Auxotrophy of Burkholderia (Pseudomonas) cepacia from cystic fibrosis patients.

The nutritional status of 89 isolates of Burkholderia cepacia from 81 cystic fibrosis (CF) patients was evaluated. Forty of the isolates, from 38 patients, were not able to grow in a minimal medium containing glucose and mineral salts only and were thus auxotrophs. In contrast, all of 29 isolates from non-CF (clinical and environmental) sources were prototrophic. Addition of a pool of amino acids to the minimal medium was sufficient to promote growth of all tested CF auxotrophic isolates. Indeed, phenylalanine, tyrosine, cysteine, methionine, and histidine alone or in combination were required for growth by the majority of the nutritionally deficient B. cepacia isolates. Furthermore, extracts of sputum from CF patients, when added to minimal medium, promoted growth of 29 auxotrophic B. cepacia isolates regardless of their amino acid requirements. Finally, auxotrophic and prototrophic isolates from the same patient exhibited a conserved genotype, as determined by macrorestriction analysis of chromosomal DNA. These results suggest that the auxotrophic mutants are selected from the prototrophic population and maintained by the nutritionally rich environment of the CF airways.