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WHY DO MYCOBACTERIA SHOW DIFFERENT PATHOGENICITY?
The various Mycobacterium species causing pulmonary disease show different virulence, with M avium complex causing mainly airway inflammation while M tuberculosis primarily affects the alveoli. In this issue of Thorax Middleton and colleagues describe several original observations on the interaction of three mycobacterial species with respiratory mucosa. Although the initial interaction of the individual mycobacteria is similar, differences were observed after 14 days in an organ culture model. M avium complex multiplies on the mucosal surface and the number of bacteria recovered increased, M tuberculosis decreased on the surface and multiplied in the tissue showing invasion, while M smegmatis—which is considered non-pathogenic—was eradicated. This study raises a number of issues for further research, particularly the mechanisms of mucosal invasion by mycobacteria.
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FISH AND FRUIT FOR CHILDREN
Wide variations in the prevalence of asthma in different countries have suggested that diet may be an important risk factor. In a questionnaire study of over 20 000 children from six Central and Eastern European countries, four respiratory symptoms (winter cough, persistent cough, wheeze ever, and current wheeze) showed associations with dietary factors. A clear association was found between low fish intake and persistent cough and wheeze, while low fruit consumption was a predictor of cough. The effects of fruit consumption were stronger than those of vegetable consumption. As the authors point out, the odds ratios for these effects were relatively small; however, as this study involved common childhood respiratory symptoms, diet may be a significant factor affecting the health burden.
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HEALTH STATUS AFTER CANCER SURGERY
Few patients with lung cancer are eligible for surgery, so little information is available on health related quality of life (QoL) after lung resection for lung cancer. In this issue of Thorax Myrdal and colleagues report on a study of QoL using the SF-36 health questionnaire, Hospital Anxiety and Depression scores, and some lung specific questions. QoL in patients undergoing lung cancer resection was similar to that of patients undergoing coronary artery bypass surgery except in physical function on the SF-36 questionnaire. As McManus points out in the accompanying editorial, relatively few patients are left with respiratory impairment or are housebound after surgery, so health status issues should not be a deterrent to potentially curative lung surgery.
CCR5Δ32: FROM CHILDHOOD TO ADULT ASTHMA
A 32 base pair deletion of the CCR5 gene that produces a non-functioning CCR5 receptor has been shown to protect against the development of asthma in children aged 5–15, although this finding has not been reproduced in older children or young adults. Srivastava and colleagues describe a follow up study at 10 years of a cohort of children. The results confirm the protective effect of the CCR5Δ32 polymorphism on the expression of childhood asthma, although this protection is lost in the transition between childhood and early adulthood. As discussed in the paper, this finding suggests that different candidate genes contribute to different asthma phenotypes and that these genes change with increasing age. It may also be the reason for the variation seen in outcome of association studies.
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ADD-ON LEUKOTRIENE RECEPTOR ANTAGONISTS
As Thomson and Shepherd point out in their accompanying editorial to two trials in adult asthmatics which evaluate the effects of the leukotriene receptor antagonist montelukast as add-on therapy to inhaled steroids, the challenge in asthma management is to achieve good asthma control in those with moderate to severe disease. In this issue of Thorax Vaquerizo and colleagues report that adding montelukast to inhaled steroids improves asthma control, while Price and colleagues in a study with a different design show that the addition of montelukast to inhaled steroids is as effective in asthma control as doubling the inhaled steroid dose. However, long acting β2 agonists are also effective as add-on therapy to inhaled steroids and are the first choice recommendation in the new guidelines on the management of asthma. As the editorial states, further large studies are required to evaluate the role and safety of the various available add-on therapies in asthma using appropriate outcomes such as exacerbation rates.
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