The present study was undertaken to investigate the appearance and location of Pseudomonas aeruginosa in the
cystic fibrosis (CF) lung and in sputum. Samples include preserved tissues of CF patients who died due to chronic P. aeruginosa lung
infection prior to the advent of intensive
antibiotic therapy, explanted lungs from 3 intensively treated chronically P. aeruginosa infected CF patients and routine sputum from 77 chronically P. aeruginosa infected CF patients. All samples were investigated microscopically using
hematoxylin-
eosin (HE), Gram and
alcian-blue stain, PNA FISH and immunofluorescence for
alginate.Investigation of the preserved tissues revealed that prior to aggressive
antibiotic therapy, P. aeruginosa
infection and destruction of the CF lung correlated with the occurrence of mucoid (
alginate) bacteria present in aggregating structures surrounded by pronounced polymorphonuclear-leukocyte (PMN)
inflammation in the respiratory zone (9/9). Non-mucoid bacteria were not observed here, and rarely in the conductive zone (1/9). However, in the explanted lungs, the P. aeruginosa aggregates were also mucoid but in contrast to the autopsies, they were very rare in the respiratory zone but abundant in the sputum of the conductive zone (3/3), which also contained abundances of PMNs (3/3). Non-mucoid and planktonic P. aeruginosa were also observed here (3/3).In conclusion, the present intensive
antibiotic therapy of chronic P. aeruginosa
infections, at the Copenhagen CF Centre, seems to restrain but not eradicate the bacteria from the conductive zone, whereas the remaining healthy respiratory zone appears to be protected, for a long period, from massive biofilm
infection. This strongly suggests that the conductive zone serves as a bacterial reservoir where the bacteria are organized in mucoid biofilms within the mucus, protected against
antibiotics and host defenses.