THE HIGH AMINO-ACID CONTENT OF SPUTUM FROM CYSTIC-FIBROSIS PATIENTS PROMOTES GROWTH OF AUXOTROPHIC PSEUDOMONAS-AERUGINOSA

Many isolates of Pseudomonas aeruginosa from cystic fibrosis (CF) pati ents are auxotrophic and require amino acids for growth. A quantitativ e assay was used to determine the total content of free amino acids of sputum sol-phase extracts from CF and non-CF patients to assess the p resence of amino acids in the airway. CF patients colonised with auxot rophic P. aeruginosa had a higher sputum amino-acid content (mean 6.77 mg/ml) than those colonised with prototrophs (mean 3.77 mg/ml); overa ll, CF specimens (mean 5.70 mg/ml) had a higher amino-acid content tha n non-CF samples (2.52 mg/ml). The amino-acid profile of sputum extrac ts was assessed by one-dimensional thin layer chromatography (TLC). Se veral amino acids were identified in the extracts, in particular, leuc ine, isoleucine, phenylalanine, tyrosine, alanine, serine and methioni ne or valine or both. All sputum specimens except two (which contained <1.5 mg of amino acids/ml), promoted the growth, of 34 auxotrophic st rains of P. aeruginosa from CF patients in a minimal medium. These res ults indicate, therefore, that amino acids are plentiful in the sputum of CF patients and are able to supply the requirements of auxotrophic strains. It is suggested that the increased amino-acid content in the airways of CF patients plays a significant role in the selection and maintenance of nutritionally deficient P. aeruginosa.