The combination of PCR and serology increases the diagnosis of Pseudomonas aeruginosa colonization/infection in cystic fibrosis.

BACKGROUND: Early diagnosis of Pseudomonas aeruginosa colonization/infection in patients with cystic fibrosis (CF) using microbiological culturing methods may be difficult. Serology and polymerase chain reaction (PCR) may be useful techniques for early detection of P. aeruginosa in children with CF.
METHODS: A cross-sectional analysis comparing results obtained by three different methods for P. aeruginosa identification was performed in 87 CF patients with a mean age of 9.7 years. Microbiological culturing and PCR targeting the algD GDP mannose dehydrogenase gene of P. aeruginosa were performed in sputum or oropharyngeal swabs samples, and serum antibodies against three P. aeruginosa antigens (elastase, alkaline protease, and exotoxin A) were assessed once.
RESULTS: It was possible to isolate P. aeruginosa by culture in samples from 42 patients (48.2%), while PCR was positive in 53 (60.9%) patients. Serology was positive in 38 patients (43.6%), with a higher positivity for elastase (37.9%), followed by alkaline protease (29.9%) and exotoxin A (19.5%). The difference among the three isolated methods was not statistically significant. The combination of PCR + serology was significantly superior to single methods, to PCR + culture and also to culture + serology.
CONCLUSIONS: PCR identified a higher number of patients with P. aeruginosa than serology and conventional culture, but the difference did not reach statistical significance. Any of the combination methods that included PCR resulted in significantly statistical differences in relation to isolated microbiological or serology methods, but not to the PCR method alone, suggesting that PCR may be the main additive method for P. aeruginosa identification. (c) 2007 Wiley-Liss, Inc.