. There were 313 patients with definite TB, defined as positive on Xpert and/or culture. The 82.8% sensitivity of Xpert was significantly higher than that of smear (61.0%) and culture (67.8%). Conclusion: GS obtained by aspiration under routine programme conditions is useful for detecting TB and drug-resistant TB in adult patients unable to expectorate. Xpert, with its rapid testing, high proportion of interpretable results and better sensitivity, can substantially improve the diagnosis of bacteriologically confirmed TB and rifampicin resistance.

Perceived risk of tuberculosis infection among healthcare workers in Swaziland

BACKGROUND

The incidence of tuberculosis (TB) in the Kingdom of Swaziland is extremely high. How healthcare workers (HCWs) in Swaziland perceive infection control (IC) measures for preventing TB transmission is unclear. This study aimed to determine perceived risk of TB infection in relation to IC measures among HCWs in three institutions of Swaziland.

METHODS

A cross-sectional questionnaire survey was conducted in 2014. Demographic data and IC measures were collected from main and allied HCWs.

RESULTS

In total, 186 HCWs (19 doctors, 99 nurses, and 68 allied HCWs) were enrolled. The multivariate logistic regression analyses revealed that nurses (OR = 39.87, 95% CI = 2.721-584.3) and other HCWs (OR =99.34, 95% CI = 7.469-1321) perceived a higher TB infection risk than did doctors. Moreover, HCWs working for <4 years at the TB department perceived a lower TB infection risk (OR = 0.099, 95% CI = 0.022-0.453). Availability of N95 respirator masks (OR = 0.055, 95% CI = 0.005-0.586) and a designated sputum collection area (OR = 0.142, 95% CI = 0.037-0.545) also carried lower TB infection risks.

CONCLUSION

This study depicts the current status of IC measures for TB infection in a high prevalence country. The results suggest that HCWs perceived a greater TB infection risk at inadequate environmental IC measures.