High diversity of Achromobacter sp. isolation from children with CF, a retrospective case-control study

Background Achromobacter spp. are opportunistic pathogens in cystic fibrosis. Recent studies have suggested that colonization by Achromobacter is associated with adverse effects on respiratory function. However, this is still understudied in children, as is the relative involvement of different species of Achromobacter . Methods Children from whom Achromobacter was isolated between 2014 and 2020 were retrospectively included. A control group, never infected by Achromobacter , was case-matched by sex, age, and Pseudomonas aeruginosa colonization status. Pulmonary function was compared between the two groups after the first Achromobacter isolation. Species were identified by nrdA gene sequencing and strains were genotyped by multi-locus sequence typing. Results Twenty-seven cases were included. Eight Achromobacter species were identified, Achromobacter xylosoxidans being predominant (63 % of children). We observed high genetic diversity, with 41 % of patients harboring strains not previously described (new species, sequence type, or nrdA allele). Thirty-three percent of children evolved towards chronic colonization by A. xylosoxidans , A.dolens or, or A.insolitus . Two years prior to the isolation of Achromobacter , cases showed a significantly lower forced expiratory volume in 1 s than controls (86 ± 17 % vs 103 ± 16 %, p = 0.02). The mean decline in forced expiratory volume in 1 s was −1.31 %/year for cases versus +0.99 %/year for controls (p = 0.07). In terms of Achromobacter species involved, there was no significant difference in the slope of the decline in forced expiratory volume in 1 s over the total follow-up time between cases infected by A. xylosoxidans versus other Achromobacter species. Conclusion A high diversity of strains was found in children with cystic fibrosis. There may be a potential association between more severe lung pathology and Achromobacter sp. infection.