Background-Pseudomonas aeruginosa is a frequent cause of infection in patie
nts with bronchiectasis. Differentiation between non-infected patients and
those with different degrees of P aeruginosa infection could influence the
management and prognosis of these patients. The diagnostic usefulness of se
rum IgG antibodies against P aeruginosa outer membrane proteins was determi
ned in patients with bronchiectasis without cystic fibrosis.
Methods-Fifty six patients were classified according to sputum culture into
three groups: group A (n=18) with no P aeruginosa in any sample; group B (
n=18) with P aeruginosa alternating with other microorganisms; and group C
(n=20) with P aeruginosa in all sputum samples. Each patient had at least t
hree sputum cultures in the 6 months prior to serum collection. Detection o
f antibodies was performed by Western blot and their presence against 20 pr
otein bands (10-121 kd) was assessed.
Results-Antibodies to more than four bands in total or to five individual b
ands (36, 26, 22, 20 or 18 kd) differentiated group B from group A, while a
ntibodies to a total of more than eight bands or to 10 individual bands (10
4, 69, 63, 56, 50, 44, 30, 25, 22, 13 kd) differentiated group C from group
B. When discordant results between the total number of bands and the frequ
ency of P aeruginosa isolation were obtained, the follow up of patients sug
gested that the former, in most cases' predicted chronic P aeruginosa colon
Conclusion-In patients with bronchiectasis the degree of P aeruginosa infec
tion can be determined by the number and type of outer membrane protein ban
ds indicating which serum antibodies are present.