Development of a quantitative immunofluorescence assay for detection of Stenotrophomonas maltophilia antibodies in patients with cystic fibrosis.

BACKGROUND: To describe a simple quantitative immunofluorescence assay (IFA) for the detection of specific Stenotrophomonas maltophilia antibodies in serum of CF patients.
METHODS: A total of 100 sera (64 CF patients and 36 healthy subjects) were collected over a period of 2 years at the University Hospital Essen, Germany. Sputum culture status classified CF patients into groups. Serologic response was determined after Pseudomonas aeruginosa absorption by indirect IFA to Sm whole cell.
RESULTS: CF patients with "chronic S. maltophilia" showed significantly higher S. maltophilia antibody levels compared with healthy individuals (P<0.0001) and CF patients with "intermittent" (P=0.0315) or "never S. maltophilia/P. aeruginosa" (P=0.0002). A discriminant cut-off value of >1:120 titre was established to differentiate "CF chronic S. maltophilia" from the other groups. For "CF chronic S. maltophilia", the IFA showed sensitivity and specificity values of 70.7% and 84.7%, respectively.
CONCLUSION: Our data demonstrated that quantitative IFA is a simple serological assay for the detection of specific S. maltophilia antibodies, which could be useful as a diagnostic tool for monitoring immune response of CF patients to S. maltophilia.