Intrapatient diversity of Achromobacter spp. involved in chronic colonization of Cystic Fibrosis airways.

Achromobacter spp. are increasingly identified in Cystic Fibrosis (CF) patients and their ability to persistently colonize the CF respiratory tract (CFRT) suggests that Achromobacter species possess adaptive characteristics. We studied genome dynamics in 118 isolates recovered from 13 patients with Achromobacter chronic colonization (5-26 isolates per patient recovered over 13-61 months). Isolates were identified to species level by nrdA gene sequencing, subjected to Pulsed-Field Gel Electrophoresis (PFGE) and multiplex rep-PCR (MR-PCR), and rrs intragenomic diversity was studied by PCR-Temporal Temperature Gel Electrophoresis (TTGE). Intrapatient diversity was assessed: (i) from dynamics of XbaI and/or SpeI-based pulsotypes, (ii) from comparison of MR-PCR profiles, and (iii) by longitudinal analysis of rrs intragenomic diversity. Patients were chronically colonized by Achromobacter xylosoxidans (n=10), Achromobacter dolens (n=1) or Achromobacter insuavis (n=2). All strains displayed genomic diversification over time but A. insuavis showed higher pulsotype diversity compared to other species. Intragenomic rrs heterogeneity was found in strains from 6 of 13 patients and may be persistently observed. Achromobacter genome evolution observed during chronic colonization of the CFRT warrants further investigation of the adaptation features of the different species, as well as of the selective forces driving this adaptation in the CFRT.
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