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Microbiome on the Bone-Anchored Hearing System: A Prospective Study


Microbiome on the Bone-Anchored Hearing System: A Prospective Study

Tim G A Calon et al. Front Microbiol.


The bone-anchored hearing system (BAHS) has evolved to a common treatment option for various types of hearing revalidation. The BAHS consists of an implant in the skull that breeches the skin. Soft tissue reactions are a common complication associated with BAHS and are generally poorly understood. This study aims to investigate the influence of BAHS and associated skin reactions around the implant. A total of 45 patients were prospectively followed from implantation up to at least 1 year. Swabs were obtained at baseline, 12 weeks follow-up and during cases of inflammation (Holgers score ≥2). The microbiota was assessed using IS-proTM, a bacterial profiling method based on the interspace region between the 16S-23S rRNA genes. Detection of operational taxonomic units, the Shannon Diversity Index, sample similarity analyses and Partial Least Squares Discriminant Analysis (PLS-DA) were employed. Staphylococcus epidermidis, Streptococcus pneumoniae/mitis, Propionibacterium acnes, Staphylococcus capitis, Staphylococcus hominis, Bifidobacterium longum, Haemophilus parainfluenzae, Lactobacillus rhamnosus, Bordetella spp., Streptococcus sanguinis, Peptostreptococcus anaerobius, Staphylococcus aureus, Lactococcus lactis, Enterobacter cloacae, and Citrobacter koseri were the most commonly found bacterial species. S. pneumoniae/mitis was significantly more often observed after implantation, whereas P. acnes was significantly less observed after implantation compared with baseline. The relative abundance of S. epidermidis (17%) and S. aureus (19.4%) was the highest for the group of patients with inflammation. The Shannon Diversity Index was significantly increased after implantation compared with pre-surgical swabs for Firmicutes, Actinobacteria, Fusobacteria, Verrucomicrobia (FAFV), but not for other phyla. When combining all phyla, there was no significant increase in the Shannon Diversity Index. The diversity index was similar post-surgically for patients experiencing inflammation and for patients without inflammation. With a supervised classifier (PLS-DA), patients prone to inflammation could be identified at baseline with an accuracy of 91.7%. In addition, PLS-DA could classify post-surgical abutments as non-inflamed or inflamed with an accuracy of 97.7%. This study shows the potential of using IS-proTM to describe and quantify the microbiota associated with the percutaneous BAHS. Furthermore, the results indicate the possibility of an early identification of patients susceptible to adverse skin reaction following implantation. Both S. aureus and S. epidermidis should be considered as relevant bacteria for BAHS-associated inflammation.

Keywords: BAHS; Holgers Index; IS-pro; bone-anchored devices; microbiome; percutaneous implant.


Prevalence of the most commonly found bacterial species associated with BAHS. Sample sites: Baseline implant skin (BIS), non-inflamed peri-abutment skin (PAS, Holgers Index score <2) and inflamed peri-abutment skin (iPAS, Holgers Index score ≥2). (A) The percentage of patients with observed bacterial species is presented. (B) Relative abundance (in percentage) of five commonly found species based on the total bacterial counts detected in the three sample types: baseline implant skin sample (BIS), peri-abutment skin site (PAS), and inflamed PAS (iPAS). Indicates p-value ≤0.05.
Clustered heatmap with IS-pro profiles for baseline implant skin samples and peri-abutment skin sites obtained at 12-week follow-up. Red dots and branches indicate the percentage of similarity between swabs below. Swabs are clustered per phylum. FAFV represents the phyla Firmicutes, Actinobacteria, Fusobacteria, and Verrucomicrobia. Patient identification numbers are indicated in dots. All baseline implant skin samples and all 12-week peri-abutment skin site swabs are included. Overall no specific pattern can be observed distinguishing baseline implant skin samples and peri-abutment skin sites or patient clusters.
Shannon Diversity Index. (A) The Shannon Diversity Index for baseline implant skin samples, 12-week peri-abutment skin site swabs, and contra-lateral samples obtained at 12-week follow-up. (B) The Shannon Diversity Index for non-inflamed peri-abutment skin swabs at 12 weeks and inflamed peri-abutment skin swabs obtained during follow-up.
Partial least square discriminant analysis. (A) Analysis of baseline implant skin samples with no inflammation (green) during the 1-year follow-up. Red dots indicate baseline implant skin samples (BIS) with inflammation during X months follow-up. (B) Analysis of peri-abutment skin site swabs (PAS) obtained at 12-week follow-up with no inflammation during X months follow-up (green dots) and peri-abutment skin site swabs obtained during inflammation (iPAS) (red dots). Inflammation was defined as a Holgers Index score ≥2. On the x-axis the first component (future) inflammation, in the PLS-DA model is displayed. On the y-axis the second component, no (future) inflammation, is displayed.

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