The early detection of Burkholderia cepacia infection in cystic fibrosis patients.

Burkholderia (Pseudomonas) cepacia is now recognised as an important pathogen in cystic fibrosis patients. The diagnosis of B. cepacia currently depends on sputum culture and isolation, using a selective medium. However, isolates are slow to grow and confusion may still occur with other organisms. There is evidence that B. cepacia infection may precede sputum culture by several months. Early and accurate diagnosis of B. cepacia is important if segregation is to prevent patient-to-patient transmission. In an attempt to establish the use of antibody studies as diagnostic indicators of B. cepacia infection, the IgG reaction to B. cepacia outer membrane proteins and lipopolysaccharide in patients colonised with B. cepacia and Pseudomonas aeruginosa, was examined. A low-iron chemically defined medium was developed to grow clinical B. cepacia strains. Outer membrane was studied by SDS-PAGE and immunoblotting. A specific anti-B. cepacia IgG reaction to outer membrane protein and lipopolysaccharide antigen was found that was not due to cross-reactivity with P. aeruginosa. The serum IgG reaction to a B. cepacia specific 80 kDa outer membrane protein was investigated. The 80 kDa protein is thought to be an important porin protein. The 80 kDa protein was recovered by electroelution from separated outer membrane protein. An ELISA test using the 80 kDa protein was able to distinguish between 21 cystic fibrosis patients colonised with B. cepacia and 21 age and sex-matched cystic fibrosis patients who were not colonised with B. cepacia but were colonised with P. aeruginosa. Polyclonal monospecific anti-B. cepacia antibodies were produced by the immunisation of rabbits with the 80 kDa protein. Using this antibody B. cepacia-specific-immunofluorescence was demonstrated. The immunofluorescence was successfully performed on cells grown in culture but sputum samples were difficult to interpret because of excessive debris in the sputum. These studies indicate that cystic fibrosis patients colonised with B. cepacia produce a B. cepacia-specific-antibody response. Specific B. cepacia antigens and antibodies can be used in the detection of B. cepacia infection in cystic fibrosis patients. Further work is needed to determine whether these B. cepacia antigens and antibodies will lead to an earlier diagnosis of infection.