Respiratory infections by Achromobacter xylosoxidans in a cohort of Cystic Fibrosis patients: identification, antimicrobial susceptibility and molecular epidemiology

Pulmonary infections by Gram-negative bacteria such as Achromobacter xylosoxidans are recovered frequently in patients with Cystic Fibrosis. Aims of this study were to value the isolation frequency of A.xylosoxidans strains in a cohort of Cystic Fibrosis patients, to investigate their antimicrobial sensitivity and to establish possible clonal likeness among strains.A retrospective study was undertaken between January 2004 and December 2008 on 300 patients receiving care at the Regional Cystic Fibrosis Centre of “Federico II” University, Naples. Sputum samples were collected and selective media as well as commercial systems for bacterial identification were used. The activity of antimicrobial agents was determined using diffusion and micro-dilution methods. For DNA-fingerprinting, a genomic DNA macrorestriction followed by pulsed-field gel electrophoresis was carried out. A total of 238 strains from 51 patients were isolated. Strains were resistant to aztreonam, about half of these were resistant to gentamicin and trimethoprim-sulphamethoxazole. They were sensitive to piperacillin, piperacillin/tazobactam, and also to carbapenems, quinolones, cephalosporines. Macrorestriction analysis applied on some isolates showed substantial heterogeneity among strains.Actually, the prognostic role of A. xylosoxidans in Cystic Fibrosis is unclear, but this finding must imply difficulties on therapeutic approach. So, it is need to be on the look out regard such microorganisms. Preliminary results of DNA-fingerprinting indicate no evidence of clonal likeness and then of patient-to-patient spread.