In vitro growth inhibition of S. aureus and P. aeruginosa.

Twenty-four P. aeruginosa isolates were collected from eight individuals with CF (SG, NN, BT, AA, TR, MF, KK, BST) at the onset of chronic colonization (numbered 1-2) or after 4.5–16.3 years of colonization (numbered 43-83). PAO1 and PA14 were included as reference strains. 5 µl spots of P. aeruginosa overnight cultures, normalized to 0.5 OD, were added to S. aureus lawn (normalized to 0.5 OD) on Mueller-Hinton agar and incubated overnight at 37°C. The table summarizes the results obtained: “weak inhibition” indicates an inhibition halo ≤15 mm; “strong inhibition” indicates an inhibition halo >15 mm and ≤25 mm; “very strong inhibition” indicates an inhibition halo >25 mm; “no inhibition“ indicates absence of inhibition halo (9 mm is the diameter of the P. aeruginosa spot).* Indicates mucoid phenotype.#Indicates hypermutable phenotype. For statistical analysis see “Results”.