A novel chromogenic medium for isolation of Pseudomonas aeruginosa from the sputa of cystic fibrosis patients.

Background: A novel chromogenic medium for isolation and identification of Pseudomonas aeruginosa from sputa of cystic fibrosis (CF) patients was evaluated and compared with standard laboratory methods.

Methods: One hundred sputum samples from distinct CF patients were cultured onto blood agar (BA), Pseudomonas CN selective agar (CN) and a Pseudomonas chromogenic medium (PS-ID). All Gram-negative morphological variants from each medium were subjected to antimicrobial susceptibility testing, and identification using a combination of biochemical and molecular methods.

Results: P. aeruginosa was isolated from 62 samples after 72 h incubation. Blood agar recovered P. aeruginosa from 56 samples (90.3%) compared with 59 samples (95.2%) using either CN or PS-ID. The positive predictive value of PS-ID (98.3%) was significantly higher than growth on CN (88.5%) for identification of P. aeruginosa (P<0.05).

Conclusions: PS-ID is a promising medium allowing for the isolation and simultaneous identification of P. aeruginosa from sputa of CF patients.