The dynamics of infection in chronic obstructive pulmonary disease (COPD) are complex, and microbiome technology has provided us with a new research tool for its better understanding. There is compartmentalization of the microbiota in the various parts of the lung.

Studies of the lower airway lumen microbiota in COPD have yielded confusing results, and additional studies with scrupulous attention to prevent and account for upper airway contamination of bronchoalveolar lavage samples are required. Lung tissue microbiota has been examined in three studies, which also demonstrate varied results based on the site of sampling (bronchial mucosa, lung parenchyma), and this variation extends to sampling sites within a lobe of the lung. The Vicious Circle Hypothesis embodies how an altered lung microbiome could contribute to COPD progression.

Relating microbiota composition to airway and systemic inflammation and clinical outcomes are important research questions. Although various obstacles need to be surmounted, ultimately lung microbiome studies will provide new insights into how infection contributes to COPD.

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Lung and cardiovascular disease are increasingly recognized to occur in the same patient populations. Infections, either through stimulation of inflammation or through direct infection, can lead to end-organ damage and have been postulated as a potential link between lung and cardiovascular diseases.

Mechanisms by which infections may link lung and cardiac diseases include effects of systemic infections, microbial translocation of pathogens from the gastrointestinal tract or other sites, damaging effects of metabolic products, or influences of smoking on the microbiome. Other mechanisms, such as alterations in the local microbiome, environmental exposures, or immune regulation by microbial communities, may be important. These relationships are likely quite complex, with multiple routes between infection and disease possible.

A better understanding of the links of infection to lung and heart disease can improve our understanding of the pathogenesis of these disorders and uncover novel therapeutic approaches.

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Pseudomonas aeruginosa is an opportunistic bacterial pathogen responsible for a high incidence of acute and chronic pulmonary infection.

These infections are particularly prevalent in patients with chronic obstructive pulmonary disease (COPD) and Cystic Fibrosis (CF): much of the morbidity and pathophysiology associated with these diseases is due to a hyper-susceptibility to bacterial infection.

Innate immunity, primarily through inflammatory cytokine production, cellular recruitment, and phagocytic clearance by neutrophils and macrophages, is the key to endogenous control of P. aeruginosa infection.

In this review, we highlight recent advances towards understanding the innate immune response to P. aeruginosa, with a focus on the role of phagocytes in control of P. aeruginosa infection. Specifically, we summarize the cellular and molecular mechanisms of phagocytic recognition and uptake of P. aeruginosa, and how current animal models of P. aeruginosa infection reflect clinical observations in the context of phagocytic clearance of the bacteria. Several notable phenotypic changes to the bacteria are consistently observed during chronic pulmonary infections, including changes to mucoidy and flagellar motility, that likely enable or reflect their ability to persist.

These traits are likewise examined in the context of how the bacteria avoid phagocytic clearance, inflammation, and sterilizing immunity.

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To derive and validate against the Ralph et al. score, a simplified chest X-ray (CXR) score (SCS) for predicting the outcome of smear-positive pulmonary tuberculosis (SPPTB) among patients with high prevalence of human immunodeficiency virus (HIV) infection.

Methods : CXR for 636 SPPTB patients (377 men, median age 31 years) from the Yaounde Jamot Hospital (Cameroon), were examined for the presence of tuberculosis lesions, and estimation of the proportion of lungs affected. SPPTB's evolution was based on sputum smear examination after two months of treatments. Logistic regressions were used to derive the SCS with internal validation via bootstrap resampling. Receiver operating characteristic curves (AUC) analyses were used to validate, determine of the optimal cut-offs and compare models’ performance.

Results : HIV co-infection was present in 191 (30%) patients. Sputum smear non-conversion was found in 45 (7.1) patients after two months of treatment. The SCS was expressed as proportion of lung affected plus 23 if cavitation present. The AUC (95% confidence interval) was 0.718 (0.640-0.795), with little variation in bootstrap validation, and no sizable difference from the Ralph model [0.714 (0.633-0.7860), p=0.717 for the difference). Both models had good calibration (Hosmer-Lemeshow p>0.183). The optimal cut-off for predicting non-conversion of the sputum at 2-month was 52 for the SCS (sensitivity/specificity 66.7%/62.8%) and 74.5 (62.2%/74.3%) with Ralph score.

Conclusions : The outcome of SPPTB among patients with high prevalence of HIV can acceptably be predicted by simple scores comprising baseline CXR variables, including the Ralph et al score and the SCS from this study.

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