Acute effects of viral respiratory tract infections on sputum bacterial density during CF pulmonary exacerbations

BACKGROUND: Airway proliferation of Pseudomonas aeruginosa bacteria is thought to trigger CF exacerbations and may be affected by the presence of viral infections. METHODS: A 2-year prospective study was conducted on 35 adults with CF. P. aeruginosa sputum density was analyzed during stable, exacerbation and post exacerbation assessments. Upon exacerbation, samples were sent for PCR detection of respiratory viruses and the sputum density of P. aeruginosa in patients with a viral infection versus those without was compared. RESULTS: Twenty-two patients experienced 30 exacerbations during the study period; 50% were associated with a viral infection. There was no change in sputum density of P. aeruginosa from the stable to exacerbation state when measured by quantitative culture or by PCR. Virus-associated exacerbations did not result in significant increases in P. aeruginosa sputum density compared to non-viral exacerbations. CONCLUSION: Sputum density of P. aeruginosa was not increased at the time of CF exacerbation and was not influenced by the presence of viral infection.