The Association of Achromobacter xylosoxidans Airway Infection with Disease Severity in Cystic Fibrosis

<b>Background/Objectives</b>: The prevalence of <i>Achromobacter xylosoxidans</i> is increasing in people with Cystic Fibrosis (pwCF), yet its clinical pathogenicity remains controversial. The objective of this study was to chart the longitudinal prevalence and examine clinical associations before and after infection. <b>Methods</b>: This observational, retrospective study was conducted at a single CF center over a 14-year period. Data were collated from patient charts and clinic databases. Patients with <i>Achromobacter</i> sputum cultures were compared to those without the bacterium and analyzed according to whether they had single, intermittent, or chronic infections. <b>Results</b>: During the study period, an annual average of 124 pwCF were followed up at our clinic, with a median age of 13.6 years (IQR = 7.6-27.7). The <i>Achromobacter</i> detection rate increased from 0 to 6.1%. Twenty-three percent (29/124) of patients had at least one positive culture. The median age at acquisition was 17 years (IQR = 14.5-33). At the time of acquisition, the median FEV₁ was 81% (IQR = 46-94), compared to 90% (IQR = 72-99) for patients without <i>Achromobacter</i>, <i>p</i> < 0.001. Patients with <i>Achromobacter</i> tended to demonstrate more chronic <i>Pseudomonas</i> (55% vs. 27%, <i>p</i> = 0.06) and pancreatic insufficiency (66% vs. 47%, <i>p</i> = 0.07). At two years post-acquisition, the median FEV₁ for patients with intermittent and chronically infected decreased by 11.5% (IQR = -3.75-7.5), compared to 1.5% (IQR = -2.5-12.5) for those with a single positive culture, <i>p</i> = 0.03. Similarly, pulmonary exacerbations per year became more frequent post-acquisition in intermittent and chronically infected patients: Median (range) 2.5 (0-8) pre-, versus 3.0 (0-9) post-acquisition, <i>p</i> = 0.036. <b>Conclusions</b>: Chronic and intermittent infection with <i>Achromobacter</i> were associated with accelerated lung function decline and increased exacerbation frequency. Larger prospective studies are needed to confirm these findings and examine the effect of eradication on the clinical course.