Should patients with acute exacerbation of chronic bronchitis be treated with antibiotics? Advantages of the use of fluoroquinolones

Abstract

The pathological changes in chronic bronchitis (CB) produce airflow obstruction, reduce the effectiveness of the mucocilliary drainage system and lead to bacterial colonisation of bronchial secretion. The presence of bacteria induces an inflammatory response mediated by leukocytes. There is a direct relationship between the degree of impairment of the mucocilliary drainage system, the density of bacteria in mucus and the number of leukocytes in the sputum. Purulent sputum is a good marker of a high bacterial load. Eventually, if the number of leukocytes is high, their normal activity could decrease the effectiveness of the drainage system, increase the bronchial obstruction and probably damage the lung parenchyma. Whenever the density of bacteria in the bronchial lumen is >or=10(6) CFU/mL, there is a high probability that the degree of inflammatory response will lead to a vicious cycle which in turn tends to sustain the process. This situation can arise during the clinical course of any acute exacerbation of CB, independently of its aetiology, provided the episode is sufficiently severe and/or prolonged. Fluoroquinolones of the third and fourth generation are bactericidal against most microorganisms usually related to acute exacerbations of CB. Their diffusion to bronchial mucus is adequate. When used in short (5-day) treatment they reduce the bacterial load in a higher proportion than is achieved by beta-lactam or macrolide antibiotics given orally. Although the clinical cure rate is similar to that obtained with other antibiotics, the time between exacerbations could be increased.

Figure 1

Development of the ‘Vicious Cycle’.

Figure 2

Sequence of events leading to the start of the VC in patients with CB: A patient with CB start from point A, where the bacterial load (left axis), and therefore the degree of purulent sputum (right axis) is low, as represented by the A′ point, due to a mild impairment of the mucocilliary drainage system. Once a cause for the acute exacerbation is present, the drainage system is hampered, and patient's status can move to B point, which corresponds to a B′ level of bacterial load and purulent sputum. If the B′ point is close to or above the threshold level (> 10⁶ cfu/ml bacterial density), the Vicious Cycle can start (see text). Adequate antibiotic treatment can reduce the degree of bacterial load, moving the patient down to point A′.