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 β-lactamics antibiotics, showed the specific band related to metal β-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.

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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.Cystic fibrosis (CF) is the most common lethal genetic disease, causing a chronic infection of the respiratory tract, which in turn leads to progressive respiratory deficiency (6,15). Pseudomonas aeruginosa is the most frequently found Gramnegative pathogen in the sputa of patients with CF, while Staphylococcus aureus is the most frequently found Gram-positive one. Recently, new pathogens have also emerged, such as Burkholderia cepacia complex, Stenotrophomonas maltophilia, and Achromobacter xylosoxidans (3,9,18,19,20,24). Although the clinical significance of A. xylosoxidans is not yet clear, it is increasingly being isolated from the sputum cultures of CF patients. Tan et al. (22) found that 2.3% of CF patients had at least 3 positive cultures for A. xylosoxidans during a 6-month period. The U.S. Cystic Fibrosis Foundation's National Patient Registry reported an increase of 4.5%, from 1995 to 2002 (1, 2), in the frequency of isolation of this microorganism from CF patients. Recently, A. xylosoxidans has been considered a nosocomial pathogen, particularly in immunocompromised patients, causing a variety of infections, including bacteremia, meningitis, pneumonia, and peritonitis (8,23,25). Achromobacter spp. are aerobic, nonfermentative, Gram-negative bacilli (5, 7, 21) that are frequently misidentified by routine laboratory tests, thus seriously compromising control ...

During in zritro cultivation of bacteria, the pathogenetic factors may change in amount and quality. Knowledge of this variability is important in vaccine production. The pathogenic variability of Pusteurella piscicida broth culture (BC), extracellular products (ECPs) and whole cells (WC) was investigated in sea bass (Dicentrarchus labras) 2-3 g wet weight, inoculated intraperitoneally. Ten Pasteurellapiscicirla field strains isolated from fish affected by different outbreaks which occurred in Italian fish farms were used. When BC and ECPs were intraperitoneally injected, no variability in virulence was observed between strains of different geographical origin and no attenuation was registered between strains of different in oitro passages. The electrophoretic (SDS-PAGE) analysis of ECP showed evidence of only quantitative differences inside the panel of strains and between the same strain collected at different in ~i t r o cultivation times. ECPs produced from a BC incubated for 18-60 h were highly toxic. This ability was heat labile and not active when ECPs were administered by immersion. No toxic capacity was observed with WC where infection was greater with a 18-60 h incubation broth culture. Results seems to indicate that the toxic activity of Pasteurella piscicida is mostly due to ECP and not bounded to the cell.

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