Do environmental pollutants influence the onset of respiratory syncytial virus epidemics or disease severity?

The trigger for annual epidemics of respiratory syncytial virus (RSV) infections and the factors contributing to the disappearance of RSV infections in late winter remain obscure. Similarly, there is no adequate explanation for the higher morbidity and admission rates in industrialised as compared with rural areas. It has been suggested that a variety of environmental factors such as temperature, daylight and humidity may influence the onset and waning of the epidemics. However, the few studies assessing these variables fail to support such a link. In many tropical countries the annual epidemic occurs in the summer or autumn, arguing against temperature having a direct influence. A number of studies have suggested that indoor pollutants, including cigarette smoke, are associated with an increased likelihood of being admitted to hospital with severe lower respiratory tract disease. One study exploring the potential role of outdoor pollutants on the pattern of RSV related illness in infancy was unable to identify a clear link between a variety of pollutants and the timing of the epidemic. Nitric oxide levels were higher in winter than during the summer and much higher winter peaks of NO were observe in industrialised areas as compared with urban and rural areas. Whether this or other environmental pollutants contribute to the higher incidence of severe disease in industrialised areas is unclear. Further work is required to explore the possible influence of NO and other environmental pollutants on both the timing and severity of epidemics.     

Exhaled nitric oxide is reduced in infants with cystic fibrosis

BACKGROUND: Exhaled nitric oxide levels are low in patients with cystic fibrosis (CF), despite the chronic inflammation present in the airways. This study aimed to determine whether levels of exhaled nitric oxide were reduced prior to the onset of respiratory symptoms in infants with CF. METHODS: The levels of exhaled nitric oxide were measured using a chemiluminescence analyser in five infants with CF and 11 healthy control subjects, both groups having a mean age of 48.6 days. RESULTS: Mean levels of exhaled nitric oxide were significantly lower in infants with CF than in the control group (4.9 ppb v 12.1 ppb; p=0.01). CONCLUSIONS: This finding may be the key to understanding the inflammatory processes in early cystic fibrosis and may lead to novel treatment approaches.     

Assessment of the efficacy of an IgM-elisa and microscopic agglutination test (MAT) in the diagnosis of acute leptospirosis

In a prospective study in Barbados between 1979 and 1989, 321 cases were diagnosed in 638 patients presenting at a hospital with symptoms of leptospirosis. Initial diagnosis was based on patient history and characteristic signs and symptoms. In 92 cases (29%), diagnosis was confirmed by isolation of organisms from the blood, urine, or dialysate fluid; in the remaining 229 cases (71%) diagnosis was confirmed by serology alone. Results of an IgM-ELISA and microscopic agglutination test (MAT) in cases with isolates and in non-leptospirosis cases were used to assess the sensitivity and specificity of the tests. The sensitivity of IgM detection by ELISA was 52% in the first acute-phase specimen, increasing to 89% and 93% in the second acute-phase and convalescent specimens, respectively. The specificity of the IgM-ELISA was high (> or = 94%) in all specimens. The sensitivity of the MAT was low (30%) in the first acute-phase specimen, increasing to 63% in the second acute-phase specimen and 76% in the convalescent specimen. The specificity of the MAT was > or = 97% in all specimens.     

Colistin stimulates the activity of neutrophil elastase and Pseudomonas aeruginosa elastase.

Nonantimicrobial effects of antibiotics may contribute to their activity in the treatment of infective airway disease. The aim of this study was to identify antibiotics used for the treatment of infection in cystic fibrosis that may alter the activity of human neutrophil elastase (HNE) and Pseudomonas aeruginosa elastase (PE). The effect of antibiotics on the activity of purified HNE and PE, and HNE in sputum was assessed using colourimetric and fluorescent substrate assays by kinetic measurements, and by examining the interaction of HNE with inhibitors. Ceftazidime, tobramycin, and gentamycin slightly inhibited purified HNE activity whereas erythromycin and colistin significantly stimulated purified HNE and PE (395 and 557%, respectively). However, only colistin increased HNE activity in sputum (+102%) and was therefore studied in more detail. This increase in activity was not due an interference with the specific inhibition of HNE by alpha1-antitrypsin but colistin was found to reverse the inhibitory effects of small molecular weight molecules like heparin. Colistin increases the activity of human neutrophil elastase and Pseudomonas aeruginosa elastase, two proteases that contribute to the pathogenesis of cystic fibrosis airway disease.