Abstract
Impaired mucocilar clearance in patients with cystic fibrosis (CF) leads to bacterial stasis conducive to polymicrobial infections. Although the species isolated from these patients are mainly Pseudomonas aeruginosa (Pa) and Staphylococcus aureus, for several years, increasing interest has been given to opportunistic pathogenic bacteria of environmental origin and multi-resistant to antibiotics such as bacteria of the genus Achromobacter (Ac). Among the 22 species composing this bacterial genus, Achromobacter xylosoxidans (Ax) and Achromobacter insuavis (Ai) are the species mainly identified in CF patients. In order to provide elements that could help explain the success of these species compared to others in infections of CF patients, we evaluated their ability to produce certain virulence/persistence factors and comparatively analyzed the results obtained according to the species determined after study of the nrdA gene and according to the origin of the strains, clinical (CF, non-CF patients) or environmental. In a first study, we explored the production of siderophores of 163 Ac strains belonging to 20 species (128 strains of clinical origin, CF and non-CF, and 35 of environmental origin) by the Chromium Azurol Sulfonate test in liquid medium. In a second study, we included 74 strains of Ax and Ai (69 of clinical origin and 5 of environmental origin) and evaluated a broader panel of virulence factors (growth, swimming and swarming motilities, profile sensitivity to antibiotics, biofilm production and ability to interact with Pa). The results of our two studies made it possible to complete current knowledge on the characteristics contributing to the pathophysiology of Achromobacter infections, while providing data on species that are rarely studied. Particularly, we We have shown that the production of siderophores, until now very little explored for this bacterial genus, is a frequent observation, carried out for 72.4% of the strains tested. The Ax species, the most frequently identified in humans, showed unique characteristics in all the tests carried out. Ax not only had the highest proportion of siderophore-producing strains but also the strains producing the highest quantities of siderophores. Significant differences were also found evidence between Ax and Ai species, with Ax exhibiting higher swimming motility and greater sensitivity to antibiotics than Ai. These two species had the capacity to establish interactions with Pa, in particular by inhibiting the production of pyocyanin from Pa. Furthermore, differences were systematically observed depending on the origin of the strains. The clinical strains, mainly from CF patients, presented greater motility, siderophore and biofilm production compared to strains from the environment. Similar results were obtained when comparing the results obtained for Ax CF strains and Ax strains derived from non-CF patients. All the observations made suggest that the epidemiological success of Ax in CF patients and more broadly in humans could in part be linked to specific characteristics presented by this species.