Achromobacter spp. Adaptation in Cystic Fibrosis Infection and Candidate Biomarkers of Antimicrobial Resistance

Abstract

Achromobacter spp. can establish occasional or chronic lung infections in patients with cystic fibrosis (CF). Chronic colonization has been associated with worse prognosis highlighting the need to identify markers of bacterial persistence. To this purpose, we analyzed phenotypic features of 95 Achromobacter spp. isolates from 38 patients presenting chronic or occasional infection. Virulence was tested in Galleria mellonella larvae, cytotoxicity was tested in human bronchial epithelial cells, biofilm production in static conditions was measured by crystal violet staining and susceptibility to selected antibiotics was tested by the disk diffusion method. The presence of genetic loci associated to the analyzed phenotypic features was evaluated by a genome-wide association study. Isolates from occasional infection induced significantly higher mortality of G. mellonella larvae and showed a trend for lower cytotoxicity than chronic infection isolates. No significant difference was observed in biofilm production among the two groups. Additionally, antibiotic susceptibility testing showed that isolates from chronically-infected patients were significantly more resistant to sulfonamides and meropenem than occasional isolates. Candidate genetic biomarkers associated with antibiotic resistance or sensitivity were identified. Achromobacter spp. strains isolated from people with chronic and occasional lung infection exhibit different virulence and antibiotic susceptibility features, which could be linked to persistence in CF lungs. This underlines the possibility of identifying predictive biomarkers of persistence that could be useful for clinical purposes.

In Vivo Inflammation Caused by Achromobacter spp. Cystic Fibrosis Clinical Isolates Exhibiting Different Pathogenic Characteristics

“…Wild-type (WT) and CFTR-knockout (KO) mice were intratracheally challenged with 8 Achromobacter spp. clinical isolates expressing different pathogenic characteristics: virulence in G. mellonella larvae, cytotoxicity in bronchial epithelial cells, and biofilm formation previously assessed [ 10 ], as shown in Table 1 and defined in Tables S1–S3 . Mice were grouped and analyzed based on the pathogenic characteristics of the isolates.…”

“…We previously evaluated the pathogenicity of Achromobacter spp. in terms of virulence in G. mellonella larvae, cytotoxicity in human bronchial epithelial cells, and biofilm formation, and observed wide differences for each of these three characteristics among clinical isolates [ 10 ]. Based on these results, in the present study, we selected eight isolates showing different pathogenic characteristics and used them to induce acute lung infection in WT and KO mice to observe eventual differences in lung inflammation, mice survival, and bacterial load that could reveal the importance of these characteristics for Achromobacter spp.…”

“…In a previous study, we observed that Achromobacter spp. clinical isolates can exhibit different pathogenic characteristics (e.g., virulence, cytotoxicity, biofilm formation) that could be associated with different clinical outcomes [ 10 ]. Lung inflammation has already been reported to be influenced by bacterial virulence for another CF pathogen, P. aeruginosa [ 11 ].…”

Polymyxin Resistance and Heteroresistance Are Common in Clinical Isolates of Achromobacter Species and Correlate with Modifications of the Lipid A Moiety of Lipopolysaccharide

“…Recent studies have highlighted the cytotoxicity of A. xylosoxidans for murine macrophages based on the potential cytotoxic role of the T3SS ubiquitin-activated phospholipase effector AxoU ( 26 ) and a giant repeats-in-toxin (RTX) adhesin ( 27 ). Comparative genomic studies of A. xylosoxidans isolated from acute and chronic infections indicate that the bacteria can adapt to chronic lung infection, as evidenced by increased antimicrobial resistance, decreased motility, alteration in biofilm formation, and reduced cytotoxicity ( 26 , 28 – 31 ).…”

TheAchromobacterType 3 secretion system drives pyroptosis and immunopathology via independent activation of NLRC4 and NLRP3 inflammasomes

“…Achromobacter infections are very difficult to treat because multi-drug resistance is common, and in cases of chronic infections the bacteria frequently acquire further resistance over time 7,8 . This genus has received less attention than more ubiquitous lung pathogens, such as Klebsiella and Pseudomonas, but its increasing prevalence 9,10 justifies further investigation.…”