Serum IgG response to an outer membrane porin protein ofBurkholderia cepaciain patients with cystic fibrosis

Abstract

Early and accurate diagnosis of Burkholderia cepacia infection is important, particularly if segregation is to prevent patient-to-patient transmission. We have examined the serum response to a B. cepacia-specific 80-kDa outer membrane protein. 21 patients colonised with B. cepacia and Pseudomonas aeruginosa for 2-51 months (mean 11 months) were age- and sex-matched with 21 patients colonised with P. aeruginosa but not B. cepacia. The 80-kDa protein was recovered by electroelution from outer membrane proteins, separated by SDS-PAGE, coated onto ELISA plates, reacted with patient sera diluted 1:200, protein A-peroxidase and chromogenic substrate. We found that 19/24 patients colonised with B. cepacia and P. aeruginosa had high values, 2/24 patients had intermediate values, and 2/24 patients had a low value. 20/21 patients colonised with P. aeruginosa alone had low values and 1/21 had an intermediate value. We found that in the longitudinal serum samples studied from four patients only one patient developed high values after the first isolation of B. cepacia suggesting that seroconversion does not occur immediately after the first sputum culture of B. cepacia. We conclude that an ELISA test using B. cepacia-specific 80-kDa outer membrane protein can distinguish B. cepacia colonised and non-colonised patients and may be useful in the early diagnosis of B. cepacia infection.