Infectious exacerbations of chronic bronchitis

Abstract

Approximately 50% of chronic bronchitis exacerbations are caused by bacteria and 25-50% by viruses. Streptococcus pneumoniae and Haemophilus influenzae are traditionally considered leading pathogens. In Italy, S. pneumoniae and N. influenzae resistance to β-lactams is low, but resistance to macrolides is more widespread. Pathogenic bacteria are isolated in the airways of most chronic bronchitis patients, impairing host respiratory defences, further predisposing towards infection and, thus, establishing a vicious circle, fuelled by damage due to cigarette smoking. The diagnosis of an exacerbation is essentially clinical. Lung function testing may show no modification, or indicate worsening airway obstruction. Blood gas analysis is performed in severe cases. The utility of culture is lessened by evidence of airway bacterial contamination in clinically stable periods. Quantitative thresholds have been identified over and above which bacterial exacerbation is considered probable. General preventative measures include the adoption of hygiene-behavioural standards. Antibiotic prophylaxis is not advisable. Prophylaxis by means of vaccination is indicated against influenza. Vaccination against S. pneumoniae is available but is seldom employed. The principal form of treatment is antibiotic therapy, but there is an ongoing debate regarding the objective criteria for its use. A recent meta-analysis showed a small but statistically significant difference in favour of antibiotic treatment. The antibiotic cost-benefit ratio is favourable in patients with severe functional impairment. Oral administration is to be preferred as more practical and less costly for equal efficacy. In selecting an antibiotic, pharmacokinetic considerations (bioavailability, tissue diffusion, half-life) must be kept in mind. Prescription should be oriented towards drugs active against the most commonly occurring pathogens. In more severe cases coverage against Gram-negative bacteria is considered. Complementary medical treatment includes bronchodilators corticosteroids, diuretics, and oxygen therapy. Chest physiotherapy may be beneficial. Ventilatory support treatment may be necessary, noninvasive ventilatory assistance being preferable early in the course of the acute episode. In a high number of cases endotracheal intubation may be avoided. Most exacerbations may be treated on an outpatient basis, but in some cases admission to hospital is indicated.