Outbreak of Achromobacter xylosoxidans in an Italian Cystic fibrosis center: genome variability, biofilm production, antibiotic resistance, and motility in isolated strains.

Cystic fibrosis (CF) patients have chronic airway infection and frequent exposure to antibiotics, which often leads to the emergence of resistant organisms. Achromobacter xylosoxidans is a new emergent pathogen in CF spectrum. From 2005 to 2010 we had an outbreak in A. xylosoxidans prevalence in our CF center, thus, the present study was aimed at deeply investigating virulence traits of A. xylosoxidans strains isolated from infected CF patients. To this purpose, we assessed A. xylosoxidans genome variability by randomly amplified polymorphic DNA (RAPD), biofilm production, antibiotic resistances, and motility. All A. xylosoxidans strains resulted to be biofilm producers, and were resistant to antibiotics usually employed in CF treatment. Hodge Test showed the ability to produce carbapenemase in some strains. Strains who were resistant to ß-lactamics antibiotics, showed the specific band related to metal ß-lactamase (blaIMP-1), and some of them showed to possess the integron1. Around 81% of A. xylosoxidans strains were motile. Multivariate analysis showed that RAPD profiles were able to predict Forced Expiratory Volume (FEV1%) and biofilm classes. A significant prevalence of strong biofilm producers strains was found in CF patients with severely impaired lung functions (FEV1% class 1). The outbreak we had in our center (prevalence from 8.9 to 16%) could be explained by an enhanced adaptation of A. xylosoxidans in the nosocomial environment, despite of aggressive antibiotic regimens that CF patients usually undergo.

Achromobacter xylosoxidans genomic characterization and correlation of randomly amplified polymorphic DNA profiles with relevant clinical features [corrected] of cystic fibrosis patients.

Achromobacter xylosoxidans is an emerging pathogen increasingly being isolated from respiratory samples of cystic fibrosis (CF) patients. Its role and clinical significance in lung pathogenesis have not yet been clarified. The aim of the present study was to genetically characterize A. xylosoxidans strains isolated from CF patients by use of randomly amplified polymorphic DNA (RAPD) profiles and to look for a possible correlation between RAPD profiles and the patients' clinical features, such as their spirometry values, the presence of concomitant chronic bacterial flora at the time of isolation, and the persistent or intermittent presence of A. xylosoxidans strains. A set of 106 strains of A. xylosoxidans were typed by RAPD analysis, and their profiles were analyzed by agglomerative hierarchical classification (AHC) and associated with the patient characteristics mentioned above by factorial discriminant analysis (FDA). The overall results obtained in this study showed that (i) there is a marked genetic relationship between strains isolated from the same patients at different times, (ii) characteristic RAPD profiles are associated with different predicted classes for forced expiratory volume in 1 s (FEV1%), (iii) some characteristic RAPD profiles are associated with different concomitant chronic flora (CCF) profiles, and (iv) there is a significant division of RAPD profiles into "persistent strains" and "intermittent strains" of A. xylosoxidans. These findings seem to imply that the lung habitats found in CF patients are capable of shaping and selecting the colonizing bacterial flora, as seems to be the case for the A. xylosoxidans strains studied.

Emerging cystic fibrosis pathogens: incidence and antimicrobial resistance.

We examined the frequency of isolation and the antimicrobial resistance of Burkholderia cepacia complex, Stenotrophomonas maltophilia and Achromobacter xylosoxidans in cystic fibrosis patients from 2000 to 2004. Strains susceptibility to tobramycin, piperacillin/tazobactam, imipenem, gentamicin, ciprofloxacin and ceftazidime was determined by disc diffusion assay. B. cepacia complex showed a very high resistance also to ciprofloxacin reaching 100% in 2004. S. maltophilia and A. xvylosoxidans showed high rates of antimicrobial resistance both aminoglycoside and ciprofloxacin. It is very important to monitor the percentage of isolation of these species over time to verify strains resistance to antibiotics and also to test new combinations of antimicrobial agents.