How to avoid the impact of environmental mycobacteria towards the efficacy of BCG vaccination against tuberculosis?

The burden of mycobacteria species among children from postvaccination abscess in Southern India

Background

From the time vaccines were introduced, their impact has been beyond measurable. Mycobacteria are pathogens increasingly isolated from postvaccination abscess. Identification of these pathogens plays a very crucial role in the management of these babies. We aimed to determine Mycobacterial spp occurrence from vaccination abscess, draw local antibiogram, and guide management of babies with vaccination abscess.

Methods

Babies with postvaccination abscess from 2016 to 2020 were included. Pus collected during incision and drainage was processed as per the standard guidelines. Mycobacterium isolates were identified by conventional methods, and all samples were confirmed by polymerase chain reaction. All babies underwent incision and drainage, and all were started with amoxicillin and clavulanic acid and changed later as per the sensitivity report.

Results

Mycobacterium abscessus was isolated from 17% (12) pus samples from 71 postdiphtheria pertussis and tetanus vaccination, and Mycobacterium bovis was isolated from 83.3% (10) babies with post-Bacillus Calmette-Guérin vaccination. The mean interval between injection and abscess formation was 32.75 days in case of M. abscessus, whereas it was 50.4 days in case of M. bovis. All the M. abscessus were sensitive to linezolid, amikacin, and clarithromycin, whereas no treatment except incision and drainage was required for M. bovis.

Conclusion

There is an increased incidence of Mycobacterial spp infection in postvaccination abscess. All babies with M abscessus responded well with combination antibiotic therapy plus drainage of abscesses, whereas M. bovis was treated by incision and drainage, and no further antibiotics were given.

BCG-mediated protection against M. tuberculosis is sustained post-malaria infection independent of parasite virulence

Tuberculosis (TB) and malaria remain serious threats to global health. Bacillus Calmette-Guerin (BCG), the only licensed vaccine against TB protects against severe disseminated forms of TB in infants but shows poor efficacy against pulmonary TB in adults. Co-infections have been reported as one of the factors implicated in vaccine inefficacy. Given the geographical overlap of malaria and TB in areas where BCG vaccination is routinely administered, we hypothesized that virulence-dependent co-infection with Plasmodium species could alter the BCG-specific immune responses thus resulting in failure to protect against Mycobacterium tuberculosis. We compared virulent Plasmodium berghei and non-virulent Plasmodium chabaudi, their effects on B cells, effector and memory T cells, and the outcome on BCG-induced efficacy against M. tuberculosis infection. We demonstrate that malaria co-infection modulates both B- and T-cell immune responses but does not significantly alter the ability of the BCG vaccine to inhibit the growth of M. tuberculosis irrespective of parasite virulence. This malaria-driven immune regulation may have serious consequences in the early clinical trials of novel vaccines, which rely on vaccine-specific T-cell responses to screen novel vaccines for progression to the more costly vaccine efficacy trials.

Bacille calmette-guérin: An ophthalmic perspective

Vaccines such as bacille Calmette-Guérin (BCG) are known for their heterologous effects mediated through a number of mechanisms, including trained immunity constituted by monocyte-macrophage based innate immunity. Other events such as direct hematogenous spread and induction of autoimmunity are also described. There has been a resurgent interest in harnessing some of the benefits of trained immunity in the management of COVID-19, even as several specific vaccines have been approved. We summarize the current knowledge of ocular effects of BCG. Potential effect of granulomatous inflammation on angiotensin converting enzyme activity and accentuation of cytokine storm that may result in undesirable ocular and systemic effects are also discussed.

Vaccine Potential of Mycobacterial Antigens against Asthma

Asthma is a cause of substantial burden of disease in the world, including both premature deaths and reduced quality of life. A leading hypothesis to explain the worldwide increase of asthma is the "hygiene hypothesis," which suggests that the increase in the prevalence of asthma is due to the reduction in exposure to infections/microbial antigens. In allergic asthma, the most common type of asthma, antigen-specific T helper (Th)2 and Th17 cells and their cytokines are primary mediators of the pathological consequences. In contrast, Th1 and T regulatory (Treg) cells and their cytokines play a protective role. This article aims to review the information on the effect of mycobacteria and their antigens in modulating Th2/Th17 responses towards Th1/Treg responses and protection against asthma in humans and animal models.

BCG and protection against inflammatory and auto-immune diseases

INTRODUCTION

Bacillus Calmette-Guérin (BCG) is the only available vaccine against tuberculosis. Although its protective efficacy against pulmonary tuberculosis is still under debate, it provides protection against other mycobacterial diseases. BCG is also an effective therapy against superficial bladder cancer and potentially decreases overall childhood mortality. Areas covered: The purpose of this paper is to provide a state-of-the-art summary of the beneficial effects of BCG in inflammatory and auto-immune diseases. As a strong inducer of Th1 type immunity, BCG has been reported to protect against atopic conditions, such as allergic asthma, a Th2-driven disorder. Its protective effect has been well documented in mice, but still awaits definitive evidence in humans. Similarly, murine studies have shown a protective effect of BCG against auto-immune diseases, such as multiple sclerosis and insulin-dependent diabetes, but studies in humans have come to conflicting conclusions. Expert commentary: Studies in mice have shown a beneficial effect of the BCG vaccine against allergic asthma, multiple sclerosis and diabetes. However, the understanding of its mechanism is still fragmentary and requires further in depth research. Some observational or intervention studies in humans have also suggested a beneficial effect, but definitive evidence for this requires confirmation in carefully conducted prospective studies.

T regulatory cells: Achilles' heel of Mycobacterium tuberculosis infection?

T regulatory cells (Treg) constitute a specialized subset of T cells that play a pivotal role in preventing the occurrence of autoimmune diseases by suppressing deleterious activities of immune cells. Contrarily, they can have adverse effect on immune response against infectious diseases where Treg weaken the host immunity leading to enhanced microbial load and thereby increase in severity of the disease. Here, we have attempted to review plethora of information documenting prevalence of Treg in tuberculosis (TB) and their involvement in progression and immunopathogenesis of the disease. Further, we have laid emphasis on the possible use of Treg as a biomarker for determining the TB treatment efficacy. Also, we have discussed the probable contribution of Treg in dampening the efficacy of BCG, the anti-TB vaccine. Finally, we have speculated some of the possible strategies which might be explored by exploiting Treg for enhancing the efficacy of TB management.

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.