© 2005 American Thoracic Society
Are Colonial Haemophilus influenzae Responsible for Exacerbations of Chronic Obstructive Pulmonary Disease After All?To the Editor:The study by Murphy and colleagues (1) reignites the debate on whether colonizing bacteria are to blame for periods of exacerbations in patients with chronic obstructive pulmonary disease. The authors speculate that the presence of Haemophilus influenzae in the respiratory tract, even in the setting of a negative sputum culture, raises the question of whether bacteria cause a greater proportion of exacerbations than is revealed by sputum culture. However, one could argue to the contrary. If the same strains of H. influenzae are continuously present in the airway, why should the colonial bacteria be responsible for exacerbations after all? Current data are contradictory. Although Sethi and colleagues (2), together with Patel and colleagues (3), have demonstrated that exacerbations are related to acquisition of new strains and colonization of H. influenzae, Bresser and colleagues (4) have shown otherwise. Murphy and colleagues also mentioned that a patient with clinical evidence of an exacerbation with a negative sputum culture would cause most clinicians to conclude that the exacerbation had a nonbacterial etiology. We would like to refute this comment, because clinicians do not merely base their judgement on sputum culture alone in deciding whether an exacerbation is infective or noninfective in nature. Other factors are taken into account, such as radiologic findings, inflammatory markers, and the presence or absence of pyrexia, together with color and consistency of sputum. Finally, and most importantly, the findings of Murphy and colleagues (1) highlight a potentially serious flaw in previous studies in which negative sputum cultures have been taken to indicate the absence of bacteria. Conversely, these may have simply represented periods of negative sputum culture in persistently colonized individuals.
a Ipswich Hospital Ipswich, United Kingdom REFERENCES
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