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.

Stenotrophomonas maltophilia in cystic fibrosis: improved detection by the use of selective agar and evaluation of antimicrobial resistance.

BACKGROUND: We implemented a selective medium for improved detection of Stenotrophomonas maltophilia in sputum samples from CF patients. We also performed antimicrobial susceptibility testing with eight antibiotics. METHODS: A total of 623 consecutive sputum samples from 165 CF patients in a German CF center were cultured onto conventional media and onto Steno medium agar (SMA). All isolates confirmed as S. maltophilia by biochemical and molecular methods were subjected to antimicrobial susceptibility testing. The following agents were tested by Etest: ceftazidime, levofloxacin, moxifloxacin, tigecycline, trimethoprim-sulfamethoxazole, fosfomycin, colistin, and ticarcillin-clavulanate acid. RESULTS: Conventional media supported the growth of S. maltophilia in 7.1% of samples, whereas SMA supported its growth in 11.6%, increasing the detection rate to 64%. Trimethoprim-sulfamethoxazole and tigecycline exhibited the highest in vitro activity, whereas ceftazidime, colistin, and ticarcillin-clavulanate acid exhibited higher resistance rates. CONCLUSIONS: SMA is a promising medium allowing improved isolation of S. maltophilia from sputum samples from CF patients. Trimethoprim-sulfamethoxazole and tigecycline demonstrated excellent inhibitory effects against S. maltophilia, which may suggest a potential clinical effect.