Genotype based evaluation of Pseudomonas aeruginosa eradication treatment success in cystic fibrosis patients

Background Longitudinal data regarding the genotypes of Pseudomonas aeruginosa isolates after eradication treatment are limited. We followed cystic fibrosis patients after a first ever isolation of P. aeruginosa and evaluated the P. aeruginosa -free time period after eradication therapy. Methods Between January 2003 and December 2008 respiratory samples were cultured prospectively from 41 patients with a first ever P. aeruginosa isolate. Twenty five patients had at least one subsequent isolate. Treatment efficacy was assessed based on the time to a second isolation and on comparison of the RAPD genotypes of the P. aeruginosa isolates. Results Eleven patients became chronically colonized during the study period. For ten of these the second isolate had the same genotype as the first isolate. Moreover, these patients had a significantly shorter P. aeruginosa -free time interval between the first ever and the second isolate compared to the 14 not chronically colonized patients (median 0months versus 7.5months, p Conclusion Our results indicate that the presence of a genotypically identical subsequent P. aeruginosa isolate and/or a short P. aeruginosa -free time interval after treatment are ominous signs and might be useful additional tools to predict impending chronic colonization. Current routine bacteriological methods for the detection of P. aeruginosa may lack the sensitivity to discriminate between true eradication and low bacterial persistence.