MICs of rifampicin and chloramphenicol for mucoid Pseudomonas aeruginosa strains are lower when human lactoferrin is present

MICs of rifampicin and chloramphenicol for mucoid strains of Pseudomonas aeruginosa were lower in the presence of human lactoferrin (0.9 mg/mL, the concentration found in cystic fibrosis sputum) than in its absence. MICs for some strains were lowered to clinically achievable levels of the antibiotics, which is compatible with impressions of greater clinical efficacy in pseudomonas infections than would be predicted by standard sensitivity tests. The routine addition of lactoferrin to sensitivity media for testing of cystic fibrosis isolates may give more useful results than conventional tests as in-vivo conditions are more closely simulated.