[Polymorphism of mucA and fpvA genes in Pseudomonas aeruginosa isolates from cystic fibrosis patients: co-existence of genetically different variants]. / Polimorfismo de los genes mucA y fpvA en Pseudomonas aeruginosa de pacientes con fibrosis quística: coexistencia de variantes genéticas en el mismo paciente.

INTRODUCTION: Pseudomonas aeruginosa is able to colonize the lungs of cystic fibrosis patients (CF) in an adaptive process that results in the selection of a dominant strain through a process of genetic variation. METHODS: One hundred and twenty tree isolates of P. aeruginosa were sequentially recovered from 6 CF patients during the routine follow-up or exacerbations over periods of 2 to 12 years in the Ramon y Cajal University Hospital (Madrid, Spain). Another 13 isolates were obtained from a single CF patient in a short-term study. They were analysed by restriction fragment length polymorphism (RFLP) and sequencing of mucA and fpvA genes, which code for the alginate biosynthesis regulator and a pyoverdin receptor, respectively, and their antibiotic susceptibility was studied by microdilution. RESULTS: A dominant colonising strain was found in each patient based on the RFLP profile. The polymorphisms of mucA and fpvA genes correlated well with these profiles, but suggested a relationship between strains isolated from two brothers, not inferred by RFLP. Stop codon mutations in mucA were unique to each dominant strain, indicating the adaptive process suffered. The alternate detection of the same mucA and/or fpvA genotypic variants suggested the coexistence of several subpopulations. This hypothesis was confirmed in a prospective study in which 6 variants were isolated in 7 days from the same patient. CONCLUSIONS: Genotypic variants of the P. aeruginosa dominant strains can coexist in the chronic colonization in CF patients. These variants can be undetected by RFLP and they might present variable antibiotic susceptibility.

Chronic colonization by Pseudomonas aeruginosa of patients with obstructive lung diseases: cystic fibrosis, bronchiectasis, and chronic obstructive pulmonary disease.

Pseudomonas aeruginosa is isolated in sputum cultures from cystic fibrosis (CF) patients and adults with bronchiectasis (BS) and chronic obstructive pulmonary disease, but it is not well known if the characteristics of colonization in these latter patients are similar to those with CF. We examined 125 P. aeruginosa isolates obtained from 31 patients suffering from these diseases by pulsed field gel electrophoresis and genotyping of mucA and fpvA genes. The pattern of colonization, with dominance of a clonal strain and incidence of mucoid phenotypes, was similar in every group of patients; however, in some CF and BS patients, we detected the replacement or coexistence of 2 main clones. The main differences were found in the nucleotide position of less common mucA mutations, other than mucA22, and in the predominance of the different types of the pyoverdine receptor. Our results support a similar colonization pattern by P. aeruginosa in the different obstructive pulmonary diseases.