Effect of Mutator P. aeruginosa on Antibiotic Resistance Acquisition and Respiratory Function in Cystic Fibrosis

Background: Cystic fibrosis patients suffer from recurrent bacterial infections that result in progressive deterioration of their respiratory function. Despite intensive antibiotic treatment, Pseudomonas aeruginosa is the main cause of such infections, with clones progressively developing multiple antibiotic resistance. We determined the relationship between the presence of P. aeruginosa mutator strains and cystic fibrosis clinical characteristics. Methods: We analyzed 136 strains of P. aeruginosa isolated from the expectorations of 36 CF patients. On all strains, mutation frequencies were determined by the mutation rate to rifampicin, and antibiotic susceptibility was determined by the disk diffusion method. The epidemiological relatedness of these 136 P. aeruginosa strains was studied by pulsed-field gel electrophoresis. The appearance of new antibiotic resistance by sequential analysis of genotypically identical strains was determined. Lung function test results, that is, forced expiratory volume in 1 sec and vital capacity, were also recorded from these patients. Results: We showed that bacteria with an enhanced mutation rate increase the rate of acquisition of new antibiotic resistance threefold and are associated with the deterioration of lung function. Conclusions: This study demonstrates the effect of mutator bacteria on the efficiency of patient treatment and on their respiratory function. Given the consequence of antibiotic treatment failure and lung deterioration on the prognosis of CF patients, antibiotic treatment strategies may need to be optimized to prevent the emergence of mutator clones. Pediatr Pulmonol. 2009; 44:820-825. (C) 2009 Wiley-Liss, Inc.